Different responses of foliar nutrient resorption efficiency in two dominant species to grazing in the desert steppe

Abstract

AbstractNitrogen and phosphorus resorption (NRE and PRE) is a critical nutrient conservation mechanism maintaining plant growth in already disturbed barren ecosystems. The complexity of plant nutrient resorption variations in long-term grazing regions is regulated by plant traits, nutritional utilization strategies, and soil conditions following changes in grazing patterns. Therefore, a detailed investigation into their underlying mechanism is still required. Here we investigated leaf nutrient concentration and resorption in dominant species Cleistogenes songorica (C. squarrosa) and Stipa breviflora (S. breviflora) response to 15-years continuous grazing (moderate and heavy grazing) in desert steppe. Moderate grazing enhanced green leaf N and P content in C. songorica and partially increased N content in S. breviflora. Heavy grazing consistently increased N content in C. songorica, but its P content as well as N and P content in S. breviflora were largely stable. Moderate grazing enhanced NRE but unaffected PRE in both S. breviflora and C. songorica. Heavy grazing reduced NRE and PRE in C. songorica. Although soil variables (nutrients and moisture) did not affect foliar nutrients, it’s a key driver of nutrient resorption efficiency. Of all measured influence factors, soil moisture is the one most important and negatively correlated with NRE and PRE in S. breviflora. While it was not observed in C. songorica. In S. breviflora, its NRE was adversely linked with soil N, in addition, both NRE and PRE were positively associated with green leaf nutrients. Senesced leaf nutrients are the predominant factor influencing nutrient resorption efficiency in C. songorica, which were adversely associated. Overall, our results indicate significant variations in nutrient resorption efficiency patterns between the two dominant species due to divergent plant adaptation strategies to grazing and the local environment. The foliar nutritional status and soil conditions may play significant roles in regulating nutrient resorption in arid long-term grazing desert steppe.