N2-fixing black locust intercropping improves ecosystem nutrition at the vulnerable semi-arid Loess Plateau region, China

• DOI: 10.1016/j.scitotenv.2019.06.245
• Publication Date: 2019-06-17T17:33:41Z
• Authors: Baoguo Du; Junzhu Pang; Bin Hu; Diane E. Allen; Tina L. Bell; Sebastian Pfautsch; Florian Netzer; Michael Dannenmann; Shuoxin Zhang; Heinz Rennenberg
• Keywords: Robinia; Intercropping; Soil carbon; Hippophae rhamnoides; Afforestation; Monoculture; Revegetation

The Loess Plateau in northwestern China constitutes one of the most vulnerable semi-arid regions in the world due to long-term decline in forest cover, soil nutrient depletion by agricultural use, and attendant soil erosion. Here, we characterize the significance of N2-fixing Robinia pseudoacacia L. and non-N2-fixing Juglans regia L. for improving nutrient availability and water retention in soil by comparing a range of biological and physicochemical features in monoculture and mixed plantations of both species. We found that N2-fixing Robinia facilitates the nitrogen and phosphorus composition of non-N2-fixing Juglans in the mixed stand as a consequence of improved soil nutrient availability, evident as higher levels of nitrogen and labile carbon compared to mono-specific stands. This demonstrates that intercropping N2-fixing Robinia with non-N2-fixing woody plants can greatly improve soil carbon and nitrogen bioavailability as well as whole-plant nutrition and can potentially mediate water retention with additional sequestration of soil organic carbon in the range of 1 t C ha-1 year-1. Thus, intercropping N2-fixing woody species (e.g. Robinia pseudoacacia or Hippophae rhamnoides L.) with locally important non-N2-fixing tree and shrub species should be considered in afforestation strategies for landscape restoration.