崇明东滩围垦区不同土地利用类型对土壤呼吸及其组分的影响

Soil respiration and its components across different land use types in the Dongtan reclamation area of Chongming Island

在崇明东滩围垦区,采用Licor-8100A土壤碳通量观测系统及分层去根法,连续测定5种土地利用类型(芦苇湿地、白茅湿地、幼龄林、中龄林和农田)的土壤呼吸、异养呼吸和自养呼吸,以及0~10 cm表层土壤温度、体积含水率和电导率等环境因子,系统地比较了崇明东滩围垦区不同用地类型土壤呼吸及其组分的差异.结果表明:①幼龄林、中龄林和农田样地的土壤呼吸显著低于芦苇湿地和白茅湿地样地;②幼林龄、中林龄和农田样地的异养呼吸占比显著高于芦苇湿地和白茅湿地样地;③土壤呼吸及其组分与土壤温度呈显著的指数关系,但与土壤含水率和电导率的相关性较弱.与残存湿地相比,不同的农林利用方式显著降低了围垦区土壤呼吸,但大幅增加了异养呼吸,这可能说明土壤有机碳库在围垦20年后仍处于净损失状态.因此,需要采取有效措施进一步提升该区域土壤的碳固持能力.

In the Chongming Dongtan reclamation area,the soil carbon flux observation system(LI-8100A)and root removal method were used to continuously measure soil respiration(R_(S)),heterotrophic respiration(R_(H)),and autotrophic respiration(R_(A))of five land use types(Phragmites australis wetland,Imperata cylindrica wetland,young forest,middle-age forest,and cropland);the methods were also used to measure the soil temperature,volumetric water content,electrical conductivity,and other environmental factors in the 0-10 cm soil layer.In this study,the differences in soil respiration and its components among different land use types in the Chongming Dongtan reclamation area were systematically compared.The results showed that:①R_(S) in the young forest,middle-age forest,and cropland plot were significantly lower than those in the P.australis wetland and the I.cylindrica wetland plot;②the proportion of R_(H) found in the young forest,middle-age forest,and cropland was significantly higher than that observed in the P.australis wetland and the I.cylindrica wetland;③R_(S) and its components showed a significant exponential relationship with soil temperature,but showed weak correlations with the soil volumetric water content and electrical conductivity.Compared with the residual wetlands,the different agroforestry utilization methods significantly reduced R_(S),but significantly increased R_(H),which may suggest that the soil organic carbon pool is still in a state of net loss after 20 years of reclamation.Thus,effective measures should be taken to improve the carbon sequestration capacity of the reclaimed soil in this area.