Significance of Legumes for the Distribution of Plant Species in Grassland Ecosystems at Different Altitudes in the Alps
Jacot, Katja A. ; Lüscher, Andreas ; Suter, Matthias ; Nösberger, Josef ; Hartwig, Ueli A.
In: Plant Ecology, 2005, vol. 180, no. 1, p. 1-12
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- The composition of plant species in grassland communities is determined in part by negative and positive interactions among neighbouring plants; such interactions could be dispersal or - in the case of legumes - symbiotic N2 fixation or resource acquisition. We hypothesised that small scale distribution of plant species may be in part affected by (i) the plant's narrow dispersal in the close neighbourhood, (ii) by the N input into the soil through symbiotic N2 fixation by legumes, and (iii) by small scale heterogeneity of N availability in the soil. To address these hypotheses, in four species-rich semi-natural and natural grasslands along an altitudinal gradient from 900 to 2100ma.s.l., the association of species that grew within a radius of 5cm of selected plant species (central plant, CP) was studied. The distribution of the plant species within the plant community was not random and the species composition that grew within a radius of 5cm of a CP varied with altitude. The strength of the association between a CP and its neighbouring species decreased with increasing altitude. The 5cm radius was most dominated by individuals of the same species as the CP, suggesting that narrow dispersal (either through seeds or through vegetative propagates) may be most important for the species composition within the sward. δ15N values of non leguminous species growing near legumes compared to non leguminous species that grew far from legumes indicate that N from symbiotic N2 fixation may be another factor influencing the association of plant species. Effects of small scale heterogeneity in apparent N availability in the soil were detected to be the least important for the species composition