Relating the visual soil structure status and the abundance of soil engineering invertebrates across land use change

Abstract

Visual Evaluation of Soil Structure (VESS) method assesses the status of soil structural quality through the examination of soil physical characteristics and biological features. Consistent relationships between VESS scores and quantitative soil physical properties have been demonstrated. However, how VESS scores correlate with quantitative soil biological properties remains unknown. This study assessed relationships between soil structural quality responses to land use change (LUC) and alterations in soil macrofauna in arable tropical soils. We simultaneously measured soil structural quality through VESS method and the abundance and community structure of macrofauna in chronosequences of land uses comprising pasture and sugarcane crop along a 1000-km-long transect through two major tropical biomes in Brazil. Correlation matrix and principal component analysis (PCA) were performed to elucidate correlations between the measured variables. Average VESS scores were 2.5 and 3.0 for pasture to sugarcane, respectively, showing a deterioration of soil structural quality following LUC. Soil macrofauna abundance and richness, as well as the abundance of individual dominant macrofauna groups, consistently decreased from pasture to sugarcane. PCA explained 56.5% of the variance, with pasture soils mostly associated with macrofauna variables, and sugarcane soils grouped near the VESS score. Correlation matrix and PCA showed positive correlation between the deterioration of soil structure after LUC and reductions in the size of macrofaunal community, especially termites (rspearman=0.36; P=0.012). These results indicate that VESS scores correlate well with the abundance and richness of major soil engineers.