Annual mowing mitigates the negative legacy effects of N enrichment on grassland nutrient use efficiency

Abstract

Abstract Aims Plant nutrient use efficiency, an important factor driving primary production, is sensitive to nitrogen (N) deposition. Because of strengthened regulations of N emissions, atmospheric N deposition is decreasing in many countries. It remains unknown whether historical N enrichment would alter plant nutrient use efficiency and whether such impacts would be mitigated by ecosystem management strategy. Methods We assessed the effects of historical N addition and mowing on plant N and phosphorus use efficiency (NUE and PUE) at both functional group and community levels in a temperate steppe after the cessation of 6-year N addition. Important Findings Historical N addition had negative legacy effects on plant NUE but not on PUE at the functional group level. There were negative legacy effects of N addition on community-level NUE and PUE, but only in the unmown plots. Mowing mitigated the negative legacy effects of N enrichment on community-level NUE and PUE by reducing the dominance of tall rhizomatous grass but enhancing that of tall bunchgrass. Our results highlight the importance of community composition variations caused by mowing in driving the legacy effects of N enrichment on community-level nutrient use efficiency. Given the slow recovery of community composition following cessation of N deposition, our findings suggest that the lower nutrient efficiency of plant community would be long-lasting.