Effects of climate on soil phosphorus cycle and availability in natural terrestrial ecosystems

Edaphic and climatic factors control the response of nutrient-cycling enzyme activity to common heavy metals in soils

Soil enzymes, which are crucial catalysts in soil nutrient cycling, are sensitive to heavy metals and metalloids (HMMs). Yet, the mechanistic understanding of soil enzyme activities (EAs) response to HMMs is still only rudimentarily known. By analyzing 1989 paired observations from 145 studies investigating HMMs effect on 14 enzymes, we found that HMMs decreased the activity of β-D-glucosidase (-25.3 %), cellulase (-10.3 %), urease (-26.8 %), protease (-22.5 %), phosphatase (-21.0 %), arylsulphatase (-37.0 %), catalase (-19.2 %) and dehydrogenase (-33.1 %), with natural ecosystems being more severely affected than croplands. This decrease in EAs was mainly due to decreased microbial biomass content and abundance and increased microbial metabolic quotient. However, HMMs increased polyphenol oxidase activity (82.2 %), possibly because HMMs can serve as cofactors or activators for polyphenol oxidase and/or because microbes produced it as a defense mechanism under stress. The response ratio of EAs is driven by cation exchange capacity (CEC) and dominantly influenced by soil organic carbon (SOC), clay, and bulk density (BD). Increased CEC, SOC and clay content and decreased BD reduced the negative effect of HMMs on EAs. Climate impact on the response ratio of EAs was mediated through soil properties. Our analysis provides a more holistic representation of EAs response to HMMs, offering comprehensive insights into the ecological consequences of HMMs on ecosystem functioning.

Soil resource acquisition strategy modulates global plant nutrient and water economics

Natural selection favors growth by selecting a combination of plant traits that maximize photosynthetic CO2 assimilation at the lowest combined carbon costs of resource acquisition and use. We quantified how soil nutrient availability, plant nutrient acquisition strategies, and aridity modulate the variability in plant costs of nutrient acquisition relative to water acquisition (β). We used an eco-evolutionary optimality framework and a global carbon isotope dataset to quantify β. Under low soil nitrogen-to-carbon (N : C) ratios, a mining strategy (symbioses with ectomycorrhizal and ericoid mycorrhizal fungi) reduced β by mining organic nitrogen, compared with a scavenging strategy (symbioses with arbuscular mycorrhizal fungi). Conversely, under high N : C ratios, scavenging strategies reduced β by effectively scavenging soluble nitrogen, compared with mining strategies. N2-fixing plants did not exhibit reduced β under low N : C ratios compared with non-N2-fixing plants. Moisture increased β only in plants using a scavenging strategy, reflecting direct impacts of aridity on the carbon costs of maintaining transpiration in these plants. Nitrogen and phosphorus colimitation further modulated β. Our findings provide a framework for simulating the variability of plant economics due to plant nutrient acquisition strategies in earth system models.

A dynamic optimization of soil phosphorus status approach could reduce phosphorus fertilizer use by half in China

Sustainable phosphorus (P) management is essential for ensuring crop production while avoiding environmental damage and the depletion of phosphate rock reserves. Despite local demonstration scale successes, the widespread mobilization of smallholder farmers to adopt sustainable management practices remains a challenge, primarily due to the associated high costs and complicated sampling. Here, we propose a dynamic optimization of soil P status (DOP) approach aimed at managing long-term soil P status within the range of agronomic and environmental soil P thresholds, which facilitates the precise determination of optimal P application rates without the need for frequent soil testing. We evaluate the DOP approach in 35,575 on-farm trials, and the results show that it is agronomically acceptable. Our evaluation extends to estimating future soil P status and P fertilizer inputs across all counties in China for three cereal crops (wheat, rice, and maize). The results indicate that, compared to current practices, the DOP approach can achieve a 47.4% reduction in P fertilizer use without any yield penalty. The DOP approach could become an effective tool for global P management to safeguard food security and enhance environmental sustainability.

Long-term adoption of plow tillage and green manure improves soil physicochemical properties and optimizes microbial communities under a continuous peanut monoculture system

Continuous monocropping of peanuts (Arachis hypogaea L.) often results in yield decline and soil degradation. The combination of green manure (GM) with tillage practices has been proposed as a sustainable strategy to maintain high crop productivity and improve soil quality. This study investigates the long-term effects of 8 years of GM application combined with plow tillage on soil microbial communities and physicochemical properties under a peanut monocropping system. Treatments included: (i) no tillage (NT); (ii) plow tillage before the winter fallow period (PT); and (iii) growing ryegrass (Lolium perenne L.) during the winter period and applying it as GM before planting next-stubble peanut (PTGM). It was found that both PTGM and PT remarkably decreased the average bulk density (BD), while elevated the mean soil porosity (SP) in 0-30 cm soil layer. Moreover, PTGM significantly increased available potassium (AK), available phosphorus (AP), total nitrogen (TN), and soil organic matter (SOM). Peanut pod yields in the PTGM treatment were 14.1 and 7.2% higher compared to the PT and NT treatments, respectively. Additionally, PTGM could promote shifts in soil bacteria compositions, increasing the abundance of Actinobacteria and Firmicutes while reducing that of Chloroflexi. For fungal abundances, PTGM elevated the abundances of Ascomycota and Basidiomycote. Redundancy analysis demonstrated that SOM, TN, AK, and AP were positively related to dominant flora of fungi and bacteria in PTGM, while negatively related to dominant flora of fungi and bacteria in NT. Overall, tillage practices have the potential to reshape the microbial community during the peanut growing season, primarily due to the influence of SOM, TN, and AP content in shaping microbial diversity and composition. Our study highlights that plow tillage combined with GM application may serve as an effective tillage practice in the future to mitigate continuous cropping obstacles by modulating soil microbial communities, improving soil nutrients and fertility, and enhancing crop productivity.

Assessing the health of climate-sensitive trees in a subalpine ecosystem through microbial community dynamics

Climate change has significantly affected the subalpine ecosystems, leading to mass die-offs of the Korean fir tree, a key climate-sensitive species in these environments. Proactive analysis of the phenotypic responses of these trees to climate change or the establishment of preemptive strategies for trees to adapt to these environmental changes remains a challenge. The current study aimed to investigate the impact of climate change on the health of Korean fir (Abies koreana) in the subalpine ecosystem of Jirisan Mountain, South Korea. We integrated soil physicochemical analyses, microbial community dynamics, neutral community model, and network analyses to examine the relationships between tree health and microbial communities. Our findings revealed significant changes in soil chemical properties, including pH and nutrient concentrations, across the various health statuses of trees. Microbial community analysis demonstrated shifts in bacterial and fungal communities corresponding to the health continuum of the trees, with decreased diversity and altered composition in the declining trees. A remarkable increase in modularity of the microbial network and a clear transition from stochastic to deterministic microbial community assembly processes were observed as the trees progressed from a healthy to a dead stage. Two bacterial genera, Bradyrhizobium and Burkholderia, along with an unclassified fungal group from Basidiomycota, were identified as key microbial indicators of good tree health. This study highlighted the importance of microbial communities as bioindicators for assessing the health of subalpine ecosystem and its resilience to climate change, offering valuable insights into the conservation and management strategies for subalpine ecosystems.

Biogeography of Soil Phosphorus-Cycling Microbes in a Changing World

Soil microbes involved in phosphorus cycling facilitate the fixation and mineralization of phosphorus through various biological processes. The biogeography of soil phosphorus‐cycling microbes is of great significance for a comprehensive understanding of their ecological roles and utilization of their functions. It is imperative to underscore the profound impact of human activities on soil phosphorus‐cycling microbes, which will significantly contribute to refining soil management practices and fostering sustainable human interactions essential for safeguarding soil ecosystems in our ever‐changing world.

The spatial variations and driving factors of C, N, P stoichiometric characteristics of plant and soil in the terrestrial ecosystem

Carbon(C), nitrogen(N), and phosphorus(P) are crucial elements in the element cycling in the terrestrial ecosystems. In the past decades, the spatial patterns and driving mechanisms of plant and soil ecological stoichiometry have been hot topics in ecological geography. So far, many studies at different spatial and ecological scales have been conducted, but systematic review has not been reported to summarize the research status. In this paper, we tried to fill this gap by reviewing both the spatial variations and driving factors of C, N, P stoichiometric characteristics of plant and soil at regional to large scale. Additionally, we synthesized researches on the relationships between plant and soil C, N and P stoichiometric characteristics. At the global scale, plant C, N, P stoichiometric characteristics exhibited some trends along latitude and temperature gradient. Plant taxonomic classification was the main factor controlling the spatial variations of plant C, N and P stoichiometric characteristics. Climate factor and soil properties showed varying impacts on the spatial variations of plant C, N, P stoichiometric characteristics across different spatial scales. Soil C, N, P stoichiometric characteristics also varied along climate gradient at large scale. Their spatial variations resulted from the combined effects of climate, topography, soil properties, and vegetation characteristics at regional scale. The spatial pattern of soil C, N, P stoichiometric characteristics and the driving effects from environmental factors could be notably different among different ecosystems and vegetation types. Plant C:N:P was obviously higher than that of soil, and there existed a positive correlation between plant and soil C:N:P. Their trends along longitude and latitude were similar, but this correlation varied significantly among different vegetation types. Finally, based on the issues identified in this paper, we highlighted eight potential research themes for the future studies.

