喀斯特断陷盆地不同植被恢复模式土壤水分动态变化

目的]以喀斯特断陷盆地小流域中典型植被恢复模式,即桉树(Eucalyptus maideni)林、冲天柏(Cupressus duclouxiana)林、马尾松(Pinus massoniana)林以及天然次生灌丛、高盖度车桑子(Dodonaea viscosa)灌丛和低盖度车桑子灌丛为研究对象,探究断陷盆地不同植被恢复模式土壤水分时空变异规律,为该地区植被生态恢复工作提供参考。方法]利用自动气象观测系统和土壤水分传感器同步监测2016年5月—2017年4月期间小流域降雨量与各林地土壤水分,采用变异系数与克里金插值分析方法,对6种植被恢复模式林地的土壤水分时空异质性以及持续干旱条件下土壤水分衰减特征进行研究。结果]表明:(1)同一植被类型不同土层雨季和旱季土壤体积含水量垂直变化趋势相同,且雨季土壤水分含量显著高于旱季(P0.05),均为中等变异(Cv:12.88%28.66%)。(2)同一乔木林雨季和旱季的土壤活跃层与次活跃层垂直分布不同,但同一灌丛雨季和旱季分布相同。(3)6种植被恢复模式土壤体积含水量均在降雨量较充足的8—9月达到最大值,其变化范围介于26.25%44.08%之间,在降雨量明显不足的3—4月达到最小值,土壤体积含水量介于9.48%17.47%之间。(4)3种乔木林0 30 cm土层、3种灌丛0 10 cm土层充分降雨后约10 d土壤水分恢复为降雨前1 d水平,低盖度和高盖度车桑子灌丛10 30 cm土层土壤水分降雨后15 d恢复为降雨前1 d水平,并且接近植物萎蔫系数。结论]不同植被恢复模式间雨季、旱季和月均土壤体积含水量均表现为桉树林天然次生灌丛冲天柏林马尾松林高盖度车桑子灌丛低盖度车桑子灌丛。喀斯特断陷盆地季节性干旱和临时性干旱问题严峻,乔木林和灌丛经充足降雨,达到田间持水量后,在连续放晴天气下林地土壤水分可供植物10 15 d的消耗。

Soil Moisture Dynamic Change of Different Vegetation Restoration Patterns in Karst Faulted Basins

Objective] This study selected the Eucalyptus maideni woodland, Cupressus duclouxiana woodland, Pinus massoniana woodland and the natural secondary shrubs, low coverage Dodonaea viscosa and high coverage D. viscosa shrubs to investigate the spatiotemporal variability of soil moisture at different vegetation restoration patterns in karst faulted basins small watershed and to provide reference for vegetation restoration in this area.Method] The rainfall and soil moisture were measured from May 2016 to April 2017 by using automatic weather observation system and soil moisture sensor. The temporal and spatial heterogeneity of soil moisture and the characteristics of soil water attenuation under drought conditions were studied by using the coefficient of variation and Kriging interpolation analysis method.Result] (1) In different soil layers of the same vegetation type, the vertical variations of soil volume water content during the rainy and dry seasons were similar, and the soil moisture content in the rainy season was significantly higher than that in the dry season (P<0.05). Each forest was moderately variant (C_v:12.88%~28.66%). (2) In rainy and dry seasons, the distribution of active layer and sub-active layer in the same woodland was different, but the distribution was same in different soil depth of the same shrub. (3) The soil volume water content of the six kinds of woodland reached the maximum value in August to September with a sufficient rainfall, ranging from 26.25%XC~.TIF]44.08%. In the case of obviously insufficient rainfall, March to April reached the minimum value, ranging between 9.48%~17.47%. (4) The soil volume water content of 0~30 cm soil layer of three kind woodlands and 0~10 cm soil layer of three shrub species decreased to 1 day before rainfall for about 10 days. The 10~30 cm soil layer of low coverage and high coverage D. viscosa samples returned to the level of 1 day before rainfall for about 15 days and close to the plant wilting coefficient.Conclusion] The soil volume water content of different vegetation restoration patterns in rainy season, dry season and average monthly shows that the E. maideni woodland > natural secondary shrubs > C. duclouxiana woodland > P. massoniana woodland > high coverage D. viscosa shrubs > low coverage D. viscosa shrubs. The seasonal drought and temporary drought in karst faulted basins are serious, after sufficient rainfall and reached the field capacity, the soil moisture of forest land and shrub in karst faulted basins is available to plants for 10~15 days.