The biomass-ratio hypothesis states that ecosystem properties are driven by the characteristics of dominant species in the community. Tardif et al. measure decomposition rates of litter from four herb species at three sites along a correlated climatic gradient of temperature and precipitation in order to test the predictive value of the hypothesis. They find that community-weighted means of monoculture values provide good predictions of mixed-species’ litter decomposition, converging to the predicted values with increasing species richness and in climates less favourable to decomposition. The results support the idea that the biomass-ratio hypothesis, operationalized as community-weighted means, could offer the opportunity to predict ecosystems processes at larger spatial scales and in a changing environment.
Light partitioning within intercropping systems is mostly modelled by using the turbid medium analogy. Barillot et al. assess this approach by comparing it with a light-projective model based on 3-D plant mock-ups for contrasting grass–legume canopies (wheat–pea, tall fescue–alfalfa, tall fescue–clover). They find that light partitioning is accurately predicted by the turbid medium approach in most of the canopies studied; however, a more detailed description of the canopy is required for mixtures exhibiting marked vertical stratification and/or inter- or intraspecies overlapping of foliage.
The productivity and stability of grazed grassland rely on dynamic interactions between the sward and the animal. Combes et al. record 3-D canopy structures of swards of white clover (Trifolium repens) using an electromagnetic digitizer and adapted software, and synthesize virtual canopies in order to calculate bite mass of grazing animals and to determine effects on light interception efficiency (LIE) of the remaining sward. They find that bite mass and LIE values after grazing are more strongly affected by the initial structure of the sward than by bite form and placement.
Genotypic diversity is essential for maintenance of plant species. Van Mölken and Stuefer examine White clover mosaic virus and Trifolium repens and show that the effects of virus infection on plant performance can differ greatly between distinct host genotypes, resulting in changes in relative fitness between virus-infected and control treatments. This suggests that virus infections may be of considerable importance for the maintenance of genotypic diversity in these host plants. FreeLink: PDF version linked here. (Link via authors names will be made free asap.)