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Priming effects of soil organic matter decomposition are critical to determine carbon budget and turnover in soil. Yet, the overall direction and intensity of soil priming remains under debate. A second‐order meta‐analysis was performed with 9296‐paired observations from 363 primary studies to determine the intensity and general direction of priming effects depending on the compound type, nutrient availability, and ecosystem type. We found that fresh carbon inputs induced positive priming effects (+37%) in 97% of paired observations. Labile compounds induced larger priming effects (+73%) than complex organic compounds (+33%). Nutrients (e.g., N, P) added with organic compounds reduced the intensity of priming effects compared to compounds without N and P, reflecting "nutrient mining from soil organic matter" as one of the main mechanisms of priming effects. Notably, tundra, lakebeds, wetlands, and volcanic soils showed much larger priming effects (+125%) compared to soils under forests, croplands, and grasslands (+24...+32%). Our findings highlight that positive priming effects are predominant in most soils at a global scale. Optimizing strategies to incorporate fresh organic matter and nutrients is urgently needed to offset the priming‐induced accelerated organic carbon turnover and possible losses. [ABSTRACT FROM AUTHOR]

In recent decades, the ubiquity of micro and nanoplastics (MNPs) pollution has emerged as a global concern due to its potential risks to both ecological and human health. The detrimental effects of MNPs have resulted in significant changes in the physicochemical and biological properties of terrestrial soil and benthic sediment. These alterations have led to a disrupted nutrient cycle, potential future climate hazards, and further impacts on ecosystem services. This review aims to discuss the possible origins, composition, abundance, life cycle, and transport processes of MNPs in aquatic and terrestrial ecosystems. It seeks to understand the potential ecological and human health risks associated with MNPs pollution and explores their implications for biodiversity conservation and ecosystem services. Moreover, this review highlights the advanced analytical techniques used to detect and quantify MNPs. It further suggests policy frameworks to combat this pollution in natural environments. The findings of this review are intended to assist environmentalists, microbiologists, hydrologists, and policymakers in identifying scientific gaps and pragmatic solutions to reduce MNPs pollution. Future research should investigate the intake mechanism and impact of MNPs on plants in different ecosystems, as well as their effects on food chains and human health. This will ensure that the ecological and human health risks associated with MNPs pollution can be timely mitigated. [ABSTRACT FROM AUTHOR]

Variation in herbivore pressure has often been predicted from patterns in plant traits considered as antiherbivore defences. Here, we tested whether spatial variation in field insect herbivory is associated with the variation in plant quality by conducting a meta‐analysis of 223 correlation coefficients between herbivory levels and the expression of selected plant traits. We found no overall correlation between herbivory and either concentrations of plant secondary metabolites or values of physical leaf traits. This result was due to both the large number of low correlations and the opposing directions of high correlations in individual studies. Field herbivory demonstrated a significant association only with nitrogen: herbivore pressure increased with an increase in nitrogen concentration in plant tissues. Thus, our meta‐analysis does not support either theoretical prediction, i.e., that plants possess high antiherbivore defences in localities with high herbivore pressure or that herbivory is low in localities where plant defences are high. We conclude that information about putative plant defences is insufficient to predict plant losses to insects in field conditions and that the only bottom‐up factor shaping spatial variation in insect herbivory is plant nutritive value. Our findings stress the need to improve a theory linking plant putative defences and herbivory. [ABSTRACT FROM AUTHOR]

Land use change (LUC) alters the global carbon (C) stock, but our estimation of the alteration remains uncertain and is a major impediment to predicting the global C cycle. The uncertainty is partly due to the limited number and geographical bias of observations, and limited exploration of its predictors. Here we generated a comprehensive global database of 5,980 observations from 790 articles. The number of sites evaluated is at least seven times larger than in previous meta‐analyses. Our constrained estimates of different LUC's effects on soil organic C (SOC) and their variations across global climates reveal underestimation/overestimation in previous estimates. Converting forests and grasslands to croplands reduced SOC by 24.5% ± 1.53% (−11.03 ± 1.06 Mg ha−1) and 22.7% ± 1.22% (−8.09 ± 0.67 Mg ha−1), while 28.0% ± 1.56% (4.46 ± 0.42 Mg ha−1) and 33.5% ± 1.68% (5.8 ± 0.38 Mg ha−1) increases, respectively, were obtained in the reverse processes. Converting forests to grasslands decreased SOC by 2.1% ± 1.22% (−1.13 ± 0.44 Mg ha−1), while the reverse process increased SOC by 18.6% ± 1.73% (3.31 ± 0.51 Mg ha−1). Modeled relative importance of 10 drivers of LUC's impact on SOC revealed that higher initial SOC (iSOC) does not solely determine SOC loss in SOC‐negative LUC scenarios as previously proposed. Across four decades, reconverting croplands to forests and grasslands recovered only 49.5% (6.1 ± 0.51 Mg ha−1) and 75.3% (7.0 ± 0.38 Mg ha−1) of the iSOC, respectively, indicating the need for protecting C‐rich ecosystems. Our global data set advances information on LUC's effect on SOC and can be valuable to constrain Earth system models to reliably estimate global SOC stocks and plan climate change mitigation strategies. Plain Language Summary: Land use change (LUC) could increase or decrease the global soil organic carbon (SOC) stock and affect carbon cycling and climate change, but estimating its effect size is the most uncertain aspect of the global carbon cycle. Available estimates vary among studies, most of which often use few observations that do not cover most global regions. To provide more accurate estimates of different LUC types' effects on SOC, we compiled a comprehensive database that contains 5,980 observations across all global regions; and revealed that previous studies have underestimated/overestimated these effects. We modeled the predictors of SOC change and found that previous conclusions that higher initial SOC is the main reason for higher organic carbon loss under negative LUC scenarios were inexact. We show that land use practices aimed at restoring SOC could only recover part of the amount lost during similar time frames; hence, it is important to protect carbon‐rich ecosystems. Our study provides robust estimates of LUC's effect on SOC and provides data sets that can reliably assess and model the global carbon cycle and plan strategies for controlling global climate change. Key Points: Comprehensive global database advances robust estimates of land use change's (LUCs) effect on soil organic carbon (SOC) vital for Earth system modelingHigher initial SOC does not solely control rapid SOC loss in carbon‐negative LUC as often proposedDespite SOC buildup in the past four decades, the amount lost cannot be regained by restoration during similar time frames [ABSTRACT FROM AUTHOR]

East Asia (China, Japan, Koreas, and Mongolia) has been the world's economic engine over at least the past two decades, exhibiting a rapid increase in fossil fuel emissions of greenhouse gases (GHGs) and has expressed the recent ambition to achieve climate neutrality by mid‐century. However, the GHG balance of its terrestrial ecosystems remains poorly constrained. Here, we present a synthesis of the three most important long‐lived greenhouse gases (CO2, CH4, and N2O) budgets over East Asia during the decades of 2000s and 2010s, following a dual constraint approach. We estimate that terrestrial ecosystems in East Asia is close to neutrality of GHGs, with a magnitude of between −46.3 ± 505.9 Tg CO2eq yr−1 (the top‐down approach) and −36.1 ± 207.1 Tg CO2eq yr−1 (the bottom‐up approach) during 2000–2019. This net GHG sink includes a large land CO2 sink (−1229.3 ± 430.9 Tg CO2 yr−1 based on the top‐down approach and −1353.8 ± 158.5 Tg CO2 yr−1 based on the bottom‐up approach) being offset by biogenic CH4 and N2O emissions, predominantly coming from the agricultural sectors. Emerging data sources and modeling capacities have helped achieve agreement between the top‐down and bottom‐up approaches, but sizable uncertainties remain in several flux terms. For example, the reported CO2 flux from land use and land cover change varies from a net source of more than 300 Tg CO2 yr−1 to a net sink of ∼−700 Tg CO2 yr−1. Although terrestrial ecosystems over East Asia is close to GHG neutral currently, curbing agricultural GHG emissions and additional afforestation and forest managements have the potential to transform the terrestrial ecosystems into a net GHG sink, which would help in realizing East Asian countries' ambitions to achieve climate neutrality. Plain Language Summary: East Asia (China, Japan, Koreas and Mongolia) is not only the hotspot of anthropogenic greenhouse gas (GHG, including CO2, CH4 and N2O) emissions, but also a region with large CO2 sink. However, the greenhouse gas balance of greenhouse gases over the region is poorly understood. In this study, we performed a synthesis for over 40 flux terms to provide the first‐of‐its‐kind GHG budget assessment over the decades of 2000s and 2010s. We find terrestrial ecosystems in East Asia is close to neutrality of GHGs. The bottom‐up approach summing up component fluxes estimated a net balance of −36.1 ± 207.1 Tg CO2eq yr−1, while the top‐down approach based on atmospheric inversions estimated a net balance of −46.3 ± 505.9 Tg CO2eq yr−1. This results from compensation of the large CO2 sink by CH4 and N2O emissions, and from compensation of net GHG sink over natural ecosystems by net GHG source over agricultural ecosystems. Thus, curbing agricultural GHG emissions has the potential to realizing the ambitious goal of achieving climate neutrality over East Asia. Key Points: A comprehensive greenhouse gas (CO2, CH4 and N2O) accounting including about 40 flux terms over East Asia is reportedTerrestrial ecosystems in East Asia are close to greenhouse gas neutralNatural ecosystems is a net greenhouse gas sink, compensated by a net source from agricultural ecosystems [ABSTRACT FROM AUTHOR]

