葛藤覆被下干热河谷冲沟沟岸土壤水热变化特征

干热河谷冲沟沟岸裸露、陡立、土壤水热变化剧烈,导致植被恢复极端困难。通过野外调查和定位监测,在葛藤覆被沟岸,根据藤本生物量设置4个处理(T1:309.70g/m~2鲜藤覆被地块,T2、T3、T4:594.34、1103.43、1693.27g/m~2枯藤覆被地块),并选取裸露地块作为对照CK,研究了葛藤不同覆被状况对沟岸土壤水分和温度在单次降雨过程变化的影响。结果表明:相比裸露沟岸而言,1)鲜藤覆被沟岸土壤含水率仅为8.68%,较裸露沟岸还降低了4.47%;枯藤覆被沟岸土壤含水率则相对增加,T2—T4土壤含水率分别为14.91%、16.75%、19.44%,较裸露沟岸增加了1.76%、3.6%、6.29%。2)鲜藤覆被可明显增加土壤水分活跃层深度、变化幅度和变异程度,枯藤覆被下土壤水分活跃层深度、变化幅度和变异程度则相对减小。3)随鲜、枯藤覆被量增加,水分补给过程中土壤含水率的增加量增大,同时水分衰减过程中土壤含水率的散失量减小;增加枯藤覆被量后,沟岸表层土壤含水率变化率的波形逐渐平缓、波动依次减小、波长稳步增大。4)随鲜、枯藤覆被量的增加,沟岸表层土壤温度波动逐渐减小。研究成果对干热河谷冲沟沟岸生境改良与植被恢复具有重要的指导意义。

Effect of Kudzu coverage on soil moisture and temperature in the gully bank of the Dry-hot Valley Region

Soil moisture and temperature change sharply in the gully bank of the Dry-hot Valley Region, and vegetation restoration is extremely difficult in this area. Based on field investigation and in situobservation in the gully bank under the coverage of Kudzu, we set four treatments depending on the biomass of Kudzu cover (T1:309.70g/m² fresh Kudzu; T2, T3, and T4:594.34, 1103.43, and 1693.27g/m² withered Kudzu, respectively), and used plots without Kudzu coverage as control. The effect of the different extents of Kudzu coverage on soil moisture and temperature in the gully bank were studied in situ. The results showed that (1) soil water content in the gully bank under fresh coverage of Kudzu (T1) was 8.68%, which was 4.47% lower than that in the bare gully bank. However, soil water content in areas under withered Kudzu coverage (i.e., T2, T3, and T4) was 14.91%, 16.75%, 19.44%, respectively, which were greater than that in the bare gully bank by 1.76%, 3.60%, 6.29%, respectively. (2) Fresh coverage of Kudzu resulted in larger active layer, range ability, and variation degree than those in the bare gully bank, whereas withered coverage of Kudzu revealed the opposite trend. (3) In the soil moisture-supplying period, the soil moisture increased with increase in Kudzu biomass. However, the rate of soil moisture loss decreased with increase in Kudzu biomass during this period. Furthermore, with increase in biomass of withered Kudzu, the rate of soil moisture waveform reduced, fluctuation decreased, and wavelength increased. (4) With increase in the biomass of Kudzu, soil temperature fluctuation in the surface layer of the gully bank decreased. Our findings have potential applications in vegetation restoration and habitat improvement of the gully bank.