太行山区不同植被条件下土壤水分动态变化特征研究

Soil water variation of different vegetation community in Taihang Mountain Area

为了解太行山区主要植被类型的土壤水分状况,选取太行山区4种典型植被--小麦/玉米(农作物)、黄背草(草本)、荆条(灌木)和核桃(乔木),利用大型称重式蒸渗仪,监测了4种植被2018年和2019年生长季(4-10月)的土壤水分、深层渗漏和蒸散发要素,并利用数理统计方法分析了土壤含水量的变化特征。结果表明,2018年小麦/玉米、黄背草、荆条和核桃地平均土壤含水量分别为0.30 cm^3×cm^-3、0.35 cm^3×cm^-3、0.32 cm^3×cm^-3和0.36 cm^3×cm^-3,而2019年平均土壤含水量分别为0.28 cm^3×cm^-3、0.26 cm^3×cm^-3、0.23 cm^3×cm^-3和0.31 cm^3×cm^-3,相比于2017年生长季末(11月)土壤含水量,2018年小麦/玉米、黄背草、荆条和核桃地土壤含水量下降幅度分别为0.05 cm^3×cm^-3、0.04 cm^3×cm^-3、0.09 cm^3×cm^-3和0.05 cm^3×cm^-3,2019年下降幅度分别为0.07 cm^3×cm^-3、0.13 cm^3×cm^-3、0.18 cm^3×cm^-3和0.10 cm^3×cm^-3,荆条地土壤水分的下降幅度最大,小麦/玉米地下降幅度最小。在垂直方向上,4种植被土壤水分变化趋势一致,随着土层深度的增加土壤含水量逐渐降低,但对土壤水分的获取深度有所差异。土壤水分获取深度小麦/玉米主要为45~100 cm,黄背草和核桃主要为100~150 cm,荆条主要为150~180 cm。形成这一结果的原因可能是根系分布的差异,小麦/玉米和黄背草为禾本科植物,根系分布在浅层土壤,虽然核桃为乔木,但其为浅根植物,而荆条在主根周围分布有丰富的侧根,且主根延伸到土层深部,能够获取深层土壤水分。这表明荆条是该地区主要耗水物种,在太行山区绿化植被的选取和生态系统的管理和修复中,应尽量减少荆条的覆盖面积。

Soil water storage and movement are highly heterogeneous across ecosystems.However,variation characteristics of soil moisture are not well understood at present,due to the high heterogeneity of environmental conditions.The Taihang Mountain region is an important water collection area of the North China Plain,and a functional area for water conservation in the national Beijing-Tianjin-Hebei coordinated development strategy.However,little is known about the soil water regime of the main plant species that inhabit this region.In this study,the soil water content for four representative vegetation types,Triticum aestivum/Zea mays,Themeda triandra var.Japonica,Vitex negundo var.heterophylla and Juglans regia,that are widely distributed in the semi-arid area of the Taihang Mountain,were observed using large scale weighing lysimeters,during the growing season(April to October)in 2018 and 2019.Weighing lysimeters systematically measured the soil water content,seepage,and evapotranspiration among different vegetation communities,and the collected data on the variation characteristic of soil moisture content for four vegetation types were analyzed by means of statistical analysis.The results showed that average soil water content for T.aestivum/Z.mays,T.triandra,V.negundo,and J.regia were 0.30 cm^3×cm^-3,0.35 cm^3×cm^-3,0.32 cm^3×cm^-3 and 0.36 cm^3×cm^-3 in 2018,and 0.28 cm^3×cm^-3,0.26 cm^3×cm^-3,0.23 cm^3×cm^-3 and 0.31 cm^3×cm^-3 in 2019,respectively.Similarly,the decrease of soil water content for T.aestivum/Z.mays,T.triandra,V.negundo,and J.regia were 0.05 cm^3×cm^-3,0.04 cm^3×cm^-3,0.09 cm^3×cm^-3,and 0.05 cm^3×cm^-3 in 2018,and 0.07 cm^3×cm^-3,0.13 cm^3×cm^-3,0.18 cm^3×cm^-3,and 0.10 cm^3×cm^-3 in 2019,respectively,compared to the soil water content at the end of growing season(December)of 2017.The decrease of the soil water content for V.negundo was greatest,and that for T.aestivum/Z.mays was the smallest,among the four vegetation types.The direction of vertical gradient of soil water content was consistent among the four vegetation types,with the soil water content decreasing as the depth of soil increased.However,the depth of water uptake from soil was discrepant.In T.aestivum/Z.mays fields,the main depth was between 45-100 cm.In T.triandra and J.regia fields,the main soil depth was between 100-150 cm.In V.negundo fields,the main soil depth was between 150-180 cm.These results may be due to differences in root distribution.T.aestivum/Z.mays and T.triandra are from Gramineae family,and their root systems are distributed in shallow soil.Although J.regia is arboreal,it has shallow-rooted plants.V.exnegundo has lateral roots radiating out from the main root crown,one or more deeply penetrating tap(sinker)roots,and can uptake water from deep soil.This indicated that V.exnegundo was the species with the greatest water consumption.The pattern of plant water consumption needs to be considered in plant species selection,ecological management,and restoration of semi-arid ecosystems in the Taihang Mountain region.