Summary: Potassium (K+) is the most abundant inorganic cation in plant cells, playing a critical role in various plant functions. However, the impacts of K on natural terrestrial ecosystems have been less studied compared with nitrogen (N) and phosphorus (P).Here, we present a global meta‐analysis aimed at quantifying the response of aboveground production to K addition. This analysis is based on 144 field K fertilization experiments. We also investigate the influences of climate, soil properties, ecosystem types, and fertilizer regimes on the responses of aboveground production.We find that: K addition significantly increases aboveground production by 12.3% (95% CI: 7.4–17.5%), suggesting a widespread occurrence of K limitation across terrestrial ecosystems; K limitation is more prominent in regions with humid climates, acidic soils, or weathered soils; the effect size of K addition varies among climate zones/regions, and is influenced by multiple factors; and previous N : K and K : P thresholds utilized to detect K limitation in wetlands cannot be applied to other biomes.Our findings emphasize the role of K in limiting terrestrial productivity, which should be integrated into future terrestrial ecosystems models. [ABSTRACT FROM AUTHOR]

The carbon balance of the global ecosystems is significantly influenced by the soil organic carbon (SOC) pool in China's terrestrial ecosystems. Nevertheless, the current understanding of the main controlling factors of SOC in different ecosystems and their discrepancies is limited. The goal of this research was to better understand the human and environmental variables affecting SOC in China's terrestrial ecosystems. We designed a conceptual framework using 2674 samples collected from four ecosystems (grasslands, shrublands, wetlands, and croplands) in China during the 2000–2014 period, combining geodetector and multiple regression (MR) approaches to investigate the effects of environmental conditions, human activity, and their interplay on surface SOC (0–20 cm). Results showed that there were large discrepancies in the strength of influencing factors among different ecosystems. Total nitrogen (TN), mean annual temperature (MAT), and bulk density (BD) were the major factors influencing SOC in grasslands. BD, TN, and pH dominated in shrublands. For wetlands, SOC stocks were primarily attributed to maximum temperature (TMMX), MAT, and potential evapotranspiration (PET). Croplands are predominantly controlled by minimum temperature (TMMN), MAT, and TN. These results highlight that natural factors, particularly climatic and soil characteristics, were the dominant factors controlling SOC stocks in China's terrestrial ecosystems. This work also highlights that the interaction of two influencing factors, especially, pairs of soil characteristics factors, pairs of climate and soil characteristics factors, can well explain the drivers of SOC on the surface soil in China. Our study emphasizes the spatial heterogeneity of the factors that influence SOC in terrestrial ecosystems, enhancing knowledge of SOC at the national level, and providing the guideline for devising better policy to improve C sequestration and mitigate climate changes. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems play a central role in the global carbon cycle and climate mitigation due to their offering of a large carbon sink. More than one‐fifth of the geographical area of India, one of the largest nations on the Earth, is forested, which is highly diverse in vegetation and climate types, offers huge potential for carbon sequestration, but remains vulnerable to climate change. Hence, it is imperative to know the future changes in the terrestrial carbon budget over this region. Gross primary productivity (GPP) represents the carbon uptake by terrestrial ecosystems. The multimodel ensembles of GPP simulated by the sixth phase of the Coupled Model Intercomparison Project (CMIP6) provide a useful means in this regard. In this work, we study the strength and variability of GPP over India in the near‐past and future using these simulations. In future, all the models show an increasing trend in GPP, however, with widely varying trends. The preferred month of carbon uptake differs among the models. A comparison with a satellite biophysical record shows the models underestimated the GPP during the near‐past over India. The carbon uptake in the Eastern Himalaya dominates the Western Himalaya and central Indian regions. Specifically, till 2100, the growth rate of GPP varies from 4.9 to 16.69 gC m−2 y−2, from 2.47 to 18.91 gC m−2 y−2, and from 0.32 to 21.95 gC m−2 y−2 over these three regions, respectively. Plain Language Summary: Climate change is an imminent problem driven by greenhouse gases, with adverse impacts on the Earth system. Carbon dioxide is a major greenhouse gas. Plants offer a natural strategy to mitigate climate change by their photosynthetic carbon uptake. For climate change impact assessment, projections of climate models are widely used, developed from our understanding of the Earth system, as measured by the observations. India is a large and populous country that remains highly vulnerable to climate change; it also plays a key role in global climate change and its mitigation. However, to devise a suitable mitigation strategy the future carbon sequestration by the natural ecosystems in this region needs to be quantified. The World Climate Research Program developed the Coupled Model Intercomparison Project, a multi‐model ensemble study providing future projections of climate variables under different climate change scenarios. In this work, we use these ensembles to study the future photosynthetic carbon uptake over India and its three key forested regions. We find the photosynthetic carbon uptake to increase manifold over India, with significant inter‐model uncertainties. We also find the Eastern Himalaya to have stronger biospheric carbon removal from the atmosphere than the Western Himalaya and Central Indian regions. Key Points: Photosynthetic carbon uptake increases over India in future with the annual growth rate varying from 3 to 15 gC m−2 y−2The photosynthetic carbon uptake is larger in Eastern Himalaya compared to Western Himalaya and Central IndiaThere is a large discord on the strength, trend and variability of Gross primary productivity over India among CMIP6 models and Moderate Resolution Imaging Spectroradiometer [ABSTRACT FROM AUTHOR]

The biosphere is changing rapidly due to human endeavour. Because ecological communities underlie networks of interacting species, changes that directly affect some species can have indirect effects on others. Accurate tools to predict these direct and indirect effects are therefore required to guide conservation strategies. However, most extinction‐risk studies only consider the direct effects of global change—such as predicting which species will breach their thermal limits under different warming scenarios—with predictions of trophic cascades and co‐extinction risks remaining mostly speculative. To predict the potential indirect effects of primary extinctions, data describing community interactions and network modelling can estimate how extinctions cascade through communities. While theoretical studies have demonstrated the usefulness of models in predicting how communities react to threats like climate change, few have applied such methods to real‐world communities. This gap partly reflects challenges in constructing trophic network models of real‐world food webs, highlighting the need to develop approaches for quantifying co‐extinction risk more accurately. We propose a framework for constructing ecological network models representing real‐world food webs in terrestrial ecosystems and subjecting these models to co‐extinction scenarios triggered by probable future environmental perturbations. Adopting our framework will improve estimates of how environmental perturbations affect whole ecological communities. Identifying species at risk of co‐extinction (or those that might trigger co‐extinctions) will also guide conservation interventions aiming to reduce the probability of co‐extinction cascades and additional species losses. [ABSTRACT FROM AUTHOR]

Soil pH is critically important in regulating soil nutrients and thus influencing the biodiversity and ecosystem functions of terrestrial ecosystems. Despite the ongoing threat of nitrogen (N) pollution especially in the fast-developing regions, it remains unclear how increasing N deposition affects soil pH across global terrestrial ecosystems. By conducting a global meta-analysis with paired observations of soil pH under N addition and control from 634 studies spanning major types of terrestrial ecosystems, we show that soil acidification increases rapidly with N addition amount and is most severe in neutral-pH soils. Grassland soil pH decreases most strongly under high N addition while wetlands are the least acidified. By extrapolating these relationships to global mapping, we reveal that atmospheric N deposition leads to a global average soil pH decline of -0.16 in the past 40 years and regions encompassing Eastern United States, Southern Brazil, Europe, and South and East Asia are the hotspots of soil acidification under N deposition. Our results highlight that anthropogenically amplified atmospheric N deposition has profoundly altered global soil pH and chemistry. They suggest that atmospheric N deposition is a major threat to global terrestrial biodiversity and ecosystem functions. [ABSTRACT FROM AUTHOR]

Existing quantitative syntheses on how biodiversity responds to anthropogenic habitat change appear to sometimes mix different biodiversity metrics in drawing inferences. This "mixing metrics" practice, if prevalent, would considerably bias our understanding of biodiversity responses and render uninterpretable conclusions. However, the prevalence of this practice remains unknown, and the bias it potentially renders has not been empirically assessed. We fill this gap by conducting a systematic literature assessment of existing syntheses on biodiversity responses to habitat change, along with an analysis of a global database specifically on forest restoration. We found that the "mixing metrics" practice was used in almost a quarter of existing syntheses across a wide range of ecosystem and habitat change types. This practice predictably altered the quantitative, and frequently even the qualitative, inferences on biodiversity responses to forest restoration, in ways contingent on the composition of metrics mixed. We call on future syntheses to be cognizant of the difference in metric meaning and behaviors, and to avoid mixing different metrics in studying biodiversity responses to habitat change. [ABSTRACT FROM AUTHOR]

Forests sequester ∼25% of anthropogenic carbon (C) emissions annually and are of increasing interest for their potential as Nature‐based Climate Solutions (NbCS). Emergent from the need to assess terrestrial ecosystem health and quantify C storage and fluxes, several gridded products documenting terrestrial C and changes in C stocks over time have been developed. However, researchers have not yet systematically compared C distributions across products, or developed a clear path forward for investigating and leveraging this cross‐product uncertainty in estimates of terrestrial C. Alaniz et al. (2022, https://doi.org/10.1029/2021EF002560) synthesize multiple published products to constrain the distribution of forest C stocks and fluxes globally. Building off of their results, we comment on opportunities for advancing both basic science and NbCS policy recommendations through systematic product cross‐comparisons and targeting of areas with differing levels of uncertainties in the terrestrial C sink. Plain Language Summary: Forests absorb and store a large amount of the carbon from the CO2 emitted by humans. These forests also provide the potential for storing more human emitted CO2 that helps delay climate change through targeted forest management. However, for both natural sciences and management, careful documentation of the amount of carbon in forests and how it is changing is necessary. Over time the number of ways to measure and evaluate this carbon has increased. The synthesis in Alaniz et al. (2022, https://doi.org/10.1029/2021EF002560) of these numerous efforts provides an integrated view of carbon in forests and how it is changing. We propose expanding these observational synthesis efforts, leveraging uncertainty to help direct both basic scientific research and the potential for managing ecosystems to delay climate change. Key Points: Monitoring forest carbon is important both for basic science and climate change mitigationCross‐dataset comparisons are increasingly important with increasing data availability to characterize uncertaintyUncertainty in terrestrial carbon stocks and fluxes can be used to gain better process understanding and make policy recommendations [ABSTRACT FROM AUTHOR]