Lithology and elevated temperature impact phoD-harboring bacteria on soil available P enhancing in subtropical forests

Plants are generally limited by soil phosphorus (P) deficiency in forest ecosystems. Soil available P is influenced by lithology, temperature, and soil microbes. However, the interactive effects of these factors on soil P availability in subtropical forests remain unclear. To assess their impacts, we measured soil inorganic and available P fractions and the diversity, composition, and co-occurrence network of phoD-harboring bacteria in two contrasting forest soils (lithosols in karst forests and ferralsols in non-karst forests) in the subtropical regions of southwestern China across six temperature gradients. The present results showed that the complexities in composition and network and the diversity indices of phoD-harboring bacteria were higher in the karst forest soils than those in the non-karst forest soils, with marked differences in composition. In both types of forest soils, the complexities of composition and networks and the diversity indices were higher in the high-temperature regions (mean annual temperature (MAT) > 16 °C) compared to the low-temperature regions (MAT <16 °C). Soil total inorganic and available P contents were lower in the karst forest soils compared to the non-karst forest soils. Soil total available P contents were lower in the high temperature regions than those in the low temperature regions in both forest soils, whereas soil total inorganic P contents were contrary. Variance partitioning analysis showed that soil inorganic and available P fractions were predominantly explained by lithology and its interaction with soil microbes and climate. The present findings demonstrate that soil P availability in subtropical forests of southwestern China is influenced by lithology and temperature, which regulate the diversity, composition, and network connectivity of phoD-harboring bacteria. Furthermore, this study highlights the significance of controlling the composition of phoD-harboring bacteria for mitigating plant P deficiency in karst ecosystems.

Transect approach for assessing major and trace elemental contamination in agricultural soils of the palamaner division, chittoor district, andhra pradesh, india

Three soil transects located in the granitic regions of Palamaner mandal, Andhra Pradesh, India, were examined to assess the pollution levels of both primary and secondary metals (Si, Al, Fe, Ca, Mg, Na, K, Cu, Mn, P, and Zn) and to ascertain the degree of soil pollution in agricultural areas. The soils along these transects are slightly acid to neutral, with dark brown to red rubified argillic clay-rich B horizons alongside a moderate cation exchange capacity. The A horizon soils display low organic carbon levels with a moderate variability and contain over 70% SiO2, exhibiting low variability due to limited leaching in a semiarid climate. The findings suggest that iron (Fe) and manganese (Mn) oxides play a role in reducing contamination levels through oxidation and precipitation processes. Furthermore, the soils show low to moderate cation exchange capacity, which restricts the retention of absorbed heavy metals, thus lessening their negative impacts. A two-way ANOVA revealed significant differences in CEC, organic carbon, and total zinc content across different horizons and landscape positions. Si, Al, and Cu had small increases and negative geoaccumulation indices in all soil profiles, suggesting no pollution. However, the Nemerow and mean contamination degree over 6 point to slight to moderate pollution. The analysis identified three distinct clusters with significant variations in contamination factors for SiO2 and Cu. Five principal components were determined, explaining 76% of the total variance, primarily derived from geogenic sources and remaining within acceptable limits. This research on soil transects in granitic regions contributes to a better understanding of the distribution, movement, and concentration of elemental oxides based on slope position, which is essential for pollution assessment and soil quality enhancement.

Phosphorus dynamics in volcanic soils of Weizhou Island, China: implications for environmental and agricultural applications

The dynamics of phosphorus are intricately governed by geological and ecological processes. Examining phosphorus dynamics in volcanic islands can enhance our comprehension of its behavior within such unique geological systems. However, research on phosphorus dynamics in volcanic islands remains limited. We investigated the phosphorus content of volcaniclastic rocks and basalt soils from Weizhou Island, China, to understand the influencing factors on phosphorus dynamics. The results indicate that in the volcaniclastic profile, phosphorus concentrates at 20-40 cm (17 mg/kg), decreases at 40-60 cm (11.9 mg/kg), and increases at 80-200 cm up to 46.4 mg/kg proximate to the bedrock, for the basalt profile, phosphorus content increases from the surface (80.2 mg/kg) towards the bedrock (83.9 mg/kg). The differences in phosphorus distribution between volcaniclastic rocks and basalts reflect the influence of parent material, rock weathering degree, carbonate content, topographic elevation, sea level changes, and geological activities. A strong positive correlation (R = 0.96907) between total and available phosphorus has been observed, suggesting that total phosphorus content effectively predicts available phosphorus content. Volcaniclastic rocks in wharves and high-elevation areas show low total phosphorus, while forest land with dense vegetation and neutral to alkaline soil supports higher total phosphorus due to enhanced bioavailability for plant absorption and utilization. Overall, the basalt soil of the volcanic island Weizhou Island demonstrates superior long-term fertility compared to the volcaniclastic soil. Despite its low total phosphorus content, it mainly exists in a highly bioavailable form, facilitating plant absorption, which is crucial for enhancing agricultural yields and ecosystem restoration on volcanic islands.

Enhanced aqueous phosphorus removal and mechanism by water spinach (Ipomoea aquatica Forsk) pretreated with lanthanum nitrate

Excess nutrients such as phosphate (PO43-) entering surface waters promote eutrophication, and phosphorous (P) removal is important to clear the water. Phytoremediation efforts have been used to improve water quality by varieties of P removal plants, such as water spinach (Ipomoea aquatica Forsk). Water spinach can reduce both internal and external resources of phosphorus from waterbody. The ion of lanthanum (La), one rare earth element (REE), is an immobilization substance for aqueous phosphate and also a fertilizer for plants. Therefore, lanthanum nitrate La (NO3)3 was used further to improve the phytoextraction of P from the polluted water. This study investigated the effects of La on the aqueous P removal by two genotypes of water spinach, green stem large leaves (GSLL) and green stem willow leaves (GSWL). The low concentration La (NO3)3 helped the plant to remove more phosphorous from eutrophic water, but La at high concentration lowered the removal of P. Under La (NO3)3 treatments, the optimum concentration for maximum P removal in GSLL is 3 mg/L, and for GSWL, it is 10 mg/L and P removal rates were enhanced to 95% and 96%, respectively. When the concentration of La (NO3)3 is 100 mg/L, the removal percentage of P was only 10% for both genotypes. The very high concentration of La will impose toxicity and even cause the death of the water spinach and produce secondary pollution; for example, under some specific circumstances, the bond between lanthanum and nitrates dissociates into lanthanum ions (La3⁺) and nitrate ions (NO₃⁻). If the concentration is high, then it accumulates in the aquatic water organisms and plants and causes toxicity in their bodies. If humans eat up these plants and fish, it causes toxic effects in humans. The La (NO3)3 positively affects different parameters of plants. La (NO3)3 increases the growth, pigments, enzyme activity, and malondialdehyde (MDA) of plants which were also discussed in this study. The biological mechanism should be responsible for the enhanced aqueous phosphorus removal by water spinach using lanthanum nitrate.

The Role of Phosphate-Solubilizing Microbial Interactions in Phosphorus Activation and Utilization in Plant-Soil Systems: A Review

To address the issue of phosphorus limitation in agricultural and forestry production and to identify green and economical alternatives to chemical phosphorus fertilizers, this paper reviews the utilization of phosphorus in plant-soil systems and explores the considerable potential for exploiting endogenous phosphorus resources. The application of phosphate-solubilizing microorganisms (PSMs) is emphasized for their role in phosphorus activation and plant growth promotion. A focus is placed on microbial interactions as an entry point to regulate the functional rhizosphere microbiome, introducing the concept of synthetic communities. This approach aims to deepen the understanding of PSM interactions across plant root, soil, and microbial interfaces, providing a theoretical foundation for the development and application of biological regulation technologies to enhance phosphorus utilization efficiency.

