Shrub encroachment does not reduce the activity of some soil enzymes in Mediterranean semiarid grasslands

Shrub encroachment is a worldwide phenomenon with implications for desertification and global change. We evaluated its effects on the activities of urease, phosphatase and β-glucosidase in Mediterranean semiarid grasslands dominated by Stipa tenacissima by sampling 12 sites with and without resprouting shrubs along a climatic gradient. The presence of shrubs affected the evaluated enzymes at different spatial scales. Soils under S. tenacissima tussocks and in bare ground areas devoid of vascular plants had higher values of phosphatase and urease when the shrubs were present. For the β-glucosidase, this effect was site-specific. At the scale of whole plots (30 m × 30 m), shrubs increased soil enzyme activities between 2% (β-glucosidase) and 22% (urease), albeit these differences were significant only in the later case. Our results indicate that shrub encroachment does not reduce the activity of extracellular soil enzymes in S. tenacissima grasslands.