Evidence for the multifaceted responses of terrestrial ecosystems has been shown by the weakening of CO2 fertilization-induced and warming-controlled productivity gains. The intricate relationship between vegetation productivity and various environmental controls still remains elusive spatially. Here several inherent preponderances make China a natural experimental setting to investigate the interaction and relative contributions of five drivers to gross primary productivity for the period from 1982 to 2018 (i.e., elevated atmospheric CO2 concentrations, climate change, nutrient availability, anthropogenic land use change, and soil moisture) by coupling multiple long-term datasets. Despite a strikingly prominent enhancement of vegetation productivity in China, it exhibits similar saturation responses to the aforementioned environmental drivers (elevated CO2, climatic factors, and soil moisture). The CO2 fertilization-dominated network explains the long-term variations in vegetation productivity in humid regions, but its effect is clearly attenuated or even absent in arid and alpine environments controlled by climate and soil moisture. Divergence in interactions also provides distinct evidence that water availability plays an essential role in limiting the potential effects of climate change and elevated CO2 concentrations on vegetation productivity. Unprecedented industrialization and dramatic surface changes may have breached critical thresholds of terrestrial ecosystems under the diverse natural environment and thus forced a shift from a period dominated by CO2 fertilization to a period with nonlinear interactions. These findings suggest that future benefits in terrestrial ecosystems are likely to be counteracted by uncertainties in the complicated network, implying an increasing reliance on human societies to combat potential risks. Our results therefore highlight the need to account for the intricate interactions globally and thus incorporate them into mitigation and adaptation policies. [ABSTRACT FROM AUTHOR]

Elevated atmospheric CO2 (eCO2) influences the carbon assimilation rate and stomatal conductance of plants, thereby affecting the global cycles of carbon and water. Yet, the detection of these physiological effects of eCO2 in observational data remains challenging, because natural variations and confounding factors (e.g., warming) can overshadow the eCO2 effects in observational data of real‐world ecosystems. In this study, we aim at developing a method to detect the emergence of the physiological CO2 effects on various variables related to carbon and water fluxes. We mimic the observational setting in ecosystems using a comprehensive process‐based land surface model QUINCY to simulate the leaf‐level effects of increasing atmospheric CO2 concentrations and their century‐long propagation through the terrestrial carbon and water cycles across different climate regimes and biomes. We then develop a statistical method based on the signal‐to‐noise ratio to detect the emergence of the eCO2 effects. The eCO2 effect on gross primary productivity (GPP) emerges at relatively low CO2 increase (∆[CO2] ~ 20 ppm) where the leaf area index is relatively high. Compared to GPP, the eCO2 effect causing reduced transpiration water flux (normalized to leaf area) emerges only at relatively high CO2 increase (∆[CO2] >> 40 ppm), due to the high sensitivity to climate variability and thus lower signal‐to‐noise ratio. In general, the response to eCO2 is detectable earlier for variables related to the carbon cycle than the water cycle, when plant productivity is not limited by climatic constraints, and stronger in forest‐dominated rather than in grass‐dominated ecosystems. Our results provide a step toward when and where we expect to detect physiological CO2 effects in in‐situ flux measurements, how to detect them and encourage future efforts to improve the understanding and quantification of these effects in observations of terrestrial carbon and water dynamics. [ABSTRACT FROM AUTHOR]

Urbanization, agricultural production, natural resource extractions and climate change are global drivers of terrestrial ecosystem degradation and decline in ecosystem health. Assessing vegetation structures provides valuable direct and indirect information on biodiversity and ecosystem health, since plant communities govern terrestrial ecosystem functions and overall biodiversity.A growing body of literature supports the hypothesis that acoustic profiling and characterization of soundscapes may reveal natural patterns and ecosystem responses to environmental disturbances. Although assessments of ecosystem soundscapes are a promising tool for ecological monitoring, the influence of vegetation structure on acoustic indices remains largely unaddressed. An effective non‐invasive approach to monitoring ecosystem health includes use of active acoustic transducers, which convert mechanical/acoustic energy into electrical energy and visa‐versa.This article reviews and discusses possible applications (and also constraints) of active acoustic transducers in monitoring and assessments of terrestrial ecosystem health. Specifically, this article includes a brief introduction to the basic principles of sound and types of active acoustic transducers. Moreover, we provide reviews of common uses of active acoustic transducers in assessing plant structures and plant functional traits.We emphasize that active acoustic transducers can be used to analyse plant characteristics in a remote, scalable, non‐invasive and cost‐effective manner to characterize overall terrestrial ecosystem health. Suggestions and recommendations for future research and management directions that may facilitate applications of acoustic transducers to natural terrestrial landscapes are provided. [ABSTRACT FROM AUTHOR]

Terrestrial mammals shape their ecosystems, and mammalian community assemblages can be important indicators of ecosystem functioning and ecosystem changes over time. Numerous taxa of terrestrial mammals are currently threatened by habitat loss and face displacement to new geographical areas or systems to which they are less suited and where they may affect the original communities.Understanding past ecosystem changes is important for predicting future responses of species assemblages to changes in their environments. Thus, ecological and evolutionary history, as well as adaptive capacity, are important predictors of future population viability. Genomic and metagenomic approaches using environmental or ancient DNA offer a wealth of information regarding genome‐wide variation of changing communities or of taxonomic groups over time, which may help explain past changes and predict future responses of communities to changes in their environment; however, to date, such studies are relatively scarce.We review studies on environmental DNA and environmental genomics of terrestrial mammals to assess the potential of such approaches regarding past, contemporary, and future terrestrial ecosystems, identify inherent challenges, and discuss potential applications. We elaborate on lessons to be learned from mammal genomics of past ecosystems and compare metabarcoding with general metagenetic and metagenomic techniques. We provide a comprehensive overview of current applications, challenges, and future potential of environmental DNA with regards to terrestrial mammals.As current major challenges regarding mammalian eDNA we identify its scarcity and patchy distribution, along with the persistent necessity of genomic reference data. While the latter are steadily increasing, the former can only be tackled by explicitly mapping the environment to gain understanding of spatial eDNA distribution. Such understanding may facilitate informed choices of sample sites and substrates and, together with new sequencing techniques, this can allow mammalian eDNA to be maximally exploited as a source of biodiversity data. [ABSTRACT FROM AUTHOR]

To detect the response of permafrost to climate change in various terrestrial ecosystems, we established a permafrost monitoring network in 2007, which includes eight boreholes to monitor ground temperatures in forest, meadow, steppe, moderately dry steppe, and wetland ecosystems and three Automatic Weather Stations (AWS) to monitor climatic factors, such as wind speed (Ws), air temperature (Ta), relative humidity (RH), precipitation (P), solar radiation (Rs), net radiation (Rn), soil heat flux (SHF), soil temperature (Ts), and soil water content (SWC), in forest, meadow, and steppe ecosystems in north‐central Mongolia. Major indicators, including mean annual ground temperature (MAGT), active layer thickness (ALT), and depth of zero annual amplitude (DZAA), were estimated to detect permafrost degradation. The results show that MAGT has increased by 0.00–0.02°C per year (almost no change) in the ice‐poor permafrost areas and by 0.03–0.06°C per year in the ice‐rich permafrost on pingos and wetlands. ALT showed an annual increase of −0.78 to 0.36 cm (almost no change) in the forest and meadow ecosystems and 2.3–7.2 cm in wetland ecosystems, whereas it increased by 23.0–28.9 cm per year in the steppe ecosystems over the last decade. This implies that the permafrost has degraded more rapidly in the steppe ecosystems than in other ecosystems. Based on correlation analysis, ALT is correlated to P in the meadow ecosystems and to SWC in the forest ecosystem, and MAGT is correlated to RH. However, both ALT and MAGT show a close correlation with major climatic factors, such as Ta, RH, SHF, and SWC in the steppe ecosystem. DZAA shows a close negative correlation with Ta in all ecosystems. These results provide evidence for permafrost degradation and its different responses to climate change in various terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Plant litter decomposition is a key process for carbon (C) turnover in terrestrial ecosystems. Sunlight has been shown to cause and accelerate C release in semiarid ecosystems, yet the dose–response relationships for these effects have not been evaluated.We conducted a two‐phase experiment where plant litter of three species was subjected to a broad range of cumulative solar radiation (CSR) exposures under field conditions. We then evaluated the relationships between CSR exposure and abiotic mass loss, litter quality and the subsequent biotic decomposition and microbial activity in litter.Dose–response relationships demonstrated that CSR exposure was modestly correlated with abiotic mass loss but highly significantly correlated with lignin degradation, saccharification, microbial activity and biotic decay of plant litter across all species. Moreover, a comparison of these dose–response relationships suggested that small reductions in litter lignin due to exposure to sunlight may have large consequences for biotic decay.These results provide strong support for a model that postulates a critical role for lignin photodegradation in the mechanism of photofacilitation and demonstrate that, under natural field conditions, biotic degradation of plant litter is linearly related with the dose of solar radiation received by the material before coming into contact with decomposer microorganisms. [ABSTRACT FROM AUTHOR]