The Effect of Intercropping with Different Leguminous Green Manures on the Soil Environment and Tea Quality in Tea Plantations

Intercropping with green manure is a soil-sustainable cultivation practice that has demonstrated positive impacts on tea growth and the soil environment in tea plantations. Nevertheless, research examining the effect of leguminous green manure varieties in tea plantations is scarce. This study aimed to analyze the tea quality and soil environment components in response to intercropping with three distinct leguminous green manures, Cassia sophera cv. Chafei 1 (CF), Sesbania cannabina (Retz.) Pers. (SC), and Chamaecrista rotundifolia (Pers.) Greene (CR), with 70% chemical fertilizer, and compare them to non-intercropped green manures with 100% chemical fertilizer (CK) in tea plantations. The findings indicated that intercropping with SC increased the amino acids content of tea leaves, the soil organic carbon (SOC), the soil acid phosphatase (ACP), the soil acid protease (ACPT), and the bacterial diversity compared to the CK treatment. Intercropping with CR improved the ACP activity and bacterial diversity while intercropping with CF improved the polyphenols. Proteobacteria, Acidobacteria, Actinomycetes, and Firmicutes were identified as the dominant bacterial taxa in tea plantations with intercropped green manure. A strong positive correlation was indicated between the SOC contents and the amino acids content in tea leaves after intercropping. A canonical correspondence analysis indicated significant associations between the ACP and the urease activity, and between the ACP and ACPT, and both were closely linked to SC. This finding provides an explanation that intercropping with SC may positively affect tea quality by influencing the SOC content, the soil enzyme activity, and the soil bacterial diversity. Green manure intercropping may replace part of chemical fertilizers, improve the soil environment in tea gardens, and enhance the quality of tea. These findings offer a theoretical reference for selecting leguminous green manure and advancing the sustainable development of tea plantations.

Geotechnologies on the phosphorus stocks determination in tropical soils: General impacts on society

Phosphorus (P) is a critical nutrient for primary production in terrestrial and aquatic ecosystems. As P mineral reserves are finite and non-renewable, there is an increasing discussion on its sustainable utilization to safeguard food security for future generations. Understanding the spatial distribution of soil P is central in advancing effective phosphorus management and fostering sustainable agricultural practices. This study aims to digitally map the stocks of available P (AP) and total P (TP) in Brazil at a fine resolution (30 m). Using the Random Forest machine learning algorithm and a database of topsoil (0-20 cm) with 28,572 samples for AP and 3154 for TP, we predicted P stocks based on environmental covariates related to soil formation processes. By dividing Brazil into two sub-regions, representing areas with native coverage and anthropogenic ones, we built independent predictive models for each sub-region. Our results show that Brazil has a TP stock of 531 Tg and an AP stock of 17.4 Tg. The largest soil TP stocks are in the Atlantic Forest biome (73.8 g.m2), likely due to higher organic carbon stocks in this biome. The largest AP stocks were in the Caatinga biome (2.51 g.m2) because of younger soils with low P adsorption capacity. We also found that fertilizer use significantly increased AP stocks in agricultural areas compared to native ones. Our results indicated that AP stocks strongly influenced Brazil's agricultural production, with a correlation coefficient ranging from 0.20 for coffee crops to 0.46 for soybean. The maps generated in this study are expected to contribute to the sustainable use of P in agriculture and environmental systems.

Prospects of phosphate solubilizing microorganisms in sustainable agriculture

Phosphorus (P), an essential macronutrient for various plant processes, is generally a limiting soil component for crop growth and yields. Organic and inorganic types of P are copious in soils, but their phyto-availability is limited as it is present largely in insoluble forms. Although phosphate fertilizers are applied in P-deficit soils, their undue use negatively impacts soil quality and the environment. Moreover, many P fertilizers are lost because of adsorption and fixation mechanisms, further reducing fertilizer efficiencies. The application of phosphate-solubilizing microorganisms (PSMs) is an environmentally friendly, low-budget, and biologically efficient method for sustainable agriculture without causing environmental hazards. These beneficial microorganisms are widely distributed in the rhizosphere and can hydrolyze inorganic and organic insoluble P substances to soluble P forms which are directly assimilated by plants. The present review summarizes and discusses our existing understanding related to various forms and sources of P in soils, the importance and P utilization by plants and microbes,, the diversification of PSMs along with mixed consortia of diverse PSMs including endophytic PSMs, the mechanism of P solubilization, and lastly constraints being faced in terms of production and adoption of PSMs on large scale have also been discussed.

Reducing Application of Nitrogen Fertilizer Increases Soil Bacterial Diversity and Drives Co-Occurrence Networks

Reducing nitrogen fertilizer application highlights its role in optimizing soil bacterial communities to achieve sustainable agriculture. However, the specific mechanisms of bacterial community change under these conditions are not yet clear. In this study, we employed long-term field experiments and high-throughput sequencing to analyze how varying levels of nitrogen application influence the soil bacterial community structure and co-occurrence networks. The results show that reducing the nitrogen inputs significantly enhances the diversity and evenness of the soil bacterial communities, possibly due to the diminished dominance of nitrogen-sensitive taxa, which in turn liberates the ecological niches for less competitive species. Furthermore, changes in the complexity and stability of the bacterial co-occurrence networks suggest increased community resilience and a shift toward more mutualistic interactions. These findings underline the potential of reduced nitrogen application to alleviate competitive pressures among bacterial species, thereby promoting a more diverse and stable microbial ecosystem, highlighting the role of competitive release in fostering microbial diversity. This research contributes to our understanding of how nitrogen management can influence soil health and offers insights into sustainable agricultural practices.

Acceleration of phosphorus weathering under warm climates

The release of phosphorous (P) via chemical weathering is a vital process that regulates the global cycling of numerous key elements and shapes the size of the Earth's biosphere. It has long been postulated that global climate should theoretically play a prominent role in governing P weathering rates. Yet, there is currently a lack of direct evidence for this relationship based on empirical data at the global scale. Here, using a compilation of temperature and P content data of global surface soils (0 to 30 cm), we demonstrate that P release does enhance at high mean annual surface temperatures. We propose that this amplification of nutrient supply with warming is a critical component of Earth's natural thermostat, and that this relationship likely caused expanded oceanic anoxia during past climate warming events. The potential acceleration of phosphorus loss from soils due to anthropogenic climate warming may pose threats to agricultural production, terrestrial and marine ecosystems, and alter marine redox landscapes.

Urban Stormwater Phosphorus Export Control: Comparing Traditional and Low-impact Development Best Management Practices

Data from the International Stormwater Best Management Practices (BMP) Database were used to compare the phosphorus (P) control performance of six categories of stormwater BMPs representing traditional systems (stormwater pond, wetland basin, and detention basin) and low-impact development (LID) systems (bioretention cell, grass swale, and grass strip). Machine learning (ML) models were trained to predict the reduction or enrichment factors of surface runoff concentrations and loadings of total P (TP) and soluble reactive P (SRP) for the different categories of BMP systems. Relative to traditional BMPs, LIDs generally enriched TP and SRP concentrations in stormwater surface outflow and yielded poorer P runoff load control. The SRP concentration reduction and enrichment factors of LIDs also tended to be more sensitive to variations in climate and watershed characteristics. That is, LIDs were more likely to enrich surface runoff SRP concentrations in drier climates, when inflow SRP concentrations were low, and for watersheds exhibiting high impervious land cover. Overall, our results imply that stormwater BMPs do not universally attenuate urban P export and that preferentially implementing LIDs over traditional BMPs may increase TP and SRP export to receiving freshwater bodies, hence magnifying eutrophication risks.

Water addition but not reduction alters plant biomass-diversity relationship

The relationship between plant aboveground biomass and diversity typically follows a unimodal pattern, showing a positive correlation in resource-poor habitats and a negative correlation in resource-rich environments. Precipitation is a crucial resource for both plant biomass and diversity in terrestrial ecosystems. However, the impact of precipitation changes on the relationship between plant biomass and diversity remains unclear. We conduct a water addition field experiment in a semiarid grassland and identify a unimodal relationship between plant biomass and species richness under ambient conditions. Water addition delays the declining phase of this unimodal curve and shift it upward compared to ambient conditions. Our meta-analysis of water addition experiments conducted across major biomes worldwide (grassland, shrubland, desert, and forest) supports this finding, while water reduction does not alter the biomass-diversity relationship. Water addition increases biomass in all climate but only increases species richness in arid and semiarid climate. Similarly, water reduction decreases biomass in all climate but only reduces species richness in arid and semiarid climate. Species richness in dry subhumid and humid climate does not change significantly. Furthermore, our field experiment shows that water addition increases plant diversity while decreasing soil inorganic nitrogen levels. The increase in one resource, such as water, leads to the scarcity of another, such as nutrient, thus postponing the declining phase of the plant biomass-diversity relationship typically observed in resource-rich habitats. Our research contributes to predicting the plant biomass-diversity relationship under changing precipitation conditions and highlights the complex interplay between water availability, nutrient level, and plant diversity.

Warming enhances the negative effects of shrub removal on phosphorus mineralization potential

Shrubs have developed various mechanisms for soil phosphorus utilization. Shrub encroachment caused by climate warming alters organic phosphorus mineralization capability by promoting available phosphorus absorption and mediating root exudates. However, few studies have explored how warming regulates the effects of dominant shrubs on soil organic phosphorus mineralization capability. We provide insights into warming, dominant shrub removal, and their interactive effects on the soil organic phosphorus mineralization potential in the Qinghai-Tibetan Plateau. Real-time polymerase chain reaction was used to quantify the soil microbial phosphatase genes (phoC and phoD), which can characterize the soil organic phosphate mineralization potential. We found that warming had no significant effect on the soil organic phosphate-mineralized components (total phosphate, organic phosphate, and available phosphate), genes (phoC and phoD), or enzymes (acid and alkaline phosphatases). Shrub removal negatively influenced the organic phosphate-mineralized components and genes. It significantly decreased soil organic phosphate mineralization gene copy numbers only under warming conditions. Warming increased fungal richness and buffered the effects of shrub removal on bacterial richness and gene copy numbers. However, the change in the microbial community was not the main factor affecting organic phosphate mineralization. We found only phoC copy number had significant correlation to AP. Structural equation modelling revealed that shrub removal and the interaction between warming and shrub removal had a negative direct effect on phoC copy numbers. We concluded that warming increases the negative effect of shrub removal on phosphorus mineralization potential, providing a theoretical basis for shrub encroachment on soil phosphate mineralization under warming conditions.

