Shifts in resource allocation and aggravation of foliage development restrict the growth rate of Picea abies under increasing atmospheric humidity at high latitudes

Global warming is accompanied by rising precipitation, atmospheric water vapour content, and specific humidity at high latitudes. The rising amount and frequency of rainfall increase the air relative humidity (RH) on a local scale, especially within forest canopies. We studied the effects of artificially elevated environmental humidity (RH and soil moisture) on leaf gas exchange, stomatal responses and growth of young Picea abies trees at the Free Air Humidity Manipulation site in eastern Estonia. Manipulation did not affect the net assimilation rate (An) but affected the stomatal responses, net photosynthetic efficiency (An/ci), and photosynthetic water-use efficiency (WUE). At an elevated air humidity (H), trees exhibited the highest stomatal conductance (gS) and lowest WUE, An/ci, and stomatal sensitivity to air vapour pressure deficit compared to trees growing under ambient conditions (C) and elevated soil moisture (I). Compared to C trees, H trees demonstrated reduced height growth, foliage biomass, and enhanced investments in fine roots referring to worsening soil nutrient availability. Tree growth decline can be explained by (1) foliage development retardation, (2) resource allocation changes, causing a shift in the photosynthetic to non-photosynthetic tissue ratio in favour of the latter, and (3) impaired nutrient uptake from the soil. Changes in stomatal responses make trees grown in a higher RH more vulnerable to weather extremes, also limiting tree growth and forest productivity. Increasing precipitation with concomitant increase in atmospheric humidity at high latitudes counteracts the expected enhancement of tree growth due to climate warming in mesic northern forests.

Embracing imperfection: Carbon offset markets must learn to mitigate the risk of overcrediting

The role of carbon offset markets in accelerating climate action has been widely anticipated. Recently, fundamental questions have emerged about the role of carbon credits in the wake of widespread quality critiques of existing carbon offset projects. In tandem, many large corporate buyers are slowing their voluntary investments in carbon credits or shifting to less public vehicles for those investments. The discourse to date has focused on raising the quality bar of carbon credits, which is critical. However, it has broadly overlooked the fact that heterogeneous quality and uncertainty may be an inherent attribute of carbon projects. Carbon credits are an intangible good that may always have imperfect accounting. The success of carbon offset markets in part depends on embracing this imperfection, rather than obscuring or ignoring it. Thus, we propose that carbon offset markets need new mechanisms that account for-and encourage-iterative methodological improvements in how carbon credits are issued. These may include a variety of insurance-like mechanisms, warranties, and ex post adjustment mechanisms. They each work to guarantee that issued credits deliver on their promises, much like how carbon storage reversals are already guaranteed by credit registries. Market actors have already started testing such solutions, from true insurance products to buffer pools to discounted credit portfolios. Here, we highlight opportunities and challenges to achieve this goal, including the potential role of carbon registries, private actors, and large institutions.

Susceptibility to Photosynthesis Suppression From Extreme Storms Is Highly Site-Dependent

Extreme storms are becoming more intense and frequent under climate change. Although these extreme wet events are smaller in extent and duration than drought events, recent evidence suggests the global impact of both extremes is similar. However, the impact of individual extreme storms on photosynthesis-and therefore on vegetation and the carbon cycle-remains difficult to predict, as photosynthesis may be suppressed via waterlogging or increased by the alleviation of moisture stress. Here, we use random forest models to calculate daily photosynthesis anomalies attributable to extreme soil moisture using data from 54 FLUXNET sites across the globe. We hypothesize that photosynthesis' response to a given extreme event is primarily controlled by storm intensity, and to a lesser degree by site vegetation, climate, soil, and topography. However, we find instead that photosynthesis responses are better explained by site characteristics (soil texture, climate, topography, and vegetation density) than by storm intensity, such that the likelihood of waterlogging from a given storm is heavily site-dependent. Although storms that induce waterlogging are roughly as common as those that induce stress alleviation overall, photosynthesis rarely declines at sites not prone to waterlogging. Instead, photosynthesis anomalies at these sites show a much weaker relationship with storm intensity. Increasingly intense storms are therefore unlikely to impact all locations equally. This highlights the potential to use site characteristics to enhance prediction of storm effects on ecosystems and the land carbon sink.

Effects of Ecosystem Recovery Types on Soil Phosphorus Bioavailability, Roles of Plant and Microbial Diversity: A Meta-Analysis

Strategies for restoring degraded ecosystems vary widely in the levels of human intervention. It has commonly been assumed that recovery with artificial inputs would be quicker and more efficient. However, is this truly the situation? We conducted a meta-analysis to evaluate the differences and applicability between ecological restoration and ecological rehabilitation. Relationships between soil phosphorus content, plant diversity, and soil microbial diversity were analyzed using 463 valid experimental data points collected from 72 publications. The results indicated that in grassland ecosystems, ecological restoration outperformed rehabilitation by 35%, 68%, 38%, and 48% in belowground biomass, community coverage, plant richness, and Shannon diversity, respectively. In forests, rehabilitation trailed behind restoration by 58%, 26%, and 92% in belowground biomass, Simpson diversity, and bacterial Shannon diversity. Furthermore, there was minimal difference in the recovery mode among different fungal and bacterial phyla. Rehabilitation demonstrated lower stability and efficiency in long-term phosphorus cycling compared to restoration. Overall, ecological restoration offers more stable and efficient long-term phosphorus cycling, thereby questioning the effectiveness of ecological rehabilitation for sustainable ecosystem recovery, especially for species diversity and phosphorus cycling.

Hedging our bet on forest permanence for the economic viability of climate targets

Achieving the Paris Agreement's CO2 emission reduction goals heavily relies on enhancing carbon storage and sequestration in forests globally. Yet, the increasing vulnerability of carbon stored in forests to both climate change and human intervention is often neglected in current mitigation strategies. Our study explores modelled interactions between key emission sectors, indicating that accelerated decarbonization could meet climate objectives despite forest carbon losses due to disturbances. However, delaying action on forest carbon loss by just five years consistently doubles the additional mitigation costs and efforts across key sectors, regardless of the assessed forest disturbance rates. Moreover, these myopic responses to forest carbon loss are as stringent, or even more demanding, than immediate responses to twice the forest disturbance rate. Our results underline the urgent need to monitor and safeguard forests for the economic feasibility of the Paris Agreement's climate goals.

Ectomycorrhizal Dominance Increases Temporal Stability of Productivity at Multiple Spatial Scales Across US Forests

Mycorrhizas are fundamental to plant productivity and plant diversity maintenance, yet their influence on the temporal stability of forest productivity across scales remains uncertain. The multiscale stability theory clarifies that the temporal stability (γ stability) of metacommunity-several local communities connected through species dispersal-can be decomposed into the temporal stability of local communities (α stability) and asynchrony among them. Here, based on the forest inventory dataset from the United States and the multiscale stability theory, we explored how mycorrhizal strategy influences forest stability across scales and their underlying mechanisms. At the local scale, we found that α stability increased with ectomycorrhizal dominance due to the higher temporal stability of ectomycorrhizal trees. Additionally, higher α diversity associated with mixed mycorrhizal strategies promoted species asynchrony. At the metacommunity scale, the stabilizing effect of ectomycorrhizal dominance surpassed that of mixed mycorrhizal strategies on the asynchrony among local communities (i.e., spatial asynchrony), resulting in higher γ stability with increasing ectomycorrhizal dominance. Our research suggests the stabilizing effects of ectomycorrhizal dominance on the temporal stability of forest productivity, highlighting the importance of protecting ectomycorrhizal forests to maintain productivity under climate change, especially in the boreal-temperate ecotone where ectomycorrhizal trees are threatened by global change.

Integrating Network and Meta-Ecosystem Models for Developing a Zoogeochemical Theory

Human activities have caused significant changes in animal abundance, interactions, movement and diversity at multiple scales. Growing empirical evidence reveals the myriad ways that these changes can alter the control that animals exert over biogeochemical cycling. Yet a theoretical framework to coherently integrate animal abundance, interactions, movement and diversity to predict when and how animal controls over biogeochemical cycling (i.e., zoogeochemistry) change is currently lacking. We present such a general framework that provides guidance on linking mathematical models of species interaction and diversity (network theory) and movement of organisms and non-living materials (meta-ecosystem theory) to account for biotic and abiotic feedback by which animals control biogeochemical cycling. We illustrate how to apply the framework to develop predictive models for specific ecosystem contexts using a case study of a primary producer-herbivore bipartite trait network in a boreal forest ecosystem. We further discuss key priorities for enhancing model development, data-model integration and application. The framework offers an important step to enhance empirical research that can better inform and justify broader conservation efforts aimed at conserving and restoring animal populations, their movement and critical functional roles in support of ecosystem services and nature-based climate solutions.