The premise that the intensity of biotic interactions decreases with increasing latitudes and elevations is broadly accepted; however, whether these geographical patterns can be explained within a common theoretical framework remains unclear. Our goal was to identify the general pattern of elevational changes in trophic interactions and to explore the sources of variation among the outcomes of individual studies. Meta‐analysis of 226 effect sizes calculated from 134 publications demonstrated a significant but interaction‐specific decrease in the intensity of herbivory, carnivory and parasitism with increasing elevation. Nevertheless, this decrease was not significant at high latitudes and for interactions involving endothermic organisms, for herbivore outbreaks or for herbivores living within plant tissues. Herbivory similarly declined with increases in latitude and elevation, whereas carnivory showed a fivefold stronger decrease with elevation than with latitude and parasitism increased with latitude but decreased with elevation. Thus, although these gradients share a general pattern and several sources of variation in trophic interaction intensity, we discovered important dissimilarities, indicating that elevational and latitudinal changes in these interactions are partly driven by different factors. We conclude that the scope of the latitudinal biotic interaction hypothesis cannot be extended to incorporate elevational gradients. [ABSTRACT FROM AUTHOR]

Aim: Soil fauna has a wide range of ecosystem functions. Anthropogenic atmospheric nitrogen (N) deposition affects the structure and function of soil fauna by changing the microenvironment and resources. Given that soil faunal responses can vary considerably among taxonomic groups, N deposition rate, and ecosystems, however, there is little consensus. We aimed to evaluate the effects of N deposition on different soil faunal taxa across different terrestrial ecosystems. Location: Global. Time period: 1970–2021. Major taxa studied: Soil fauna. Methods: We conducted a meta‐analysis that yielded 264 observations from 43 publications. We evaluated the responses to N addition of soil faunal abundance for three different taxa (nematodes, mites, collembolans) in three ecosystem types (cropland, forest, and grassland). Results: Our results showed an overall negative effect of N addition on soil fauna. However, the effect varied among soil faunal taxa. Specifically, N addition had no significant effects on the abundance of collembolans and mites in any ecosystem. On the other hand, N addition significantly reduced the abundance of all nematode trophic groups except bacterivores. The overall reduction of soil fauna is likely driven by the nematode response. The negative effects of N addition on nematode abundance were contingent on the N addition rate, N addition form, and ecosystem type. N addition decreased nematode abundance at N addition rates of more than 100 kg/ha/year. Inorganic N addition negatively affected nematode abundance. Finally, N addition had a greater adverse effect on nematodes in cropland and grassland compared to forest ecosystems. Main conclusions: Our results demonstrate the overall negative effects of N addition on nematode abundance. Excessive N addition should be avoided in cropland and grassland management. Further, we suggest the application of organic fertilizer instead of inorganic fertilizer to minimize the N‐induced negative effects on soil nematodes. [ABSTRACT FROM AUTHOR]

Land ecosystems contribute to climate change mitigation by taking up approximately 30% of anthropogenically emitted carbon. However, estimates of the amount and distribution of carbon uptake across the world's ecosystems or biomes display great uncertainty. The latter hinders a full understanding of the mechanisms and drivers of land carbon uptake, and predictions of the future fate of the land carbon sink. The latter is needed as evidence to inform climate mitigation strategies such as afforestation schemes. To advance land carbon cycle modeling, we have developed a matrix approach. Land carbon cycle models use carbon balance equations to represent carbon exchanges among pools. Our approach organizes this set of equations into a single matrix equation without altering any processes of the original model. The matrix equation enables the development of a theoretical framework for understanding the general, transient behavior of the land carbon cycle. While carbon input and residence time are used to quantify carbon storage capacity at steady state, a third quantity, carbon storage potential, integrates fluxes with time to define dynamic disequilibrium of the carbon cycle under global change. The matrix approach can help address critical contemporary issues in modeling, including pinpointing sources of model uncertainty and accelerating spin‐up of land carbon cycle models by tens of times. The accelerated spin‐up liberates models from the computational burden that hinders comprehensive parameter sensitivity analysis and assimilation of observational data to improve model accuracy. Such computational efficiency offered by the matrix approach enables substantial improvement of model predictions using ever‐increasing data availability. Overall, the matrix approach offers a step change forward for understanding and modeling the land carbon cycle. Plain Language Summary: Earth system models (ESMs) are the tools we have to predict future states of climate and ecosystems. However, land carbon cycle models, a critical component of ESMs, are highly diverse in both structures and predictions, hindering our ability to obtain consistent future projections. The latter is needed as part of the evidence base to inform climate change mitigation strategies. This paper describes a matrix approach that unifies land carbon cycle models in one matrix form. The matrix models offer consistency and simplicity in structure that make the models analytically tractable. In addition, the matrix approach provides a theoretical framework for understanding the general behavior of the land carbon cycle. More importantly, the matrix approach solves some key contemporary issues in land carbon cycle modeling, such as pinning down sources of model uncertainty and accelerating spin‐up. The accelerated spin‐up speeds up land carbon cycle simulations by tens of times, making it feasible to perform parameter sensitivity analysis and data assimilation to constrain models with big data. Overall, the matrix approach represents a step change forward for understanding and modeling the land carbon cycle. Key Points: The matrix approach unifies land carbon cycle models in a matrix form and thus helps gain simplicity in model structureThe matrix approach provides a theoretical framework to understand the general behavior of land carbon cycleIt helps address contemporary issues in land carbon cycle modeling, including pinning down model uncertainty and accelerating spin‐up [ABSTRACT FROM AUTHOR]

Phosphorus (P) control is critical to mitigating eutrophication in aquatic ecosystems, but the effectiveness of controlling P export from soils has been limited by our poor understanding of P dynamics along the land‐ocean aquatic continuum as well as the lack of well‐developed process models that effectively couple terrestrial and aquatic biogeochemical P processes. Here, we coupled riverine P biogeochemical processes and water transport with terrestrial processes within the framework of the Dynamic Land Ecosystem Model to assess how multiple environmental changes, including fertilizer and manure P uses, land use, climate, and atmospheric CO2, have affected the long‐term dynamics of P loading and export from the Mississippi River Basin to the Gulf of Mexico during 1901–2018. Simulations show that riverine exports of dissolved inorganic phosphorus (DIP), dissolved organic phosphorus, particulate organic phosphorus (POP), and particulate inorganic phosphorus (PIP) increased by 42%, 53%, 60%, and 53%, respectively, since the 1960s. Riverine DIP and PIP exports were the dominant components of the total P flux. DIP export was mainly enhanced by the growing mineral P fertilizer use in croplands, while increased PIP and POP exports were a result of the intensified soil erosion due to increased precipitation. Climate variability resulted in substantial interannual and decadal variations in P loading and export. Soil legacy P continues to contribute to P loading. Our findings highlight the necessity to adopt effective P management strategies to control P losses through reductions in soil erosion, and additionally, to improve P use efficiency in crop production. Plain Language Summary: Phosphorus enrichment in aquatic systems is one of the critical reasons for water quality degradation. Terrestrial ecosystems have received large amounts of phosphorus inputs and are a major phosphorus source for water bodies. Linking the phosphorus cycles in both terrestrial and aquatic ecosystems is helpful for understanding phosphorus flux from land to ocean. In this study, we simulated phosphorus processes in both terrestrial and aquatic systems and estimated phosphorus exports from the Mississippi River Basin to the Gulf of Mexico during 1901–2018. The simulated results show that riverine phosphorus exports have increased since the 1960s. The increasing usage of fertilizer and manure in agricultural activities as well as intensified erosion due to increasing extreme precipitation could be the major causes for the increasing riverine phosphorus export. This study provides insight into the mechanisms mediating riverine phosphorus exports over the past century in the context of global change. Key Points: An aquatic phosphorus module was incorporated into a land biosphere model to investigate phosphorus dynamics along the land‐ocean continuumSimulated riverine exports of dissolved inorganic phosphorus, dissolved organic phosphorus, particulate inorganic phosphorus, and particulate organic phosphorus from the Mississippi River Basin increased remarkably during 1901–2018The growing use of fertilizer and intensified soil erosion were the primary reasons for the increasing phosphorus exports [ABSTRACT FROM AUTHOR]

Potential for, and limits to, adaptation to environmental changes are critical for resilience and risk mitigation. The Mediterranean basin is a mosaic of biodiversity‐rich ecosystems long affected by human influence, whose resilience is now questioned by climate change. After reviewing the different components of biological adaptation, we present the main characteristics of marine and terrestrial biodiversity in the Mediterranean basin and of the pressures they face. Taking climatic trends into consideration, we discuss the adaptive potential of a range of ecosystems dominated by species without active dispersal. We argue that the high heterogeneity of Mediterranean landscapes and seascapes constitutes a laboratory for the study of adaptation when environmental conditions change rapidly and may provide opportunities for adaptation and adaptability of species and ecosystems. Adaptive management in the Mediterranean can and should harness the nature‐based solutions offered by both ecological and evolutionary processes for increasing the resilience of ecosystems to climate change. [ABSTRACT FROM AUTHOR]

