Climate factors determine the utilization strategy of forest plant resources at large scales

Effects of Nitrogen Addition on Leaf Functional Traits of Dominant Species in Bayanbulak Grassland, Xinjiang, China

Nitrogen inputs exert significant impacts on plant species composition and ecosystem stability within alpine grasslands. The exploration of leaf functional traits holds great potential in uncovering plants' adaptive strategies and competitive edges, and is pivotal in comprehending the ramifications of nitrogen inputs on biodiversity. In this study, the Bayanbulak grassland was selected as the research subject to investigate the impact of nitrogen addition on leaf functional traits of different plant functional groups. Specifically, various gradients of nitrogen addition were established to observe changes in leaf dry matter content (LDMC) and leaf area (LA) among three distinct plant functional groups. Furthermore, structural equation modeling (SEM) was employed to analyze the pathways through which nitrogen addition influenced the LDMC of these plant functional groups. The results were as follows: (1) LA and leaf length (LL) of Poaceae changed significantly (p < 0.05) under different N addition gradients, and leaf nutrient contents of Poaceae, Rosaceae and Fabaceae showed significant changes under different N addition gradients. (2) Pearson correlation analyses showed that total nitrogen (TN), total carbon (TOC) and leaf width (LW) of Rosaceae leaves had a significant positive correlation, and the TOC and total phosphorus (TP) of Fabaceae leaves showed a significant negative correlation. (3) SEM of the three plant functional groups showed direct and indirect effects of N addition on leaf dry matter content of Poaceae and Rosaceae, and only indirect effects on Fabaceae.

Comparative Foliar Atmospheric Mercury Accumulation across Functional Types in Temperate Trees

Vegetation assimilation of atmospheric gaseous elemental mercury (GEM) represents the largest dry deposition pathway in global terrestrial ecosystems. This study investigated Hg accumulation mechanisms in deciduous broadleaves and evergreen needles, focusing on how ecophysiological strategies─reflected by δ13C, δ18O, leaf mass per area, and leaf dry matter content-mediated Hg accumulation. Results showed that deciduous leaves exhibited higher total Hg (THg) concentrations and accumulation rates (THgrate), which were 85.3 ± 17.7 and 110.0 ± 0.3% higher than those in evergreen needles. The two tree types exhibited distinct ecophysiological strategies: deciduous broadleaves, with higher stomatal conductance and photosynthetic rates, rapidly adjust stomata to changes in meteorological and pollutant factors, playing a key role in controlling THgrate. In contrast, evergreen needles featured stable stomatal control, highlighting the direct positive effect of GEM on their THgrate. Precipitation and wind speed negatively influenced foliar THgrate. Correlations between PM2.5, NO2, and THgrate in evergreen needles suggested synergistic patterns between atmospheric Hg and pollutants. This study underscores distinct GEM accumulation mechanisms across tree functional types and emphasizes the importance of species-specific foliar ecophysiological strategies. An empirical model linking THgrate with ecophysiological, meteorological, and atmospheric pollution factors was provided, contributing to the refinement of foliar Hg accumulation models.

Quercus cerris Leaf Functional Traits to Assess Urban Forest Health Status for Expeditious Analysis in a Mediterranean European Context

In the Mediterranean basin, urban forests are widely recognized as essential landscape components, playing a key role in nature-based solutions by enhancing environmental quality and providing a range of ecosystem services. The selection of woody plant species for afforestation and reforestation should prioritize native species that align with the biogeographical and ecological characteristics of the planting sites. Among these, Quercus cerris L. (Turkey oak) is considered a promising candidate for urban reforestation. However, its fitness within urban forest environments remains poorly understood. This study aimed to identify suitable leaf functional traits for assessing the response of Q. cerris in urban forests and to analyze the main climatic variables influencing its performance in urban contexts. We also proposed practical, rapid monitoring tools to compare urban and natural forests across different seasons. The results demonstrated that Q. cerris experiences significant water stress in urban forests due to the combined effects of drought and high temperatures. To find the tools to mitigate this stress, the differences between leaf traits such as specific leaf area, thickness, and the contents of chlorophyll, anthocyanins, and flavonols in urban and natural forests were analyzed. Our findings underscore the high adaptability of Q. cerris to varied climatic and environmental conditions. This study provides a practical method for rapidly assessing the responses of tree species to climate change. In the future, this approach will be tested on other native species that are characteristic of Mediterranean forest ecosystems to help with choosing afforestation and reforestation strategies.

