The importance of species richness to ecosystem functioning and services is a central tenet of biological conservation. However, most of our theory and mechanistic understanding is based on diversity found aboveground. Our study sought to better understand the relationship between diversity and belowground function by studying root biomass across a plant diversity gradient. We collected soil cores from 91 plots with between 1 to 12 aboveground tree species in three natural secondary forests to measure fine root (≤ 2 mm in diameter) biomass. 

A subset of 91 plots, representing a gradient in tree species richness, were chosen: 30 plots for PM (ranging from 2 to 9 tree species); 31 plots for CA (1-12 tree species); and 30 plots for CG (1-11 tree species). In August 2016, we sampled one soil core ( 10 cm in internal diameter) to 30 cm depth (i.e. down to bedrock) in the centre of each plot. Fine roots (defined here as roots ≤ 2 mm in diameter) were collected from soil samples at each depth and placed into separated plastic bags in the field. A total of 273 soil samples were collected and transported to the laboratory to determine the total fine root biomass.