Summary: Biodiversity today has the unusual property that 85% of plant and animal species live on land rather than in the sea, and half of these live in tropical rainforests. An explosive boost to terrestrial diversity occurred from c. 100–50 million years ago, the Late Cretaceous and early Palaeogene. During this interval, the Earth‐life system on land was reset, and the biosphere expanded to a new level of productivity, enhancing the capacity and species diversity of terrestrial environments. This boost in terrestrial biodiversity coincided with innovations in flowering plant biology and evolutionary ecology, including their flowers and efficiencies in reproduction; coevolution with animals, especially pollinators and herbivores; photosynthetic capacities; adaptability; and ability to modify habitats. The rise of angiosperms triggered a macroecological revolution on land and drove modern biodiversity in a secular, prolonged shift to new, high levels, a series of processes we name here the Angiosperm Terrestrial Revolution. [ABSTRACT FROM AUTHOR]

Impacts of nitrogen (N) enrichment on soil carbon (C) budgets in terrestrial ecosystems have been well documented by numerous field experiments and syntheses. Although previous studies have largely attributed this phenomenon to the increased organic C inputs, the potential mechanisms of how N enrichment increases soil organic C (SOC) remain contentious.In this study, we conducted a meta‐analysis comprising 234 published field N‐addition experiments from multiple terrestrial ecosystems across China to evaluate the impacts of N enrichment on the SOC budget.Although the meta‐analysis revealed that N‐addition significantly enhanced plant biomass and SOC concentration across the selected studies, we found that SOC concentration was independent of, or even decreased with, the enhanced plant biomass due to increased soil C loss as increasing organic C inputs. The negative correlation between plant C inputs and SOC under N enrichment, meanwhile, appeared reversible by the concomitant changes in soil pH, which depended on the magnitude of soil acidification. Increased SOC in terrestrial ecosystems was closely associated with decreased soil pH, which reduced soil C losses by limiting microbial degradation.Synthesis and applications. We suggest that soil carbon (C) budget is determined by the trade‐off between plant C inputs and nitrogen (N)‐induced soil acidification. In contrast to other studies, our findings demonstrate that N‐mediated soil acidification, rather than increased above‐ground C inputs, is the main driver increasing soil organic C (SOC) under elevated N inputs in terrestrial ecosystems of China. [ABSTRACT FROM AUTHOR]

Aim: Although some long‐term studies have been conducted to quantify the impacts of nitrogen (N) on plant productivity, uncertainties remain regarding whether these impacts change over time and the underlying mechanisms. By overlooking this, we might over‐ or underestimate the impacts of N on terrestrial ecosystems. Our goal was to determine whether the impacts of N on plant productivity change in the long term and what controls these dynamics. Location: Global. Time period: 1999–2018. Major taxa studied: Effects of N on plant productivity. Methods: We synthesized 63 N addition studies with duration ≥ 8 years in natural terrestrial ecosystems. Results: Our results showed temporally dynamic impacts of N on plant productivity in terrestrial ecosystems. The interannual coefficient of variation (CV) of N impacts ranged from 19 to 768% across 63 studies, with higher variability in acidic soils. Moreover, a substantial proportion (44%) of studies showed evidence of a consistent directional change in the strength of the impacts of N over time. The direction of change varied with biome type (forests, decrease; grasslands and shrublands, increase). The temporal pattern of the impacts of N was mostly responsive to mean annual precipitation (MAP), mean annual temperature (MAT) and initial soil pH, which accounted for 24%, 19% and 19% of the variation, respectively. Main conclusions: Our findings indicate that temporally dynamic impacts of long‐term N addition on plant productivity and large fluctuations of the impacts of N between years are generally observed among studies in terrestrial ecosystems. Therefore, not only the magnitude of N impacts on plant productivity, but also their temporal pattern and variability should be considered in future experimental and model research. [ABSTRACT FROM AUTHOR]

The Latitudinal Biotic Interaction Hypothesis (LBIH) states that the intensity of biotic interactions increases from high to low latitudes. This hypothesis, which may partly explain latitudinal gradients in biodiversity, remains hotly debated, largely due to variable outcomes of published studies. We used meta‐analysis to identify the scope of the LBIH in terrestrial ecosystems. For this purpose, we explored the sources of variation in the strength of latitudinal changes in herbivory, carnivory and parasitism (119 publications) and compared these gradients with gradients in the diversity of the respective groups of animals (102 publications). Overall, both herbivory and carnivory decreased towards the poles, while parasitism increased. The latitudinal gradient in herbivory and carnivory was threefold stronger above 50–60° than at lower latitudes and was significant due to interactions involving ectothermic consumers, studies using standardised prey (i.e. prey lacking local anti‐predator adaptations) and studies aimed at testing LBIH. The poleward decrease in biodiversity did not differ between ectothermic and endothermic animals or among climate zones and was fourfold stronger than decrease in herbivory and carnivory. The discovered differences between the gradients in biotic interactions and biodiversity suggest that these two global macroecological patterns are likely shaped by different factors. [ABSTRACT FROM AUTHOR]

Microplastic (plastic particles measuring <5mm) pollution is ubiquitous. Unlike in other well‐studied ecosystems, for example, marine and freshwater environments, microplastics in terrestrial systems are relatively understudied. Their potential impacts on terrestrial environments, in particular the risk of causing ecological surprise, must be better understood and quantified. Ecological surprise occurs when ecosystem behavior deviates radically from expectations and generally has negative consequences for ecosystem services. The properties and behavior of microplastics within terrestrial environments may increase their likelihood of causing ecological surprises as they (a) are highly persistent global pollutants that will last for centuries, (b) can interact with the abiotic environment in a complex manner, (c) can impact terrestrial organisms directly or indirectly and (d) interact with other contaminants and can facilitate their transport. Here, we compiled findings of previous research on microplastics in terrestrial environments. We systematically focused on studies addressing different facets of microplastics related to their distribution, dispersion, impact on soil characteristics and functions, levels of biological organization of tested terrestrial biota (single species vs. assemblages), scale of experimental study and corresponding ecotoxicological effects. Our systematic assessment of previous microplastic research revealed that most studies have been conducted on single species under laboratory conditions with short‐term exposures; few studies were conducted under more realistic long‐term field conditions and/or with multi‐species assemblages. Studies targeting multi‐species assemblages primarily considered soil bacterial communities and showed that microplastics can alter essential nutrient cycling functions. More ecologically meaningful studies of terrestrial microplastics encompassing multi‐species assemblages, critical ecological processes (e.g., biogeochemical cycles and pollination) and interactions with other anthropogenic stressors must be conducted. Addressing these knowledge gaps will provide a better understanding of microplastics as emerging global stressors and should lower the risk of ecological surprise in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2] (iCO2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2, albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change. See also the Commentary on this article by Way et al., 229: 2383–2385. [ABSTRACT FROM AUTHOR]

Summary: Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2] (iCO2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2, albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change. See also the Commentary on this article by Way et al., 229: 2383–2385. [ABSTRACT FROM AUTHOR]

Initial errors and model parameter errors are two of the main factors that produce uncertainties in numerical simulations and predictions. It is crucial to determine in advance which of these types of errors should be reduced to improve numerical simulations and increase their prediction skill. In this study, a fundamental issue related to studies of the predictability about terrestrial carbon cycle is discussed. The relative importance of initial errors and model parameter errors in causing the prediction uncertainty of net primary production (NPP), which is part of the terrestrial carbon cycle, is assessed. The errors in NPP predictions related to initial errors and parameter errors are evaluated within the Lund–Potsdam–Jena (LPJ) model using the conditional nonlinear optimal perturbation approach for these two types of errors (CNOP‐I and CNOP‐P, respectively). This method explores the upper bounds of the prediction errors caused by initial errors and model parameter errors at a particular time in the future. The contributions of initial errors and model parameter errors to NPP prediction uncertainty are found to depend on climate backgrounds and the prediction timescale. For the moist and semimoist regions of China, initial errors play a more important role than model parameter errors in the prediction uncertainty of NPP for short prediction times. As the prediction time scale increases, model parameter errors lead to large errors in NPP predictions. However, in the arid and semiarid regions of China, the uncertainty in NPP predictions caused by model parameter errors is always larger than that caused by initial errors. The above results can be explained by analyzing variations in photosynthesis and autotrophic respiration. The numerical results also suggest that the skill of predictions of the terrestrial carbon cycle may be improved by reducing the different types of errors for different climatic regions and prediction timescales. [ABSTRACT FROM AUTHOR]

Aims: Soil dissolved organic carbon (DOC) is a primary form of labile carbon in terrestrial ecosystems, and therefore plays a vital role in soil carbon cycling. This study aims to quantify the budgets of soil DOC at biome and global levels and to examine the variations in soil DOC and their environmental controls. Location: Global. Time period: 1981–2019. Methods: We compiled a global dataset and analysed the concentration and distribution of DOC across 10 biomes. Results: Large variations in DOC are found among biomes across space and the soil DOC concentration declines exponentially along soil depths. Tundra has the highest soil DOC concentration in 0–30 cm soils [453.75 (95% confidence interval: 324.95–633.5) mg/kg], whereas tropical and temperate forests have relatively lower DOC concentrations, ranging from 30.20 (24.78–36.80) to 54.54 (49.77–59.77) mg/kg. DOC generally accounts for < 1% of total organic carbon in soils, and DOC in 0–30 cm contributes more than half of the total DOC in the 0–100 cm soil profile. Furthermore, variations in DOC are primarily controlled by soil texture, moisture, and total organic carbon. Main conclusions: A global synthesis is combined with an empirical model to extrapolate the DOC concentration along soil profiles across the globe, and global budgets of DOC are estimated as 7.20 Pg C in the top 0–30 cm and 12.97 Pg C in the 0–100 cm soil profile, respectively, with a considerable variation among biomes. The strong soil texture control but weak total organic carbon (TOC) control on DOC variations suggest that the investigation of physical protection of soil organic carbon might need to expand to consider the labile C in soils. The global maps of DOC concentration serve as a benchmark for validating land surface models in estimating carbon storage in soils. [ABSTRACT FROM AUTHOR]

