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Asexual reproduction plays a fundamental role in the structure, dynamics and persistence of perennial grasslands. Thus, assessing how asexual reproductive traits of plant communities respond to drought may be key for understanding grassland resistance to drought and recovery following drought.Here, we quantified three asexual reproductive traits (i.e. above‐ground tiller abundance, below‐ground bud abundance and the ratio of tillers to buds) during a 4‐year severe drought and a 2‐year drought recovery period in four grasslands that spanned an aridity gradient in northern China. We also assessed the relationship between these traits and the resistance and recovery of above‐ground net primary productivity (ANPP).We found that drought had limited and largely inconsistent effects on asexual reproduction among drought and recovery years and grasslands overall. Drought increased tiller abundance in the first treatment year and reduced bud banks by the fourth treatment year across grasslands. However, neither of the three asexual reproductive traits were correlated with drought resistance of ANPP. Drought legacies differed among the four grasslands with positive, negative and no legacies evident for the three asexual reproductive traits, and no clear relationship with aridity. Bud banks and tiller to bud ratio decreased and increased, respectively, in the first recovery year, but not in the second recovery year. In contrast to drought resistance, community bud abundance was strongly related to recovery, such that communities with higher bud abundance had greater ANPP recovery following drought.Synthesis. These results suggest that asexual reproductive traits may be important drivers of ecosystem recovery after drought, but that variable responses of these asexual reproduction traits during drought complicates predictions of overall grassland responses. [ABSTRACT FROM AUTHOR]

Plant traits are useful proxies of plant strategies and can influence community and ecosystem responses to climate extremes, such as severe drought. Few studies, however, have investigated both the immediate and lagged effects of drought on community‐weighted mean (CWM) plant traits, with even less research on the relative roles of interspecific vs. intraspecific trait variability in such responses.We experimentally reduced growing season precipitation by 66% in two cold‐semi‐arid grassland sites in northern China for four consecutive years to explore the drought resistance of CWM traits as well as their recovery 2 years following the drought. In addition, we isolated the effects of both interspecific and intraspecific trait variability on shifts in CWM traits.At both sites, we observed significant effects of drought on interspecific and intraspecific trait variability which, in some cases, led to significant changes in CWM traits. For example, drought led to reduced CWM plant height and leaf phosphorous content, but increased leaf carbon content at both sites, with responses primarily due to intraspecific trait shifts. Surprisingly, these CWM traits recovered completely 2 years after the extreme drought. Intraspecific trait variability influenced CWM traits via both positive and negative covariation with interspecific trait variability during drought and recovery phases.These findings highlight the important role of interspecific and intraspecific trait variability in driving the response and recovery of CWM traits following extreme, prolonged drought. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Biodiversity can stabilise productivity through different mechanisms, such as asynchronous species responses to environmental variability and species stability. Global changes, like intensified drought, could negatively affect species richness, species asynchrony and species stability, but it is unclear how changes in these mechanisms will affect the stability of above‐ground primary productivity (ANPP) across ecosystems.We studied the effects of a 4‐year extreme drought on ANPP stability and the underlying mechanisms (species richness, species asynchrony and species stability) across six grasslands in Northern China. We also assessed the relative importance of these mechanisms in determining ANPP stability under extreme drought.We found that extreme drought decreased ANPP stability, species richness, species asynchrony and species stability across the six grasslands. However, structural equation modelling revealed that species asynchrony, not species richness or species stability, was the most important mechanism promoting stability of ANPP, regardless of drought across the six grasslands.Synthesis. Our results suggest that species asynchrony, not species richness and species stability, consistently buffers ecosystem stability against extreme drought across and within grasslands spanning a broad precipitation gradient. Thus, species asynchrony may be a more general mechanism for promoting stability of ANPP in grasslands in the face of intensified drought. [ABSTRACT FROM AUTHOR]

Background and aims: Grasslands are expected to experience droughts of unprecedented magnitude and duration in this century. Plant traits can be useful for understanding community and ecosystem responses to climate extremes. Few studies, however, have investigated the response of community-scale traits to extreme drought on broad spatial/temporal scales, with even less research on the relative contribution of species turnover vs. intraspecific trait variation to such responses. Methods: We experimentally removed ~66% of growing season rainfall for three years across three semi-arid grasslands of northern China and tracked changes in community functional composition, defined as the community mean and variation of several leaf economic traits. Results: Community trait variations were more sensitive to drought than community trait means, which suggests this component of functional composition may be a better indicator of initial community drought responses than trait values themselves. The greatest change in trait variation was observed at the high aridity site and was driven largely by intraspecific trait variability. Apart from specific leaf area, trait variability increased with increasing aridity across sites, largely due to species turnover. Variations in soil moisture and fertility likely mediated the responses of community trait variations to water stress. Conclusions: These results highlight the importance of measuring community trait variability in response to drought and support the well-documented pattern of increased community drought sensitivity of more arid ecosystems. [ABSTRACT FROM AUTHOR]

