Carbon cycling traits of plant species are linked with mycorrhizal strategy

Abstract

Ecosystem carbon cycling depends strongly on the productivity of plant species and the decomposition rates of the litter they produce. We tested the hypothesis that classifying plant functional types according to mycorrhizal association explains important interspecific variation in plant carbon cycling traits, particularly in those traits that feature in a hypothesized feedback between vegetation productivity and litter turnover. We compared data from standardized 'screening' tests on inherent potential seedling relative growth rate (RGR), foliar nutrient concentrations, and leaf litter decomposability among 83 British plant species of known mycorrhizal type. There was important variation in these parameters between mycorrhizal plant types. Plant species with ericoid mycorrhiza showed consistently low inherent RGR, low foliar N and P concentrations, and poor litter decomposability; plant species with ectomycorrhiza had an intermediate RGR, higher foliar N and P, and intermediate to poor litter decomposability; plant species with arbuscular-mycorrhiza showed comparatively high RGR, high foliar N and P, and fast litter decomposition. Within the woody species subset, differentiation in RGR between mycorrhizal types was mostly confounded with deciduous versus evergreen habit, but the overall differentiation in litter mass loss between mycorrhizal types remained strong within each leaf habit. These results indicate that, within a representative subset of a temperate flora, ericoid and ectomycorrhizal strategies are linked with low and arbuscular-mycorrhizal species with high ecosystem carbon turnover. The incorporation of mycorrhizal association into current functional type classifications is a valuable tool in the assessment of plant-mediated controls on carbon and nutrient cycling.