Microbial phosphorus-cycling genes in soil under global change

The ongoing climate change on the Tibetan Plateau, leading to warming and precipitation anomalies, modifies phosphorus (P) cycling in alpine meadow soils. However, the interactions and cascading effects of warming and precipitation changes on the key "extracellular" and "intracellular" P cycling genes (PCGs) of bacteria are largely unknown for these P-limited ecosystems. We used metagenomics to analyze the individual and combined effects of warming and altered precipitation on soil PCGs and P transformation in a manipulation experiment. Warming and increased precipitation raised Olsen-P (bioavailable P, AP) by 13% and 20%, respectively, mainly caused by augmented hydrolysis of organic P compounds (NaOH-Po). The decreased precipitation reduced soil AP by 5.3%. The richness and abundance of the PCGs' community in soils on the cold Tibetan plateau were more sensitive to warming than altered precipitation. The abundance of PCGs and P cycling processes decreased under the influence of individual climate change factors (i.e., warming and altered precipitation alone), except for the warming combined with increased precipitation. Pyruvate metabolism, phosphotransferase system, oxidative phosphorylation, and purine metabolism (all "intracellular" PCG) were closely correlated with P pools under climate change conditions. Specifically, warming recruited bacteria with the phoD and phoX genes, which encode enzymes responsible for phosphoester hydrolysis (extracellular P cycling), strongly accelerated organic P mineralization and so, directly impacted P bioavailability in alpine soil. The interactions between warming and altered precipitation profoundly influenced the PCGs' community and facilitated microbial adaptation to these environmental changes. Warming combined with increased precipitation compensated for the detrimental impacts of the individual climate change factors on PCGs. In conclusion, warming combined with rising precipitation has boosting effect on most P-related functions, leading to the acceleration of P cycling within microbial cells and extracellularly, including mineralization and more available P release for microorganisms and plants in alpine soils.

Distinct latitudinal patterns and drivers of topsoil nitrogen and phosphorus across urban forests in eastern China

Nitrogen (N) and phosphorus (P) are the two most important macronutrients supporting forest growth. Unprecedented urbanization has created growing areas of urban forests that provide key ecosystem services for city dwellers. However, the large-scale patterns of soil N and P content remain poorly understood in urban forests. Based on a systematic soil survey in urban forests from nine large cities across eastern China, we examined the spatial patterns and key drivers of topsoil (0-20 cm) total N content, total P content, and N:P ratio. Topsoil total N content was found to change significantly with latitude in the form of an inverted parabolic curve, while total P content showed an opposite latitudinal pattern. Variance partition analysis indicated that regional-scale patterns of topsoil total N and P contents were dominated by climatic drivers and partially regulated by time and pedogenic drivers. Conditional regression analyses showed a significant increase in topsoil total N content with lower mean annual temperature (MAT) and higher mean annual precipitation (MAP), while topsoil total P content decreased significantly with higher MAP. Topsoil total N content also increased significantly with the age of urban park and varied with pre-urban soil type, while no such effects were found for topsoil total P content. Moreover, topsoil N:P ratio showed a latitudinal pattern similar to that of topsoil total N content and also increased significantly with lower MAT and higher MAP. Our findings demonstrate distinct latitudinal trends of topsoil N and P contents and highlight a dominant role of climatic drivers in shaping the large-scale patterns of topsoil nutrients in urban forests.

Correlations between root phosphorus acquisition and foliar phosphorus allocation reveal how grazing promotes plant phosphorus utilization

Overgrazing and phosphorus (P) deficiency are two major factors limiting the sustainable development of grassland ecosystems. Exploring plant P utilization and acquisition strategies under grazing can provide a solid basis for determining a reasonable grazing intensity. Both foliar P allocation and root P acquisition are crucial mechanisms for plants to adapt to environmental P availability; however, their changing characteristics and correlation under grazing remain unknown. Here, we investigated foliar P fractions, root P-acquisition traits and gene expression, as well as rhizosphere and bulk soil properties of two dominant plant species, Leymus chinensis (a rhizomatous grass) and Stipa grandis (a bunchgrass), in a field grazing intensity gradient site in Inner Mongolia. Grazing induced different degrees of compensatory growth in the two dominant plant species, increased rhizosphere P availability, and alleviated plant P limitation. Under grazing, the foliar metabolite P of L. chinensis increased, whereas the nucleic acid P of S. grandis increased. Increased P fractions in L. chinensis were positively correlated with increased root exudates and rapid inorganic P absorption. For S. grandis, increased foliar P fractions were positively correlated with more fine roots, more root exudates, and up-regulated expression of genes involved in defense and P metabolism. Overall, efficient root P mobilization and uptake traits, as well as increases in leaf metabolic activity-related P fractions, supported plant compensatory growth under grazing, a process that differed between tiller types. The highest plant productivity and leaf metabolic activity-related P concentrations under medium grazing intensity clarify the underlying basis for sustainable livestock production.

Dynamics of soil biota and nutrients at varied depths in a Tamarix ramosissima-dominated natural desert ecosystem: Implications for nutrient cycling and desertification management

The underground community of soil organisms, known as soil biota, plays a critical role in terrestrial ecosystems. Different ecosystems exhibit varied responses of soil organisms to soil physical and chemical properties (SPCPs). However, our understanding of how soil biota react to different soil depths in naturally established population of salinity tolerant Tamarix ramosissima in desert ecosystems, remains limited. To address this, we employed High-Throughput Illumina HiSeq Sequencing to examine the population dynamics of soil bacteria, fungi, archaea, protists, and metazoa at six different soil depths (0-100 cm) in the naturally occurring T. ramosissima dominant zone within the Taklimakan desert of China. Our observations reveal that the alpha diversity of bacteria, fungi, metazoa, and protists displayed a linear decrease with the increase of soil depth, whereas archaea exhibited an inverse pattern. The beta diversity of soil biota, particularly metazoa, bacteria, and protists, demonstrated noteworthy associations with soil depths through Non-Metric Dimensional Scaling analysis. Among the most abundant classes of soil organisms, we observed Actinobacteria, Sordariomycetes, Halobacteria, Spirotrichea, and Nematoda for bacteria, fungi, archaea, protists, and metazoa, respectively. Additionally, we identified associations between the vertical distribution of dominant biotic communities and SPCPs. Bacterial changes were mainly influenced by total potassium, available phosphorus (AP), and soil water content (SWC), while fungi were impacted by nitrate (NO3-) and available potassium (AK). Archaea showed correlations with total carbon (TC) and AK thus suggesting their role in methanogenesis and methane oxidation, protists with AP and SWC, and metazoa with AP and pH. These correlations underscore potential connections to nutrient cycling and the production and consumption of greenhouse gases (GhGs). This insight establishes a solid foundation for devising strategies to mitigate nutrient cycling and GHG emissions in desert soils, thereby playing a pivotal role in the advancement of comprehensive approaches to sustainable desert ecosystem management.

Available sulfur and phosphorus transformation mechanism and functional microorganisms during sheep manure composting on Qinghai-Tibet Plateau under two moisture contents

Understanding the mechanisms of sulfur and phosphorus transformation during composting is important for improving compost fertility. This study aims to investigate the microbial mechanism of available sulfur and phosphorus transformation during sheep manure composting under different moisture contents (45%: M45 and 60%: M60) on the Qinghai-Tibet Plateau using metagenomics technology. The results showed that the final available sulfur and phosphorus contents of M45 were 11% and 13% higher than those of M60, respectively. M45 enhanced sulfur oxidation, sulfate reduction, and thiosulfate disproportionation. These steps were significantly positively correlated with available sulfur, and Pseudomonas, Thermobifida, Luteimonas, Brevibacterium, Planifilum, and Xinfangfangia were the main participants. Available phosphorus was significantly positively correlated with polyphosphate degradation and inorganic P solubilization, and the main participants in these steps were Luteimonas, Brachybacterium, Corynebacterium, Jeotgalicoccus, Microbacterium, Streptomyces, and Pseudoxanthomonas. These findings reveal the microbial mechanisms of available and phosphorus transformation during composting at two moisture contents.

