A matter of time: Recovery of plant species diversity in wild plant communities at declining nitrogen deposition

Frank Berendse,Rob H E M Geerts,Paul W Goedhart,Wei Xue,Erik Noordijk,Wim Th Elberse,Hein Korevaar,Cajo J F Ter Braak,Thiemo Martijn Bezemer,Juliano Sarmento Cabral

doi:10.1111/ddi.13266

Abstract

AbstractAimHigh levels of nitrogen deposition have been responsible for important losses of plant species diversity. It is often assumed that reduction of ammonia and nitrogen oxide emissions will result in the recovery of the former biodiversity. In Western Europe, N deposition peaked between 1980 and 1988 and declined thereafter. In a 60‐year experiment in hay meadows, we tested the hypothesis that increasing and declining nitrogen deposition had negative, respectively, positive effects on plant species diversity.LocationWageningen, the Netherlands.MethodDuplicated plots received different fertilization treatments from 1958 onwards (control, Ca, K, P, PK, N, NPK). Productivity, soil pH and species composition were measured at regular intervals. In the control plots, the correlations between N deposition, diversity, production and soil acidification were analysed. Subsequently, we tested whether the treatment effects (e.g. N addition and liming) confirmed the hypothesized interactions.ResultsIn the control plots, soil pH, species diversity and the abundance of legumes and short forbs declined between 1958 and 1987 when atmospheric N deposition was high but recovered after 1987 when N deposition decreased. However, also in the N addition plots species diversity recovered partly after 1987, although the soil pH of the acidified soils in these plots did not. In addition, also in the limed plots diversity decreased rapidly during the first 30 years while in this treatment soil acidification was more than compensated.Main conclusionsWe conclude that declining N deposition resulted in the recovery of plant species diversity, but not in recovery of the former species composition. Time appears to be an additional, but crucial factor for the recovery of diverse, flowering meadows. Species not adapted to the new management conditions created at the start of the experiment disappeared during the first decades, while species fit for the new environment needed many years to establish.

Highlights

The emissions of ammonia from intensive animal husbandry and nitrogen oxides from traffic and industry increased markedly from 1950 onwards with dramatic impacts on many wild plant populations both through soil acidification and eutrophication (Bakker & Berendse, 1999; Berendse et al, 2001; Bobbink et al, 2010; Duprè et al, 2010; Stevens et al, 2004, 2010)
Long-term experiments addressing the impacts of nitrogen inputs and soil acidification are rare, but all experiments covering more than one decade show that nitrogen addition leads to a rapid decline of plant species diversity (Bobbink, 1991; Clark & Tilman, 2008; Isbell et al, 2013; Storkey et al, 2015; Tian et al, 2016) or to important changes in species composition (Avolio et al, 2014)
We investigate in the control plots the changes in plant species diversity over a period of 60 years and examine the changes in soil pH and productivity as the two most plausible explaining variables

Summary

| INTRODUCTION

The emissions of ammonia from intensive animal husbandry and nitrogen oxides from traffic and industry increased markedly from 1950 onwards with dramatic impacts on many wild plant populations both through soil acidification and eutrophication (Bakker & Berendse, 1999; Berendse et al, 2001; Bobbink et al, 2010; Duprè et al, 2010; Stevens et al, 2004, 2010). The response of the vegetation to the raise and decline in N deposition is possibly confounded with the impacts of climatic change To unravel this complex relationship, we investigated the impacts of changes in seasonal temperature and precipitation on the species diversity and the abundance of the individual plant species in the control plots. 1. Does the observed increase (before 1987) and decline (after 1987) in atmospheric nitrogen deposition have the hypothesized negative, respectively, positive effects on species richness, species diversity and the abundance of short forbs and legumes?. 3. Do the impacts of the liming, N addition and other treatments confirm the observed effects of the increase and decline in atmospheric nitrogen deposition on species richness and diversity in the control plots?

| METHODS

| DISCUSSION

Findings

| CONCLUSIONS