Abstract Grazing exclusion is widely used for grassland restoration but often improves productivity slowly, whereas nitrogen (N) addition can rapidly boost productivity yet may erode plant diversity and community stability over the long term. Identifying an optimal N‐addition level that complements grazing exclusion while enhancing community diversity and stability remains unresolved. To address this gap, we conducted a 4‐year field experiment to test the effects of fence‐based grazing exclusion, low (5 kg N·ha −1 ·year −1 ) and high‐N (15 kg N·ha −1 ·year −1 ) additions, and their combinations on plant community dynamics in a degraded alpine grassland. Grazing exclusion alone increased plant diversity and community stability (defined as the temporal stability of above‐ground biomass over 4 years), and low‐N addition further amplified these benefits. Specifically, compared with the control, grazing exclusion combined with low‐N addition increased richness, Shannon diversity, Pielou's evenness and Margalef's richness by 45.08%, 16.84%, 4.98% and 15.77%, respectively, reduced Simpson's dominance by 34.27% and enhanced community stability by 62.67% relative to the control. Mechanistically, under grazing exclusion combined with low‐N addition, soil pH played a predominant role in shaping plant diversity and community stability by regulating soil microbial biomass and dissolved organic nutrients. We conclude that coupling low‐level N addition with grazing exclusion generates synergistic benefits for plant growth and ecosystem stability, providing a scientifically grounded ‘natural–artificial’ restoration framework for degraded grasslands. Read the free Plain Language Summary for this article on the Journal blog.
Zhang et al. (Wed,) studied this question.