Species-rich grassland can persist under nitrogen-rich but phosphorus-limited conditions

Abstract

Aim Deposition of nitrogen is assumed to cause loss of botanical diversity, probably through increased production and exclusion of less competitive species. However, if production is (co-)limited by phosphorus, acceleration of the phosphorus cycle may be responsible for the diversity loss and, where that is the case, nitrogen emission reduction may turn out to be an ineffective mitigation strategy. Here we study the feasibility of this mechanism through adding potassium and phosphorus to grassland where nitrogen limitation is absent. Methods We made vegetation relevés in a long-term agricultural fertilisation experiment where potassium, phosphorus and nitrogen were being added to grassland on drained peat where nitrogen availability was high, even in unfertilised plots. We applied a multivariate analysis to investigate the effect of additions of K, K + P and K + P + N on the species composition. Results Unfertilised plots had a very low biomass production and were rich in plant species despite their high nitrogen availability. Addition of potassium led to a strongly increased production but did not result in a reduction of species numbers. Phosphorus in addition to potassium increased production still further and decreased species numbers, most notably the number of endangered species. Conclusions Even under nitrogen rich conditions species richness may be high in grasslands where phosphorous provides a limitation to plant growth. Phosphorus limitation and phosphorus enrichment are both common in grassland, at least in north-western Europe. Part of the general decrease in species numbers that is commonly ascribed to nitrogen enrichment may therefore be due to phosphorus enrichment. If phosphorus and nitrogen are co-limiting (which is often the case) the current nitrogen emission reduction policies may be effective, but not sufficient to restore grassland diversity to its preindustrial level.

Changes in Diversity Due to Long-Term Management in a High Natural Value Grassland

“…The treatment with 20 t ha −1 manure further determines the biodiversity restriction (Carex pallescens, Luzula multiflora, Leontodon autumnalis). Luzula multiflora is present in oligotrophic or mesotrophic grassland, and K-based fertilization favors it [64]. Leontodon autumnalis is disadvantaged by this fertilizer amount, because it is a weakly competitive species in the lush conditions of vegetation clearing determined by the fertilizer application.…”

Effect of fertiliser application and cutting regime on temporal differentiation of mesic semi-natural grassland vegetation

“…Potassium (K) is considered a less important factor affecting plant diversity of grassland. The field experiments suggest that plant composition of grassland is quite insensible to K addition (Elberse et al, 1983;Hejcman et al, 2007;van Dobben et al, 2017).…”

Relaties tussen de hoeveelheid stikstofdepositie en de kwaliteit van habitattypen

“…Verzuring treedt ook op door zwavel (de huidige zuurgraad is dus mede bepaald door zwaveldepositie, die in het verleden veel hoger was dan nu). Eutrofiëring treedt ook op door bijvoorbeeld fosfor of kalium (Van Dobben et al, 2017). In oppervlaktewater of grondwater gevoede habitattypen wordt stikstof ook via het water aangevoerd.…”