Leaf nutrient traits exhibit greater environmental plasticity compared to resource utilization traits along an elevational gradient

Studying key leaf functional traits is crucial for understanding plant resource utilization strategies and growth. To explore the patterns and driving factors of key leaf functional traits in forests along elevational gradients under global change, we collected survey data from 697 forests across China from 2008 to 2020. This study examined the elevational patterns of Specific Leaf Area (SLA, m²/kg), Leaf Dry Matter Content (LDMC, g/g), Leaf Nitrogen (LN, mg/g), and Leaf Phosphorus (LP, mg/g), and their responses to climate, soil nutrients, and stand factors. The results showed distinct differences in these key leaf traits at different elevational gradients. Generally, as elevation increased, SLA decreased, while LDMC significantly increased (P < 0.001), and LN first increase and then decreased (P < 0.001). The direct influence of elevation on the spatial variation of key leaf traits was greater than its indirect effects (through environmental and stand factors). The elevational patterns of leaf traits related to resource utilization strategies (SLA and LDMC) were mainly influenced by climate (temperature and precipitation) and soil nutrient factors, showing opposite trends in response to environmental changes. The patterns of leaf nutrient traits (LN and LP) along elevational gradients were primarily influenced by climatic factors, with LN exhibiting greater environmental plasticity. Compared to other stand factors, forest age predominantly influenced the spatial variation of key leaf traits, especially SLA. These findings have significant theoretical implications for revealing how plants adapt to global change.

Leaf Functional Traits and Their Influencing Factors in Six Typical Vegetation Communities

Leaf functional traits (LFTs) have become a popular topic in ecological research in recent years. Here, we measured eight LFTs, namely leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC), in six typical vegetation communities (sclerophyllous evergreen broad-leaved forests, temperate evergreen coniferous forests, cold-temperate evergreen coniferous forests, alpine deciduous broad-leaved shrubs, alpine meadows, and alpine scree sparse vegetation) in the Chayu River Basin, southeastern Qinghai-Tibet Plateau. Our aim was to explore their relationships with evolutionary history and environmental factors by combining the RLQ and the fourth-corner method, and the method of testing phylogenetic signal. The results showed that (i) there were significant differences in the eight LFTs among the six vegetation communities; (ii) the K values of the eight LFTs were less than 1; and (iii) except for LCC, all other LFTs were more sensitive to environmental changes. Among these traits, LA was the most affected by the environmental factors, followed by LNC. It showed that the LFTs in the study were minimally influenced by phylogenetic development but significantly by environmental changes. This study further verified the ecological adaptability of plants to changes in environmental factors and provides a scientific basis for predicting the distribution and diffusion direction of plants under global change conditions.

Climate factors dominate the elevational variation in grassland plant resource utilization strategies

