三峡库岸带土壤净氮矿化的温度敏感性及驱动因子

Temperature Sensitivity and Its Driving Factors of Soil Net Nitrogen Mineralization in the Bank Zone of the Three Gorges Reservoir

【目的】三峡库岸带土壤氮矿化过程对三峡水库水体富营养化及生态安全影响显著,明确三峡库岸带土壤净氮矿化对温度升高的响应和驱动因子。【方法】在整个三峡库岸带分9个断面,分别采集消落区(高程145~155 m、155~165 m、165~175 m)和非淹水区(高程175~185 m)共108个表层土样,在15、22、29和36℃四个温度下培养28 d,测定培养前后土壤铵态氮、硝态氮含量变化,计算净氨化速率、净硝化速率和净氮矿化速率及其对温度升高的响应。【结果】在四个温度下三峡库岸带土壤净硝化速率、净氮矿化速率均与高程显著正相关(P<0.05),而净氨化速率在高程之间无显著差异(P>0.05);总体上,三峡库岸带净氮矿化速率的温度敏感性(Q_(10))在0.62~3.21之间,且消落区比非淹水区土壤净氮矿化对升温更加敏感。降雨是消落区和非淹水区Q_(10)变化的共同驱动因子;此外,消落区Q_(10)与高程、p H值、年均降水量、微生物生物量碳(P<0.05)以及到三峡大坝的距离呈显著负相关(P<0.01)。【结论】在未来气候变暖条件下,与非淹水区相比,预期将有更多消落区氮素通过矿化途径进入水体,进而增加三峡水体营养负荷。

[Objective]The process of soil nitrogen mineralization in the bank zone of the Three Gorges Reservoir has a significant impact on water eutrophication and ecological security of the Three Gorges reservoir.However,the response and driving factors of soil nitrogen mineralization to warming have not been paid attention.[Method]A total of 108 topsoils were collected from the riparian area(elevation 145-155 m,155-165 m,165-175 m)and the nonflooded area(elevation 175-185m)of the Three Gorges Reservoir bank zone in nine sections of the Yangtze river.The soils were incubated at 15,22,29 and 36℃for 28 days.The contents of soil ammonium nitrogen and nitrate nitrogen before and after incubation were measured,and the net ammoniation rate,net nitrification rate and net nitrogen mineralization rate and their response to warming were calculated.[Result]The results showed that the soil net nitrification rate and net nitrogen mineralization rate in the reservoir bank were significantly positively correlated with the elevation under the four temperatures(P 0.05),but the net ammoniation rate had no significant difference between the elevations(P 0.05).In general,the temperature sensitivity(Q_(10))of the net nitrogen mineralization rate in the reservoir bank is between 0.62 and 3.21,and the soil net nitrogen mineralization in the riparian area is more sensitive to warming than that in the non-flooded area.Rainfall is the common driving factor of Q_(10)change in the riparian area and non-flooded area.In addition,Q_(10)in the riparian area was significantly negatively correlated with elevation,pH value,annual precipitation,microbial biomass carbon(P 0.05)and the distance to the Three Gorges Dam(P 0.01).[Conclusion]Therefore,it is expected more nitrogen in the riparian area will enter the water through mineralization,thus increasing the eutrophication load of the Three Gorges reservoir in the context of global warming.