Understanding the effects of diversity on ecosystem stability in the context of global change has become an important goal of recent ecological research. However, the effects of diversity at multiple scales and trophic levels on ecosystem stability across environmental gradients remain unclear. Here, we conducted a field survey of α‐, β‐, and γ‐diversity of plants and soil biota (bacteria, fungi, and nematodes) and estimated the temporal ecosystem stability of normalized difference vegetation index (NDVI) in 132 plots on the Mongolian Plateau. After climate and soil environmental variables were controlled for, both the α‐ and β‐diversity of plants and soil biota (mainly via nematodes) together with precipitation explained most variation in ecosystem stability. These findings evidence that the diversity of both soil biota and plants contributes to ecosystem stability. Model predictions of the future effects of global changes on terrestrial ecosystem stability will require field observations of diversity of both plants and soil biota.

1. Stability is a useful indicator of the functioning and sustainability of an ecosystem, and much studies have explored the effects of anthropogenic disturbance on the inter-annual stability of plant community. However, the effects of multiple anthropogenic stressors on seasonal community stability have not been clearly elucidated, especially for vulnerable semi-arid grasslands.2. During the growing season in the 5th year of the experiment, we determined how nitrogen (N) addition, water addition and shrub removal altered seasonal community stability in a semi-arid grassland dominated by the shrub Caragana microphylla on the Mongolian Plateau.3. We found that shrub removal, N addition and water addition had different effects on the stability of community and plant functional groups (PFGs). Shrub removal increased seasonal community stability mostly via increases in the stability of perennial forbs and C 4 plants, and shrub removal did not alter the effects of N addition or water addition on seasonal community stability or PFG stability. 4. N addition decreased seasonal community stability mostly via decreases in the stability of perennial rhizome grasses and C 4 plants. Water addition increased seasonal community stability mostly via increases in the stability of annuals and biennials, perennial forbs, perennial rhizome grasses, dominant species and C 4 plants. Species asynchrony and PFG stability but not species richness or soil abiotic or biotic variables helped to maintain seasonal community stability under N addition or water addition. 5.Our findings indicate that future scenarios of increases in N deposition and shrub encroachment will strongly reduce community stability in drylands, and that future scenarios of increases in precipitation together with shrub removal might help to maintain the stability of this and other dryland ecosystems.

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