Responses Of Soil And Chinese Fir Seeds Phosphorus To Simulated Warming And Precipitation Exclusion Application In Mid-subtropical Forest

Phosphorus is a limited element for plant growth and its low efficiently restricted plant production in tropical forest. Tropical forest have highly weathered soil, and abundant iron and aluminum oxide. Phosphorus fixed by iron and aluminum oxide were account for 95% to 99% in the soil. Climate change have effected on the soil temperature and moisture, the effectiveness of soil P and the absorption of plant. However, many related research focused on the temperate regions, and little report about tropical and subtropical regions. The relevant mechanism is unclearing. To further study the impact of climate change on soil phosphorus cycle, experiments that simulate global warming and precipitation exclusion have been conducted in the Sanming Research Station of Forest Ecosystem and Global Change, Fujian. Through in situ observations on field soil temperature and moisture, Chinese fir seedling growth situation, combined with different forms of soil phosphorus, rootlets of Chinese fir seedlings and Chinese fir seedling leaves phosphorus content changes under different treatments, this dissertation is in hope of exploring the impact of climate change on the subtropical soil phosphorus forms and Chinese fir seedlings phosphorus utilization. The following conclusions can be reached:Compared with the contrast treatment, the warming treatment led soil organic P and soil microbial biomass P content reduced by 9.5% and 9.5%, soil available P increased by 24%, but have no significant to soil total phosphorus ?P>0.05?. Precipitation exclusion treatment make soil organic P and microbial biomass P reduced by 15.7% and 23.6%, but have no significant to soil total phosphorus and available phosphorus ?P>0.05?; warming and precipitation exclusion interactive treatment make the soil microbial biomass P reduced by 38.9%, soil available P increased by 12.7%, but have no significant to total phosphorus and organic phosphorus content ?P>0.05?. Overall, compared with contrast treatment total phosphorus content, there was no significant among warming treatment, precipitation exclusion treatment, warming and precipitation exclusion interactive treatment ?P>0.05?, but they all reduced soil organic phosphorus and the content of microbial biomass P, and increased the effective phosphorus content in the soil.Warming and the interactive of warming and precipitation exclusion have significant correlation to NaHCO₃-Po, soil organic phosphorus grade portion ?P<0.05?. Warming and precipitation exclusion can enhance phosphatase activity in soil and promote the mineralization of soil organic phosphorus, reducing the soil labile organic ?NaHCO₃-Po, NaHCO₃-Pi? content, but increasing the labile inorganic phosphorus ?NaHCO₃-Pi? content of the soil components. The research found that simulated warming and precipitation exclusion can be applied to shift soil phosphorus cycle by increasing the soil organic phosphorus mineralization.In order to research how the Chinese fir seedling respond to soil warming, C, N, and P element content in Chinese fir seedlings leaves and roots are tested and analyzed, the results of which indicate that compared with contrast treatment, warming treatment improved 14.7% and 15.7% of N and N:P respectively, precipitation exclusion treatment increased 9.4% and 10% of N and N:P respectively, warming and precipitation exclusion interactive treatment gained 51.2% and 19% of N and N:P respectively of the leaves of Chinese fir seedling. The research of the Chinese fir seedling rootlets indicated, compared contrast treatment, warming improved 34.6% of N,25.4% of C:P, but decreased 16% of P, precipitation exclusion treatment increased 18.4% and 21% of rootlets N and N:P respectively. The research found N:P, C:P of the leaves of Chinese fir seedling in growing season higher than in non-growing season. Different treatments lead to varied P restrictions. N:P has been augmented in the Chinese fir seedling rootlets under different treatments, indicating that the rootlets intake of P has been restricted.