Specific leaf area (SLA) and leaf dry matter content (LDMC) are key leaf functional traits often used to reflect plant resource utilization strategies and predict plant responses to environmental changes. In general, grassland plants at different elevations exhibit varying survival strategies. However, it remains unclear how grassland plants adapt to changes in elevation and their driving factors. To address this issue, we utilized SLA and LDMC data of grassland plants from 223 study sites at different elevations in China, along with climate and soil data, to investigate variations in resource utilization strategies of grassland plants along different elevational gradients and their dominant influencing factors employing linear mixed-effects models, variance partitioning method, piecewise Structural Equation Modeling, etc. The results show that with increasing elevation, SLA significantly decreases, and LDMC significantly increases (P < 0.001). This indicates different resource utilization strategies of grassland plants across elevation gradients, transitioning from a "faster investment-return" at lower elevations to a "slower investment-return" at higher elevations. Across different elevation gradients, climatic factors are the main factors affecting grassland plant resource utilization strategies, with soil nutrient factors also playing a non-negligible coordinating role. Among these, mean annual precipitation and hottest month mean temperature are key climatic factors influencing SLA of grassland plants, explaining 28.94% and 23.88% of SLA variation, respectively. The key factors affecting LDMC of grassland plants are mainly hottest month mean temperature and soil phosphorus content, with relative importance of 24.24% and 20.27%, respectively. Additionally, the direct effect of elevation on grassland plant resource utilization strategies is greater than its indirect effect (through influencing climatic and soil nutrient factors). These findings emphasize the substantive impact of elevation on grassland plant resource utilization strategies and have important ecological value for grassland management and protection under global change.

A review of factors affecting the soil microbial community structure in wetlands

Microbial community in wetland soils is crucial for maintaining the stability of the wetland ecosystem. Nevertheless, the soil microbial community is sensitive to the environmental stress in wetlands. This leads to the possibility that the microbial community structure may be influenced by environmental factors. To gain an in-depth understanding in the response of microbial community structure in wetland soils under different environmental factors, this review comprehensively explores the factors of natural conditions (e.g., different types of wetland, soil physical and chemical properties, climate conditions), biological factors (e.g., plants, soil animals), and human activities (e.g., land use, soil pollution, grazing). Those factors can affect microbial community structure and activities in wetland soils through different ways such as (i) affecting the wetland soil environment in which soil microorganisms survived in, (ii) influencing the available nutrients (e.g., carbon, nitrogen) required for microbial activity, and (iii) the direct effects on soil microorganisms (toxicity or promotion of resistant species). This review can provide references for the conservation of microbial diversity in wetland soils, the maintenance of wetland ecosystem balance, and the wetland ecological restoration.

Effects of different fertilization practices on maize yield, soil nutrients, soil moisture, and water use efficiency in northern China based on a meta-analysis

The application of fertilizer to ensure the steady improvement of crop yield has become the main means of agricultural production. However, it remains to be determined whether fertilization practices with different combinations of nitrogen (N), phosphorus (P), potassium (K), and organic (O) fertilizers play a positive role in the sustainability of maize yield and the soil in which it is grown. Therefore,this meta-analysis extracted 2663 data points from 76 studies to systematically analyze and explore the effects of different fertilization measures on maize yield, soil nutrients, water content and water use efficiency (WUE) in northern China. Articles addressing this topic showed that fertilization effectively increased the soil nutrient content and maize yield. The soil organic matter (SOM) increased by 2.36 (N)-55.38% (NPO), total nitrogen content increased by 6.10 (N)-56.39% (NPO), available phosphorus content increased by 17.12 (N)-474.74% (NPO), and available potassium content changed by - 2.90 (NP)-64.40% (NPO). Soil moisture increased by 3.59% under a single organic fertilizer application and decreased by 4.27-13.40% under the other treatments. Compared with no fertilization, the yield increase of fertilized maize reached 11.65-220.42%. NP, NPK and NPKO contributed the most to increased yield in lithological, black and fluvo-aquic soils, respectively. The effects of different fertilization practices on maize yield varied in response to the same meteorological factors. The WUE increased from 9.51 to 160.72%. In conclusion, rational fertilization can improve the soil nutrient content and increase maize yield. The combined application of chemical and organic fertilizer showed the greatest increase in yield and WUE. Organic fertilizer application alone increased soil moisture. Our results provide a theoretical basis for fertilizer application and for improving the soil structure for maize cultivation in northern China.