Nitrogen (N) enrichment often increases aboveground net primary productivity (ANPP) of the ecosystem, but it is unclear if belowground net primary productivity (BNPP) track responses of ANPP. Moreover, the frequency of N inputs may affect primary productivity but is rarely studied. To assess the response patterns of above‐ and belowground productivity to rates of N addition under different addition frequencies, we manipulated the rate (0–50 g N m−2 year−1) and frequency (twice vs. monthly additions per year) of NH4NO3 inputs for six consecutive years in a temperate grassland in northern China and measured ANPP and BNPP from 2012 to 2014. In the low range of N addition rates, BNPP showed the greatest negative response and ANPP showed the greatest positive responses with increases in N addition (<10 g N m−2 year−1). As N addition increased beyond 10 g N m−2 year−1, increases in ANPP dampened and decreases in BNPP ceased altogether. The response pattern of net primary productivity (combined above‐ and belowground; NPP) corresponded more closely to ANPP than to BNPP. The N effects on BNPP and BNPP/NPP (fBNPP) were not dependent on N addition frequency in the range of N additions typically associated with N deposition. BNPP was more sensitive to N addition frequency than ANPP, especially at low rates of N addition. Our findings provide new insights into how plants regulate carbon allocation to different organs with increasing N rates and changing addition frequencies. These root response patterns, if incorporated into Earth system models, may improve the predictive power of C dynamics in dryland ecosystems in the face of global atmospheric N deposition. [ABSTRACT FROM AUTHOR]

• Soil samples were collected along an isohyet to minimize the precipitation effect. • Soil C, N, P and their ratios responded negatively to increasing temperature. • Soil C and N decreased faster than soil P as temperature increased. • Changing temperature induced the imbalance of soil C-N-P. Responses of terrestrial ecosystems to global warming have gained widespread attention. Soil carbon: nitrogen: phosphorus (C:N:P) stoichiometry regulate various functions and services in terrestrial ecosystems. Investigating the stoichiometric changes of soil C:N:P along the temperature gradient provides valuable insights into the long-term impacts of global warming. However, the inconsistent results were found in previous studies. The collinearity between temperature and precipitation might account for it since the variation in precipitation was rarely limited in previous studies. To make the precipitation effect become minimized, we conducted a 6000-km soil investigation along the 400 mm isohyet in China with a broad mean annual temperature (MAT) range of 14.2 °C. Soil C, N and P concentrations and soil C:N, C:P and N:P ratios all decreased with increasing MAT. Most of these temperature patterns were not affected by vegetation type and soil type, which indicated that the decreasing trends of soil C:N:P stoichiometry with increasing temperature might be common phenomena. MAT is the most important influential factor of soil C and N concentrations and soil C:P and N:P ratios along the temperature gradient; and soil properties, vegetation and soil types also exerted some effects on the changes of soil C and N concentrations and soil C:P and N:P ratios. For soil P, its variation was jointly influenced by MAT, soil properties, vegetation and soil types. The change of soil C:N ratio was mainly influenced by MAT and vegetation type. Furthermore, the decreased soil C:P and N:P ratios with increasing MAT indicated that soil C and N lowered faster than soil P as temperature increased, leading to the imbalanced soil C-N-P. [ABSTRACT FROM AUTHOR]

• Resistance and resilience of grassland to multi-year extreme drought were tested. • Resistance decreased as the drought progressed over time. • Longer recovery time was critical to ensure resilience post-drought. • Functional groups mediate community resistance and resilience. Globally, extreme droughts are likely to become more frequent, more intense, and longer in duration with climate change. Understanding the impacts of drought on ecosystem function (i.e., resistance) and its recovery after drought (i.e., resilience) is critical for long-term sustainability of ecosystem services under climate change. We tested the effects of drought duration on ecosystem resistance by imposing four years of extreme drought (<5th percentile), and examined resilience by imposing two years of extreme drought followed by two years of recovery in a semi-arid grassland in Inner Mongolia, China. We found that the resistance of aboveground net primary productivity (ANPP) decreased as the drought progressed, i.e., ANPP was reduced from 33% in the first treatment year and 60% in the fourth treatment year. Resilience of the ecosystem was such that ANPP of drought plots was 83% of ambient plots one year post-drought. By the second year, ANPP of the drought plots fully recovered to ambient plot levels. Decreasing drought resistance through time was largely driven by forb reductions. High resilience of the system was due to grasses compensating for reductions in forb productivity. Based on these findings, we suggest that droughts may have progressively larger impacts as their duration increases, so single year responses may underpredict the effects of longer droughts likely to occur in the future. Additionally, longer recovery times after extreme drought events may be critical to ensure resilience and recovery of all plant functional types. Overall, we suggest that management should strive to support and maintain the high proportion of high drought resistance and resilience plant functional types in the community may enhance the stability of biomass production in a future climate with longer and more intense extreme droughts. [ABSTRACT FROM AUTHOR]