Source vs sink limitations on tree growth: from physiological mechanisms to evolutionary constraints and terrestrial carbon cycle implications

The potential for widespread sink-limited plant growth has received increasing attention in the literature in the past few years. Despite recent evidence for sink limitations to plant growth, there are reasons to be cautious about a sink-limited world view. First, source-limited vegetation models do a reasonable job at capturing geographic patterns in plant productivity and responses to resource limitations. Second, from an evolutionary perspective, it is nonadaptive for plants to invest in increasing carbon assimilation if growth is primarily sink-limited. In this review, we synthesize the potential evidence for and underlying physiology of sink limitation across terrestrial ecosystems and contrast mechanisms of sink limitation with those of source-limited productivity. We highlight evolutionary restrictions on the magnitude of sink limitation at the organismal level. We also detail where mechanisms regulating sink limitation at the organismal and ecosystem scale (e.g. the terrestrial carbon sink) diverge. Although we find that there is currently no direct evidence for widespread organismal sink limitation, we propose a series of follow-up growth chamber manipulations, systematized measurements, and modeling experiments targeted at diagnosing nonadaptive buildup of excess nonstructural carbohydrates that will help illuminate the prevalence and magnitude of organismal sink limitation.

Interactions Between Climate Mean and Variability Drive Future Agroecosystem Vulnerability

Agriculture is crucial for global food supply and dominates the Earth's land surface. It is unknown, however, how slow but relentless changes in climate mean state, versus random extreme conditions arising from changing variability, will affect agroecosystems' carbon fluxes, energy fluxes, and crop production. We used an advanced weather generator to partition changes in mean climate state versus variability for both temperature and precipitation, producing forcing data to drive factorial-design simulations of US Midwest agricultural regions in the Energy Exascale Earth System Model. We found that an increase in temperature mean lowers stored carbon, plant productivity, and crop yield, and tends to convert agroecosystems from a carbon sink to a source, as expected; it also can cause local to regional cooling in the earth system model through its effects on the Bowen Ratio. The combined effect of mean and variability changes on carbon fluxes and pools was nonlinear, that is, greater than each individual case. For instance, gross primary production reduces by 9%, 1%, and 13% due to change in mean temperature, change in temperature variability, and change in both temperature mean and variability, respectively. Overall, the scenario with change in both temperature and precipitation means leads to the largest reduction in carbon fluxes (-16% gross primary production), carbon pools (-35% vegetation carbon), and crop yields (-33% and -22% median reduction in yield for corn and soybean, respectively). By unambiguously parsing the effects of changing climate mean versus variability and quantifying their nonadditive impacts, this study lays a foundation for more robust understanding and prediction of agroecosystems' vulnerability to 21st-century climate change.

From benefit to burden: Assessing the full range of health impacts in urban green spaces using a threshold model

Urban residents increasingly value the health benefits of natural exposure, highlighting the role of green spaces in early disease prevention. While the positive health impacts of green space exposure are well-documented, the negative physiological effects remain less understood. This study introduces an advanced threshold model designed to capture both the positive and negative physiological impacts of green space exposure. In a comparative experiment, participants were virtually exposed to images of Healthy Urban Greenery (HUG) and Distressed Urban Greenery (DUG), with continuous electroencephalogram (EEG) monitoring as the physiological measure. The results showed that: (1) physiological responses to both HUG and DUG closely aligned with the proposed threshold model; (2) DUG exposure negatively impacts health, beyond merely reducing the positive effects typically associated with green spaces; (3) women are more susceptible to the negative effects of DUG than men; and (4) restorative effects are stronger after prolonged DUG exposure, with greater initial negative impacts leading to more significant recovery in HUG. These findings demonstrate the threshold model's effectiveness in capturing the complex interactions between humans and their environments, offering a nuanced understanding of the health impacts of green space exposure.

Variable impacts of land-based climate mitigation on habitat area for vertebrate diversity

Pathways to achieving net zero carbon emissions commonly involve deploying reforestation, afforestation, and bioenergy crops across millions of hectares of land. It is often assumed that by helping to mitigate climate change, these strategies indirectly benefit biodiversity. Here, we modeled the climate and habitat requirements of 14,234 vertebrate species and show that the impact of these strategies on species' habitat area tends not to arise through climate mitigation, but rather through habitat conversion. Across locations, reforestation tends to provide species more habitat through both land-cover change and climate mitigation, whereas habitat loss from afforestation and bioenergy cropping typically outweighs the climate mitigation benefits. This work shows how and where land-based mitigation strategies can be deployed without inadvertently reducing the area of habitat for global biodiversity.

Increased but not pristine soil organic carbon stocks in restored ecosystems

Ecosystem restoration can contribute to climate change mitigation, as recovering ecosystems sequester atmospheric CO2 in biomass and soils. It is, however, unclear how much soil organic carbon (SOC) stocks recover across different restored ecosystems. Here, we show SOC recovery in different contexts globally by consolidating 41 meta-analyses into a second-order meta-analysis. We find that restoration projects have, since their inception, led to significant SOC increases compared to the degraded state in 12 out of 16 ecosystem-previous land-use combinations, with mean SOC increases thus far that range from 25% (grasslands; 10-39%, 95% CI) to 79% (shrublands; 38-120% CI). Yet, we observe a SOC deficit in restored ecosystems compared to pristine sites, ranging from 14% (forests; 12-16% CI) to 50% (wetlands; 14-87% CI). While restoration does increase carbon sequestration in SOC, it should not be viewed as a way to fully offset carbon losses in natural ecosystems, whose conservation has priority.

Population and community ecology: past progress and future directions

Population and community ecology as a science are about 100 years old, and we discuss here our opinion of what approaches have progressed well and which point to possible future directions. The three major threads within population and community ecology are theoretical ecology, statistical tests and models, and experimental ecology. We suggest that our major objective is to understand what factors determine the distribution and abundance of organisms within populations and communities, and we evaluate these threads against this major objective. Theoretical ecology is elegant and compelling and has laid the groundwork for achieving our overall objectives with useful simple models. Statistics and statistical models have contributed informative methods to analyze quantitatively our understanding of distribution and abundance for future research. Population ecology is difficult to carry out in the field, even though we may have all the statistical methods and models needed to achieve results. Community ecology is growing rapidly with much description but less understanding of why changes occur. Biodiversity science cuts across all these subdivisions but rarely digs into the necessary population and community science that might solve conservation problems. Climate change affects all aspects of ecology but to assume that everything in population and community ecology is driven by climate change is oversimplified. We make recommendations on how to advance the field with advice for present and future generations of population and community ecologists.

Tree Lifespans in a Warming World: Unravelling the Universal Trade-Off Between Growth and Lifespan in Temperate Forests

Tree growth and lifespan are key determinants of forest dynamics, and ultimately control carbon stocks. Warming and increasing CO2 have been observed to increase growth but such increases may not result in large net biomass gains due to trade-offs between growth and lifespan. A deeper understanding of the nature of the trade-off and its potential spatial variation is crucial to improve predictions of the future carbon sink. This study aims to identify key drivers of growth and lifespan, assess the universality of tree growth-lifespan trade-offs, explore the possible latitudinal patterns of trade-off strengths and their determinants, and project growth and lifespan under future climate scenarios. We analyzed 21,193 trees of 69 species (48 included in further analysis) at 445 sites (417 included in further analysis) in temperate forests in northeastern China to estimate early growth rate and tree lifespan. We find that temperature and human pressure enhance tree growth and reduce lifespan, while altitude increases lifespan. We further find evidence for growth-lifespan trade-offs at all studied levels, that is, among trees, among species and communities, and within species and communities. Trade-offs are stronger at colder, higher latitudes compared to warmer sites, because of larger variation in tree growth and climate, larger range sizes for individual species, and lower species' diversity for communities at high latitudes. We predict future increases in growth and reductions in tree lifespan in response to climate change for the 2050s. Taking growth lifespan trade-offs into account resulted in even larger predictions of decreases in tree lifespan of up to 8%. In conclusion, growth-lifespan trade-offs are universal, but the strengths may vary by environment and between different forests. Its effects are important to include in predictions of forest responses to global change and need to be considered more widely.

