Understanding the impacts of biodiversity loss on ecosystem functioning and services has been a central issue in ecology. Experiments in synthetic communities suggest that biodiversity loss may erode a set of ecosystem functions, but studies in natural communities indicate that the effects of biodiversity loss are usually weak and that multiple functions can be sustained by relatively few species. Yet, the mechanisms by which natural ecosystems are able to maintain multiple functions in the face of diversity loss remain poorly understood. With a long‐term and large‐scale removal experiment in the Inner Mongolian grassland, here we showed that losses of plant functional groups (PFGs) can reduce multiple ecosystem functions, including biomass production, soilNO₃‐N use, net ecosystem carbon exchange, gross ecosystem productivity, and ecosystem respiration, but the magnitudes of these effects depended largely on whichPFGs were removed. Removing the two dominantPFGs (perennial rhizomatous grasses and perennial bunchgrasses) simultaneously resulted in dramatic declines in all examined functions, but such declines were circumvented when either dominantPFGwas present. We identify the major mechanism for this as a compensation effect by which each dominantPFGcan mitigate the losses of others. This study provides evidence that compensation ensuing fromPFGlosses can mitigate their negative consequence, and thus natural communities may be more resilient to biodiversity loss than currently thought if the remainingPFGs have strong compensation capabilities. On the other hand, ecosystems without well‐developed compensatory functional diversity may be much more vulnerable to biodiversity loss.

Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland.

With the consequences of anthropogenic activities such as overgrazing and cropland expansion, grasslands in China suffer severe degradation since the 1980s. The national grassland restoration policy enacted at the beginning of the 21th century has the potential to increase plant growth and productivity and hence regional carbon (C) sequestration. Here, we assessed plant and soil organic C (SOC) stocks for both degraded and restored/non‐degraded plots at 802 sites in Northern and Northwest China using pairwise field sampling and quantified the C sequestration potential (CSP) of China's grasslands. A geostatistical model was performed to upscale the field measurements to national scale. Averaged across the 802 paired grassland sites, the mean plant biomass C andSOCdensity in the top 1 m depth were 0.44 ± 0.17 and 8.82 ± 1.78 kg C/m², respectively. Compared to the degraded grasslands, the restored grasslands had an average of 0.11 ± 0.17 (29.2%) and 1.02 ± 1.28 kg C/m²(12.3%) greater plant biomass C andSOCdensity, respectively. The geostatistical model produced a totalCSPof 17.3 ± 2.3 Pg C in China's grasslands, with 94% in soils. If theCSPestimated in this study could be achieved, the current grasslandSOCstock would increase by 61%, offsetting 11 yr (2000–2010) of national fossilCO₂emissions.

Nutrient resorption processes in the plants infected by pathogen remain poorly understood. Huanglongbing (HLB) is a destructive disease of citrus. HLB-pathogen ‘CandidatusLiberibacter asiaticus’ grows specifically in the phloem of hosts and may cause problems in the plant vascular system after infection. Therefore, it brings a great concern about the phloem nutrient transport and nutrient intra-cycling in HLB-affected plants. We investigated the effects of ‘Ca.L. asiaticus’ infection on nitrogen (N) and phosphorus (P) concentrations and resorption in different citrus species (i.e.Citrus reticulata,Citrus limonandCitrus maxima). HLB-pathogen infection had distinctive impacts on nutrient resorption in different species. P resorption efficiency substantially decreased in infectedC. reticulataplants relative to the healthy plants in summer, which may account for the marked decrease in the average fruit yield. P resorption was more efficient in infectedC. limonplants than in the healthy plants. However, forC. maximaplants, HLB had no significant effects on N:P ratio in live leaves and resorption efficiency as well as on fruit yield. Keeping efficient internal nutrient cycling can be a strategy of citrus species being tolerant to HLB.