Estimating the biodiversity of hay meadows in north-eastern Switzerland on the basis of vegetation structure

Abstract

Biological diversity is a major criterion in evaluating the effectiveness of measures to enhance the ecological quality of rural areas. Assessments of biodiversity based on selected groups of indicator organisms, including both animal and plant groups, are time-consuming and require a high level of expert knowledge: simpler methods are therefore needed. The biodiversity of 18 hay meadows in north-eastern Switzerland (Schaffhauser Randen, Canton Schaffhausen) was investigated using three indicator groups (angiosperms, spiders and true bugs). Simple structural parameters describing the vegetation canopy were investigated in terms of their usefulness as surrogates for biodiversity measures. Eighteen sites varied widely in terms of species richness, diversity and abundance for all indicator groups. Numbers of angiosperm species varied from 21 to 57, spiders 25 to 45, and true bugs 12 to 37. Species numbers of the three indicator groups were significantly correlated with each other (angiosperms versus spiders: r = 0.53, P = 0.02; angiosperms versus true bugs: r = 0.59, P = 0.01; true bugs versus spiders: r = 0.61, P = 0.01). Management had a strong influence on species richness, the sites under extensive management showing the highest species number and diversity. The strongest correlations were those between true bugs and the two other indicator groups. However, the number of angiosperm species per 120 m2, which was easy to assess, was also an acceptable predictor of the other two indicator groups. Several parameters of the vegetation canopy were significantly related to species numbers and multiple regression models based on these parameters explained 25-60% of the variance in species richness and composition. Canopy density, plant biomass distribution and plant height were the most important parameters for all indicator groups. The results indicate that parameters describing the structure of the vegetation provide useful information about the relative species richness of sites. In combination with parameters describing the surrounding land-use and an inventory of the angiosperms present, they offer a promising method for assessing biodiversity on a large scale. © 2002 Elsevier Science B.V. All rights reserved.