石漠化治理区不同植被类型浅层土壤水分对降雨的响应

【目的】揭示石漠化治理区不同植被类型浅层土壤水分入渗过程的差异性,分析降雨对土壤水分的补给特征,因地制宜地开展灌溉工作。【方法】以花椒地、金银花地、火龙果地、荒地为研究对象,监测了地区降雨量和植被0~10、10~25 cm土层土壤含水率,并计算了土壤储水量、滞后时间、补给速率、补给效率等指标。【结果】①4种植被浅层土壤含水率变化趋势与降雨一致,6、8、9月为二者的峰值期;浅层土壤含水率为火龙果地最高,而后依次为荒地、金银花地、花椒地;火龙果地土壤含水率变异系数最小,荒地最大。②植被土壤含水率对小雨量降雨事件的响应较小,仅火龙果地增长11.97%;随降雨量级增大,土壤含水率增长率为火龙果地(7.89%~17.94%),其次为金银花地(0~45.09%)、荒地(0~59.86%)、花椒地(0~126.95%);火龙果地浅层土壤含水率增长率在大雨事件中最小,其他3种样地均为小雨量时增长率小,大雨量时增长率大。③不同植被浅层土壤水分对降雨响应时间有显著差异,大雨量条件下响应快于小、中雨量,0~10 cm土层优于10~25 cm土层;平均滞后时间为荒地0.3 h、火龙果地0.5 h、花椒地0.9 h、金银花地3.0 h;补给效率为火龙果地(64.87%)>荒地(38.16%)>花椒地(31.94%)>金银花地(29.23%)。【结论】丰水期,对火龙果地适当减少人为灌溉,增加地表覆盖以减轻水土流失;对金银花地、花椒地可采取相应保墒措施提高土壤对降雨的利用效率且在雨量较小时增加灌溉,提高入渗量。

Vegetation Types Affect Responsive Change in Soil Moisture to Rainfall in under Karst Rocky Desertification Control Areas

【Objective】The uniqueness in geomorphology and vegetation coverage in karst rocky desertification control areas makes water infiltration and plant growth in them differ from those in other areas.As plant growth relies on soil water in their root zone,it is important to understand how vegetation types affect the responsive change in root-zone soil moisture to rainfall.The purpose of this paper is to address this.【Method】We studied Zanthoxylum bungeanum land,Lonicera japonica land,Hylocereus undulates growing in land and wasteland.On each site,we measured rainfall and soil moisture content in 0~10 cm and 10~25 cm soil layers.These data were used to calculate soil moisture storage and its lagging response to rainfall,as well as effective recharge rate and recharge efficiency.【Result】①The responsive change in soil moisture content in the four vegetation types to rainfall was consistent,peaking in June,August and September.The soil moisture in top soil under the four vegetations was ranked in Hylocereus undulatus land>Hylocereus undulatus wasteland>Lonicera japonica land>Zanthoxylum bungeanum land.The variation coefficient of the soil moisture content was the least in Hylocereus undulatus land and the highest in Hylocereus undulatus wasteland.②The responsive change in soil moisture content to sprinkle irrigation was not significant between the four vegetations,increasing only in the Hylocereus undulatus land by 11.97%.With the increase in rainfall,the change in soil moisture content was the least in Hylocereus undulatus land varying from 7.89%to 17.94%,followed by Lonicera japonica land varying from 0 to 45.09%,Hylocereus undulatus wasteland varying from 0 to 59.86%,and Zanthoxylum bungeanum land varying from 0 to 126.95%.The increasing rate in soil moisture content in Hylocereus undulatus land after heavy rain events was the least,while the increasing rate in other three treatments after light rainfalls and large torrential rainfalls was small.③The response of soil moisture to rainfall varied significantly between vegetation types,faster to heavy rainfall than to small and moderate rainfall.The response of water in 0~10 cm soil layer was faster than that in 10~25 cm soil layer.The average lag in soil moisture response was 0.3 h in Hylocereus undulatus wasteland,0.5 h in Hylocereus undulatus land,0.9 h in Zanthoxylum bungeanum land,and 3.0 h in Lonicera japonica land.The order of the effective recharge efficiency was Hylocereus undulatus land(64.87%)>Hylocereus undulatus wasteland(38.16%)>Zanthoxylum bungeanum land(31.94%)>Lonicera japonica land(29.23%).【Conclusion】Reducing irrigation and increasing vegetation coverage in Hylocereus undulatus land in wet season can reduce soil erosion, while in Lonicera japonica andZanthoxylum bungeanum lands, efforts should focus on improving use efficiency of rainfall and water infiltrationduring dry seasons.