典型岩溶丘陵区生长季土壤CO_2、CH_4通量研究

Study on soil carbon dioxide, methane flux of growing season in karst hilly area

我国西南岩溶丘陵区生长季漫长,而土壤表面CO_2、CH_4通量受地表植被覆盖的影响较大。为探究岩溶丘陵区生长季有植被覆盖(有草)和无植被覆盖(无草)的土壤表面CO_2、CH_4通量及其日变化特征,采用静态箱-气相色谱法对重庆市南川岩溶丘陵区土壤表面CO_2、CH_4通量进行观测,结合土壤温、湿度进行研究。结果表明:岩溶丘陵区土壤表面在生长季表现为CO_2源、CH_4汇,有草的土壤表面CO_2通量明显高于无草土壤表面CO_2通量,CH_4通量则无明显差别,说明在生长季地表植被覆盖是影响土壤CO_2通量的重要因素,而植被覆盖对土壤CH_4通量无显著影响,土壤表面有草和无草的CO_2通量分别为552、352 mg/m2·h,CH_4通量分别为-80、-75μg/m2·h(生长季6个月平均值)。在生长季日变化尺度上,土壤也表现为CO_2源、CH_4汇,有草土壤表面的CO_2通量明显高于无草土壤表面CO_2通量,且二者的变化特征一致,CH_4通量受到植被覆盖的影响较小;生长季土壤CO_2、CH_4通量受土壤温、湿度的共同影响,其中土壤CO_2通量与土壤温度呈正相关关系,即土壤温度升高会促进土壤CO_2通量的提高,而土壤CH_4通量与土壤温度无相关关系,即土壤温度对土壤CH_4通量无显著影响;由于生长季土壤湿度变化较土壤温度小,因此土壤湿度对土壤CO_2、CH_4通量的影响较土壤温度小。

The growing season in the karst hilly area of southwest China is long,and the flux of CO2 and CH4 on the soil surface is greatly affected by the vegetation cover on the surface.To investigate the CO2 and CH4 fluxes and their diurnal variations of soil surface covered with vegetation(with grass)and non-vegetation cover(without grass)in the growing season of karst hilly area,the CO2 and CH4 fluxes on the soil surface in the Nanchuan karst hilly area in Chongqing were studied by static box-gas chromatography,combined with soil temperature and humidity research.The results showed that the surface of soil in karst hilly area showed CO2 source and CH4 sink during the growing season.The soil CO2 fluxes were significantly higher than that of grass-free CO2 fluxes,while there was no significant difference between grass and grass-free CH4 fluxes on the soil surface.It indicates that vegetation cover on the surface of the growing season is an important factor affecting soil CO2 flux,while vegetation cover has no significant effect on soil CH4 flux.Soil CO2 flux and grass-free CO2 flux were 552 mg/m2·h,352 mg/m2·h;Soil grass CH4 flux and grass-free CH4 flux were-80μg/m2·h,-75μg/m2·h(6-month average of growing season).On the scale of the growing season,the soil also appears as CO2 source and CH4 sink.The CO2 flux of grasses was significantly higher than that of grass-free CO2 fluxes,and the change characteristics of the two were consistent;however,the CH4 flux on the soil surface is less affected by vegetation cover.There is a positive correlation between soil CO2 flux and soil temperature.That is,soil temperature increase will promote soil CO2 flux,while soil CH4 flux has no correlation with soil temperature,so soil temperature has no significant effect on soil CH4 flux.Since the soil moisture change during the growing season is smaller than the soil temperature,the effect of soil moisture on soil CO2 flux and soil CH4 flux is smaller than soil temperature.