Global change progressively increases foliar nitrogen-phosphorus ratios in China's subtropical forests

Globally increased nitrogen (N) to phosphorus (P) ratios (N/P) affect the structure and functioning of terrestrial ecosystems, but few studies have addressed the variation of foliar N/P over time in subtropical forests. Foliar N/P indicates N versus P limitation in terrestrial ecosystems. Quantifying long-term dynamics of foliar N/P and their potential drivers is crucial for predicting nutrient status and functioning in forest ecosystems under global change. We detected temporal trends of foliar N/P, quantitatively estimated their potential drivers and their interaction between plant types (evergreen vs. deciduous and trees vs. shrubs), using 1811 herbarium specimens of 12 widely distributed species collected during 1920-2010 across China's subtropical forests. We found significant decreases in foliar P concentrations (23.1%) and increases in foliar N/P (21.2%). Foliar N/P increased more in evergreen species (22.9%) than in deciduous species (16.9%). Changes in atmospheric CO2 concentrations (P CO 2 $$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$ ), atmospheric N deposition and mean annual temperature (MAT) dominantly contributed to the increased foliar N/P of evergreen species, whileP CO 2 $$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$ , MAT, and vapor pressure deficit, to that of deciduous species. Under future Shared Socioeconomic Pathway (SSP) scenarios, increasing MAT andP CO 2 $$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$ would continuously increase more foliar N/P in deciduous species than in evergreen species, with more 12.9%, 17.7%, and 19.4% versus 6.1%, 7.9%, and 8.9% of magnitudes under the scenarios of SSP1-2.6, SSP3-7.0, and SSP5-8.5, respectively. The results suggest that global change has intensified and will progressively aggravate N-P imbalance, further altering community composition and ecosystem functioning of subtropical forests.

Soil fertility mapping of a cultivated area in Resunga Municipality, Gulmi, Nepal

Soil fertility maps are crucial for sustainable soil and land use management system for predicting soil health status. However, many regions of Nepal lack updated or reliable soil fertility maps. This study aimed to develop the soil fertility map of agricultural areas in Resunga Municipality, Gulmi district of Nepal using the geographical information system (GIS) technique. A total of 57 composite geo-referenced soil samples from the depth (0-20 cm) were taken from the agricultural land of an area of 52 km2. Soil samples were analyzed for their texture, pH, organic matter, total nitrogen, available phosphorous, available potassium, available boron, and available zinc. These parameters were modelled to develop a soil quality index (SQI). Using the kriging tool, obtained parameters were interpolated and digital maps were produced along with soil quality and nutrient indices. The result showed that the study area lies within the fair (0.4 to 0.6) and good (0.6 to 0.8) range of SQI representing 96% and 3% respectively. Soil organic matter and nitrogen showed moderate variability exhibiting a low status in 95% and 86% of the total study area. Phosphorous and potassium showed medium status in 88% and 75% of the study area, respectively. Zinc was low and boron status was medium in most of the area. To maintain soil fertility is by improving the rate of exogenous application of fertilizers and manures. The application of micronutrients like boron and zinc is highly recommended in the study area along with organic manures. The soil fertility map can be used as a baseline for soil and land use management in Resunga Municipality. We recommend further studies to validate the map and assess the factors affecting soil fertility in this region. Soil fertility maps provide researchers, farmers, students, and land use planners with easier decision-making tools for sustainable crop production systems and land use management systems.

Role of Soil Microbiota Enzymes in Soil Health and Activity Changes Depending on Climate Change and the Type of Soil Ecosystem

The extracellular enzymes secreted by soil microorganisms play a pivotal role in the decomposition of organic matter and the global cycles of carbon (C), phosphorus (P), and nitrogen (N), also serving as indicators of soil health and fertility. Current research is extensively analyzing these microbial populations and enzyme activities in diverse soil ecosystems and climatic regions, such as forests, grasslands, tropics, arctic regions and deserts. Climate change, global warming, and intensive agriculture are altering soil enzyme activities. Yet, few reviews have thoroughly explored the key enzymes required for soil fertility and the effects of abiotic factors on their functionality. A comprehensive review is thus essential to better understand the role of soil microbial enzymes in C, P, and N cycles, and their response to climate changes, soil ecosystems, organic farming, and fertilization. Studies indicate that the soil temperature, moisture, water content, pH, substrate availability, and average annual temperature and precipitation significantly impact enzyme activities. Additionally, climate change has shown ambiguous effects on these activities, causing both reductions and enhancements in enzyme catalytic functions.

The dominant genera of nitrogenase (nifH) affects soil biological nitrogen fixation along an elevational gradient in the Hengduan mountains

Biological nitrogen (N) fixation by diazotrophic microbes is an essential process for the N input. However, the patterns of biological N fixation and its biological or environmental mechanism along an elevational gradient in mountain ecosystems are not fully understood. In this study, a field experiment was conducted in the Hengduan Mountains to investigate the biological N fixation associated with the diversity and abundance of the nifH gene. Our results showed that both the abundance of the nifH gene and the biological N fixation displayed hump-shaped trends along an elevation gradient in the wet and dry seasons. However, the diversity of the nifH gene showed an inverse unimodal trend along an elevation gradient. We observed that biological N fixation was jointly associated with the abundance of the nifH gene, especially dominant genera, as well as soil chartacteristics. Among them, clay content played a preeminent role in the regulation of N fixation potentially through the formation of microaggregates and microenvironments. In general, our results revealed that biological N fixation was correlated with the abundance of microorganisms, especially dominant genera, and soil texture. These results highlighted the importance of dominant genera, which should be considered in the modeling and forecasting of N cycling under future environmental change.

Managing mineral phosphorus application with soil residual phosphorus reuse in Canada

With limited phosphorus (P) supplies, increasing P demand, and issues with P runoff and pollution, developing an ability to reuse the large amounts of residual P stored in agricultural soils is increasingly important. In this study, we investigated the potential for residual soil P to maintain crop yields while reducing P applications and losses in Canada. Using a P cycling model coupled with a soil P dynamics model, we analyzed soil P dynamics over 110 years across Canada's provinces. We found that using soil residual P may reduce mineral P demand as large as 132 Gg P year-1 (29%) in Canada, with the highest potential for reducing P applications in the Atlantic provinces, Quebec, Ontario, and British Columbia. Using residual soil P would result in a 21% increase in Canada's cropland P use efficiency. We expected that the Atlantic provinces and Quebec would have the greatest runoff P loss reduction with use of residual soil P, with the average P loss rate decreasing from 4.24 and 1.69 kg ha-1 to 3.45 and 1.38 kg ha-1 , respectively. Ontario, Manitoba, and British Columbia would experience relatively lower reductions in P loss through use of residual soil P, with the average runoff P loss rate decreasing from 0.44, 0.36, and 4.33 kg ha-1 to 0.19, 0.26, and 4.14 kg ha-1 , respectively. Our study highlights the importance of considering residual soil P as a valuable resource and its potential for reducing P pollution.

Long-term ecological responses of a lowland dipterocarp forest to climate changes and nutrient availability

Understanding the long-term impact of projected climate change on tropical rainforests is critical given their central role in the Earth's system. Palaeoecological records can provide a valuable perspective on this problem. Here, we examine the effects of past climatic changes on the dominant forest type of Southeast Asia - lowland dipterocarp forest. We use a range of proxies extracted from a 1400-yr-old lacustrine sedimentary sequence from north-eastern Philippines to determine long-term vegetation responses of lowland dipterocarp forest, including its dominant tree group dipterocarps, to changes in precipitation, fire and nutrient availability over time. Our results show a positive relationship between dipterocarp pollen accumulation rates (PARs) and leaf wax hydrogen isotope values, which suggests a negative effect of drier conditions on dipterocarp abundance. Furthermore, we find a positive relationship between dipterocarp PARs and the proxy for phosphorus availability, which suggests phosphorus controls the productivity of these keystone trees on longer time scales. Other pollen taxa show widely varying relationships with the abiotic factors, demonstrating a high diversity of plant functional responses. Our findings provide novel insights into lowland dipterocarp forest responses to changing climatic conditions in the past and highlight potential impacts of future climate change on this globally important ecosystem.

Industrial and agricultural waste amendments interact with microorganism activities to enhance P availability in rice-paddy soils

Adding industrial and agricultural wastes to farmland can increase soil available phosphorus (P) pool and boost crop production, but the process affecting soil P transformation and bioavailability is still poorly understood. We studied the effects of straw (ST), biochar (BC) and Si-modified biochar (Si-BC) amendments on the available-P content and its fraction transformation in rice-paddy soils. Our results showed that these three soil amendments significantly increased the concentrations of both microbial biomass carbon (MBC) and microbial biomass-P (MBP) during the first rice season; by contrast, the effects of ST and BC application were relatively poor on acid-phosphatase (ACP) activity, which was increased by 24 % under ST and 14 % under BC. Soil total P concentrations did not differ significantly, although the concentration and percentage of each P-fraction were altered significantly among treatments. Although all three applications increase soil available-P concentration by promoting the transformation of organic-P (Po) components to inorganic-P (Pi), there are differences in the transformation efficiency of the soil P fraction between these amendments. Redundancy analysis results also showed significant clustering of soil P-fraction transformations after ST and BC treatments. Structural equation model analysis further indicated that all amendments regulated microbial processes by changing soil pH and dissolved organic carbon (DOC), thereby promoting soil P transformation and improving P efficiency. Sodium bicarbonate-extractable Po (NaHCO3-Po) contributed most to soil available-P under the different amendments. Compared to ST and Si-BC, BC application improved more soil microbial status and the transformation of soil unavailable-P into available-P, therefore the application of BC in rice fields is the most beneficial method to promote phosphorus use and production sustainability in rice. These findings helped to understand the effects of using industrial and agricultural waste (e.g. straw, biochar and Si-modified biochar) on soil P-fractions and so provided a reference for sustainable resource use and green production in rice-paddy ecosystems.