Forest Age Drives the Resource Utilization Indicators of Trees in Planted and Natural Forests in China

Specific leaf area (SLA) and leaf dry matter content (LDMC) are key leaf functional traits commonly used to reflect tree resource utilization strategies and predict forest ecosystem responses to environmental changes. Previous research on tree resource utilization strategies (SLA and LDMC) primarily focused on the species level within limited spatial scales, making it crucial to quantify the spatial variability and driving factors of these strategies. Whether there are discrepancies in resource utilization strategies between trees in planted and natural forests, and the dominant factors and mechanisms influencing them, remain unclear. This study, based on field surveys and the literature from 2008 to 2020 covering 263 planted and 434 natural forests in China, using generalized additive models (GAMs) and structural equation models (SEMs), analyzes the spatial differences and dominant factors in tree resource utilization strategies between planted and natural forests. The results show that the SLA of planted forests is significantly higher than that of natural forests (p < 0.01), and LDMC is significantly lower (p < 0.0001), indicating a "faster investment-return" resource utilization strategy. As the mean annual high temperature (MAHT) and mean annual precipitation (MAP) steadily rise, trees have adapted their resource utilization strategies, transitioning from a "conservative" survival tactic to a "rapid investment-return" model. Compared to natural forests, planted forest trees exhibit stronger environmental plasticity and greater variability with forest age in their resource utilization strategies. Overall, forest age is the dominant factor influencing resource utilization strategies in both planted and natural forests, having a far greater direct impact than climatic factors (temperature, precipitation, and sunlight) and soil nutrient factors. Additionally, as forest age increases, both planted and natural forests show an increase in SLA and a decrease in LDMC, indicating a gradual shift towards more efficient resource utilization strategies.

Climate Factors Influence Above- and Belowground Biomass Allocations in Alpine Meadows and Desert Steppes through Alterations in Soil Nutrient Availability

Biomass is a direct reflection of community productivity, and the allocation of aboveground and belowground biomass is a survival strategy formed by the long-term adaptation of plants to environmental changes. However, under global changes, the patterns of aboveground-belowground biomass allocations and their controlling factors in different types of grasslands are still unclear. Based on the biomass data of 182 grasslands, including 17 alpine meadows (AMs) and 21 desert steppes (DSs), this study investigates the spatial distribution of the belowground biomass allocation proportion (BGBP) in different types of grasslands and their main controlling factors. The research results show that the BGBP of AMs is significantly higher than that of DSs (p < 0.05). The BGBP of AMs significantly decreases with increasing mean annual temperature (MAT) and mean annual precipitation (MAP) (p < 0.05), while it significantly increases with increasing soil nitrogen content (N), soil phosphorus content (P), and soil pH (p < 0.05). The BGBP of DSs significantly decreases with increasing MAP (p < 0.05), while it significantly increases with increasing soil phosphorus content (P) and soil pH (p < 0.05). The random forest model indicates that soil pH is the most important factor affecting the BGBP of both AMs and DSs. Climate-related factors were identified as key drivers shaping the spatial distribution patterns of BGBP by exerting an influence on soil nutrient availability. Climate and soil factors exert influences not only on grassland biomass allocation directly, but also indirectly by impacting the availability of soil nutrients.

Leaf functional traits vary among growth forms and vegetation zones in the Himalaya

Compression of life zones along elevational gradients in mountains supports diverse vegetation types, and therefore offers ideal setting to study plant functional traits. Functional traits, the features that enable plants to live in varied environmental conditions, help in understanding ecological interactions, evolutionary adaptations, and predicting plant response to global change drivers. To date, little is known how the trait diversity varies across different growth forms and vegetation zones in mountains. Here, we aimed to investigate interspecific leaf trait variability among different growth forms and vegetation zones along a wide elevation gradient (2000-4200 m) in Kashmir Himalaya. We measured leaf functional traits (specific leaf area-SLA, leaf thickness - LT, leaf dry matter content -LDMC) of 76 plant species corresponding to three growth forms (trees, shrubs and herbs) and three vegetation zones (Himalayan dry temperate forests, subalpine forests and alpine grasslands). Our results revealed high trait variability across the regional species pool studied. We found significant variation in leaf functional traits among the different growth forms, with higher values of LT and LDMC recorded for woody species than herbaceous ones. Among different vegetation zones, the SLA was found to be significantly higher at lower to middle elevations, while the other leaf traits (LT and LDMC) showed an opposite trend. Across all the vegetative zones, we also found a negative correlation between SLA and the other leaf traits, and the latter showed a positive trait-trait correlation. Overall, our study contributes to a deeper understanding of trait-trait, trait-growth form and trait-vegetation zone relationships. Our findings suggest that the variation in leaf functional traits among different growth forms seems to be a trade-off mechanism between resource acquisition and leaf construction, and also help in identifying species' adaptive functional traits that are critical for plant survival in the face of ongoing climate change in the Himalaya.

