Soil organic carbon stocks and belowground biomass in patches in heterogeneous grassland

Abstract

BackgroundSelective grazing creates stable patches of contrasting sward height, thereby providing different growth conditions for the grass sward above and below ground and potentially affecting soil organic carbon (SOC) stocks. We hypothesized that the presence of patches leads to greater spatial variability in belowground biomass (BGB) and SOC stocks than occurs between pastures managed under different stocking intensities.MethodsA long‐term grazing experiment consisting of three stocking intensities was used for this study. We studied BGB, SOC, and soil total nitrogen (Ntot) stocks in the 0–15 cm soil depth. Shannon diversity of plant species, soil bulk density, soil phosphorus, potassium, and magnesium contents were considered.ResultsThere were no significant effects of patch or stocking intensity on BGB, SOC, and Ntot stocks. Short patches had a greater Shannon diversity than tall patches (p < 0.05) and plant‐available nutrients in soil correlated positively with sward height (p < 0.05).ConclusionsWe conclude from the current results and previous studies that higher plant species diversity with lower soil nutrient contents in short‐patch areas and higher nutrient contents together with light competition in tall‐patch areas might balance each other out with respect to BGB and SOC stocks.

Introduction to the XXV International Grassland Congress virtual special issue

“…One paper in this special section synthesized available literature on soil organic carbon changes with long-term grassland management in the southeastern United States (Silveira et al, 2024) and another paper presented new results of an unique calculation method to separate pedogenic from management-controlled soil organic carbon and nitrogen changes with long-term pasture management (Franzluebbers et al, 2023). In a grazing intensity experiment, the hypothesis that patches will lead to greater spatial variability in belowground biomass and soil organic carbon stocks was not validated (Komainda et al, 2023). Rather, greater plant species diversity with lower soil nutrient contents in short-patch areas and higher nutrient contents together with light competition in tall-patch areas appeared to offset each other.…”