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Grazing can affect plant community composition and structure directly by foraging and indirectly by increasing wind erosion and dust storms and subsequently influence ecosystem functioning and ecological services. However, the combined effects of grazing, wind erosion, and dust deposition have not been explored. As part of a 7-year (2010–2016) field manipulative experiment, this study was conducted to examine the impacts of grazing and simulated aeolian processes (wind erosion and dust deposition) on plant community cover and species richness in a temperate steppe on the Mongolian Plateau, China. Grazing decreased total cover by 4.2%, particularly the cover of tall-stature plants (> 20 cm in height), but resulted in 9.1% greater species richness. Wind erosion also reduced total cover by 17.0% primarily via suppressing short-stature plants associated with soil nitrogen loss, but had no effect on species richness. Dust deposition enhanced total cover by 5.7%, but resulted in a 7.3% decrease in species richness by driving some of the short-stature plant species to extinction. Both wind erosion and dust deposition showed additive effects with grazing on vegetation cover and species richness, though no detectable interaction between aeolian processes and grazing could be detected due to our methodological constraints. The changes in gross ecosystem productivity, ecosystem respiration, and net ecosystem productivity under the wind erosion and dust deposition treatments were positively related to aeolian process-induced changes in vegetation cover and species richness, highlighting the important roles of plant community shifts in regulating ecosystem carbon cycling. Our findings suggest that plant traits (for example, canopy height) and soil nutrients may be the key for understanding plant community responses to grassland management and natural hazards.

Asymmetrically seasonal warming has been widely observed on the Earth, but great uncertainties remain for its effects on terrestrial carbon (C) cycling. As a part of a 7-year seasonal warming experiment in an old-field grassland in Central China, this study demonstrated that spring and autumn warming reduced soil respiration by 8.3% and 9.8%, respectively. In addition, spring warming decreased soil respiration by 1.0% and 15.9% without and with autumn warming, respectively. Autumn warming suppressed soil respiration by 2.5% and 17.2% without and with spring warming, respectively. Decreased soil respiration in summer under both spring and autumn warming dominated the treatment-induced suppressions in annual mean soil respiration, which could be primarily attributable to the reductions in plant photosynthesis and growth (aboveground net primary productivity). These observations suggest that the asymmetrically seasonal warming may diminish soil C loss and its feedback to climate warming. Our findings highlight the urgent need of incorporating the interactive and legacy effects of seasonal warming into models used in the IPCC reports for the robust projections of future climate change.

Changing precipitation regimes can profoundly affect plant growth in terrestrial ecosystems, especially in arid and semi-arid regions. However, how changing precipitation, especially extreme precipitation events, alters plant diversity and community composition is still poorly understood. A 3-year field manipulative experiment with seven precipitation treatments, including - 60%, - 40%, - 20%, 0% (as a control), + 20%, + 40%, and + 60% of ambient growing-season precipitation, was conducted in a semi-arid steppe in the Mongolian Plateau. Results showed total plant community cover and forb cover were enhanced with increased precipitation and reduced under decreased precipitation, whereas grass cover was suppressed under the - 60% treatment only. Plant community and grass species richness were reduced by the - 60% treatment only. Moreover, our results demonstrated that total plant community cover was more sensitive to decreased than increased precipitation under normal and extreme precipitation change, and species richness was more sensitive to decreased than increased precipitation under extreme precipitation change. The community composition and low field water holding capacity may drive this asymmetric response. Accumulated changes in community cover may eventually lead to changes in species richness. However, compared to control, Shannon-Weiner index (H) did not respond to any precipitation treatment, and Pielou's evenness index (E) was reduced under the + 60% treatment across the 3 year, but not in each year. Thus, the findings suggest that plant biodiversity in the semi-arid steppe may have a strong resistance to precipitation pattern changes through adjusting its composition in a short term.

Direct quantification of terrestrial biosphere responses to global change is crucial for projections of future climate change in Earth system models. Here, we synthesized ecosystem carbon-cycling data from 1,119 experiments performed over the past four decades concerning changes in temperature, precipitation, CO2 and nitrogen across major terrestrial vegetation types of the world. Most experiments manipulated single rather than multiple global change drivers in temperate ecosystems of the USA, Europe and China. The magnitudes of warming and elevated CO2 treatments were consistent with the ranges of future projections, whereas those of precipitation changes and nitrogen inputs often exceeded the projected ranges. Increases in global change drivers consistently accelerated, but decreased precipitation slowed down carbon-cycle processes. Nonlinear (including synergistic and antagonistic) effects among global change drivers were rare. Belowground carbon allocation responded negatively to increased precipitation and nitrogen addition and positively to decreased precipitation and elevated CO2. The sensitivities of carbon variables to multiple global change drivers depended on the background climate and ecosystem condition, suggesting that Earth system models should be evaluated using site-specific conditions for best uses of this large dataset. Together, this synthesis underscores an urgent need to explore the interactions among multiple global change drivers in under-represented regions such as semi-arid ecosystems, forests in the tropics and subtropics, and Arctic tundra when forecasting future terrestrial carbon-climate feedback. National Natural Science Foundation of ChinaNational Natural Science Foundation of China [31430015, 31830012]; US NSFNational Science Foundation (NSF) [DEB-0955771]; ClimMani COST actionEuropean Cooperation in Science and Technology (COST) [ES1308] We thank J. Wang (Hebei University), S. Yang (Institute of Botany, Chinese Academy of Sciences), L. Zhou (East China Normal University), C. Qiao (Xinyang Normal University) and H. Li (Henan University) for their help in meta-analyses and interaction analyses, and H. Li, Y. Liu (Institute of Tibetan Plateau Research, Chinese Academy of Sciences) and Y. He (Peking University) for their help in plotting figures. This work was financially supported by the National Natural Science Foundation of China (grant nos. 31430015 and 31830012). This study emerged from the INTERFACE Workshop in Beijing, China (https://www.bio.purdue.edu/INTERFACE/) supported by the US NSF DEB-0955771. We also acknowledge support from the ClimMani COST action (ES1308). Public domain – authored by a U.S. government employee

Numerous ecosystem manipulative experiments have been conducted since 1970/80 s to elucidate responses of terrestrial carbon cycling to the changing atmospheric composition (CO2 enrichment and nitrogen deposition) and climate (warming and changing precipitation regimes), which is crucial for model projection and mitigation of future global change effects. Here, we extract data from 2,242 publications that report global change manipulative experiments and build a comprehensive global database with 5,213 pairs of samples for plant production (productivity, biomass, and litter mass) and ecosystem carbon exchange (gross and net ecosystem productivity as well as ecosystem and soil respiration). Information on climate characteristics and vegetation types of experimental sites as well as experimental facilities and manipulation magnitudes subjected to manipulative experiments are also included in this database. This global database can facilitate the estimation of response and sensitivity of key terrestrial carbon-cycling variables under future global change scenarios, and improve the robust projection of global change‒terrestrial carbon feedbacks imposed by Earth System Models., Measurement(s) organic material • plant production • carbon exchange Technology Type(s) digital curation Factor Type(s) climate characteristics • vegetation traits Sample Characteristic - Environment climate system Sample Characteristic - Location global Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12932843