Impact of patch age and size on forest soil characteristics in European agricultural landscapes

Many landscapes worldwide are characterized by the presence of a mosaic of forest patches with contrasting age and size embedded in a matrix of agricultural land. However, our understanding of the effects of these key forest patch features on the soil nutrient status (in terms of nitrogen, carbon, and phosphorus) and soil pH is still limited due to a lack of large-scale data. To address this research gap, we analyzed 830 soil samples from nearly 200 forest patches varying in age (recent versus ancient forests) and size (small versus larger patches) along a 2500-km latitudinal gradient across Europe. We also considered environmental covariates at multiple scales to increase the generality of our research, including variation in macroclimate, nitrogen deposition rates, forest cover in a buffer zone, basal area and soil type. Multiple linear mixed-effects models were performed to test the combined effects of patch features and environmental covariates on soil nutrients and pH. Recent patches had higher total soil phosphorus concentrations and stocks in the mineral soil layer, along with a lower nitrogen to phosphorus ratio within that layer. Small patches generally had a higher mineral soil pH. Mineral soil nitrogen stocks were lower in forest patches with older age and larger size, as a result of a significant interactive effect. Additionally, environmental covariates had significant effects on soil nutrients, including carbon, nitrogen, phosphorus, and their stoichiometry, depending on the specific covariates. In some cases, the effect of patch age on mineral soil phosphorus stocks was greater than that of environmental covariates. Our findings underpin the important roles of forest patch age and size for the forest soil nutrient status. Long-term studies assessing edge effects and soil development in post-agricultural forests are needed, especially in a context of changing land use and climate.

Response of soil phosphorus fractions to litter removal in subalpine coniferous forest

Litter plays a crucial role in phosphorus (P) cycling, and its role in forest ecosystems may vary with different treatments and forest types. In this study, we investigated soil P fraction responses to litter removal in different forest types and how forest conversion affects the acquisition pathway of bioavailable P through an in situ controlled litter experiment. The results showed that the soil P content increased with the conversion of primary to secondary forest, which may be mostly related to the differences in nutrients and species richness between the two forest types. In addition, the main source of bioavailable P in primary forests was active organic P, while mineral P was the main bioavailable P source in secondary forests. Moreover, the three-year litter removal treatment significantly decreased the primary forest soil P fraction content while significantly increasing the secondary forest bioavailable P content. The main driving factors of the soil P fraction are also different between the two forest types, with AP activity and SOC as the major factors in the primary forest and pH as the main factor in the secondary forest.

Applied phosphorus is maintained in labile and moderately occluded fractions in a typical meadow steppe with the addition of multiple nutrients

Phosphorus (P) is a limiting nutrient second only to nitrogen (N) in the drylands of the world. Most previous studies have focused on N transformation processes in grassland ecosystems, particularly under artificial fertilization with N and atmospheric N deposition. However, P cycling processes under natural conditions and when P is applied as an inorganic P fertilizer have been understudied. Therefore, it is essential to examine the fate of applied P in grassland ecosystems that have experienced long-term grazing and, under certain circumstances, continuous hay harvest. We conducted a 3-year field experiment with the addition of multiple nutrient elements in a typical meadow steppe to investigate the fate of the applied P in various fractions of P pools in the top soil. We found that the addition of multiple nutrients significantly increased P concentrations in the labile inorganic P (Lab-Pi) and moderately occluded inorganic P (Mod-Pi) fractions but not in the recalcitrant inorganic P (Rec-Pi) fraction. An increase in the concentration of total inorganic P was found only when P and N were applied together. However, the addition of other nutrients did not change P concentrations in any fraction of the mineral soil. The addition of P and N significantly increased the total amount of P taken up by the aboveground plants but had no effect on the levels of organic and microbial P in the soil. Together, our results indicate that the P applied in this grassland ecosystem is taken up by plants, leaving most of the unutilized P as Lab-Pi and Mod-Pi rather than being immobilized in Rec-Pi or by microbial biomass. This implies that the grassland ecosystem that we studied has a relatively low P adsorption capacity, and the application of inorganic P to replenish soil P deficiency in degraded grasslands due to long-term grazing of livestock or continuous harvest of forage in the region could be a practical management strategy to maintain soil P fertility.

Response of soil extracellular enzyme activity and stoichiometry to short-term warming and phosphorus addition in desert steppe

Background

Phosphorus (P) is regarded as one of the major limiting factors in grassland ecosystems. Soil available phosphorus deficiency could affect soil extracellular enzyme activity, which is essential for microbial metabolism. Yet it is still unclear how soil available phosphorus affects soil extracellular enzyme activity and microbial nutrient limitation of desert steppe in the context of climate warming.

Methods

This study carried out a short-term open-top chambers (OTCs) experiment in a desert steppe to examine the effects of warming, P addition, and their interaction on soil properties, the activities of soil extracellular enzymes, and stoichiometries.

Results

The findings demonstrated that soil acquisition enzyme stoichiometry of C: N: P was 1.2:1:1.5 in this experiment region, which deviated from the global mean scale (1:1:1). Warming increased soil AN (ammonium nitrogen and nitrate nitrogen) contents and decreased microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN). Phosphorus addition raised soil available phosphorus and microbial biomass phosphorus (MBP) contents. Soil extracellular enzyme activities and stoichiometries in desert steppe are largely impacted by soil AN, MBC: MBP, and MBN: MBP. These results revealed that the changes of soil available nutrients and stoichiometries induced by short-term warming and P addition could influence soil microbial activities and alleviate soil microbial carbon and phosphorus limitation. Our findings highlight that soil available phosphorus played a critical role in regulating soil extracellular enzyme activity and microbial nutrient limitation of desert steppe. Further research on soil microbial communities should explore the microbiological mechanisms underlying these findings.

Soil Conditioner Affects Tobacco Rhizosphere Soil Microecology

Reasonable fertilization management can increase nutrient content and enzyme activity in rhizosphere soil, and even increase soil microbial richness. However, different fertilizers could raise distinct influences on the soil properties, including soil environmental factors (physicochemical properties and enzymatic activities) and microbial community. Here, the effects of two soil amendments (microbial fertilizer and woody peat) on environmental factors and microbial community structure in tobacco rhizosphere soil were evaluated, with the correlations between microbes and environmental factors explored. As the results, microbial fertilizer could effectively alleviate soil acidification, increase available potassium and organic matter contents in soil, and was also beneficial to increase nitrate reductase activity in rhizosphere soil. Fertilizers cause changes in the abundance of certain microbes in the soil. Besides, it was shown that the candidate phyla Gal15, Acidobacterota, Latescibacterota, Mortierellommycota, Basidiomycota, and Rozellomycota in tobacco rhizosphere soil had significant correlation with soil environmental factors. Through the functional analysis of these populations, it can be deduced that the changes in the abundance of certain microorganisms may be an important reason for the differences in environmental factors. All these indicated that the differences of environmental factors in different treatments are closely related to the abundance of some special soil microorganisms. Studying the life activities of these microbes would provide good guidance for exploring the interaction among crops, soil, and microorganisms and improving crop yields.

Phosphorus-induced greater enhancement in carbon supply and storage for oil synthesis during the crucial period made cottonseed kernel oil yield have a higher increment than protein

Cottonseed has a high utilization value due to its luxuriant oil and protein, but low phosphorus (P) in cropland reduces its yield and quality. A limited understanding of the physiological mechanism underlying these results restricted the exploration of P efficient management in cotton cultivation. A 3-year experiment was performed with Lu 54 (low-P sensitive) and Yuzaomian 9110 (low-P tolerant) under 0 (deficient-P), 100 (critical-P), and 200 (excessive-P) kg P₂O₅ ha^-1 in a field having 16.9 mg kg^-1 available P to explore the key pathway for P to regulate cottonseed oil and protein formation. P application markedly increased cottonseed oil and protein yields, with the enhanced acetyl-CoA and oxaloacetate contents during 20-26 days post anthesis being a vital reason. Notably, during the crucial period, decreased phosphoenolpyruvate carboxylase activity weakened the carbon allocation to protein, making malonyl-CoA content increase greater than free amino acid; Meanwhile, P application accelerated the carbon storage in oil but retarded that in protein. Consequently, cottonseed oil yield increased more than protein. Oil and protein synthesis in Lu 54 was more susceptible to P, resulting in greater increments in oil and protein yields than Yuzaomian 9110. Based on acetyl-CoA and oxaloacetate contents (the key substrates), the critical P content in the subtending leaf to cotton boll needed by oil and protein synthesis in Lu 54 (0.35%) was higher than Yuzaomian 9110 (0.31%). This study provided a new perception of the regulation of P on cottonseed oil and protein formation, contributing to the efficient P management in cotton cultivation.