Disturbance impacts on Mediterranean forests across climate and management scenarios

In the climate-vulnerable Mediterranean basin, the severity and frequency of disturbances such as windthrows, droughts and fires are intensifying. Forests are generally resilient, but struggle to adapt to abrupt changes, which can impact their functionality and service provision. Various forest management alternatives aim to reduce forest vulnerability to disturbances, but few studies have evaluated the impact of management alternatives on multiple disturbances and service provision simultaneously. We aimed at filling this gap by conducting simulations of forest dynamics between 2020 and 2100 for 261 pine-dominated forest plots in Catalonia (NE Spain), under two emissions scenarios (RCP4.5 and RCP8.5) and four management scenarios (business-as-usual, promotion of bioenergy, maximum carbon storage, and ecohydrological forest management). We used the annual simulated output of forest structure and composition and future climatic projections to produce annual estimates of six ecosystem services, and we determined the annual potential impact on forests of the three main abiotic disturbances in the Mediterranean region: fire, droughts, and windstorms. We also evaluated trade-offs and synergies between disturbance impact and the provision of ecosystem services. Our simulations predicted a greater influence of management over climate scenario on the potential impact caused by all disturbances. The business-as-usual scenario consistently predicted higher impacts than the other three management scenarios, regardless of the disturbance considered or the climate scenario (fire impact 175% higher, drought impact 300%; wind impact 130%). The other three management scenarios showed similar patterns in predicted impact, but differences among them increased under more severe climate conditions. In general, there was a positive correlation between the impact by the three disturbance agents, particularly drought and fire (Pearson's r = 0.69). We observed that the provision of some services is highly correlated to disturbance impacts, suggesting that, under certain management schemes, service provision may be compromised due to abiotic disturbance impacts. Our work supports the need for an "adaptation-first" model in which the promotion of forest adaptation is placed at the core of forest management as the only way to ensure forest persistence and the delivery of services.

Quantifying the Cooling Effect of Urban Greening Driven by Ecological Restoration Projects in China

Urban greening (UG) affects local climate by altering surface energy balance, while long-term UG cooling potential, patterns, and contribution to curbing urban warming remain unclear. Here, we designed an novel statistical model to evaluate the cooling potential of UG (CPUG) and created the first CPUG map for China. By exploring the trends in observed and simulated urban surface temperatures (UST), we quantified the CPUG of 0.20 K over the past two decades, which slowed down the warming trend by 14.17% in Chinese cities. We found that the CPUG varied significantly between the urban core and sprawl areas. Specifically, the CPUG in the urban core was approximately 1.01 K, and it contributed to curbing urban warming by 56.08%, which was more than 7.2 times higher than in the sprawl areas, where the CPUG was only 0.14 K and contributed to curbing urban warming by 9.93%. We further revealed that urbanization and major ecological restoration projects are the key factors influencing CPUG, emphasizing the need for anthropogenic vegetation management to curb urban warming. The proposed model in this study provides a powerful tool for quantitatively assessing the impact of long-term UG trends on urban warming. The results of the study are an important reference for building climate-adaptive cities.

The return of tall forests: Reconstructing the canopy resilience of an extensively harvested primary forest in Mediterranean mountains

Understanding recovery times and mechanisms of ecosystem dynamics towards the old-growth stage is crucial for forest restoration, but still poorly delineated in Mediterranean. Through tree-ring methods, we reconstructed the return of a tall canopy after severe human disturbance in a mixed beech (Fagus sylvatica) and silver fir (Abies alba) forest, located at a mountain site in the southern edge of both species' range (Gariglione, south Italy). The primary forest was extensively harvested between 1930 and 1950, removing up to 91 % of the biomass. Growth histories, climate-growth relationships and time-series of growth dominance in Gariglione were compared with a network of protected mature and old-growth beech forests distributed along a wide elevational gradient in the same region. We found that the renewed tall canopy of Gariglione is mainly composed of remnant trees, which include uncut trees and saplings, and the post-harvesting regeneration mostly represented by fir. Canopy beech trees reached maximum basal area increment (BAI) in the 1970s, 40-50 years after cutting. Then, beech BAI shifted towards negative trends in phase with drying climate (PDSI), while fir maintained a sustained growth until 2000. This growth asynchrony between the two species conferred community stability over the last decades. The network comparison highlighted the common negative impact of summer drought on high-frequency growth signals of beech in south Italy. However, analysis of long-term mean growth trends indicates decreasing BAI limited to Gariglione beech, revealing relevant differences due to site ecology and its interactions with legacy effects of past management in driving growth responses to climate change. Indeed, lowland mature beech forests showed increasing BAI in the last decades, while primary high-mountain forests displayed a remarkably stable low oscillating growth. In all the Mediterranean forests we studied, large and old trees showed a marked growth acclimation despite ongoing climate warming, demonstrating the effectiveness of landscape rewilding.

Complex imprint of air pollution in the basal area increments of three European tree species

The impact of atmospheric pollution on the growth of European forest tree species, particularly European beech, Silver fir and Norway spruce, is examined in five mesic forests in the Czech Republic. Analyzing of basal area increment (BAI) patterns using linear mixed effect models reveals a complex interplay between atmospheric nitrogen (N) and sulphur (S) deposition, climatic variables and changing CO2 concentrations. Beech BAI responds positively to N deposition (in tandem with air CO2 concentration), with soil phosphorus (P) availability emerging as a significant factor influencing overall growth rates. Fir BAI, on the other hand, was particularly negatively influenced by S deposition, although recent growth acceleration suggests growth resilience in post-pollution period. This fir growth surge likely coincides with stimulation of P acquisition following the decline of acidic pollution. The consequence is the current highest productivity among the studied tree species. The growth dynamics of both conifers were closely linked to the stoichiometric imbalance of phosphorus in needles, indicating the possible sensitivity of exogenous controls on nutrient uptake. Furthermore, spruce BAI was positively linked to calcium availability across sites. Despite enhanced water-use efficiency under elevated CO2, spruce growth is constrained by precipitation deficit and demonstrates weakening resilience to increasing growing season air temperatures. Overall, these findings underscore the intricate relationships between atmospheric pollution, nutrient availability, and climatic factors in shaping the growth dynamics of European forest ecosystems. Thus, incorporating biogeochemical context of nutrient availability is essential for realistic modelling of tree growth in a changing climate.

Contributions of ecological restoration policies to China's land carbon balance

Unleashing the land sector's potential for climate mitigation requires purpose-driven changes in land management. However, contributions of past management changes to the current global and regional carbon cycles remain unclear. Here, we use vegetation modelling to reveal how a portfolio of ecological restoration policies has impacted China's terrestrial carbon balance through developing counterfactual 'no-policy' scenarios. Pursuing conventional policies and assuming no changes in climate or atmospheric carbon dioxide (CO2) since 1980 would have led China's land sector to be a carbon source of 0.11 Pg C yr-1 for 2001-2020, in stark contrast to a sink of 175.9 Tg C yr-1 in reality. About 72.7% of this difference can be attributed to land management changes, including afforestation and reforestation (49.0%), reduced wood extraction (21.8%), fire prevention and suppression (1.6%) and grassland grazing exclusion (0.3%). The remaining 27.3% come from changes in atmospheric CO2 (42.2%) and climate (-14.9%). Our results underscore the potential of active land management in achieving 'carbon-neutrality' in China.

