The effect of artificial vegetation recovery on the soil nutrients and enzyme activities in subhumid desert land on the southeast Qinghai-Tibetan Plateau, China

Revegetation is an effective strategy for enhancing soil quality, but the impact of revegetation on soil processes is currently not well understood, especially in subhumid desert lands across a chronosequence of recovery. Therefore, this study aims to assess the soil nutrients and enzyme activities under successive (from 2013 to 2016) revegetation by Avena sativa, Festuca sinensis and Elymus nutans in subhumid desert on the southeast Qinghai-Tibetan Plateau. The soil organic carbon (SOC), total nitrogen (STN), total phosphorus (STP), ammonium nitrogen (SAN), nitrate nitrogen (SNN), available phosphorus (SAP), saccharase, alkaline phosphatase and urease activities were measured in the 0-10 cm and 10-20 cm soil layers during the growing season in 2016. The results indicated that the restoration by grasses promoted soil nutrients and enzyme activities, but there was a sharp decrease in soil nutrients and enzyme activities after one-year of recovery in the subhumid desert. Compared to the control, revegetation significantly decreased the SOC (36.5%), STN (40.8%), STP (31.5%), saccharase (44.7%), urease (38.5%) and alkaline phosphatase (18.0%) activities in the 0-10 cm soil layer (P < 0.05) after one-year restoration. Recovering by grasses was an efficient way to restore the subhumid desert. However, this process might consume large amounts of soil nutrients and limit soil enzyme activities at the beginning succession stage, which was different from dry or semiarid desert land. Choosing a suitable mixing ratio of artificial grasses and adding fertilizer to the soil at the beginning stage of revegetation are advised for restoring desert lands in alpine areas.