Impacts of shrub encroachment on soil quality in the native Monte rangelands of Southwestern Buenos Aires, Argentina

Abstract

Purpose Shrub encroachment has been associated with changes in the spatio-temporal distribution of soil nutrient and vegetation. We determined the effect of shrub cover on chemical and biochemical indicators of soil quality (SQ) in a semiarid Monte rangeland of Argentina. Methods In spring 2017 and 2018, 6 paddocks were selected and 10 m transects were placed in an area with (Sh) and without shrubs (WSh). Within each transect, composite soil samples (0–10 cm depth; n = 6) were taken from sites with bare ground-litter (BL), grass (G) and shrub (S) cover. Soil samples were analyzed to determine chemical and biochemical parameters associated with the efficient use of water, nutrients, functionality and activity of microbial communities. Results When these indicators were evaluated individually, Sh-G and Sh-S sites presented high values of soil organic matter (SOM), soil organic nitrogen (SON), particulate organic matter (POM) and cellulase activity (CA); the shrub effect was not consistent for the other parameters related to nitrogen and phosphorus cycle. In multivariate analysis, values of POM, SON, CA and anaerobic nitrogen were positively correlated between them in both years; Sh-G and WSh-G sites were associated with different SQ parameters, and BL soils of Sh and WSh transects behaved similarly. Conclusions We demonstrated that shrubs do not have a negative effect on SQ. Moreover, in the context of appropriate grazing management and moderate shrub cover presence of woody species has a beneficial effect on POM, SON and CA with direct impacts on organic matter decomposition, nutrient availability and microbial activity.