Long-term annual estimation of forest above ground biomass, canopy cover, and height from airborne and spaceborne sensors synergies in the Iberian Peninsula

The Mediterranean Basin has experienced substantial land use changes as traditional agriculture decreased and population migrated from rural to urban areas, which have resulted in a large forest cover increase. The combination of Landsat time series, providing spectral information, with lidar, offering three-dimensional insights, has emerged as a viable option for the large-scale cartography of forest structural attributes across large time spans. Here we develop and test a comprehensive framework to map forest above ground biomass, canopy cover and forest height in two regions spanning the most representative biomes in the peninsular Spain, Mediterranean (Madrid region) and temperate (Basque Country). As reference, we used lidar-based direct estimates of stand height and forest canopy cover. The reference biomass and volume were predicted from lidar metrics. Landsat time series predictors included annual temporal profiles of band reflectance and vegetation indices for the 1985-2023 period. Additional predictor variables including synthetic aperture radar, disturbance history, topography and forest type were also evaluated to optimize forest structural attributes retrieval. The estimates were independently validated at two temporal scales, i) the year of model calibration and ii) the year of the second lidar survey. The final models used as predictor variables only Landsat based metrics and topographic information, as the available SAR time-series were relatively short (1991-2011) and disturbance information did not decrease the estimation error. Model accuracies were higher in the Mediterranean forests when compared to the temperate forests (R2 = 0.6-0.8 vs. 0.4-0.5). Between the first (1985-1989) and the last (2020-2023) decades of the monitoring period the average forest cover increased from 21 ± 2% to 32 ± 1%, mean height increased from 6.6 ± 0.43 m to 7.9 ± 0.18 m and the mean biomass from 31.9 ± 3.6 t ha-1 to 50.4 ± 1 t ha-1 for the Mediterranean forests. In temperate forests, the average canopy cover increased from 55 ± 4% to 59 ± 3%, mean height increased from 15.8 ± 0.77 m to 17.3 ± 0.21m, while the growing stock volume increased from 137.8 ± 8.2 to 151.5 ± 3.8 m3 ha-1. Our results suggest that multispectral data can be successfully linked with lidar to provide continuous information on forest height, cover, and biomass trends.

Carbon, climate, and natural disturbance: a review of mechanisms, challenges, and tools for understanding forest carbon stability in an uncertain future

In this review, we discuss current research on forest carbon risk from natural disturbance under climate change for the United States, with emphasis on advancements in analytical mapping and modeling tools that have potential to drive research for managing future long-term stability of forest carbon. As a natural mechanism for carbon storage, forests are a critical component of meeting climate mitigation strategies designed to combat anthropogenic emissions. Forests consist of long-lived organisms (trees) that can store carbon for centuries or more. However, trees have finite lifespans, and disturbances such as wildfire, insect and disease outbreaks, and drought can hasten tree mortality or reduce tree growth, thereby slowing carbon sequestration, driving carbon emissions, and reducing forest carbon storage in stable pools, particularly the live and standing dead portions that are counted in many carbon offset programs. Many forests have natural disturbance regimes, but climate change and human activities disrupt the frequency and severity of disturbances in ways that are likely to have consequences for the long-term stability of forest carbon. To minimize negative effects and maximize resilience of forest carbon, disturbance risks must be accounted for in carbon offset protocols, carbon management practices, and carbon mapping and modeling techniques. This requires detailed mapping and modeling of the quantities and distribution of forest carbon across the United States and hopefully one day globally; the frequency, severity, and timing of disturbances; the mechanisms by which disturbances affect carbon storage; and how climate change may alter each of these elements. Several tools (e.g. fire spread models, imputed forest inventory models, and forest growth simulators) exist to address one or more of the aforementioned items and can help inform management strategies that reduce forest carbon risk, maintain long-term stability of forest carbon, and further explore challenges, uncertainties, and opportunities for evaluating the continued potential of, and threats to, forests as viable mechanisms for forest carbon storage, including carbon offsets. A growing collective body of research and technological improvements have advanced the science, but we highlight and discuss key limitations, uncertainties, and gaps that remain.

Overconfidence in climate overshoot

Global emission reduction efforts continue to be insufficient to meet the temperature goal of the Paris Agreement1. This makes the systematic exploration of so-called overshoot pathways that temporarily exceed a targeted global warming limit before drawing temperatures back down to safer levels a priority for science and policy2-5. Here we show that global and regional climate change and associated risks after an overshoot are different from a world that avoids it. We find that achieving declining global temperatures can limit long-term climate risks compared with a mere stabilization of global warming, including for sea-level rise and cryosphere changes. However, the possibility that global warming could be reversed many decades into the future might be of limited relevance for adaptation planning today. Temperature reversal could be undercut by strong Earth-system feedbacks resulting in high near-term and continuous long-term warming6,7. To hedge and protect against high-risk outcomes, we identify the geophysical need for a preventive carbon dioxide removal capacity of several hundred gigatonnes. Yet, technical, economic and sustainability considerations may limit the realization of carbon dioxide removal deployment at such scales8,9. Therefore, we cannot be confident that temperature decline after overshoot is achievable within the timescales expected today. Only rapid near-term emission reductions are effective in reducing climate risks.

Aridity affects soil organic carbon concentration and chemical stability by different forest types and soil processes across Chinese natural forests

Forest soils play a critical role in carbon (C) reservoirs and climate change mitigation globally. Exploring the driving factors of soil organic carbon (SOC) concentration and stability in forests on a large spatial scale can help us evaluate the role of forest soils in regulating C sequestration. Based on SOC quantification and solid-state 13C nuclear magnetic resonance spectroscopy, we investigated the SOC concentration and SOC chemical stability (indicated by alkyl-to-O-alkyl ratio and hydrophobic-to-hydrophilic ratio) in top 0-5 and 5-10 cm soils from 65 Chinese natural forest sites and explored their driving factors. Results showed that SOC concentration in 0-5 cm soils were highest in mixed forests but SOC chemical stability in 0-5 cm soils were highest in coniferous forests, while SOC concentration and chemical stability in 5-10 cm soil layers did not differ across forest types. SOC concentration in 0-5 cm was directly related to soil pH and soil bacterial diversity. Structural equation models showed that aridity indirectly affected SOC concentration in 0-5 cm by directly affecting soil pH. While SOC chemical stability in 0-5 cm soils was higher with increased aridity. According to the correlations, the potential mechanisms could be attributed to higher proportion of coniferous forests in more arid forest sites, lower relative abundance of O-alkyl C, higher MgO and CaO contents, and higher bacterial diversity in soils from more arid forest sites. Our study reveals the important role of aridity in mediating SOC concentration and chemical stability in top 0-5 cm soils in Chinese natural forests on a large-scale field investigation. These results will help us better understand the different mechanisms underlying SOC concentration and stability in forests and assess the feedback of forest SOC to future climate change.

Stability of gross primary productivity and its sensitivity to climate variability in China

Identifying the stability and sensitivity of land ecosystems to climate change is vital for exploring nature-based solutions. However, the underlying mechanisms governing ecosystem stability and sensitivity, especially in regions with overlapping ecological projects, remain unclear. based on Mann-Kendall, stability analysis method, and multiple regression method, this study quantified the stability and sensitivity of gross primary productivity (GPP) to climate variables [temperature, vapor pressure deficit (VPD), soil moisture, and radiation] in China from 1982 to 2019. Our findings revealed the following: (1) GPP demonstrated an increased trend with lower stability in Eastern regions, whereas a decreasing trend with higher stability was observed in Western and Southwest China. Notably, the stability of GPP was highest (74.58%) in areas with five overlapping ecological projects: Grain to Green, Natural Forest Resource Protection Project, Three-River Ecological Conservation and Restoration Project, Return Grazing to Grassland Project, and Three-North Shelter Forestation Project. (2) In regions with minimal or no overlapping ecological projects, temperature and radiation jointly dominated GPP variations. In contrast, water-related factors (VPD and soil moisture) significantly affected GPP in areas with multiple overlapping ecological projects. (3) In the southwestern and northeastern regions, GPP exhibited the highest sensitivity to climate change, whereas, in the eastern coastal areas and Tibet, GPP showed low sensitivity to climate change. In the Loess Plateau, where five ecological projects overlap extensively, carbon sinks primarily demonstrate a monotonic increasing trend, high stability, and low sensitivity to climate change. This study aimed to assess the stability of the land ecosystems and delineate their sensitivity to climate changes, thereby laying the groundwork for understanding ecosystem resilience.

