For a while now, I have been thinking about how functional traits can be used to evaluate restoration efforts in more depth. Functional traits research has largely been carried out across sites, regions and continents, and remarkably interesting patterns have held across landscapes and land-uses. Can this strategy be applied to individual sites to evaluate more comprehensively restoration efforts?
In a new study, Pottier et al. (2009) demonstrate how linking functional traits with spatially explicit methods can provide us with more information on the response of vegetation to ecological restoration at one site. Pottier et al. (2009) set-up more than 80 plots along a river in France where restoration efforts have been ongoing for 20 years or more. In these plots, they measured species composition, and collated values for 12 plant traits from databases (138 species). They also measured several environmental characteristics of the soil in plots along the river (i.e. coarse particle content, and coarse and fine particle size) and the vegetation (i.e. tree number, shrub cover, mean herbaceous cover and herbaceous cover heterogeneity).They were able to separate the effects of environmental changes caused by restoration efforts and natural biotic processes (dispersal limitations) on plant traits. They found the heterogeneity of plant traits increased as a result of both restoration efforts and dispersal limitations. This was a goal of this restoration project because heterogeneity of plant traits has been linked to increased resilience to invasion, higher productivity and more efficient resource use.
I wonder if the results would have differed if some of the plant functional traits were also measured like the environmental characteritics. Intraspecific variation is rarely considered in plant trait research. In my opinion, this is a limitation with trait values from databases because many herbaceous species are highly plastic so one value may not be an accurate description of function. This means, a species could vary in its traits considerably depending on the environmental conditions, disturbance and competition, even within a site.
Is intraspecific variation important to consider then or is an average trait value sufficient for evaluation purposes?
Pottier, J., A. Bedecarrats, and R. H. Marrs. 2009. Analysing the spatial heterogeneity of emergent groups to assess ecological restoration. Journal of Applied Ecology 46:1248-1257.