Soil Respiration and Microbial Biomass in Sycamore (Platanus occidentalis L.) Plantations Treated with Irrigation and Nitrogen Fertilization

摘要

It is well known that carbon storage capacity of forests will change in response to management practices such as fertilization However, the influence of fertilization on belowground processes such as soil respiration and microbial biomass is still unc lear I measured soil respiration and microbial biomass along a fertilization gradient(0, 56, 112, and 224 kg N ha~(-1)yr~(-1)) and irrigation in 7-year-old sycamore plantations, established on identical soils, in northwest Florida, Soil respiration was m easured monthly from June 2001 to May 2002 using the soda-lime technique Miciobial biomass C, annual litter production, soil temperature, moisture, soil pH, and organic matter were also measured along the same gradient. Annual soil respiration rate was r anged from 527 to 655 g Cm~(-2)yr~(-1), Nitrogen fertilization had a significant negative effect on soil respiration Mean daily soil respiration rates exhibited a significant exponential relationship with soil temperature(r~2 =0.53). N fertilization redu ced microbial biomass C and increased annual litter production only in 224 N kg ha-1 yr-1 treatment Annual soil respiration rates were positively correlated with microbial biomass C(r~2=0.37). In addition, microbial biomass C was positively correlated wi th soil organic matter (r~2 =0.57) and soil pH(r~2=0.61) Multiple regression analysis indicated that microbial biomass, soil organic matter, and soil pH were the major factors affecting soil respiration in the sycamore plantation. Total below-ground C al location estimates were 452, 343, 328, 299, and 254 g Cm~(-2)yr~(-1) for control, irrigation, 56 N, 112 N, and 224 N treatments, respectively. The decreased below-ground carbon allocation in irrigation and fertilization treatment indicates that a larger portion of production was allocated in the above-ground compared to the water and/or nutrient stressed stands.