Local spatiotemporal dynamics of particulate matter and oak pollen measured by machine learning aided optical particle counters

Conventional techniques for monitoring pollen currently have significant limitations in terms of labour, cost and the spatiotemporal resolution that can be achieved. Pollen monitoring networks across the world are generally sparse and are not able to fully represent the detailed characteristics of airborne pollen. There are few studies that observe concentrations on a local scale, and even fewer that do so in ecologically rich rural areas and close to emitting sources. Better understanding of these would be relevant to occupational risk assessments for public health, as well as ecology, biodiversity, and climate. We present a study using low-cost optical particle counters (OPCs) and the application of machine learning models to monitor particulate matter and pollen within a mature oak forest in the UK. We characterise the observed oak pollen concentrations, first during an OPC colocation period (6 days) for calibration purposes, then for a period (36 days) when the OPCs were distributed on an observational tower at different heights through the canopy. We assess the efficacy and usefulness of this method and discuss directions for future development, including the requirements for training data. The results show promise, with the derived pollen concentrations following the expected diurnal trends and interactions with meteorological variables. Quercus pollen concentrations appeared greatest when measured at the canopy height of the forest (20-30 m). Quercus pollen concentrations were lowest at the greatest measurement height that is above the canopy (40 m), which is congruent with previous studies of background pollen in urban environments. The attenuation of pollen concentrations as sources are depleted is also observed across the season and at different heights, with some evidence that the pollen concentrations persist later at the lowest level beneath the canopy (10 m) where catkins mature latest in the season compared to higher catkins.

A consistent budgeting of terrestrial carbon fluxes

Accurate estimates of CO2 emissions from anthropogenic land-use change (ELUC) and of the natural terrestrial CO2 sink (SLAND) are crucial to precisely know how much CO2 can still be emitted to meet the goals of the Paris Agreement. In current carbon budgets, ELUC and SLAND stem from two model families that differ in how CO2 fluxes are attributed to environmental and land-use changes, making their estimates conceptually inconsistent. Here we provide consistent estimates of ELUC and SLAND by integrating environmental effects on land carbon into a spatially explicit bookkeeping model. We find that state-of-the-art process-based models overestimate SLAND by 23% (min: 8%, max: 33%) in 2012-2021, as they include hypothetical sinks that in reality are lost through historical ecosystem degradation. Additionally, ELUC increases by 14% (8%, 23%) in 2012-2021 when considering environmental effects. Altogether, we find a weaker net land sink, which makes reaching carbon neutrality even more ambitious. These results highlight that a consistent estimation of terrestrial carbon fluxes is essential to assess the progress of net-zero emission commitments and the remaining carbon budget.

From carbon neutral to carbon negative: a theoretical bioenergy and CO2 removal retrofit at Ngāwhā geothermal power station

For countries like New Zealand with high renewable electricity generation (≥80%) but large emissions per capita, traditional decarbonisation methods are limited or costly. However, carbon dioxide removal (CDR) technologies can drive multiple sectors of the economy across the net-zero barrier through negative CO2 emissions. We argue that the key to scaling up CDR begins with the preponderance of New Zealand's geothermal and biomass resources. New Zealand has a proud and innovative history with geothermal energy, currently producing ∼20% of the country's electricity. Modern advances in geothermal energy have demonstrated that it is peerless amongst renewable energy-sources in the ability to facilitate onsite CDR by repurposing existing wells. We examine a theoretical bioenergy retrofit at the Ngāwhā geothermal plant to increase capacity by 1 MWe, with as much biogenic CO2 as permissible dissolved in reinjectate. Forestry residues are the feedstock of choice due to their abundance in the Far North. We show that up to 15.9 ktCO2/year can be removed effectively from the atmosphere. Only 6% of the Far North's forestry residues are required to achieve this. Under 2024s emissions trading scheme (ETS), the annual revenue of CDR ($0.79 million) could exceed that of new electricity ($0.47 million).

Tree Resilience Indices of Norway Spruce Provenances Tested in Long-Term Common Garden Experiments in the Romanian Carpathians

Provenance trials provide a valuable opportunity to evaluate the impact of extreme events on growth and wood properties. In this study, we have evaluated 81 Norway spruce provenances, tested in three provenance trials established in the Romanian Carpathians in 1972. The response to drought of the Norway spruce provenances has been examined using the following tree resilience indices: resistance, recovery, resilience, and relative resilience. The relationship between climate and growth, the correlations between wood traits, and the coordinates of the origin and tree resilience indices were also analysed. In each provenance trial, there were significant differences between provenances and years regarding wood widths and latewood percentage (LWP). Regarding drought extreme events, the years when they occurred in all three provenance trials were 2000 and 2003. Significant differences between provenances for at least one tree resilience index have been found in all provenance trials, for the year 2000. By using subperiods of 25 years, changes in the relationship between climate and growth have been observed. Several provenances with high radial growth and good resistance and/or recovery have been identified. Provenances that performed better in common garden experiments could be used in assisted migration, even in the proximity of the current natural range.

Sapling recruitment as an indicator of carbon resiliency in forests of the northern USA

Tree regeneration shapes forest carbon dynamics by determining long-term forest composition and structure, which suggests that threats to natural regeneration may diminish the capacity of forests to replace live tree carbon transferred to the atmosphere or other pools through tree mortality. Yet, the potential implications of tree regeneration patterns for future carbon dynamics have been sparsely studied. We used forest inventory plots to investigate whether the composition of existing tree regeneration is consistent with aboveground carbon stock loss, replacement, or gain for forests across the northeastern and midwestern USA, leveraging a recently developed method to predict the likelihood of sapling recruitment from seedling abundance tallied within six seedling height classes. A comparison of carbon stock predictions from tree and seedling composition suggested that 29% of plots were poised to lose carbon based on seedling composition, 55% were poised for replacement of carbon stocks (<5 Mg ha-1 difference) and 16% were poised to gain carbon. Forests predicted to lose carbon tended to be on steeper slopes, at lower latitudes, and in rolling upland environments. Although plots predicted to gain and lose carbon had similar stand ages, carbon loss plots had greater current carbon stocks. Synthesis and applications. Our results demonstrate the utility of considering tree regeneration through the lens of carbon replacement to develop effective management strategies to secure long-term carbon storage and resilience in the context of global change. Forests poised to lose C due to climate change and other stressors could be prioritized for regeneration strategies that enhance long-term carbon resilience and stewardship.

Dynamic shifts of functional diversity through climate-resilient strategies and farmland restoration in a mountain protected area

Land-use land-cover (LULC) change contributes to major ecological impacts, particularly in areas undergoing land abandonment, inducing modifications on habitat structure and species distributions. Alternative land-use policies are potential solutions to alleviate the negative impacts of contemporary tendencies of LULC change on biodiversity. This work analyzes these tendencies in the Montesinho Natural Park (Portugal), an area representative of European abandoned mountain rural areas. We built ecological niche models for 226 species of vertebrates (amphibians, reptiles, birds, and mammals) and vascular plants, using a consensus modelling approach available in the R package 'biomod2'. We projected the models to contemporary (2018) and future (2050) LULC scenarios, under four scenarios aiming to secure relevant ecosystem services and biodiversity conservation for 2050: an afforestation and a rewilding scenario, focused on climate-smart management strategies, and a farmland and an agroforestry recovery scenario, based on re-establishing human traditional activities. We quantified the influences of these scenarios on biodiversity through species habitat suitability changes for 2018-2050. We analyzed how these management strategies could influence indices of functional diversity (functional richness, functional evenness and functional dispersion) within the park. Habitat suitability changes revealed complementary patterns among scenarios. Afforestation and rewilding scenarios benefited more species adapted to habitats with low human influence, such as forests and open woodlands. The highest functional richness and dispersion was predicted for rewilding scenarios, which could improve landscape restoration and provide opportunities for the expansion and recolonization of forest areas by native species. The recovery of traditional farming and agroforestry activities results in the lowest values of functional richness, but these strategies contribute to complex landscape matrices with diversified habitats and resources. Moreover, this strategy could offer opportunities for fire suppression and increase landscape fire resistance. An integrative approach reconciling rewilding initiatives with the recovery of extensive agricultural and agroforestry activities is potentially an harmonious strategy for supporting the provision of ecosystem services while securing biodiversity conservation and functional diversity within the natural park.

