黑河下游荒漠河岸地带土壤水盐和养分的空间分布特征

Spatial Characterization of Soil Water-salt and Nutrient in a Desert Riparian Area Along the Lower Reaches of Heihe River, China

探讨干旱区内陆河流域荒漠河岸地带土壤水盐和养分的变化特征,对荒漠河岸生态系统的保育和恢复具有重要指导意义。以黑河下游垂直于河道的乌兰图格嘎渣监测断面为研究对象,通过野外采样调查,分析距河道4500m范围内荒漠河岸地带土壤水盐和养分在沿河梯度上的空间分布特征。结果表明:在0-50cm土层,土壤含水量、土壤容重、土壤pH、土壤电导率、土壤总碳、土壤总氮、土壤速效磷和土壤速效钾在沿河梯度上表现出显著的差异性。随着沿河距离增加,土壤含水量大体表现为下降的变化趋势,在300m和2950m处达到峰值,均值分别为26.57%和8.72%;而土壤容重呈相反的变化趋势,在4500m处最高,均值为1.73g·cm^-3。土壤pH值随着沿河距离的增加呈凹型变化趋势,较大值出现在距河岸300-800m和4000-4500m处,均值分别为9.21-9.24和8.7-9.18,而土壤电导率则大体呈凸型变化趋势,较大值出现在距河岸2200-3200m,均值为5.69-14.92ms·cm^-1,盐分表聚现象严重。随着沿河距离增加,土壤总碳、土壤总氮、土壤速效磷和土壤速效钾含量基本都表现出显著下降的变化趋势,在4000-4500m处值最小,均值分别为5.71、0.11、2.81和73.76mg·kg^-1,土壤养分(0-10cm)波动最为明显,由表层向下呈逐渐降低趋势。在沿河梯度上,生态输水对近河岸地带土壤的演变机制和恢复趋势有明显的促进作用,随沿河距离增加影响力渐小。在荒漠河岸生态系统恢复中,可在垂直河岸梯度上延长生态输水距离,促进地下水水位回升,有利于改善土壤结构和理化属性。

Exploring the changes of soil water-salt and nutrient across a desert riparian area in an arid endorheic basin are conducive to the conservation and restoration of desert riparian ecosystem. We analyzed the variation of soil water-salt and nutrient along river gradient in a desert riparian zone within 4 500 m from river based on field investigations in the Wulantuge monitoring section perpendicular to the channel in the lower reaches of the Heihe River. The results showed that in 0.50 cm soil layer, soil water content, soil bulk density, soil pH, soil electrical conductivity, soil total C, soil total N, soil available P and soil available K were significantly different among different sampling sites along the river gradient. With increasing distance from river, soil water content showed a downward trend, peaking at the distances of 300 and 2 950 m from the river, and the mean value were 26.57% and 8.72%, respectively. But soil bulk density showed the opposite trend to the soil water content with increased distance from river, and peaking at the distance of 4 500 m from river, and the mean value was 1.73 g·cm^-3. In general, soil pH formed a concave curve trend with increased distance from river, peaking at 300-800 m and 4 000-4 500 m, and the mean value were 9.21-9.24 and 8.73-9.18, respectively. Soil electrical conductivity, however, formed a convex curve trend with increased distance from river, by peaking at 2 200-3 200 m, and the mean value was 5.69-14.92 ms·cm^-1, where surface soil salt accumulation was serious. Soil total C, soil total N, soil available P and soil available K all showed a significant decline with increased distance from river, and the minimum values were 5.71, 0.11, 2.81 and 73.76 mg·kg^-1 around 4 000-4 500 m from the river, respectively, the fluctuation of topsoil (0.10 cm) was most obvious and soil nutrients gradually decreased with increased soil depth. Our observations indicate that ecological water conveyance prominently promotes the evolution mechanism and recovery trend of soil in the desert riparian zone, and impact is less when the distance from river is increased. Therefore, in the process of desert riparian ecosystem restoration, we recommend extending the distance of ecological water conveyance on the vertical river bank gradient to promote the groundwater level and benefit the soil water content, which could contribute greatly to the improvement of soil structure and physico-chemical properties.