Response of photosynthetic characteristics of Caragana microphylla in different soil phosphorus supplies

摘要

Over the past several decades, grassland degradation has become severe in Inner Mongolia, leading to decreased grass coverage and increased distribution of Caragana microphylla. In order to find out new explanation for the expansion of C. microphylla in degraded grassland, we grew two-year seedlings in phosphorus (P) deficient soil supplemented with P supply ranging from 0 to 60 mg kg~(-1). The simulation parameters of light response curves and chlorophyll fluorescence parameters were all generally similar among different soil P supplies. Only maximum total photosynthetic rate (Pmax) and PSII potential activity (Fv/Fo) were reduced at 0 mg kg~(-1) soil supply, and high P supply caused P toxicity. C. microphylla was non-limited by P-deficiency and adapted well to the low-P Inner Mongolia steppe. The advantage of C. microphylla in P-limited natural grassland provided new explanation for the expanding of C. microphylla in degraded Inner Mongolia steppe.