Testing hypotheses of plant community productivity dependence on species and functional diversity

Abstract

In this article, we tested two hypotheses about the dependence of primary aboveground biomass on community-weighted mean functional traits of dominant plant species (mass ratio hypothesis) and on functional diversity (niche complementarity hypothesis). The vegetation cover of the area under study consists of grassland communities and forest understory communities. The material analyzed comprised the above-ground biomass of plants. The following functional traits of leaves were measured: area (LA), dry mass (LDM), specific leaf area (SLA), and their community weighted means (CWM). Functional diversity was numerically expressed using the indices of functional richness (Fric), evenness (Feve), and divergence (Fdiv). The testing of the biomass correlation hypothesis revealed a significant positive relationship between the biomass of grassland communities and the CWM values of the LA and SLA traits. The testing of the niche complementarity hypothesis showed no statistically significant relationships between the biomass and functional diversity indices for both grassland and forest communities. The indices of functional diversity of the forest understory communities had markedly more pronounced positive relationships with the layer biomass. The mass ratio hypothesis best explains the relationship between the biomass and CWM of the grassland traits, while the niche complementarity hypothesis elucidates the relationship between the biomass and the functional diversity of plants in the forest communities.

Keywords

• functional diversity
• mass ratio hypothesis
• niche complementarity hypothesis
• la
• ldm
• sla
• cwm