Estimation of changes in carbon sequestration and its economic value with various stand density and rotation age of Pinus massoniana plantations in China

Plantations actively participate in the global carbon cycle and play a significant role in mitigating global climate change. However, the influence of forest management strategies, especially planting density management, on the biomass carbon storage and production value of plantations for ensuring carbon sink benefits is still unclear. In this study, we estimated the carbon sequestration and economic value of Pinus massoniana plantations with various stand densities and rotation ages using a growth model method. The results revealed that with increasing stand age, low-density plantations at 2000 trees·ha-1 (358.80 m3·ha-1), as well as high-density plantations at 4500 trees·ha-1 (359.10 m3·ha-1), exhibited nearly identical standing volumes, which indicated that reduced inter-tree competition intensity favors the growth of larger trees during later stages of development. Furthermore, an increase in planting density led to a decrease in the average carbon sequestration rate, carbon sink, and number of trees during the rapid growth period, indicating that broader spacing between trees is favorable for biomass carbon accumulation. Further, extending the rotation period from 15 to 20 years or 25 years and reducing the optimal planting density from 3000 to 2000 trees·ha-1 increased the overall benefits of combined timber and carbon sink income by 2.14 and 3.13 times, respectively. The results highlighted that optimizing the planting density positively impacts the timber productivity and carbon sink storage of Pinus massoniana plantations and boosts the expected profits of forest managers. Thus, future afforestation initiatives must consider stand age and planting density management to shift from a scale-speed pattern to a quality-benefit design.

Tree species explain only half of explained spatial variability in plant water sensitivity

Spatiotemporal patterns of plant water uptake, loss, and storage exert a first-order control on photosynthesis and evapotranspiration. Many studies of plant responses to water stress have focused on differences between species because of their different stomatal closure, xylem conductance, and root traits. However, several other ecohydrological factors are also relevant, including soil hydraulics, topographically driven redistribution of water, plant adaptation to local climatic variations, and changes in vegetation density. Here, we seek to understand the relative importance of the dominant species for regional-scale variations in woody plant responses to water stress. We map plant water sensitivity (PWS) based on the response of remotely sensed live fuel moisture content to variations in hydrometeorology using an auto-regressive model. Live fuel moisture content dynamics are informative of PWS because they directly reflect vegetation water content and therefore patterns of plant water uptake and evapotranspiration. The PWS is studied using 21,455 wooded locations containing U.S. Forest Service Forest Inventory and Analysis plots across the western United States, where species cover is known and where a single species is locally dominant. Using a species-specific mean PWS value explains 23% of observed PWS variability. By contrast, a random forest driven by mean vegetation density, mean climate, soil properties, and topographic descriptors explains 43% of observed PWS variability. Thus, the dominant species explains only 53% (23% compared to 43%) of explainable variations in PWS. Mean climate and mean NDVI also exert significant influence on PWS. Our results suggest that studies of differences between species should explicitly consider the environments (climate, soil, topography) in which observations for each species are made, and whether those environments are representative of the entire species range.

Changes in planned and unplanned canopy openings are linked in Europe's forests

Canopy openings are increasing in Europe's forests, yet the contributions of anthropogenic and ecological agents of disturbance to this increase remain debated. Here we attribute the root cause of all stand-replacing canopy disturbances identified for Europe in the period 1986-2020 from Landsat data (417,000 km²), distinguishing between planned and unplanned canopy openings (i.e., disturbance by human land use versus by wind, bark beetles, and wildfire). We show that canopy openings by humans dominate the European forest disturbance regime, accounting for 82% of the area disturbed. Both planned and unplanned canopy openings increased in the early 21st century (+24% and +30% relative to the late 20th century). Their changes are linked, with simultaneous increases in planned and unplanned canopy openings on 68% of Europe's forest area. We conclude that an important direction for tackling disturbance change in policy and management is to break the link between planned and unplanned canopy openings in Europe's forests.

Carbon stock projection for four major forest plantation species in Japan

Carbon sequestration via afforestation and forest growth is effective for mitigating global warming. Accurate and robust information on forest growth characteristics by tree species, region, and large-scale land-use change is vital and future prediction of forest carbon stocks based on this information is of great significance. These predictions allow exploring forestry practices that maximize carbon sequestration by forests, including wood production. Forest inventories based on field measurements are considered the most accurate method for estimating forest carbon stocks. Japan's national forest inventories (NFIs) provide stand volumes for all Japanese forests, and estimates from direct field observations (m-NFIs) are the most reliable. Therefore, using the m-NFI from 2009 to 2013, we selected four major forest plantation species in Japan: Cryptomeria japonica, Chamaecyparis obtusa, Pinus spp., and Larix kaempferi and presented their forest age-carbon density function. We then estimated changes in forest carbon stocks from the past to the present using the functions. Next, we investigated the differences in the carbon sequestration potential of forests, including wood production, between five forestry practice scenarios with varying harvesting and afforestation rates, until 2061. Our results indicate that, for all four forest types, the estimates of growth rates and past forest carbon stocks in this study were higher than those considered until now. The predicted carbon sequestration from 2011 to 2061, assuming that 100 % of harvested carbon is retained for a long time, twice the rate of harvesting compared to the current rate, and a 100 % afforestation rate in harvested area, was three to four times higher than that in a scenario with no harvesting or replanting. Our results suggest that planted Japanese forests can exhibit a high carbon sequestration potential under the premise of active management, harvesting, afforestation, and prolonging the residence time of stored carbon in wood products with technology development.

Importance of soil moisture conservation in mitigating climate change

A troubling feedback loop, where drier soil contributes to hotter climates, has been widely recognized. This study, drawing on climate model simulations, reveals that maintaining current global soil moisture levels could significantly alleviate 32.9% of land warming under low-emission scenarios. This action could also postpone reaching critical warming thresholds of 1.5 °C and 2.0 °C by at least a decade. Crucially, preserving soil moisture at current levels could prevent noticeable climate change impacts across 42% of the Earth's land, a stark deviation from projections suggesting widespread impacts before the 2060s. To combat soil drying, afforestation in mid-to-low latitude regions within the next three decades is proposed as an effective strategy to increase surface water availability. This underscores the substantial potential of nature-based solutions for managing soil moisture, benefiting both climate change mitigation and ecological enhancement.

The largest European forest carbon sinks are in the Dinaric Alps old-growth forests: comparison of direct measurements and standardised approaches

BACKGROUND

Carbon (C) sink and stock are among the most important ecosystem services provided by forests in climate change mitigation policies. In this context, old-growth forests constitute an essential reference point for the development of close-to-nature silviculture, including C management techniques. Despite their small extent in Europe, temperate old-growth forests are assumed to be among the most prominent in terms of biomass and C stored. However, monitoring and reporting of C stocks is still poorly understood. To better understand the C stock amount and distribution in temperate old-growth forests, we estimated the C stock of two old-growth stands in the Dinaric Alps applying different assessment methods, including direct and indirect approaches (e.g., field measurements and allometric equations vs. IPCC standard methods). This paper presents the quantification and the distribution of C across the five main forest C pools (i.e., aboveground, belowground, deadwood, litter and soil) in the study areas and the differences between the applied methods.

RESULTS

We report a very prominent C stock in both study areas (507 Mg C ha- 1), concentrated in a few large trees (36% of C in 5% of trees). Moreover, we found significant differences in C stock estimation between direct and indirect methods. Indeed, the latter tended to underestimate or overestimate depending on the pool considered.

CONCLUSIONS

Comparison of our results with previous studies and data collected in European forests highlights the prominence of temperate forests, among which the Dinaric Alps old-growth forests are the largest. These findings provide an important benchmark for the development of future approaches to the management of the European temperate forests. However, further and deeper research on C stock and fluxes in old-growth stands is of prime importance to understand the potential and limits of the climate mitigation role of forests.

A global meta-analysis on the effects of organic and inorganic fertilization on grasslands and croplands

A central role for nature-based solution is to identify optimal management practices to address environmental challenges, including carbon sequestration and biodiversity conservation. Inorganic fertilization increases plant aboveground biomass but often causes a tradeoff with plant diversity loss. It remains unclear, however, whether organic fertilization, as a potential nature-based solution, could alter this tradeoff by increasing aboveground biomass without plant diversity loss. Here we compile data from 537 experiments on organic and inorganic fertilization across grasslands and croplands worldwide to evaluate the responses of aboveground biomass, plant diversity, and soil organic carbon (SOC). Both organic and inorganic fertilization increase aboveground biomass by 56% and 42% relative to ambient, respectively. However, only inorganic fertilization decreases plant diversity, while organic fertilization increases plant diversity in grasslands with greater soil water content. Moreover, organic fertilization increases SOC in grasslands by 19% and 15% relative to ambient and inorganic fertilization, respectively. The positive effect of organic fertilization on SOC increases with increasing mean annual temperature in grasslands, a pattern not observed in croplands. Collectively, our findings highlight organic fertilization as a potential nature-based solution that can increase two ecosystem services of grasslands, forage production, and soil carbon storage, without a tradeoff in plant diversity loss.

