Photosynthesis and nutrient-use efficiency in response to N and P addition in three dominant grassland species on the semiarid Loess Plateau

摘要

Understanding the ecophysiological and nutrient-use strategies of dominant species is important for clarifying plant growth and an ecological process in their community under unbalanced N and P inputs. This study investigated effects of N and P addition main plot: 0, 25, 50, and 100 kg(N) ha -1 year -1 ; subplot: 0, 20, 40, and 80 kg(P) ha -1 year -1 on leaf N and P contents (LNC a and LPC a ), photosynthetic capacity ( P Nmax ) and photosynthetic N- and P-use efficiencies (PNUE and PPUE) in three species ( Stipa bungeana , Bothriochloa ischaemum , and Lespedeza davurica ) in a semiarid grassland in China. At the assessing time, N addition alone significantly increased LNC a and LNC a /LPC a ratio of Stipa bungeana (C 3 grass) only, while P Nmax increased significantly in all three species. Under N addition, P addition caused significantly lower LNC a , but higher PNUE and P Nmax in Bothriochloa isch aemum (C 4 grass) and Stipa bungeana . The LNC a , P Nmax , and PNUE of Lespedeza davurica (C 3 legume) increased significantly after P addition regardless of N application. The LNC a /LPC a for optimum PNUE changed with species. The P Nmax and PNUE of Bothriochloa ischaemum and Stipa bungeana had a peak when LNC a /LPC a attained ~ 11 and ~ 20. Lespedeza davurica tended to retain greater P Nmax and PNUE at lower LNC a /LPC a . Our results indicated that the C 3 grass was more sensitive to N and P addition than the C 4 grass and the C 3 legume in terms of leaf N and P contents and P Nmax . Such interspecific variations of nutrient use in response to N and/or P addition are favorable for maintaining the diversity and the stability of the grassland community.