Climate factors affect forest biomass allocation by altering soil nutrient availability and leaf traits

Biomass in forests sequesters substantial amounts of carbon; although the contribution of aboveground biomass has been extensively studied, the contribution of belowground biomass remains understudied. Investigating the forest biomass allocation is crucial for understanding the impacts of global change on carbon allocation and cycling. Moreover, the question of how climate factors affect biomass allocation in natural and planted forests remains unresolved. Here, we addressed this question by collecting data from 384 planted forests and 541 natural forests in China. We evaluated the direct and indirect effects of climate factors on the belowground biomass proportion (BGBP). The average BGBP was 31.09% in natural forests and was significantly higher (38.75%) in planted forests. Furthermore, we observed a significant decrease in BGBP with increasing temperature and precipitation. Climate factors, particularly those affecting soil factors, such as pH, strongly affected the BGBP in natural and planted forests. Based on our results, we propose that future studies should consider the effects of forest type (natural or planted) and soil factors on BGBP.

Precipitation Dominates the Allocation Strategy of Above- and Belowground Biomass in Plants on Macro Scales

The allocation of biomass reflects a plant's resource utilization strategy and is significantly influenced by climatic factors. However, it remains unclear how climate factors affect the aboveground and belowground biomass allocation patterns on macro scales. To address this, a study was conducted using aboveground and belowground biomass data for 486 species across 294 sites in China, investigating the effects of climate change on biomass allocation patterns. The results show that the proportion of belowground biomass in the total biomass (BGBP) or root-to-shoot ratio (R/S) in the northwest region of China is significantly higher than that in the southeast region. Significant differences (p < 0.05) were found in BGBP or R/S among different types of plants (trees, shrubs, and herbs plants), with values for herb plants being significantly higher than shrubs and tree species. On macro scales, precipitation and soil nutrient factors (i.e., soil nitrogen and phosphorus content) are positively correlated with BGBP or R/S, while temperature and functional traits are negatively correlated. Climate factors contribute more to driving plant biomass allocation strategies than soil and functional trait factors. Climate factors determine BGBP by changing other functional traits of plants. However, climate factors influence R/S mainly by affecting the availability of soil nutrients. The results quantify the productivity and carbon sequestration capacity of terrestrial ecosystems and provide important theoretical guidance for the management of forests, shrubs, and herbaceous plants.

Effects of Soil Nutrients on Plant Nutrient Traits in Natural Pinus tabuliformis Forests

In light of global warming, the interaction between plant nutrient traits and soil nutrients is still unclear. Plant nutrient traits (e.g., N and P) and their stoichiometric relationships (N/P ratio) are essential for plant growth and reproduction. However, the specific role of soil nutrients in driving variation in plant nutrient traits remains poorly understood. Fifty natural Pinus tabuliformis forests were used as the research object to clarify the interaction between plant nutrient traits and soil nutrients. We show that: (1) The N_mass, P_mass and N/P ratios of leaves were significantly higher than those of roots. The N/P ratio of both leaves and roots was less than 14. (2) Leaf nutrient traits showed diverse relationship patterns with root nutrient traits throughout the growing period. Significant changes were found in root nutrient PC2 (the second principal component of root nutrient traits) and leaf nutrient PC1 (the first principal component of leaf traits), and non-significant changes were found in other relationships between leaf and root traits (p > 0.05). Root nutrient traits explained 36.4% of the variance in leaf nutrient traits. (3) With the increase in soil nutrient PC2 (related to N), leaf PC2 (related to N) showed a significant trend of first decreasing and then increasing (p < 0.05). Only the soil N_mass was significantly correlated with the leaf N_mass (p < 0.05), which demonstrated that the growth and survival of Pinus tabuliformis forests were mainly affected by N-limitation.

