| Global climate change with air warming, snowmelt, extremely climate and so many is changing process of terrestrial ecosystem, extremely effects of warmly winter on soil carbon and nitrogen process in cold bioregions. However, seasonal snow covers and freeze-thaw cycles obvious affect cold bioregion and there should have different responses in soil carbon and nitrogen process to climate change at different critical periods, but little study have showed it. Alpine forest of western Sichuan is located in eastern Tibet pleat and headwaters of Yangtze River where has important strategic position in water conservation, biological diversity, absorb CO2 in atmosphere, indicate global climate change and others, also a fragile ecosystem area and a region sensitive to climate change with seasonal snow covers and freeze-thaw cycles. Climate changing in future influence soil carbon and nitrogen process not only in soil absorb carbon and release carbon and soil nitrogen content, but influence water environment of stream and river conterminous with soil. Therefore, in order to understand the effect of climate change on the process of soil carbon and nitrogen in the alpine forest, an experiment of three years in different elevations to simulate climate warming. soil columns sampled from the alpine primeval fir forest at 3600-m elevation were incubated on the forest floor at the 3600-m (Al),3300-m (A2) and 3000-m (A3) elevation, and we discussed climate warming effect on soil carbon and nitrogen transformation process, soil microbial biomass carbon and nitrogen and leaching of carbon and nitrogen from floor and soil layers of alpine forest ecosystem in cold region at different critical periods, which could provide a scientific basis for manage alpine forest ecosystem in cold region under climate change in future.Effect of simulate climate warming on soil carbon transformation process of alpine forest western Sichuan changed at different critical periods and in soil layers. And effect of simulate climate warming on soil carbon transformation in soil organic layer was more heavy than in mineral soil layer. Simulate climate warming decreased soil carbon content of soil organic layer and mineral soil layer (except mineral soil layer in A2 elevation), and decreased soil carbon of soil organic layer was more than decreased soil carbon of mineral soil layer, but effect of simulate climate warming never significantly. Simulate climate warming enlarged fluctuation of soil carbon transformation, but effect of simulate climate warming never significantly. Carbon transformation values of soil organic layer and mineral soil layer in growing season were negative values that soil carbon content decreasing, it was showed in soil organic layer:A2 (-7.26 mg/(kg·d))> Al (-12.96 mg/(kg·d))> A3 (-86.06 mg/(kg·d)) and in mineral soil layer:A1 (-17.22 mg/(kg·d))> A2 (-23.02 mg/(kg-d))> A3 (-25.16 mg/(kg·d)); but a reverse result was showed in non-growing that soil carbon increasing, it was showed in soil organic layer: A3 (83.83 mg/(kg·d))> A1 (18.28 mg/(kg·d))> A2 (-26.99 mg/(kg·d)) and in mineral soil layer:A2 (53.67 mg/(kg·d))> A3 (24.36 mg/(kg·d))> A1 (11.06 mg/(kg·d)); but effect of simulate climate warming never significantly. A similar result of carbon transformation of soil organic layer and mineral soil layer in years, and simulate climate warming never significantly effect on carbon transformation in years.Effect of simulate climate warming on soil nitrogen mineralization in soil organic layer was heavier than in mineral soil layer. Simulate climate warming decreased soil nitrogen content of soil organic layer (except soil organic soil layer of A2 elevation) and mineral soil layer, decreased nitrogen of soil organic was more than mineral soil layer, but effect of simulate climate warming never significantly. Simulate climate warming decreased ammonization of soil organic layer and mineral soil layer (except mineral soil layer of A2 elevation), but increased nitration of soil organic layer and mineral soil layer, and nitration was more than ammonization, simulate climate warming increased soil nitrogen mineralization and simulate climate warming effect nitration significantly. Ammonization and nitration was negative values in growing season with simulate climate warming, soil mineral nitrogen was consumption, and simulate climate warming promoted soil mineral nitrogen consumption (except nitrate nitrogen of A2 elevation). However, effect of simulate climate warming never significantly. Ammonization and nitration was positive value in non-growing season with simulate climate warming and nitration was heavier than ammonization, nitrogen was mineralization, and simulate climate warming increased soil