Functional response to land use change in grasslands: Comparing species and trait data

Abstract

:The search for general plant community patterns that explain plant responses to land use changes is at present a major focus of studies related to grassland conservation. Traditionally, vegetation change has been documented by identifying species-based changes over time. Recent studies suggest that species-based assessments should be complemented with functional assessments of species characteristics. We examined land use change along a successional gradient by comparing grasslands with long grazing history, abandoned formerly grazed grasslands, and pastures with a short grazing history by using i) species data, i.e., species richness, composition, growth form, and homogenization, and ii) functional characteristics, using three core traits, seed mass, specific leaf area (SLA), and plant height. Analyzing species data directly in terms of species richness, composition, or growth form was a more straightforward tool than analyzing species function based on selected core traits. No functional groups, based on the investigated traits, were supported. Functional response trends were, however, detected, as height increased and SLA decreased along the successional gradient. Analyses based on species data followed documented response patterns associated with grassland succession, i.e., decrease in species richness, decrease in the number of plant species favoured by grazing, and shifts in species composition and growth form towards less dominance of herbs. Due to idiosyncrasy of individual species responses, we question the benefit of using a small number of response traits or functional groupings compared to species-based analyses for documenting vegetation changes in grazing systems over time.