Maximizing carbon sequestration potential in Chinese forests through optimal management

Forest carbon sequestration capacity in China remains uncertain due to underrepresented tree demographic dynamics and overlooked of harvest impacts. In this study, we employ a process-based biogeochemical model to make projections by using national forest inventories, covering approximately 415,000 permanent plots, revealing an expansion in biomass carbon stock by 13.6 ± 1.5 Pg C from 2020 to 2100, with additional sink through augmentation of wood product pool (0.6-2.0 Pg C) and spatiotemporal optimization of forest management (2.3 ± 0.03 Pg C). We find that statistical model might cause large bias in long-term projection due to underrepresentation or neglect of wood harvest and forest demographic changes. Remarkably, disregarding the repercussions of harvesting on forest age can result in a premature shift in the timing of the carbon sink peak by 1-3 decades. Our findings emphasize the pressing necessity for the swift implementation of optimal forest management strategies for carbon sequestration enhancement.

Hurricanes pose a substantial risk to New England forest carbon stocks

Nature-based climate solutions (NCS) are championed as a primary tool to mitigate climate change, especially in forested regions capable of storing and sequestering vast amounts of carbon. New England is one of the most heavily forested regions in the United States (>75% forested by land area), and forest carbon is a significant component of climate mitigation policies. Large infrequent disturbances, such as hurricanes, are a major source of uncertainty and risk for policies relying on forest carbon for climate mitigation, especially as climate change is projected to alter the intensity and extent of hurricanes. To date, most research into disturbance impacts on forest carbon stocks has focused on fire. Here, we show that a single hurricane in the region can down between 121 and 250 MMTCO2e or 4.6%-9.4% of the total aboveground forest carbon, much greater than the carbon sequestered annually by New England's forests (16 MMTCO2e year-1). However, emissions from hurricanes are not instantaneous; it takes approximately 19 years for downed carbon to become a net emission and 100 years for 90% of the downed carbon to be emitted. Reconstructing hurricanes with the HURRECON and EXPOS models across a range of historical and projected wind speeds, we find that an 8% and 16% increase in hurricane wind speeds leads to a 10.7- and 24.8-fold increase in the extent of high-severity damaged areas (widespread tree mortality). Increased wind speed also leads to unprecedented geographical shifts in damage, both inland and northward, into heavily forested regions traditionally less affected by hurricanes. Given that a single hurricane can emit the equivalent of 10+ years of carbon sequestered by forests in New England, the status of these forests as a durable carbon sink is uncertain. Understanding the risks to forest carbon stocks from disturbances is necessary for decision-makers relying on forests as a NCS.

How megadrought causes extensive mortality in a deep-rooted shrub species normally resistant to drought-induced dieback: The role of a biotic mortality agent

Southern California experienced unprecedented megadrought between 2012 and 2018. During this time, Malosma laurina, a chaparral species normally resilient to single-year intense drought, developed extensive mortality exceeding 60% throughout low-elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposed M. laurina to extensive shoot dieback and whole-plant death. We found that hydraulic conductance of stem xylem (Ks, native ) was reduced seven to 11-fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid-blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus, Botryosphaeria dothidea. We inoculated healthy M. laurina saplings with fungal isolates and compared hyphal elongation rates under well-watered, water-deficit, and carbon-deficit treatments. Relative to controls, we found that both water deficit and carbon-deficit increased hyphal extension rates and the incidence of shoot dieback.

Insights into Reactive Oxygen Species Production-Scavenging System Involved in Sugarcane Response to Xanthomonas albilineans Infection under Drought Stress

Plants must adapt to the complex effects of several stressors brought on by global warming, which may result in interaction and superposition effects between diverse stressors. Few reports are available on how drought stress affects Xanthomonas albilineans (Xa) infection in sugarcane (Saccharum spp. hybrids). Drought and leaf scald resistance were identified on 16 sugarcane cultivars using Xa inoculation and soil drought treatments, respectively. Subsequently, four cultivars contrasting to drought and leaf scald resistance were used to explore the mechanisms of drought affecting Xa-sugarcane interaction. Drought stress significantly increased the occurrence of leaf scald and Xa populations in susceptible cultivars but had no obvious effect on resistant cultivars. The ROS bursting and scavenging system was significantly activated in sugarcane in the process of Xa infection, particularly in the resistant cultivars. Compared with Xa infection alone, defense response via the ROS generating and scavenging system was obviously weakened in sugarcane (especially in susceptible cultivars) under Xa infection plus drought stress. Collectively, ROS might play a crucial role involving sugarcane defense against combined effects of Xa infection and drought stress.

Global production patterns: Understanding the relationship between greenhouse gas emissions, agriculture greening and climate variability

Climate change due to increased greenhouse gas emissions (GHG) in the atmosphere has been consistently observed since the mid-20th century. The profound influence of global climate change on greenhouse gas (GHG) emissions, encompassing carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), has established a vital feedback loop that contributes to further climate change. This intricate relationship necessitates a comprehensive understanding of the underlying feedback mechanisms. By examining the interactions between global climate change, soil, and GHG emissions, we can elucidate the complexities of CO2, CH4, and N2O dynamics and their implications. In this study, we evaluate the global climate change relationship with GHG globally in 246 countries. We find a robust positive association between climate and GHG emissions. By 2100, GHG emissions will increase in all G7 countries and China while decreasing in the United Kingdom based on current economic growth policies, resulting in a net global increase, suggesting that climate-driven increase in GHG and climate variations impact crop production loss due to soil impacts and not provide climate adaptation. The study highlights the diverse strategies employed by G7 countries in reducing GHG emissions, with France leveraging nuclear power, Germany focusing on renewables, and Italy targeting its industrial and transportation sectors. The UK and Japan are making significant progress in emission reduction through renewable energy, while the US and Canada face challenges due to their industrial activities and reliance on fossil fuels.

Global pattern of forest disturbances and its shift under climate change

Forests are continuously altered by disturbances. Yet, knowledge of global pattern of forest disturbance agents, its drivers, and shifts under changing climate remain scarce. Here we present a meta-analysis of current and projected (+2° and + 4 °C) distribution of forest disturbance agents causing immediate tree mortality (i.e., fire, pest outbreak, hydro-geomorphic, and wind) at country, continental, biome, and global scales. The model including combination of climatic (precipitation of driest quarter, actual evapotranspiration, and minimum temperature), geographical (distance to coast and topography complexity), and forest characteristics (tree density) performs better than any other model in explaining the distribution of disturbance agents (R2 = 0.74). We provide global maps (0.5° × 0.5°) of current and potential future distribution of forest disturbance agents. Globally, the most frequent disturbance agent was fire (46.09 %), followed by pest outbreak (23.27 %), hydro-geomorphic disturbances (18.97 %), and wind (11.67 %). Our projections indicate spatially contrasting shifts in disturbance agents, with fire and wind risk increase between ~50°S and ~ 40°N under warming climate. In particular, the substantial increase in fire risk, exceeding 31 % in the most affected areas, is projected over Mediterranean, the western and southeast USA, African, Oceanian, and South American forests. On the other hand, pest outbreak and hydro-geomorphic disturbances are projected to increase in more southern (> ~ 50°S) and northern (> ~ 40°N) latitudes. Our findings are critical for understanding ongoing changes and developing mitigation strategies to maintain the ecological integrity and ecosystem services under shifts in forest disturbances. We suggest that projected shifts in the global distribution of forest disturbance agents needs to be considered to future models of vegetation or carbon sink dynamics under projected climate change.

