Sensitivity of soil nutrient pools, but stability of microbial processes, under reduced rainfall and altered grazing management in northern mixed-grass prairie

Nutrient cycling is a soil function that may be impacted by global change-induced droughts and alterations to grazing pressure. While belowground responses to drought are increasingly studied, the combined effects of altered rainfall and grazing on soil nutrients and microbial processes remain poorly understood. We tested how a two-year rainfall reduction interacted with a grazing intensity gradient during drought and two years of recovery to influence soil nutrient pools and microbial processes at two northern mixed-grass prairie sites. Rainfall reductions decreased soil available P and micronutrients between 10 and 50 %, but increased soil NO 3 − up to 4-fold during drought and into recovery years. In contrast, bacterial and fungal community compositions and extracellular enzyme activities were relatively resistant to rainfall reduction and grazing intensity treatments. Together, these results highlight the sensitivity of soil nutrient pools to drought, contrasted with the relative stability of belowground microbial processes in semi-arid rangelands in the face of drought and grazing management strategies. • Soil NO 3 − increased 2-fold in recovery years following experimental drought. • Rainfall reductions decreased soil available phosphorous and micronutrients. • Soil microbial composition was insensitive to drought and grazing intensity. • Extracellular enzyme activity was insensitive to drought and grazing intensity.