三峡水库不同高程消落区水分变化对土壤有机碳的影响

Effects of Water Variation at Different Altitudes in the Hydro-Fluctuating Areas of Three Gorges Reservoir on Soil Organic Carbon

以位于重庆市涪陵区珍溪镇的三峡典型消落区为研究区,紫色土和水稻土为供试培养土壤,在研究区内按7个高程(152,157,162,167,172,177和182 m)实地布设培养试验;同时,多点、分层采集研究区内不同高程段(150～155,155～160,160～165,165～170,170～175,175～180和180～185 m)的剖面(0～40 cm)土样,探讨三峡水库不同高程消落区水分变化对土壤有机碳(SOC)的影响.结果表明,两种供试土壤在研究区不同高程点位实地培养1 a后,其SOC质量分数相较于培养前均有所降低;其中,水稻土在高程152 m处的减少量最大,其显著大于非消落区的177 m和182 m高程;紫色土在152 m和157 m高程处的总有机碳变化量(ΔT_(SOC))均显著大于172,177和182 m高程(p<0.05),但两高程间无明显差异,由此可见,与≥177 m的高程段相比,消落区低高程段(152 m)的水分环境更有利于培养土壤SOC分解;此外,实地培养1 a后,在152 m高程下两种培养土壤的老碳损失量(ΔL_(SOC))均较大,水稻土和紫色土在该高程下的老碳损失比例分别为14.33%和40.22%,且两种土壤的ΔL_(SOC)与ΔT_(SOC)间均存在明显的正相关.这表明,老碳损失是导致消落区152 m高程段培养SOC损失量较高的主要原因.另外,结合不同高程原位土壤有机碳分布特征,得出三峡水库消落区在160～165 m高程段的碳汇效应最强.

In order to investigate the effect of water variation at different altitudes of the hydro-fluctuating areas on soil organic carbon (SOC), the typical hydro-fluctuating area of the Three Gorges Reservoir (TGR) at Zhenxi town in Fuling District of Chongqing was used as the research area, and purple soil and paddy soil were used as the culture soil. An in situ culture experiment was carried out at the altitude of 152, 157, 162, 167, 172, 177 and 182 m. Meanwhile, soil samples were collected from the 0-40 cm layer at the altitude of 150-155, 155-160, 160-165, 165-170, 170-175, 175-180 and 180-185 m. The result showed that SOC content decreased after one-year field cultivation. The SOC decrement of paddy soil at the altitude of 152 m was the largest, which was significantly higher than the decrement of paddy soil at the altitude of 177 m or 182 m. The total organic carbon change (ΔTSOC ) of purple soil at the altitude of 152 m and 157 m was significantly larger than that at the altitude of 172 m, 177 m and 182 m ( p <0.05), but there was no significant difference between the altitude of 152 m and 157 m. Compared with that of the altitude of ≥ 177 m, the water environment of the low altitude (152 m) in the hydro-fluctuating areas was more favorable for the decomposition of soil SOC. In addition, after one-year culture experiment, the old carbon loss (Δ L SOC ) of the two soils at the altitude of 152 m was large, the loss ratio of the paddy soil and the purple soil was 14.33% and 40.22%, respectively. Meanwhile there was a significant positive correlation between Δ L SOC and ΔTSOC of the two soils. This indicated that the decrease of ΔLSOC was the primary cause that resulted in the reduction of SOC at the altitude of 152 m. In addition, combined with distribution characteristics of soil organic carbon at different altitudes, the results showed that the carbon sink capacity was highest in the hydro-fluctuating areas of 160-165 m altitude of the TGR.