Biological nitrogen (N) fixation plays an important role in terrestrial N cycling and represents a key driver of terrestrial net primary productivity (NPP). Despite the importance of N fixation in terrestrial ecosystems, our knowledge regarding the controls on terrestrial N fixation remains poor. Here, we conducted a meta‐analysis (based on 852 observations from 158 studies) of N fixation across three types of ecosystems with different status of disturbance (no management, restoration [previously disturbed], and disturbance [currently disturbed]) and in response to multiple environmental change factors (warming, elevated carbon dioxide [CO2], increased precipitation, increased drought, increased N deposition, and their combinations). We explored the mechanisms underlying the changes in N fixation by examining the variations in soil physicochemical properties (bulk density, texture, moisture, and pH), plant and microbial characteristics (dominant plant species numbers, plant coverage, and soil microbial biomass), and soil resources (total carbon, total N, total phosphorus (P), inorganic N, and inorganic P). Human disturbance inhibited non‐symbiotic N fixation but not symbiotic N fixation. Terrestrial N fixation was stimulated by warming (+152.7%), elevated CO2 (+19.6%), and increased precipitation (+73.1%) but inhibited by increased drought (−30.4%), N deposition (−31.0%), and combinations of available multiple environmental change factors (−14.5%), the extents of which varied among biomes and ecosystem compartments. Human disturbance reduced the N fixation responses to environmental change factors, which was associated with the changes in soil physicochemical properties (2%‒56%, p <.001) and the declines in plant and microbial characteristics (3%‒49%, p ≤.003) and soil resources (6%‒48%, p ≤.03). Overall, our findings reveal for the first time the effects of multiple environmental change factors on terrestrial N fixation and indicate the role of human disturbance activities in inhibiting N fixation, which can improve our understanding, modeling, and prediction of terrestrial N budgets, NPP, and ecosystem feedbacks under global change scenarios. [ABSTRACT FROM AUTHOR]

The growth of the global terrestrial sink of carbon dioxide has puzzled scientists for decades. We propose that the role of land management practices—from intensive forestry to allowing passive afforestation of abandoned lands—have played a major role in the growth of the terrestrial carbon sink in the decades since the mid twentieth century. The Forest Transition, a historic transition from shrinking to expanding forests, and from sparser to denser forests, has seen an increase of biomass and carbon across large regions of the globe. We propose that the contribution of Forest Transitions to the terrestrial carbon sink has been underestimated. Because forest growth is slow and incremental, changes in the carbon density in forest biomass and soils often elude detection. Measurement technologies that rely on changes in two‐dimensional ground cover can miss changes in forest density. In contrast, changes from abrupt and total losses of biomass in land clearing, forest fires and clear cuts are easy to measure. Land management improves over time providing important present contributions and future potential to climate change mitigation. Appreciating the contributions of Forest Transitions to the sequestering of atmospheric carbon will enable its potential to aid in climate change mitigation. [ABSTRACT FROM AUTHOR]

Aim: The protection of phylogenetic diversity has become a priority in conservation biology, but its achievement requires a detailed understanding of (a) hotspots of phylogenetic diversity on a management‐relevant scale and (b) the land use and climate factors determining local phylogenetic diversity. In this study, we identified spatial patterns of taxonomic and phylogenetic diversity and their environmental drivers. Location: Bavaria, Germany. Methods: To map the cross‐taxon phylogenetic diversity, we combined species distribution data obtained from country‐wide monitoring programmes and phylogenetic trees of birds, bats, dragonflies, grasshoppers and butterflies and calculated the phylogenetic diversity standardized by species richness. Generalized additive models were used to test the effects of land use and climate on phylogenetic diversity. We identified hotspots of phylogenetic diversity and assessed the extent to which established protected areas in Bavaria cover these hotspots. Results: High coverage by urban areas, arable land and water bodies negatively affected the phylogenetic diversity of most species groups. The phylogenetic diversity of birds increased with increasing meadow cover. Climate did not influence the phylogenetic diversity of the studied groups. We identified 10 regional hotspots that contained the highest standardized phylogenetic diversity across the examined species groups. There was a strong mismatch between hotspots of phylogenetic diversity among the species groups. Protected areas (national parks, natural reserves and areas of the Flora‐Fauna‐Habitat Directive) overlapped only to ~9.6% with these hotspots of standardized phylogenetic diversity. Main conclusions: Cross‐taxon approaches are required to identify hotspots of phylogenetic diversity at a management‐relevant scale. At regional scales, land use was more important than climate in determining phylogenetic diversity. Our study highlights the importance of involving land users into strategies for protecting phylogenetic diversity. [ABSTRACT FROM AUTHOR]

As a carbon dioxide removal measure, the Norwegian government is currently considering a policy of large‐scale planting of spruce (Picea abies (L) H. Karst) on lands in various states of natural transition to a forest dominated by deciduous broadleaved tree species. Given the aspiration to bring emissions on balance with removals in the latter half of the 21st century in effort to limit the global mean temperature rise to "well below" 2°C, the effectiveness of such a policy is unclear given relatively low spruce growth rates in the region. Further convoluting the picture is the magnitude and relevance of surface albedo changes linked to such projects, which typically counteract the benefits of an enhanced forest CO2 sink in high‐latitude regions. Here, we carry out a rigorous empirically based assessment of the terrestrial carbon dioxide removal (tCDR) potential of large‐scale spruce planting in Norway, taking into account transient developments in both terrestrial carbon sinks and surface albedo over the 21st century and beyond. We find that surface albedo changes would likely play a negligible role in counteracting tCDR, yet given low forest growth rates in the region, notable tCDR benefits from such projects would not be realized until the second half of the 21st century, with maximum benefits occurring even later around 2150. We estimate Norway's total accumulated tCDR potential at 2100 and 2150 (including surface albedo changes) to be 447 (±240) and 852 (±295) Mt CO2‐eq. at mean net present values of US$ 12 (±3) and US$ 13 (±2) per ton CDR, respectively. For perspective, the accumulated tCDR potential at 2100 represents around 8 years of Norway's total current annual production‐based (i.e., territorial) CO2‐eq. emissions. [ABSTRACT FROM AUTHOR]

The feedback between plant, soil and climate is partly determined by plant litter turnover time, which is influenced by climate, litter quality and soil properties. However, the spatial patterns of litter turnover time and its interrelation with these variables are rarely quantified. With a database of 1,378 litter turnover times and key associated climate, litter quality and soil properties (total of 20 variables), this study investigated the driving factors and spatial patterns of litter turnover time across Chinese terrestrial ecosystems. The mean litter turnover time was the longest in forest ecosystems, followed by that in grassland and cropland ecosystems. The litter turnover time varied significantly depending on the litter quality and climate zone, and increased exponentially as latitude increased. Mean annual temperature (MAT) and mean annual precipitation (MAP) could accurately predict litter turnover time via negative exponential equations. Among these variables, MAT had the greatest influence on litter turnover time, which accounted for 37.4% of the variation, followed by litter quality (ecosystem types, litter types, C:N of litter and lignin content; 33.4%) and soil properties (sand content, soil pH and soil organic carbon (SOC); 29.2%) based on a boosted regression tree (BRT) model. Path analysis identified that MAT negatively affected litter turnover time both directly and indirectly through regulating soil properties and litter quality, which positively and directly affected litter turnover time. Finally, the spatial patterns of litter turnover time were obtained with a regional dataset of ecosystem types, MAT, sand content, soil pH and SOC as BRT model drivers. Overall, our results suggest that climate variables have contrasting effects on litter turnover time and could mediate the impact on litter turnover time by litter quality and soil properties. These results highlight important implications for climate‐smart soil management and can be used to create reliable model predictions. Highlights: We explored the driving factors and spatial patterns of litter turnover time in various ecosystemsAccurate estimates of litter turnover time were obtained from dataset from 1,378 experimental sitesLitter turnover time exponentially increased as latitude increasedClimate‐mediated litter quality and soil properties controlled the litter turnover time [ABSTRACT FROM AUTHOR]

Understanding changes in terrestrial carbon balance is important to improve our knowledge of the regional carbon cycle and climate change. However, evaluating regional changes in the terrestrial carbon balance is challenging due to the lack of surface flux measurements. This study reveals that the terrestrial carbon uptake over the Republic of Korea has been enhanced from 1999 to 2017 by analyzing long‐term atmospheric CO2 concentration measurements at the Anmyeondo Station (36.53°N, 126.32°E) located in the western coast. The influence of terrestrial carbon flux on atmospheric CO2 concentrations (ΔCO2) is estimated from the difference of CO2 concentrations that were influenced by the land sector (through easterly winds) and the Yellow Sea sector (through westerly winds). We find a significant trend in ΔCO2 of −4.75 ppm per decade (p <.05) during the vegetation growing season (May through October), suggesting that the regional terrestrial carbon uptake has increased relative to the surrounding ocean areas. Combined analysis with satellite measured normalized difference vegetation index and gross primary production shows that the enhanced carbon uptake is associated with significant nationwide increases in vegetation and its production. Process‐based terrestrial model and inverse model simulations estimate that regional terrestrial carbon uptake increases by up to 18.9 and 8.0 Tg C for the study period, accounting for 13.4% and 5.7% of the average annual domestic carbon emissions, respectively. Atmospheric chemical transport model simulations indicate that the enhanced terrestrial carbon sink is the primary reason for the observed ΔCO2 trend rather than anthropogenic emissions and atmospheric circulation changes. Our results highlight the fact that atmospheric CO2 measurements could open up the possibility of detecting regional changes in the terrestrial carbon cycle even where anthropogenic emissions are not negligible. [ABSTRACT FROM AUTHOR]

