Roots and arbuscular mycorrhizal fungi are independent in nutrient foraging across subtropical tree species

Abstract

Plant species with thin roots and high root-growth rate are thought to have greater root foraging precision than species with thick roots and low root-growth rate. However, whether root morphological traits (such as root diameter) are correlated with foraging precision of roots and mycorrhizal fungi in heterogeneous nutrient environments across tree species remains unclear. We examined 13 coexisting arbuscular mycorrhizal subtropical tree species, measured functional traits of roots, leaves and mycorrhizal fungi and assessed foraging precision of roots and mycorrhizal fungi in response to different nutrient patches using an in situ root-bag approach. Thin-root species had greater specific root length and root growth rate than thick-root species, but they showed similar root and mycorrhizal hyphae foraging precisions. As root diameter increased, root foraging precision exhibited the U-shape patterns in the nitrogen and phosphorus patches, but hyphal foraging precision showed a slightly increasing trend only in the nitrogen patch. Foraging precisions of roots and hyphae were independent, and were not influenced by plant traits across species. Our findings challenge the notion that thin-root species with high root growth rate have greater foraging precision, suggesting that root morphological traits may not be correlated with the variation in foraging strategies of roots and mycorrhizal hyphae.