Neighbourhood species richness and drought-tolerance traits modulate tree growth and δ13 C responses to drought

Mixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are more resistant to drought than monospecific forests remains contested. In particular, the trait-based mechanisms driving the role of tree diversity under drought remain elusive. Using tree cores from a large-scale biodiversity experiment, we investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; δ13 C) to changes in climate-induced water availability (wet to dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. We hypothesized that neighbourhood species richness increases growth and decreases δ13 C and that these relationships are modulated by the abiotic (i.e. climatic conditions) and the biotic context. We characterised the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance versus resource acquisition and stomatal control. Tree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods. The effects of neighbourhood species richness and climate on growth and δ13 C were modulated by the traits of focal trees and the traits of their neighbours. At either end of each drought-tolerance gradient, species responded in opposing directions during dry and wet years. We show that species' drought-tolerance traits can explain the strength and nature of biodiversity-ecosystem functioning relationships in experimental tree communities experiencing drought. Mixing tree species can increase growth but may not universally relieve drought stress.

The impact of multifactorial stress combination on plants, crops, and ecosystems: how should we prepare for what comes next?

The complexity of environmental conditions encountered by plants in the field, or in nature, is gradually increasing due to anthropogenic activities that promote global warming, climate change, and increased levels of pollutants. While in the past it seemed sufficient to study how plants acclimate to one or even two different stresses affecting them simultaneously, the complex conditions developing on our planet necessitate a new approach of studying stress in plants: Acclimation to multiple stress conditions occurring concurrently or consecutively (termed, multifactorial stress combination [MFSC]). In an initial study of the plant response to MFSC, conducted with Arabidopsis thaliana seedlings subjected to an MFSC of six different abiotic stresses, it was found that with the increase in the number and complexity of different stresses simultaneously impacting a plant, plant growth and survival declined, even if the effects of each stress involved in such MFSC on the plant was minimal or insignificant. In three recent studies, conducted with different crop plants, MFSC was found to have similar effects on a commercial rice cultivar, a maize hybrid, tomato, and soybean, causing significant reductions in growth, biomass, physiological parameters, and/or yield traits. As the environmental conditions on our planet are gradually worsening, as well as becoming more complex, addressing MFSC and its effects on agriculture and ecosystems worldwide becomes a high priority. In this review, we address the effects of MFSC on plants, crops, agriculture, and different ecosystems worldwide, and highlight potential avenues to enhance the resilience of crops to MFSC.

Spatiotemporal patterns of net primary productivity of subtropical forests in China and its response to drought

Net primary productivity (NPP) is an important indicator used to evaluate the carbon sequestration capacity of forest ecosystems. Subtropical forest ecosystems play an indispensable role in maintaining the global carbon balance, while frequently occurring drought events in recent years have seriously damaged their productivity. However, the spatiotemporal patterns of NPP, as well as its response to drought, remain uncertain. In this study, the multiscale drought characteristics in subtropical China during 1981-2015 were analyzed based on the standardized precipitation evapotranspiration index. Then, simulated and analyzed the spatiotemporal NPP of subtropical forests by the boreal ecosystem productivity simulator model. Finally, the response of NPP to drought was analyzed based on multiple statistical indices. The results show that most regions in subtropical China experienced mild and moderate drought during 1981-2015. In particular, the extent of drought severity has shown a noticeable increasing trend after 2000. The forest NPP ranged from 622.64 to 1323.82 gC·m-2·a-1, with an overall increase rate of 16.15 gC·m-2·a-1; in particular, the contribution of the western forest NPP became increasingly important. Drought stress has limited the growth of subtropical forest NPP in China, with summer and wet season time scales of drought having the greatest impact on forest NPP anomalies, followed by autumn time scales. The limitation is mostly because the drought duration continually increased, leading to differences in the impact of drought on forest NPP before and after 2000, with declines of 59.55 % and 82.45 %, respectively, mainly concentrated in southwestern regions, such as Yunnan, Guangxi, and Sichuan provinces. This study quantitatively analyzed the impact of drought on subtropical forest NPP, and provides scientific basis for subtropical forest response and adaptation to climate change.

Impact of agricultural irrigation and resettlement practices on carbon storage in arid inland river basins: A case study of the Shule river basin

Agricultural irrigation and resettlement have significant impacts on carbon storage in arid inland river basins. With the background of "Comprehensive development measures for agricultural irrigation and resettlement in Shule River Basin (SRB)", this paper uses land use data to estimate regional carbon storage through InVEST model and revises the result by using net ecosystem productivity (NEP). The influence of land use change on carbon storage and the driving factors of carbon storage spatial differentiation were analyzed by using the optimal parameters geographical detector (OPGD). It can be inferred from the results that: (1) During 2000-2020, the increase of cropland and grassland area is the main type of land use change in the central oasis area of Yumen City and Guazhou County. Cumulative carbon storage increased by 1.75 × 107 t. (2) NEP in the central oasis area of Yumen City and Guazhou County showed a fluctuating upward trend, and it generally behaves as a carbon sink. The average annual NEP was 1.78 × 105 t, and the carbon sink increased by 0.95 × 105 t. (3) The main factors responsible for driving are vegetation, elevation, potential evapotranspiration, and precipitation. The explanatory power of each factor in carbon storage spatial differentiation was enhanced by the interaction between natural and anthropogenic factors. The interaction between vegetation and the human factor is more significant than that of the human single factor. (4) Agricultural irrigation and resettlement measures did not cause a decline in ecosystem carbon storage in Yumen City and Guazhou County in the central part of SRB. Conversely, the region's ecosystems have seen an increase in carbon storage as a result of the increase in cropland. (5) The introduction of the NEP modification method and the OPGD model improves the accuracy of carbon storage estimation and obtains better driving results in spatial differentiation. The study idea provides a new perspective for the estimation of carbon storage as a whole, and provides a reference basis for the formulation of ecological protection policies.

Potential of rice tillering for sustainable food production

Tillering, also known as shoot branching, is a fundamental trait for cereal crops such as rice to produce sufficient panicle numbers. Effective tillering that guarantees successful panicle production is essential for achieving high crop yields. Recent advances in molecular biology have revealed the mechanisms underlying rice tillering; however, in rice breeding and cultivation, there remain limited genes or alleles suitable for effective tillering and high yields. A recently identified quantitative trait locus (QTL) called MORE PANICLES 3 (MP3) has been cloned as a single gene and shown to promote tillering and to moderately increase panicle number. This gene is an ortholog of the maize domestication gene TB1, and it has the potential to increase grain yield under ongoing climate change and in nutrient-poor environments. This review reconsiders the potential and importance of tillering for sustainable food production. Thus, I provide an overview of rice tiller development and the currently understood molecular mechanisms that underly it, focusing primarily on the biosynthesis and signaling of strigolactones, effective QTLs, and the importance of MP3 (TB1). The possible future benefits in using promising QTLs such as MP3 to explore agronomic solutions under ongoing climate change and in nutrient-poor environments are also highlighted.

Even cooler insights: On the power of forests to (water the Earth and) cool the planet

Scientific innovation is overturning conventional paradigms of forest, water, and energy cycle interactions. This has implications for our understanding of the principal causal pathways by which tree, forest, and vegetation cover (TFVC) influence local and global warming/cooling. Many identify surface albedo and carbon sequestration as the principal causal pathways by which TFVC affects global warming/cooling. Moving toward the outer latitudes, in particular, where snow cover is more important, surface albedo effects are perceived to overpower carbon sequestration. By raising surface albedo, deforestation is thus predicted to lead to surface cooling, while increasing forest cover is assumed to result in warming. Observational data, however, generally support the opposite conclusion, suggesting surface albedo is poorly understood. Most accept that surface temperatures are influenced by the interplay of surface albedo, incoming shortwave (SW) radiation, and the partitioning of the remaining, post-albedo, SW radiation into latent and sensible heat. However, the extent to which the avoidance of sensible heat formation is first and foremost mediated by the presence (absence) of water and TFVC is not well understood. TFVC both mediates the availability of water on the land surface and drives the potential for latent heat production (evapotranspiration, ET). While latent heat is more directly linked to local than global cooling/warming, it is driven by photosynthesis and carbon sequestration and powers additional cloud formation and top-of-cloud reflectivity, both of which drive global cooling. TFVC loss reduces water storage, precipitation recycling, and downwind rainfall potential, thus driving the reduction of both ET (latent heat) and cloud formation. By reducing latent heat, cloud formation, and precipitation, deforestation thus powers warming (sensible heat formation), which further diminishes TFVC growth (carbon sequestration). Large-scale tree and forest restoration could, therefore, contribute significantly to both global and surface temperature cooling through the principal causal pathways of carbon sequestration and cloud formation.