Influence of short-term warming on the coupling mechanism between soil nitrogen and phosphorus in a young Cunninghamia lanceolata stand in mid-subtropical China
Global warming has caused a series of ecological issues in terrestrial ecosystems and the biosphere as a whole; these issues will further aggravate because global average temperatures will continue to increase. Currently,the effects of warming,nitrogen deposition,and forest regeneration on soil nutrients such as N and P have been studied; however,the effects of warming on the coupling between soil N and P in subtropical forests remain unknown. In this study,the influence of short-term warming on the coupling mechanism between soil N and P in Chinese fir (Cunninghamia lanceolata) seedlings in a mid-subtropical plantation was investigated. In the experiment,cables were buried in the soil to increase soil temperature (temperature range (50.5)℃). The effects of short-term warming on soil water content,microbial biomass N (MBN),microbial biomass P (MBP),soil N and P,and N and P coupling were studied. The results showed that the effects of short-term warming on total N and total P were not significant. In the first year,temperature increase led to significant increase in effective N,ammonium N,and available P content,and a significant reduction in MBN content. In the second year,with the increase of temperature,the contents of available P,NH_4~+,and MBP decreased significantly. However,the increase in NH+4 /(NO-3 + NO_2~-) content significantly reduced the MBN/MBP content,and alleviated the limitation of P on microorganisms,but the effects of temperature on total N/P and available N/P were not significant. Correlation analysis showed that the coupling effect was not only influenced by the interaction between N and P,but was also influenced by soil temperature,soil water content,and other factors. These results indicated that short-term warming did not significantly affect soil N-P coupling in the subtropical Chinese fir plantation; however,it increased available N and available P contents by promoting plant growth. Thus,our findings will provide an important theoretical basis for sustainable development and scientific management of subtropical forest ecosystems in the context of future global warming.