Foliar nutrient resorption stoichiometry and microbial phosphatase catalytic efficiency together alleviate the relative phosphorus limitation in forest ecosystems

Understanding how plants adapt to spatially heterogeneous phosphorus (P) supply is important to elucidate the effect of environmental changes on ecosystem productivity. Plant P supply is concurrently controlled by plant internal conservation and external acquisition. However, it is unclear how climate, soil, and microbes influence the contributions and interactions of the internal and external pathways for plant P supply. Here, we measured P and nitrogen (N) resorption efficiency, litter and soil acid phosphatase (AP) catalytic parameters (V_max(s) and K_m ), and soil physicochemical properties at four sites spanning from cold temperate to tropical forests. We found that the relative P limitation to plants was generally higher in tropical forests than temperate forests, but varied greatly among species and within sites. In P-impoverished habitats, plants resorbed more P than N during litterfall to maintain their N : P stoichiometric balance. In addition, once ecosystems shifted from N-limited to P-limited, litter- and soil-specific AP catalytic efficiency (V_max(s) /K_m ) increased rapidly, thereby enhancing organic P mineralization. Our findings suggested that ecosystems develop a coupled aboveground-belowground strategy to maintain P supply and N : P stoichiometric balance under P-limitation. We also highlighted that N cycle moderates P cycles and together shape plant P acquisition in forest ecosystems.

Available and total phosphorus background levels in soils: a calcareous and semi-arid region

It is critical to understand the risk of element pollution in soils by evaluating their background levels. Phosphorus (P) content in agricultural soils needs to be assessed from agronomic and environmental standpoints. The current study intended to calculate the background levels of available and total P in soils. To achieve this goal, 50 sites without human activities were selected. Soils were sampled from the surface and subsurface of each site (100 soil samples). The available P forms in soils were extracted using the water-extractable P (WEP), calcium chloride-extractable P (CCEP), and Olsen-extractable P (OEP) methods. The first two extractants are being used to evaluate P leaching from soils, while the last one is being used as an agronomic indicator. The methods used to calculate background levels were the iterative 2-δ technique (2-δ) and the calculated distribution function (CDF). Results showed that the upper limits of background levels using 2-δ method were 1.45, 0.92, 8.12, and 424.4 mg kg^-1 for WEP, CCEP, OEP, and total P, respectively. Also, the upper limits of background levels using CDF method were 1.42, 1.15, 12.09, and 447.6 mg kg^-1, for WEP, CCEP, OEP, and total P, respectively. It can be concluded that using these background levels, which for the first time were calculated for P, would enable us to have an accurate examination of P excess as a result of human activities.

Roles of phosphate-solubilizing bacteria in mediating soil legacy phosphorus availability

Phosphorus (P), an essential macronutrient for all life on Earth, has been shown to be a vital limiting nutrient element for plant growth and yield. P deficiency is a common phenomenon in terrestrial ecosystems across the world. Chemical phosphate fertilizer has traditionally been employed to solve the problem of P deficiency in agricultural production, but its application has been limited by the non-renewability of raw materials and the adverse influence on the ecological health of the environment. Therefore, it is imperative to develop efficient, economical, environmentally friendly and highly stable alternative strategies to meet the plant P demand. Phosphate-solubilizing bacteria (PSB) are able to improve plant productivity by increasing P nutrition. Pathways to fully and effectively use PSB to mobilize unavailable forms of soil P for plants has become a hot research topic in the fields of plant nutrition and ecology. Here, the biogeochemical P cycling in soil systems are summarized, how to make full use of soil legacy P via PSB to alleviate the global P resource shortage are reviewed. We highlight the advances in multi-omics technologies that are helpful for exploring the dynamics of nutrient turnover and the genetic potential of PSB-centered microbial communities. Furthermore, the multiple roles of PSB inoculants in sustainable agricultural practices are analyzed. Finally, we project that new ideas and techniques will be continuously infused into fundamental and applied research to achieve a more integrated understanding of the interactive mechanisms of PSB and rhizosphere microbiota/plant to maximize the efficacy of PSB as P activators.

Effects of Regional Climate and BMP Type on Stormwater Nutrient Concentrations in BMPs: A Meta-Analysis

Nutrient treatment performance of stormwater best management practices (BMPs) is highly variable. Improved nutrient management with BMPs requires a better understanding of factors that influence stormwater BMP treatment processes. We conducted a meta-analysis of vegetated BMPs in the International Stormwater BMP Database and compared influent and effluent nitrogen and phosphorus concentrations to quantify the BMP effect on nutrient management across climates. BMP effect on nutrient concentration change was compared between vegetated BMPs in wet and dry climates. We examined paired dissolved inorganic nitrogen (DIN), total nitrogen (TN), dissolved inorganic phosphorus (DIP), total phosphorus (TP), and combinations of these analytes as dissolved inorganic ratios and N:P ratios. Meta-analysis with subgroup analysis was used to determine differences between wet and dry climates and among vegetated BMP types. We found that across both wet and dry climates, BMPs leach DIP and TP, increase the fraction of dissolved inorganic P (DIP:TP), and decrease dissolved N:P ratios. Dry-climate BMPs leach DIP and TP more consistently and at a higher magnitude than wet-climate BMPs, and bioretention leaches more DIP than grass strips and swales. These findings generally align with biogeochemical cycling, differences in influent chemistry, and BMP design types and goals.

Effects of the Ratio of Substituting Mineral Fertilizers with Manure Nitrogen on Soil Properties and Vegetable Yields in China: A Meta-Analysis

Substituting mineral fertilizers (MFs) with manure nitrogen (N) can not only reduce environmental pollution, but also improve soil quality. However, the effects of various manure N substitution ratios (SRs, the ratio of manure N over total N applied) on soil properties and vegetable yields in China are poorly studied. Here, through a meta-analysis of 667 observations, we assessed the effects of three manure N SRs (low (SR ≤ 35%), medium (35% < SR ≤ 70%), and high (SR > 70%)) on vegetable yields and soil properties (soil organic carbon, SOC; soil total nitrogen, STN; microbial biomass carbon (C) and nitrogen (N), MBC/N; and available phosphorus and potassium, (AP/AK)) in the 0-20 cm soil under different climatic conditions, initial soil properties, and management practices. The results show that the SOC and STN contents increased by 28.5% and 21.9%, respectively, under the medium SRs compared to the MF, which were the highest among the three SRs. Both soil MBC and MBN increased with the increase in the SRs, and the increased ratios in the high SRs reached 203.4% and 119.3%, respectively. In addition, the AP also increased with the increase in the SR, but the AK was not significantly changed with the low and medium SRs compared with the MF. Overall, the medium SR produced the highest vegetable yield among the three SRs with an increase of 18.6%. Additionally, a random forest analysis indicated that the N application rate, planting years, and mean annual precipitation were the most important factors influencing vegetable yield. In conclusion, the SR of 35-70% is more conducive to increasing soil nutrient contents significantly and improves vegetable yields in Chinese vegetable fields.

Effects of phosphorus application on soil phosphorus forms and phoD-harboring microbial communities in an alpine grassland on the Qinghai-Tibetan Plateau

Phosphorus (P) application to terrestrial ecosystems affects not only aboveground plants but also soil P forms and phosphatase-associated microbes. The phoD gene is widespread in soil and plays an important role in P transformation. However, it is still unclear how phoD-harboring microbial communities respond to different P application rates, and the relationships between soil properties and phoD-harboring microbial community need to be better understood. In this study, the impacts of seven P application rates [0 (P0), 10 (P10), 20 (P20), 30 (P30), 40 (P40), 50 (P50), and 60 (P60) g⋅m–2⋅a–1] on the soil physicochemical properties, P forms, and phoD-harboring microbial communities were assessed. As the results, inorganic P (i.e., Resin-Pi, NaHCO3-Pi, NaOH-Pi, and HCl-Pi) and Bio-P increased firstly and then decreased with increasing P application rate, with the highest values in the P30 treatment. Soil phoD-harboring microbial community structures in low-P (P0∼P30) treatments were significantly different from that in high-P (P40∼P60) treatments. Soil phoD-harboring microbial Shannon and Simpson diversity increased firstly and then decreased with increasing P application rate, and there was a tipping point at the P application rate of 30 g⋅m–2⋅a–1. The Mantel test and structural equation modeling (SEM) revealed that Bio-P, TC (total carbon), Fe, NaOH-organic P (NaOH-Po), and soil pH were strongly related to the soil phoD-harboring microbial community structure. In conclusion, this study demonstrated that P application affected soil P forms and phoD-harboring microbes in an alpine grassland on the Qinghai-Tibetan Plateau, and there was a P application threshold for optimistic growth of phoD-harboring microbes in an alpine grassland on the Qinghai-Tibetan Plateau.