Aim: To study global patterns and temporal changes in the seasonal dynamics (quantity and seasonal distribution) of terrestrial gross carbon uptake in response to global environmental change. Location: Global. Time period: 2000–2016. Major taxa studied: Terrestrial ecosystems. Methods: Following a phenology‐based definition of photosynthetic seasonality, we decompose gross primary production (GPP) into three periods, green‐up, maturity and senescence, and derive their corresponding GPP (GPPgp, GPPmp and GPPsp, respectively) from a newly developed time series of satellite‐based global GPP to study spatio‐temporal dynamics of seasonal GPP. Results: We find that the global fraction of GPPsp (19.8%) is larger than GPPgp (14.3%), indicating a globally asymmetric seasonal distribution of gross carbon uptake by terrestrial ecosystems. Globally, GPPmp plays a dominant role in shaping spatial patterns and increasing/decreasing trends in GPP, while GPPgp/GPPsp contributes to increasing GPP at the regional scale. Higher fractions of GPPgp/GPPmp (lower of GPPsp), as well as the co‐occurrence of increasing GPP and non‐tree vegetation cover in major croplands, are likely to be caused by agricultural intensification. Global changes in GPPgp and GPPsp are closely related to changes in their seasonal distributions (R =.86/.8, respectively), whereas this relationship is weaker for GPPmp (R =.53). Finally, high correlations are observed between changes in GPPgp and GPPsp and changes in their durations (R =.78/.78, respectively), while GPPmp shows a relatively lower correlation with its duration (R =.67). Main conclusions: The asymmetric spatio‐temporal patterns in the seasonal dynamics of global terrestrial gross carbon uptake found here have been substantially reshaped by anthropogenic land‐use/cover changes and changes in photosynthetic phenology. Compared to calendar‐based meteorological seasons more suitable for temperate/subpolar ecosystems, our phenology‐based approach is expected to provide an alternative starting point for a better understanding of global spatio‐temporal changes in the seasonal dynamics of terrestrial ecosystem processes and functioning under accelerating global change. [ABSTRACT FROM AUTHOR]

The Society for Ecological Restoration (SER) Primer identifies key ecosystem attributes for evaluating restoration outcome. Broad attribute categories could be necessary due to the large variety of restoration projects, but could make overall evaluations and assessments challenging and might hamper the development of sound and successful restoration. In this study we carry out a systematic review of scientific papers addressing evaluation of restoration outcome. We include 104 studies published after 2010 from Europe or North America, representing different types of restoration projects in terrestrial and freshwater ecosystems. We explore the main ecological and socioeconomic attributes used to evaluate restoration outcome, and related indicators and specific methods applied to measure this, in relation to ecosystem and type of restoration project. We identify a wide range of indicators within each attribute, and show that very different methods are employed to measure them. This complexity reduces the opportunity for meaningful comparison and standardization of evaluation of restoration outcome, within and between ecosystems. Socioeconomic indicators are rarely used to evaluate restoration outcome, and studies including both ecological and socioeconomic indicators are nearly absent. Based on our findings we discuss whether standardization and streamlining of indicators is useful to improve the evaluation of "on the ground" restoration, or if this is not appropriate given the diversity of goals and ecosystems involved. Species‐specific traits are used in many projects and should be considered as an addition to the original SER attributes. Furthermore, we discuss the potential for restoration evaluation that encompasses not only assessment of ecological but also socioeconomic indicators. [ABSTRACT FROM AUTHOR]

There are inherent challenges in scaling stomatal conductance (g s) from leaf to canopy particularly over seasonal time scales when species distribution and canopy structure evolve. We address this gap using carbonyl sulfide (OCS) and CO 2 fluxes from a predominantly C3 prairie and C4 maize field in the midwestern United States. The g s derived from OCS fluxes captured a transition in the stomatal limitation on gross primary productivity (GPP) through the growing season as well as seasonally persistent g s dynamics such as temperature optimum and a positive response of nighttime g s to vapor pressure deficit. Near the termination of the prairie growing season, we observed a decrease in the relative OCS to CO 2 flux that we hypothesize emerged from a rising contribution of C4 plants to productivity. The results show how plot‐scale OCS and CO 2 fluxes can be used as a trace gas diagnostic for transitions in the limiting factors for community GPP. Key Points: Canopy stomatal conductance was derived from carbonyl sulfide (OCS) fluxes at maize and prairie sites in the midwestern United StatesSeasonal changes in the ratio of canopy stomatal conductance to GPP elucidated phenological transitions in community photosynthesisDaytime and nighttime OCS and CO 2 fluxes can be used for diagnostic trace gas signatures associated with C3 and C4 productivity [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Plastic pollution is of increasing societal concern, particularly with regard to aquatic environments, where it has received widespread news media attention. However, plastic and plastic byproducts also pollute terrestrial ecosystems, and the potential impacts on organisms are currently poorly understood. Here, we show that a microplastic type used in artificial sport turfs may have negative effects on plant growth. Given the scale of plastic pollution, urgent research is needed to determine the impact of microplastics on terrestrial organisms and their communities, as well as an exploration of alternative, biodegradable materials and measures to reduce the spread of microplastics in nature. SummaryThe Anthropocene is, among other factors, characterized by the accumulation of plastic in the environment. While studies on the consequences of plastic pollution for animals, particularly in aquatic environments, have increased in recent years, much less is known about potential effects of plastic pollution on plants in terrestrial environments.Ethylene propylene diene monomer (EPDM) is a microplastic used in artificial sport turfs. Here, we tested in two separate experiments the effects of different concentrations of EPDM on the performance of Plantago lanceolata and on competition between seven grassland‐plant species.At very low concentrations of the EPDM granules, growth of P. lanceolata was slightly improved, but at concentrations of 5% and higher there were strong negative effects on survival and growth. These negative effects were found under low and high nutrient conditions, and for all tested species. The EPDM granules also negatively affected the root weight ratio, which indicates that the root system was more strongly affected than the shoot. Due to the strong negative effects on plant growth, the granules also reduced the competitive interactions between plants.Our study shows that it is not only animals in aquatic environments that may be affected by plastic pollution, and that this may also be the case for wild plants in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Uncovering the plant‐soil feedback mechanisms underlying the assembly of belowground microbial communities is essential for terrestrial biodiversity conservation. However, little is known about the small‐scale spatial assembly processes of distinct soil microorganisms, especially during natural restoration of ex‐arable ecosystems.We examined the spatial structure of soil microbiomes in arable land and reforested soils to elucidate the underlying assembly processes at a small spatial scale. The analysis was based on a MiSeq sequencing database, detecting the diversity of archaeal, bacterial and fungal communities, simultaneously, from 300 soil samples along vertical and horizontal profiles during 30‐year reforestation.Compared with environmental filtering, dispersal limitation made crucial contributions to microbial community assembly. Archaeal and bacterial communities with a wider niche breadth were governed more by dispersal limitation than were fungal communities.The effect of dispersal limitation on archaeal and bacterial communities increased first and then decreased over time, while the effect on fungi temporally increased.Synthesis and applications. Our results highlight the variation of assembly processes governing distinct soil microbiomes during reforestation, with dispersal limitation playing a prominent role. This finding suggests that the increase in soil microbial diversity during natural restoration is mainly due to the stochastic influx and dispersal of microorganisms. This greater understanding of microbial community assembly can contribute to more targeted and efficient environmental management practices for the restoration of terrestrial ecosystems, for example, by promoting the restoration practices and shortening the restoration period. These practices may thus be incorporated into policies developed for effective biodiversity conservation, especially the restoration and maintenance of subsurface soil microbial diversity and associated functions. [ABSTRACT FROM AUTHOR]

With accumulation of carbon cycle observations and model developments over the past decades, exploring interannual variation (IAV) of terrestrial carbon cycle offers the opportunity to better understand climate–carbon cycle relationships. However, despite growing research interest, uncertainties remain on some fundamental issues, such as the contributions of different regions, constituent fluxes and climatic factors to carbon cycle IAV. Here we overviewed the literature on carbon cycle IAV about current understanding of these issues. Observations and models of the carbon cycle unanimously show the dominance of tropical land ecosystems to the signal of global carbon cycle IAV, where tropical semiarid ecosystems contribute as much as the combination of all other tropical ecosystems. Vegetation photosynthesis contributes more than ecosystem respiration to IAV of the global net land carbon flux, but large uncertainties remain on the contribution of fires and other disturbance fluxes. Climatic variations are the major drivers to the IAV of net land carbon flux. Although debate remains on whether the dominant driver is temperature or moisture variability, their interaction,that is, the dependence of carbon cycle sensitivity to temperature on moisture conditions, is emerging as key regulators of the carbon cycle IAV. On timescales from the interannual to the centennial, global carbon cycle variability will be increasingly contributed by northern land ecosystems and oceans. Therefore, both improving Earth system models (ESMs) with the progressive understanding on the fast processes manifested at interannual timescale and expanding carbon cycle observations at broader spatial and longer temporal scales are critical to better prediction on evolution of the carbon–climate system. [ABSTRACT FROM AUTHOR]

