Linking leaf and root trait syndromes among 39 grassland and savannah species

Abstract

Here, we tested hypothesized relationships among leaf and fine root traits of grass, forb, legume, and woody plant species of a savannah community. CO2 exchange rates, structural traits, chemistry, and longevity were measured in tissues of 39 species grown in long-term monocultures. Across species, respiration rates of leaves and fine roots exhibited a common regression relationship with tissue nitrogen (N) concentration, although legumes had lower rates at comparable N concentrations. Respiration rates and N concentration declined with increasing longevity of leaves and roots. Species rankings of leaf and fine-root N and longevity were correlated, but not specific leaf area and specific root length. The C3 and C4 grasses had lower N concentrations than forbs and legumes, but higher photosynthesis rates across a similar range of leaf N. Despite contrasting photosynthetic pathways and N2-fixing ability among these species, concordance in above- and below-ground traits was evident in comparable rankings in leaf and root longevity, N and respiration rates, which is evidence of a common leaf and root trait syndrome linking traits to effects on plant and ecosystem processes.