Slope position- mediated soil environmental filtering drives plant community assembly processes in hilly shrublands of Guilin, China

BACKGROUND AND AIMS

A major goal of community ecology focuses on trying to understand how environmental filter on plant functional traits drive plant community assembly. However, slopes positions- mediated soil environmental factors on community-weighted mean (CWM) plant traits in shrub community has not been extensively explored to analyze and distinguish assembly processes.

METHODS

Here, we surveyed woody shrub plant communities from three slope positions (foot, middle, and upper) in a low hilly area of Guilin, China to assess differences in functional trait CWMs and environmental factors across these positions. We also measured the CWMs of four plant functional traits including specific leaf area, leaf dry matter content, leaf chlorophyll content, and leaf thickness and nine abiotic environmental factors, including soil water content, soil organic content, soil pH, soil total nitrogen, soil total phosphorus, soil total potassium, soil available nitrogen, soil available phosphorus, and soil available potassium. We used ANOVA and Tukey HSD multiple comparisons to assess differences in functional trait CWMs and environmental factors across the three slope positions. We used redundancy analysis (RDA) to compare the relationships between CWMs trait and environmental factors along three slope positions, and also quantified slope position-mediated soil environmental filtering on these traits with a three-step trait-based null model approach.

RESULTS

The CWMs of three leaf functional traits and all soil environmental factors except soil pH showed significant differences across the three slope positions. Soil total nitrogen, available nitrogen, available potassium, and soil organic matter were positively correlated with the CWM specific leaf area and leaf chlorophyll content along the first RDA axis and soil total potassium, total phosphorous, and soil water content were positively correlated with the CWM leaf dry matter content along the second RDA axis. Environmental filtering was detected for the CWM specific leaf area, leaf dry matter content, and leaf chlorophyll content but not leaf thickness at all three slope positions.

CONCLUSIONS

Ultimately, we found that soil environmental factors vary along slope positions and can cause variability in plant functional traits in shrub communities. Deciduous shrub species with high specific leaf area, low leaf dry matter content, and moderate leaf chlorophyll content dominated at the middle slope position, whereas evergreen species with low specific leaf area and high leaf dry matter content dominated in slope positions with infertile soils, steeper slopes, and more extreme soil water contents. Altogether, our null model approach allowed us to detect patterns of environmental filtering, which differed between traits and can be applied in the future to understand community assembly changes in Chinese hilly forest ecosystems.

Climatic Factors Determine the Distribution Patterns of Leaf Nutrient Traits at Large Scales

Leaf nutrient content and its stoichiometric relationships (N/P ratio) are essential for photosynthesis and plant growth and development. Previous studies on leaf nutrient-related functional traits have mainly focused on the species level and regional scale, but fewer studies have investigated the distribution patterns of the leaf N and P contents (LN, LP) and N/P ratios (N/P) in communities and their controlling factors at a large scale; therefore, we used LN, LP, and N/P data at 69 sites from 818 forests in China. The results showed significant differences (p < 0.05) in the LN, LP, and N/P at different life forms (tree, shrub, and herb). Neither LN, LP, nor N/P ratios showed significant patterns of latitudinal variation. With the increase in temperature and rainfall, the LN, LP, and leaf nutrient contents increased significantly (p < 0.001). Across life forms, LN at different life forms varied significantly and was positively correlated with soil P content (p < 0.001). The explanatory degree of climatic factors in shaping the spatial variation patterns of LN and N/P was higher than that of the soil nutrient factors, and the spatial variation patterns of the leaf nutrient traits of different life forms were shaped by the synergistic effects of climatic factors and soil nutrient factors.