E097 - Nitrogen Addition and Dynamics of Recovery from Cessation of N Addition

Introduction

To determine the dynamics of recovery after cessation of N addition, N addition was halted in 3 plots per treatment randomly chosen from among the 6 total replicates per treatment in one of the 7 N addition sites in 1993. For a description of these plots, see E002 - Long-Term Nitrogen Deposition During Grassland Succession. Current work is in all plots in the E002 field are being recorded under experiment number E002

Key Results

Although nutrient enrichment frequently decreases biodiversity, it remains unclear whether such biodiversity losses are readily reversible, or are critical transitions between alternative low- and high-diversity stable states that could be difficult to reverse. Our 30-year grassland experiment shows that plant diversity decreased well below control levels after 10 years of chronic high rates (95–270 kg N ha-1 year-1) of nitrogen addition, and did not recover to control levels 20 years after nitrogen addition ceased. Thus, the regime shifts between alternative stable states that have been reported for some nutrient-enriched aquatic ecosystems may also occur in grasslands. Isbell et al. 2013 Ecology Letters