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Although early theoretical work suggests that competition for light erodes successional diversity in forests, verbal models and recent numerical work with complex mechanistic forest simulators suggest that disturbance in such systems can maintain successional diversity. Nonetheless, if and how allocation trade-offs between competitors interact with disturbance to maintain high diversity in successional systems remains poorly understood. Here, using mechanistic and analytically tractable models, we show that a theoretically unlimited number of coexisting species can be maintained by allocational trade-offs such as investing in light-harvesting organs versus height growth, investing in reproduction versus growth or survival versus growth. The models describe the successional dynamics of a forest composed of many patches subjected to random or periodic disturbance, and are consistent with physiologically mechanistic terrestrial ecosystem models, including the terrestrial components of recent Earth System Models. We show that coexistence arises in our models because species specialize in the successional time they best exploit the light environment and convert resources into seeds or contribute to advance regeneration. We also show that our results are relevant to nonforested ecosystems by demonstrating the emergence of similar dynamics in a mechanistic model of competition for light among annual plant species. Finally, we show that coexistence in our models is relatively robust to the introduction of intraspecific variability that weakens the competitive hierarchy caused by asymmetric competition for light.

The CO 2 efflux from soil (soil respiration (SR)) is one of the largest fluxes in the global carbon (C) cycle and its response to climate change could strongly influence future atmospheric CO 2 concentrations. Still, a large divergence of global SR estimates and its autotrophic (AR) and heterotrophic (HR) components exists among process based terrestrial ecosystem models. Therefore, alternatively derived global benchmark values are warranted for constraining the various ecosystem model output. In this study, we developed models based on the global soil respiration database (version 5.0), using the random forest (RF) method to generate the global benchmark distribution of total SR and its components. Benchmark values were then compared with the output of ten different global terrestrial ecosystem models. Our observationally derived global mean annual benchmark rates were 85.5 ± 40.4 (SD) Pg C yr −1 for SR, 50.3 ± 25.0 (SD) Pg C yr −1 for HR and 35.2 Pg C yr −1 for AR during 1982–2012, respectively. Evaluating against the observations, the RF models showed better performance in both of SR and HR simulations than all investigated terrestrial ecosystem models. Large divergences in simulating SR and its components were observed among the terrestrial ecosystem models. The estimated global SR and HR by the ecosystem models ranged from 61.4 to 91.7 Pg C yr −1 and 39.8 to 61.7 Pg C yr −1 , respectively. The most discrepancy lays in the estimation of AR, the difference (12.0–42.3 Pg C yr −1 ) of estimates among the ecosystem models was up to 3.5 times. The contribution of AR to SR highly varied among the ecosystem models ranging from 18% to 48%, which differed with the estimate by RF (41%). This study generated global SR and its components (HR and AR) fluxes, which are useful benchmarks to constrain the performance of terrestrial ecosystem models.

The terrestrial ecosystems of North America have been identified as a sink of atmospheric CO 2 though there is no consensus on the magnitude. However, the emissions of non-CO 2 greenhouse gases (CH 4 and N 2 O) may offset or even overturn the climate cooling effect induced by the CO 2 sink. Using a coupled biogeochemical model, in this study, we have estimated the combined global warming potentials (GWP) of CO 2 , CH 4 and N 2 O fluxes in North American terrestrial ecosystems and quantified the relative contributions of environmental factors to the GWP changes during 1979–2010. The uncertainty range for contemporary global warming potential has been quantified by synthesizing the existing estimates from inventory, forward modeling, and inverse modeling approaches. Our “best estimate” of net GWP for CO 2 , CH 4 and N 2 O fluxes was −0.50 ± 0.27 Pg CO 2 eq/year (1 Pg = 10 15  g) in North American terrestrial ecosystems during 2001–2010. The emissions of CH 4 and N 2 O from terrestrial ecosystems had offset about two thirds (73 %±14 %) of the land CO 2 sink in the North American continent, showing large differences across the three countries, with offset ratios of 57 % ± 8 % in US, 83 % ± 17 % in Canada and 329 % ± 119 % in Mexico. Climate change and elevated tropospheric ozone concentration have contributed the most to GWP increase, while elevated atmospheric CO 2 concentration have contributed the most to GWP reduction. Extreme drought events over certain periods could result in a positive GWP. By integrating the existing estimates, we have found a wide range of uncertainty for the combined GWP. From both climate change science and policy perspectives, it is necessary to integrate ground and satellite observations with models for a more accurate accounting of these three greenhouse gases in North America.

