Warming changes soil N and P supplies in model tropical forests

Abstract

Few studies have examined the responses of soil nitrogen (N) and phosphorus (P) and the related microbial activities to warming in P-limited tropical forests. In this study, we investigated soil NO3−–N and exchangeable NH4+–N, available P, microbial biomass, enzyme activities, and nutrients of litter and leaf in response to 5-year warming by translocating model forest ecosystems with open top chambers from the altitude of 300 m to 30 m in tropical China. The average soil temperature increased in the wet and dry seasons by 1.2 and 1.0 °C in 0–40 cm, respectively. The warming induced higher P availability and lower NO3−–N concentration in both wet and dry seasons. Warming had negative effects on acid phosphomonoesterase (AP) activity but positive effects on β–1,4–N–acetylglucosaminidase (NAG) activity in the two seasons. Litter inputs and litter and leaf P increased but litter and leaf C/P and N/P decreased under warming. In the 0–40-cm soil layer, warming had stronger effects on soil P availability, AP activity, and litter P but weaker impacts on soil NO3−–N concentration and NAG activity in the wet season than in the dry season. Our results indicated that warming mitigated P limitation and increased N consumption in tropical forests.