nitration, the heaviest nitration showed in soil organic layer:A3 (0.5278 mg/(kg·d))> A2 (0.2925 mg/(kg·d))> Al (0.1746 mg/(kg-d)), and simulate climate warming effect on nitration significantly. A similar result of soil nitrogen mineralization of soil organic layer and mineral soil layer in years, and simulate climate warming never significantly effect on soil nitrogen mineralization in years.Soil microbial biomass carbon and nitrogen in soil organic layer was more than in mineral soil, simulate climate warming decreased soil microbial biomass carbon and nitrogen content in soil organic layer but increased in mineral soil layer, simulate climate warming effect on soil microbial biomass carbon and nitrogen significantly, yearly average soil microbial biomass showed in soil organic layer:A1 (1842.91 6mg/kg)> A2 (1664.84 mg/kg)> A3 (1385.72 mg/kg), and showed in mineral soil layer: A3 (300.20 mg/kg)> A2 (293.13 mg/kg)> A1 (268.18 mg/kg). Soil microbial biomass carbon and nitrogen decreased sharply at period with freeze-thaw cycles in two soil layers, simulate climate warming changed freeze-thaw cycles which decease soil microbial biomass significantly, microbial biomass in growing season was more than non-growing season, and simulate climate warming increased soil microbial biomass in growing season but decreased in non-growing season. A similar result of soil microbial biomass of soil organic layer and mineral soil layer in years, and simulate climate warming never significantly effect on soil microbial biomass in years.Leaching of dissolved organic carbon in soil of alpine forest western Sichuan concentrated in late growing season to deep freezing period, and leaching content of non-growing season was more than growing season that heavier leaching content input soil and leach out soil in these periods. There was heavily dissolved organic carbon leaching of soil with freeze-thaw cycles, and lots of dissolved organic carbon of soil leached with freeze-thaw cycles at onset of froze period. Simulate climate warming increased leach dissolved organic of floor and soil layers at late growing season to deep froze period and leached dissolved organic carbon of total soil layer in non-growing season showed:A3 (7.25 kg/hm2)> A2 (6.68 kg/hm2)> A1 (5.36 kg/hm2). There was similar leaching dissolved organic carbon of floor, soil organic layer and total soil layer with a simulate climate warming condition, though leached dissolved organic carbon of the second year and the third year of floor, soil organic layer and mineral soil layer was more than the first year, but simulate climate warming never changed dissolved carbon leaching in years.Leaching nitrogen of soil organic layer and mineral soil layer was more than floor. The most of leached nitrogen all year was dissolved inorganic nitrogen, leached nitrogen in growing season was dissolved organic nitrogen, and leached inorganic nitrogen in non-growing season was more than leached organic nitrogen all years, simulate climate warming increased nitrogen leaching of total soil layer in non-growing season, but effect of simulate climate warming never significantly. Leached nitrogen of total soil layer in non-growing season was show:A2 (1.48 kg/hm2)> A3 (1.40 kg/hm2)> A1 (1.39 kg/hm2). Freeze-thaw cycles promote leaching of soil dissolved nitrogen, and leached ammonium nitrogen of soil was more than nitrate nitrogen at critical periods with freeze-thaw cycles, and effect significantly. There was similar result in leaching of nitrogen of floor, soil organic soil layer and total soil layer yearly, and simulate climate warming never changed leaching nitrogen in years.In conclusion, simulate climate warming should effect on soil carbon and nitrogen process of alpine forest soil western Sichuan direct action and indirect action. Simulate climate warming promoted consumption of alpine forest soil western Sichuan in growing season and added mineral carbon and nitrogen content of soil in non-growing season; simulate climate warming decreased soil microbial biomass carbon and nitrogen but decreased soil microbial biomass carbon and nitrogen, and microbial biomass of soil organic layer was more than mineral soil layer that simulate climate warming limit soil microorganism use soil carbon and nitrogen recycle. Simulate climate warming promoted soil dissolved nitrogen leaching that soil carbon and nitrogen pool decrease.The results indicate that cold bioregion soil environment changed with extremely climate under global climate warming, what result in consumption of soil carbon and nitrogen pool, original microorganism population was limited, and more leached carbon and nitrogen could effect water environment of cold bioregion. |
PDF Full Text Request