Assessing the effects of land-use change on plant traits, communities and ecosystem functioning in grasslands: a standardized methodology and lessons from an application to 11 European sites

Abstract

Background and aims: A standardized methodology to assess the impacts of land-use changes on vegetation and ecosystem functioning is presented. It assumes that species traits are central to these impacts, and is designed to be applicable in different historical, climatic contexts and local settings. Preliminary results are presented to show its applicability.

Methods: Eleven sites, representative of various types of land-use changes occurring in marginal agro-ecosystems across Europe and Israel, were selected. Climatic data were obtained at the site level; soil data, disturbance and nutrition indices were described at the plot level within sites. Sixteen traits describing plant stature, leaf characteristics and reproductive phase were recorded on the most abundant species of each treatment. These data were combined with species abundance to calculate trait values weighed by the abundance of species in the communities. The ecosystem properties selected were components of above-ground net primary productivity and decomposition of litter.

Key results: The wide variety of land-use systems that characterize marginal landscapes across Europe was reflected by the different disturbance indices, and were also reflected in soil and/or nutrient availability gradients. The trait toolkit allowed us to describe adequately the functional response of vegetation to land-use changes, but we suggest that some traits (vegetative plant height, stem dry matter content) should be omitted in studies involving mainly herbaceous species. Using the example of the relationship between leaf dry matter content and above-ground dead material, we demonstrate how the data collected may be used to analyse direct effects of climate and land use on ecosystem properties vs. indirect effects via changes in plant traits.

Conclusions: This work shows the applicability of a set of protocols that can be widely applied to assess the impacts of global change drivers on species, communities and ecosystems.

Fig. 1.

Principal component analysis on climatic data: mean annual rainfall (Rainfall), mean annual temperature (Temp), annual growing degree-days (GDD, and an aridity index for each site. Annual PET and solar radiation were removed after a covariance analysis indicated they were highly correlated with, in particular, mean annual temperature.

Fig. 2.

(A) Return interval (log scale) and (B) intensity (expressed as a percentage of maximum standing biomass) of disturbance for the least (open columns) and most (shaded columns) intensively used treatments in each site. In A, a value of 0 indicates a return interval of 1 year (e.g. both treatments in FR-LAU), whereas in B a value of 0 corresponds to a lack of biomass removal (e.g. both treatments in FR-HGM).

Fig. 3.

Detrended correspondence analysis (DCA) of relative abundance of higher plant families for each recorded plot. Only families with a weight of >2 % of the maximum family's weight are shown as the first eight letters of their full name.

Fig. 4.

(A) Community-aggregated values of leaf dry matter content (LDMC), and (B) above-ground total dead material (which includes standing dead biomass and litter fallen on the ground) at the time of peak biomass for the least (open columns) and most (shaded columns) intensively used treatments in each site. Significance of tests by one-way ANOVAs within sites is indicated: ns: not significant, P>0·10; a, P < 0·10; *, P < 0·05; **, P < 0·01; ***, P < 0·001.

Fig. 5.

Relationship between community-aggregated leaf dry matter content (LDMC) and above-ground dead biomass (AGTotdead) at the time of maximum standing biomass across ten sites of the VISTA project, using the least/most used treatments in each site. r values are Pearson correlation coefficients for all data (top value) and when the five points with AGTotdead values higher than 600 g m⁻² were removed (in parentheses); n is the number of data points (***, both relationships are significant at P < 0·001).

Fig. 6.

Articulating direct and indirect effects of environmental factors and land use on plant traits and ecosystem properties. The relationships are illustrated here based on the results obtained for community-aggregated LDMC and standing litter (AGTotdead). The arrows represent significant statistical relationships, with +/− signs indicating the direction of effects.