Soil stores a large amount of the terrestrial ecosystem carbon (C) and plays an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in main types of ecosystems (including forest, grassland, cropland, and wetland) across 18 regions in China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated its changing trends during these 30 years. The SOC storage (0–100 cm) in Chinese terrestrial ecosystems was 83.46 ± 11.89 Pg C in the 1980s and 86.50 ± 8.71 Pg C in the 2010s, and the net increase over the 30 years was 3.04 ± 1.65 Pg C, with an overall rate of 0.101 ± 0.055 Pg C yr –1 . This increase was mainly observed in the topsoil (0–20 cm). Forests, grasslands, and croplands SOC storage increased 2.52 ± 0.77, 0.40 ± 0.78, and 0.07 ± 0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined 0.76 ± 0.29 Pg C, most likely because of the decrease of wetland area and SOC density. Combining these results with those of vegetation C sink (0.100 Pg C yr –1 ), the net C sink in Chinese terrestrial ecosystems was about 0.201 ± 0.061 Pg C yr –1 , which can offset 14.85%–27.79% of the fossil fuel C emissions from the 1980s to the 2010s. These first estimates of soil C sink based on field measured data supported the premise that China’s terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.

The Water Framework Directive protects groundwater-dependent terrestrial ecosystems, but its concepts and definitions remain unclear. This paper aims to clarify the margin of discretion for the Member States, by applying a cross-disciplinary legal and biological analysis. We conclude that description of the protected ecosystems must include at least key components and processes and be based on a number of well-known groundwater-dependent habitats, but not restricted to habitats fed entirely by groundwater. We argue that the potential harm to terrestrial ecosystems by lowering the groundwater table should include the impact of both water abstraction and drainage, and, despite the discretion regarding scale, we recommend basing assessments and protection at a landscape-scale that aligns with the scale of bodies of groundwater, which typically includes a range of habitats in various ecological conditions.

Over the past two decades, China has experienced frequent extreme events and substantial land cover changes. Site‐scale assessments of net ecosystem exchange (NEE) are constrained by the fixed land cover types at eddy covariance towers and short observation periods at existing sites. Using the Eurasian Meteorological Stations Net Ecosystem Exchange product (EAM‐NEE), this study evaluated China's carbon exchange dynamics from 2003 to 2018. Results show that southwestern forests exhibit the highest annual carbon sink capacity, while the establishment of national forest parks has contributed positively to enhancing the carbon sink capacity of northern forests. Substantial uncertainties in NEE evaluation were observed, largely due to variations in scales and thresholds. Our findings highlight the importance of site‐scale assessments in evaluating the carbon sink capacity and informing targeted strategies for China's dual‐carbon goals. Despite limitations in regional representation, the EAM‐NEE product provides valuable insights for localized assessments. Plain Language Summary Over the past two decades, China has faced increasingly frequent extreme events driven by global climate change, alongside significant changes in land cover. However, assessing the impacts of these changes on carbon exchange remains challenging due to limited observational data. This study analyzed carbon exchange dynamics in China from 2003 to 2018 using a carbon flux product from Eurasian meteorological stations. The findings revealed that, on an annual scale, forests in southwestern China exhibited the highest carbon sink capacity, while forests in central China demonstrated the strongest capacity during the growing season. Notably, carbon sink capacity significantly increased at northern forest sites located within national forest parks. Furthermore, most sites situated in China's national ecological function zones achieved enhanced carbon sink capacity following land cover changes. These results highlight the important role of site‐level assessments in supporting China's dual carbon goals. Additionally, our analysis of post‐drought carbon exchange recovery emphasizes the uncertainty introduced by the selection of recovery thresholds when evaluating drought impacts. Although the uneven distribution of sites in this carbon flux product poses challenges for regional studies, it offers valuable insights for site‐level assessments. Key Points China's southwestern forests have the highest annual carbon sink capacity National forest parks play a positive role in enhancing carbon sink capacity in northern forests The EAM‐NEE product provides a new perspective for site‐level carbon exchange studies in China

Crop harvested carbon (HC) is one of the most important components of the carbon cycle in cropland ecosystems, with a significant impact on the carbon budget of croplands. China is one of the most important crop producers, however, it is still unknown on the spatial and temporal variations of HC. This study collected statistical data on crop production at the province and county levels in China for all ten crop types from 1981 to 2020 and analyzed the magnitude and long-term trend of harvested crop carbon. Our results found a substantial increase of HC in cropland from 0.185 Gt C yr −1 in 1981 to 0.423 Gt C yr −1 in 2020 at a rate of 0.006 Gt C yr −1 . The results also highlighted that the average annual carbon sink removal from crop harvesting in China from 1981 to 2020 was 0.32 Gt C yr −1 , which was comparable to the net carbon sink of the entire terrestrial ecosystems in China. This study further generated a gridded dataset of HC from 2001 to 2019 in China by using jointly the statistical crop production and distribution maps of cropland. In addition, a model-data comparison was carried out using the dataset and results from seven state-of-the-art terrestrial ecosystem models, revealing substantial disparities in HC simulations in China compared to the dataset generated in the study. This study emphasized the increased importance of HC for estimating cropland carbon budget, and the produced dataset is expected to contribute to carbon budget estimation for cropland ecosystems and the entire China.

