Linking soil nutrient availability, fine root production and turnover, and species composition in a seasonally dry plant community

Abstract

We studied the relationship between seasonal nutrient availability and fine root density with soil depth to determine potential nutrient uptake strategies of evergreen and deciduous woody species in an infertile, seasonally dry plant community. PO43−, NO3−, and NH4+ were measured with soil depth and across seasons, using ion-exchange resins. Fine root density was measured seasonally by counting the first four root terminal orders (root branching from tip to base). Aboveground stem density and species composition were measured. N and P availability were highest in the shallow soil layer and peaked in the late wet season and not during the initial rains as was hypothesized. Substantial N and P were found at deeper soil depths during the early dry season. Fine root density was highest in the shallow soil layer and in the wet season and underwent substantial turnover from dry to wet season. Stem and root area were correlated. Having high fine root densities in the shallow soil layer benefits P uptake more than N or water uptake. Dormancy in deciduous species decreases fine root turnover but continued nutrient uptake in the dry season by the more abundant evergreen species appears to be of greater importance.