Effect of plant–plant interactions and drought stress on the response of soil nutrient contents, enzyme activities and microbial metabolic limitations

Abstract

Plant–plant interactions are dynamic and complicated processes that strongly influence soil nutrient cycling in ecosystems. Climate warming-induced drought stress and the duration of plant interactions may reshape or complicate this ecological process. However, little is known about how plant–plant interaction time (co-growth duration) combined with drought stress affect soil chemical properties and enzyme activities. In this study, Stipa bungeana and Bothriochloa ischaemum, which were the main plant species during the later stages of secondary succession in an abandoned cropland on the Loess Plateau of China, were planted as a single plant or in combination, in a plastic pot with two water regimes (ample water, 80 % of field capacity (FC); drought stress, 60 % of FC) for two consecutive years. The rhizosphere soil was collected each year to determine the nutrient contents and enzyme activities, and the microbial metabolic limitations were calculated. We found that plant–plant interactions, drought stress, and sampling year had a significant influence on most rhizosphere soil nutrient contents and enzyme activities. Redundancy analysis showed that soil pH, available phosphorus (aP), and total phosphorus had significant effects on soil enzyme activities in the first year, and soil total nitrogen and aP had significant effects on soil enzyme activities in the second year. Vector analysis indicated that drought stress increased microbial carbon (C) and phosphorus (P) limitation under each planting pattern, and these metabolic limitations showed a decreasing trend in the second year. An structural equation model demonstrated that plant–plant interactions on microbial C and P limitation were larger than drought stress in the first year. Conversely, in the second year, the plant–plant interactions on microbial C and P limitation were lower than that of drought stress. Our findings highlighted that the duration of plant–plant interactions had a significant influence on C flows and nutrient cycling in plant–soil systems, and improved the understanding of plant–plant interactions and drought stress on soil nutrient cycling and microbial metabolic limitations in vegetation restoration ecosystems.