Soil phosphorus availability is enhanced by nitrogen and litter addition during the growing season.

Background and aims: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Methods: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Results: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Conclusion: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition. [ABSTRACT FROM AUTHOR]