Atmospheric CO 2 variations across glacial-interglacial cycles are tightly linked to oceanic and terrestrial carbon reservoirs, but the contribution of weathering remains poorly constrained. Using a new PCM-weathering model (Past terrestrial Carbon storage Model coupling weathering sub-model), we reconstructed global silicate and carbonate weathering fluxes over the past 120,000 years. Silicate weathering was higher during interglacials (~ 125–163 Tg C/yr) and lower at glacials (~ 119–122 Tg C/yr), tracking atmospheric CO 2 . In contrast, carbonate weathering increased during glacials (~ 303–320 Tg C/yr) due to expanded land exposure resulting from glacial sea-level fall and declined at interglacials (~ 168–265 Tg C/yr). On glacial-interglacial timescales, total carbon consumption by silicate and carbonate weathering far exceeded changes in oceanic and terrestrial organic carbon pools. These results highlight a dynamic, compensatory balance between silicate and carbonate weathering in modulating Quaternary carbon fluxes.

In most terrestrial ecosystems, plant growth is limited by nitrogen and phosphorus. Adding either nutrient to soil usually affects primary production, but their effects can be positive or negative. Here we provide a general stoichiometric framework for interpreting these contrasting effects. First, we identify nitrogen and phosphorus limitations on plants and soil microorganisms using their respective nitrogen to phosphorus critical ratios. Second, we use these ratios to show how soil microorganisms mediate the response of primary production to limiting and non-limiting nutrient addition along a wide gradient of soil nutrient availability. Using a meta-analysis of 51 factorial nitrogen–phosphorus fertilization experiments conducted across multiple ecosystems, we demonstrate that the response of primary production to nitrogen and phosphorus additions is accurately predicted by our stoichiometric framework. The only pattern that could not be predicted by our original framework suggests that nitrogen has not only a structural function in growing organisms, but also a key role in promoting plant and microbial nutrient acquisition. We conclude that this stoichiometric framework offers the most parsimonious way to interpret contrasting and, until now, unresolved responses of primary production to nutrient addition in terrestrial ecosystems. A stoichiometric framework predicts the contrasting results of nutrient effects on primary production, with predicted responses supported by a meta-analysis of N–P fertilization experiments.

The global monitoring of solar-induced chlorophyll fluorescence (SIF) using satellite-based observations provides a new way of monitoring the status of terrestrial vegetation photosynthesis on a global scale. Several global SIF products that make use of atmospheric satellite data have been successfully developed in recent decades. The Terrestrial Ecosystem Carbon Inventory Satellite (TECIS-1), the first Chinese terrestrial ecosystem carbon inventory satellite, which is due to be launched in 2021, will carry an imaging spectrometer specifically designed for SIF monitoring. Here, we use an extensive set of simulated data derived from the MODerate resolution atmospheric TRANsmission 5 (MODTRAN 5) and Soil Canopy Observation Photosynthesis and Energy (SCOPE) models to evaluate and optimize the specifications of the SIF Imaging Spectrometer (SIFIS) onboard TECIS for accurate SIF retrievals. The wide spectral range of 670−780 nm was recommended to obtain the SIF at both the red and far-red bands. The results illustrate that the combination of a spectral resolution (SR) of 0.1 nm and a signal-to-noise ratio (SNR) of 127 performs better than an SR of 0.3 nm and SNR of 322 or an SR of 0.5 nm and SNR of 472 nm. The resulting SIF retrievals have a root-mean-squared (RMS) diff* value of 0.15 mW m−2 sr−1 nm−1 at the far-red band and 0.43 mW m−2 sr−1 nm−1 at the red band. This compares with 0.20 and 0.26 mW m−2 sr−1 nm−1 at the far-red band and 0.62 and 1.30 mW m−2 sr−1 nm−1 at the red band for the other two configurations described above. Given an SR of 0.3 nm, the increase in the SNR can also improve the SIF retrieval at both bands. If the SNR is improved to 450, the RMS diff* will be 0.17 mW m−2 sr−1 nm−1 at the far-red band and 0.47 mW m−2 sr−1 nm−1 at the red band. Therefore, the SIFIS onboard TECIS-1 will provide another set of observations dedicated to monitoring SIF at the global scale, which will benefit investigations of terrestrial vegetation photosynthesis from space.