The early‐successional status of lichens in modern terrestrial ecosystems, together with the role lichen‐mediated weathering plays in the carbon cycle, have contributed to the long and widely held assumption that lichens occupied early terrestrial ecosystems prior to the evolution of vascular plants and drove global change during this time. Their poor preservation potential and the classification of ambiguous fossils as lichens or other fungal–algal associations have further reinforced this view. As unambiguous fossil data are lacking to demonstrate the presence of lichens prior to vascular plants, we utilize an alternate approach to assess their historic presence in early terrestrial ecosystems. Here, we analyze new time‐calibrated phylogenies of ascomycete fungi and chlorophytan algae, that intensively sample lineages with lichen symbionts. Age estimates for several interacting clades show broad congruence and demonstrate that fungal origins of lichenization postdate the earliest tracheophytes. Coupled with the absence of unambiguous fossil data, our work finds no support for lichens having mediated global change during the Neoproterozoic‐early Paleozoic prior to vascular plants. We conclude by discussing our findings in the context of Neoproterozoic‐Paleozoic terrestrial ecosystem evolution and the paleoecological context in which vascular plants evolved. [ABSTRACT FROM AUTHOR]

Biological nitrogen (N) fixation (BNF), an important source of N in terrestrial ecosystems, plays a critical role in terrestrial nutrient cycling and net primary productivity. Currently, large uncertainty exists regarding how nutrient availability regulates terrestrial BNF and the drivers responsible for this process. We conducted a global meta‐analysis of terrestrial BNF in response to N, phosphorus (P), and micronutrient (Micro) addition across different biomes (i.e, tropical/subtropical forest, savanna, temperate forest, grassland, boreal forest, and tundra) and explored whether the BNF responses were affected by fertilization regimes (nutrient‐addition rates, duration, and total load) and environmental factors (mean annual temperature [MAT], mean annual precipitation [MAP], and N deposition). The results showed that N addition inhibited terrestrial BNF (by 19.0% (95% confidence interval [CI]: 17.7%‒20.3%); hereafter), Micro addition stimulated terrestrial BNF (30.4% [25.7%‒35.3%]), and P addition had an inconsistent effect on terrestrial BNF, i.e., inhibiting free‐living N fixation (7.5% [4.4%‒10.6%]) and stimulating symbiotic N fixation (85.5% [25.8%‒158.7%]). Furthermore, the response ratios (i.e., effect sizes) of BNF to nutrient addition were smaller in low‐latitude (<30°) biomes (8.5%‒36.9%) than in mid‐/high‐latitude (≥30°) biomes (32.9%‒61.3%), and the sensitivity (defined as the absolute value of response ratios) of BNF to nutrients in mid‐/high‐latitude biomes decreased with decreasing latitude (p ≤ 0.009; linear/logarithmic regression models). Fertilization regimes did not affect this phenomenon (p > 0.05), but environmental factors did affect it (p < 0.001) because MAT, MAP, and N deposition accounted for 5%‒14%, 10%‒32%, and 7%‒18% of the variance in the BNF response ratios in cold (MAT < 15°C), low‐rainfall (MAP < 2,500 mm), and low‐N‐deposition (<7 kg ha−1 year−1) biomes, respectively. Overall, our meta‐analysis depicts a global pattern of nutrient impacts on terrestrial BNF and indicates that certain types of global change (i.e., warming, elevated precipitation and N deposition) may reduce the sensitivity of BNF in response to nutrient enrichment in mid‐/high‐latitude biomes. [ABSTRACT FROM AUTHOR]

Land use and climate changes both affect terrestrial ecosystems. Here, we used three combinations of Shared Socioeconomic Pathways and Representative Concentration Pathways (SSP1xRCP26, SSP3xRCP60, and SSP5xRCP85) as input to three dynamic global vegetation models to assess the impacts and associated uncertainty on several ecosystem functions: terrestrial carbon storage and fluxes, evapotranspiration, surface albedo, and runoff. We also performed sensitivity simulations in which we kept either land use or climate (including atmospheric CO2) constant from year 2015 on to calculate the isolated land use versus climate effects. By the 2080–2099 period, carbon storage increases by up to 87 ± 47 Gt (SSP1xRCP26) compared to present day, with large spatial variance across scenarios and models. Most of the carbon uptake is attributed to drivers beyond future land use and climate change, particularly the lagged effects of historic environmental changes. Future climate change typically increases carbon stocks in vegetation but not soils, while future land use change causes carbon losses, even for net agricultural abandonment (SSP1xRCP26). Evapotranspiration changes are highly variable across scenarios, and models do not agree on the magnitude or even sign of change of the individual effects. A calculated decrease in January and July surface albedo (up to −0.021 ± 0.007 and −0.004 ± 0.004 for SSP5xRCP85) and increase in runoff (+67 ± 6 mm/year) is largely driven by climate change. Overall, our results show that future land use and climate change will both have substantial impacts on ecosystem functioning. However, future changes can often not be fully explained by these two drivers and legacy effects have to be considered. Key Points: Future climate change will increase terrestrial carbon stocks, while future land use change will decrease terrestrial carbon stocksFuture climate change and land use change will also affect a range of ecosystem functions beyond carbon storageHowever, future changes in ecosystem functioning can often not be explained by future climate change and future land use change alone [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) are two dominant nutrients regulating the productivity of most terrestrial ecosystems. The growing imbalance of anthropogenic N and P inputs into the future is estimated to exacerbate P limitation on land and limit the land carbon (C) sink, so that we hypothesized that P limitation will increasingly reduce C sequestered per unit N deposited into the future. Using a global land surface model (CABLE), we simulated the effects of increased N deposition with and without P limitation on land C uptake and the fate of deposited N on land from 1901 to 2100. Contrary to our hypothesis, we found that N deposition continued to induce land C sequestration into the future, contributing to 15% of future C sequestration as opposed to 6% over the historical period. P limitation reduced the future land C uptake per unit N deposited only moderately at the global scale but P limitation increasingly caused N deposition to have net negative effects on the land C balance in the temperate zone. P limitation further increased the fraction of deposited N that is lost via leaching to aquatic ecosystems, globally from 38.5% over the historical period to 53% into the future, and up to 75% in tropical ecosystems. Our results suggest continued N demand for plant productivity but also indicate growing adverse N deposition effects in the future biosphere, not fully accounted for in global models, emphasizing the urgent need to elaborate on model representations of N and P dynamics. Plain Language Summary: Human activity has altered the cycling of the most essential nutrients for live, namely nitrogen and phosphorus. Due to the use of industrial fertilizers and the combustion of fossil fuels, nitrogen enters ecosystems via atmospheric deposition in much higher rates than phosphorus, creating a nutritional imbalance. We use a global land surface model to estimate the effect of nitrogen deposition on global ecosystems in the past and in the future. We speculated that due to the heightened availability of nitrogen in the future, limitations by phosphorus would become more pronounced. We find that nitrogen deposition continues to have fertilizing effects on plant growth that is otherwise limited by nitrogen supply. Phosphorus limitations become more prevalent in the future in our simulations but not as strong as we expected. Alarmingly, however, we find that an increasing amount of nitrogen is lost from terrestrial ecosystems and enters aquatic ecosystems with expected deleterious effects. Our results highlight one possible scenario of our future world, indicating that many uncertainties remain in regard to nutrient supply and interactions, all of which, however, need to be understood and quantified to predict global vegetation responses to and interactions with the future climate. Key Points: N deposition continues to induce land C sequestration into the 21st century as N demand is sustained by CO2 fertilizationPhosphorus limitations cause nitrogen deposition to have net negative effects on plant growth in some temperate regions with excess N supplyCurrent land surface model representations likely underestimate direct negative effects of excess N supply [ABSTRACT FROM AUTHOR]

Present gaps in the representation of key soil biogeochemical processes such as the partitioning of soil organic carbon among functional components, microbial biomass and diversity, and the coupling of carbon and nutrient cycles present a challenge to improving the reliability of projected soil carbon dynamics. We introduce a new soil biogeochemistry module linked with a well‐tested terrestrial biosphere model T&C. The module explicitly distinguishes functional soil organic carbon components. Extracellular enzymes and microbial pools are differentiated based on the functional roles of bacteria, saprotrophic, and mycorrhizal fungi. Soil macrofauna is also represented. The model resolves the cycles of nitrogen, phosphorus, and potassium. Model simulations for 20 sites compared favorably with global patterns of litter and soil stoichiometry, microbial and macrofaunal biomass relations with soil organic carbon, soil respiration, and nutrient mineralization rates. Long‐term responses to bare fallow and nitrogen addition experiments were also in agreement with observations. Some discrepancies between predictions and observations are appreciable in the response to litter manipulation. Upon successful model reproduction of observed general trends, we assessed patterns associated with the carbon cycle that were challenging to address empirically. Despite large site‐to‐site variability, fine root, fungal, bacteria, and macrofaunal respiration account for 33%, 40%, 24%, and 3% on average of total belowground respiration, respectively. Simulated root exudation and carbon export to mycorrhizal fungi represent on average about 13% of plant net primary productivity. These results offer mechanistic and general estimates of microbial biomass and its contribution to respiration fluxes and to soil organic matter dynamics. Key Points: We introduce a new microbial explicit soil biogeochemistry module into a terrestrial biosphere modelUncalibrated model simulations compared favorably with global patterns of soil biogeochemistry processesResults offer mechanistic estimates of microbe contribution to soil respiration and carbon dynamics [ABSTRACT FROM AUTHOR]

Keywords: biodiversity; climate change; climate change experiments; climate projections; ecosystem functioning; global circulation models; terrestrial ecosystems Biodiversity, climate change, climate change experiments, climate projections, ecosystem functioning, global circulation models, terrestrial ecosystems. [Extracted from the article]