Novel Weighting Method for Evaluating Forest Soil Fertility Index: A Structural Equation Model

Understanding nutrient quantity and quality in forest soils is important for sustainable management of forest resources and maintaining forest ecosystem services. In this study, six soil nutrient indicators, including soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) were measured in five different aged stands of Chinese fir forests in subtropical China. A structural equation model (SEM) was developed based on these soil nutrients indicators in order to better evaluate the soil fertility index (SFI) in these studied forests. The results show that soil nutrient contents changed with the soil depth in different age groups. The SOM decreased in a specific order: over mature > mature > near mature > middle > young stands. The TN content of the soil gradually decreased with increased soil depth throughout all age groups. The SEM indicated that the TN had the highest weight of 0.4154, while the TP had the lowest weight at 0.1991 for estimating the SFI. The weights of other indicators (AN, SOM, AP, and AK) ranged 0.2138−0.3855 in our study. The established SEM satisfied the fitness reference values and was able to accurately describe the forest soil nutrient status through the SFI. The overall SFI values were significantly higher in over mature stands than in young-aged stands and in topsoil than in deeper soil in all examined forests. Soil TN, AP, and AK were the most important nutrient indicators to the evaluation of the SFI in the study sites. The results confirmed that the SEM was suitable to estimate the weights of the SFI and better describe the soil nutrient status in forests. Our research provides an innovative approach to assess a soil nutrient status and soil fertility and provides a scientific basis for accurate implementation of soil nutrient assessment in forest ecosystems.

Changes in soil micronutrients along a temperature gradient in northern China

How climate warming affected terrestrial ecosystems received considerable attention. Soil micronutrients play a vital role in regulating the growth of all living organisms and thus make a significant contribution to plant production. However, the responses of soil micronutrients to climate warming still remained unclear. While soil sampling along a temperature gradient could reveal the long-term influence of climate warming on soil nutrient dynamics, the variations of soil micronutrients with temperature might be interfered by the effect of precipitation due to the collinearity between temperature and precipitation. Moreover, changes in soil micronutrients over broad geographical scale could be affected by soil texture. Hence, this study conducted a soil investigation across a temperature transect along the 400 mm isohyet in northern China to examine the responses of soil micronutrients to changing temperature and soil texture when the effect of precipitation was minimized. We observed that soil copper (Cu), manganese (Mn) and zinc (Zn) contents all decreased along the temperature gradient. Soil Cu, Mn and Zn contents were positively correlated with soil clay and silt contents and negatively correlated with soil sand content. Temperature and soil texture together accounted for 72.0 % of the variations in soil micronutrient contents. Temperature and soil texture individually explained 10.4 % and 48.0 %, and their shared variation explained 13.6 % of the variations in soil micronutrient contents. Moreover, soil parent material also exerted an effect on soil micronutrient contents. Our results suggested that climate warming might cause a decrease in soil micronutrient contents.

Unimodal productivity-biodiversity relationship along the gradient of multidimensional resources across Chinese grasslands

Resources can affect plant productivity and biodiversity simultaneously and thus are key drivers of their relationships in addition to plant-plant interactions. However, most previous studies only focused on a single resource while neglecting the nature of resource multidimensionality. Here we integrated four essential resources for plant growth into a single metric of resource diversity (RD) to investigate its effects on the productivity-biodiversity relationship (PBR) across Chinese grasslands. Results showed that habitats differing in RD have different PBRs-positive in low-resource habitats, but neutral in medium- and high-resource ones-while collectively, a weak positive PBR was observed. However, when excluding direct effects of RD on productivity and biodiversity, the PBR in high-resource habitats became negative, which leads to a unimodal instead of a positive PBR along the RD gradient. By integrating resource effects and changing plant-plant interactions into a unified framework with the RD gradient, our work contributes to uncovering underlying mechanisms for inconsistent PBRs at large scales.

Foliar phosphorus allocation and photosynthesis reveal plants' adaptative strategies to phosphorus limitation in tropical forests at different successional stages

High atmospheric nitrogen (N) deposition and low soil phosphorus (P) availability occur simultaneously in tropical areas, and thus tropical plants need to adapt nutrient-use strategies to maintain growth and survival. Therefore, identifying the adaptative strategies of tropical plants at different successional stages under low soil P availability is indispensable. Here, we separately investigated foliar traits, photosynthetic characteristics, and P fractions of 8 species in the primary and secondary tropical forests after 10 years of N and P fertilization. P addition increased foliar P concentrations and deceased N:P ratio in the primary forest and secondary forest. The foliar photosynthetic rates did not significantly respond to nutrient additions, and the foliar photosynthetic P-use efficiency (PPUE) reduced under the P addition in the primary forest. In contrast, the foliar photosynthetic rates and photosynthetic nitrogen (N)-use efficiency (PNUE) were enhanced with nutrient additions in the secondary forest. The allocations of foliar nucleic acid P and residual P were reduced by P addition in the primary forest, whereas the allocation of metabolic P was enhanced and the allocation of residual P was reduced by P addition in the secondary forest. Additionally, a higher proportion of structural P was found in the primary forest, and a higher proportion of metabolic P was observed in the secondary forest. Interesting, structural equation model analysis revealed that the plants decreased the allocation of foliar nucleic acid P and increased the allocation of structural P in the primary forest, thereby reducing photosynthetic rates. Whereas the plants enhanced photosynthetic rates by promoting PPUE and the allocation of foliar metabolic P in the secondary forest. Our findings highlighted tropical plants at different successional stages can reasonably allocate foliar P to regulate photosynthetic rates and acclimate to low P environments.

Tree species richness as an important biotic factor regulates the soil phosphorus density in China's mature natural forests

Tree species richness has been recognized as an underlying driving factor for regulating soil phosphorus (P) status in many site-specific studies. However, it remains poorly understood whether this is true at broad scales where soil P strongly rely on climate, soil type and vegetation type. Here, based on the data of 946 mature natural forest sites from a nationwide field survey in China, we analyzed the impact of tree species richness on soil P density of China's mature natural forests (deciduous coniferous forest, DCF; evergreen coniferous forest, ECF; deciduous broad-leaved forest, DBF; evergreen broad-leaved forest, EBF; and mixed coniferous and broad-leaved forest, MF). Our results showed that tree species richness had a negative effect on soil P density in China's mature natural forests. The Random Forest regression model showed that the relative importance of tree species richness to soil P density was second only to the climate factors (mean annual temperature, MAT; mean annual precipitation, MAP). In addition, the structural equation model (SEM) results showed that the goodness fit of SEM increased when the tree species richness was included into the model. These results suggested that tree species richness was an important factor in regulating the China's mature natural forests soil P density. Furthermore, the SEM results showed that the decreased soil P density was related to the increase in ANPP and the decrease in litter P concentration induced by tree species richness. This result indicates that tree species richness could facilitate plant P absorption and inhibit plant P return into the soil, and thus reducing the soil P density in China's mature natural forests. In conclusion, we found tree species richness was an important biotic factor in regulating soil P density at broad scales, which should be fully considered in Earth models that represent P cycle.

Fine-root functional trait response to nitrogen deposition across forest ecosystems: A meta-analysis

Nitrogen (N) deposition has complex effects on vegetation dynamics and nutrient cycling in terrestrial ecosystems. However, how N deposition alters fine root traits remains unclear in forest ecosystems. Here, we carried out a synthesis based on 890 paired observations of 14 fine root traits from 79 articles to assess the effects of N deposition on fine root traits. The results showed that N deposition mainly affected root nutrient content and stoichiometry. Specifically, N deposition increased the root N content, root carbon: phosphorus (C:P) and root nitrogen: phosphorus (N:P) ratio, but decreased the root P content and root C:N ratio. Moreover, N deposition increased fine root respiration, but had no significant effect on other root morphological and physiological traits. N deposition effects on fine root biomass, root tissue density and fungal colonization decreased with N deposition duration. Compared to fine root P content, N deposition effects on fine root C content and C:P ratio increased with N deposition level. Moreover, the interaction between N deposition level and duration significantly affected fine root biomass. N deposition effects on fine-root biomass decreased with greater N deposition duration, especially in high N deposition experiments. Moreover, the effect of N deposition on root diameter decreased with mean annual temperature and mean annual precipitation. N form, forest type and soil depth significantly affect the effect of N deposition on fine root C:P. Therefore, the effects of N deposition on fine root traits were not only determined by N deposition level, duration and their interactions, but also regulated by abiotic factors. These findings highlight the diverse responses of fine root traits to N deposition have strong implications for forest ecosystems soil carbon stocks in a world of increasing N deposition associated with decreased root-derived carbon inputs and increases in fine-root respiration.