新疆安集海灌区膜下滴灌棉田根系层土壤盐分多尺度空间分布特征

Multi-scale Spatial Distribution Characteristics of Soil Salinity in Root-zone in Film-mulched Drip-irrigated Cotton Fields in Anjihai Irrigation Zone, Xinjiang

明晰土壤盐渍化空间分布特征是盐碱地改良的基础。与单一尺度相比,嵌套多尺度研究可更好地分析土壤盐分的空间变异结构特征,更精确地表达盐渍化程度的自相关随尺度的变化情况。采用传统统计学和地统计学相结合的方法,通过野外实地分层采集土样,分析了4km、500m和100m三个嵌套尺度条件下,新疆安集海灌区膜下滴灌棉田根系层土壤含盐量的空间分布规律及其变异特性。结果表明,灌区棉田各尺度根系层土壤含盐量整体水平较低(平均1.52~1.87 g·kg^(-1)),属中等变异,具有明显的连续变化和底聚特征。轻度盐化土和非盐化土在整个灌区占主导地位并主要分布于地表水矿化度较低、地势较高、排水相对通畅的灌区东南侧,盐渍化相对较重区域主要位于地下水埋深较浅的泉水溢出带,以及受平原水库和干渠渗漏影响的区域。受地形地貌等结构性因素与人为活动等随机性因素共同影响,土壤含盐量呈强空间自相关性:随尺度加大,地统计模型的块基比减小,相关距离增加,自相关性增强,结构性因素影响增强,随机因素影响减弱;反之随尺度减小,空间分布更加清晰明确,随机因素的影响则逐渐增强。对于盐渍化严重区域,有必要针对整个根系层采用嵌套方式在更小尺度上加密采样,以充分了解土壤盐分的空间分布规律与变异特性。

【Objective】The knowledge about the spatial distribution characteristics of salinization is the basis for amelioration of saline-alkali soils.Compared with research based on a single scale,nested multi-scale research can be more effectively applied to analyzing structural characteristics of the spatial variation of soil salinity with higher accuracy in describing scale-dependent self-correlated variation of salinization.【Method】In the Anjihai Irrigation Zone of Xinjiang,soil samples were collected by soil layer in the film-mulched cotton fields for analysis of rules and variabilities of the spatial distribution of salt content in the root zone of the drip-irrigated cotton field under film mulch with the method combining conventional statistics and geo-statistics,as affected by nested scales of 4 km,500 m and 100 m.【Result】Results show that,for any scale,soil salinity in the root-zone of the cotton fields in the zone is generally low,with the mean being in the range of 1.52–1.87 g·kg–1,moderate in variability,and characterized by continuous variation and accumulation at the bottom of the root zone.Non-and mildly-salinized soils dominate the irrigation zone and are mainly located in the south-east part of the zone,where the surface water is low in salinity and the ground is quite high with unobstructed drainage,while relatively seriously salinized soils are mainly distributed in areas where the ground water is shallow and overflows,and in areas that are affected by the leakage from reservoirs in the plains and trunk canals.As influenced by some structural factors(e.g.terrain landform)and stochastic factors(e.g.artificial activities),soil salt content in this area shows a significant spatial self-correlation in distribution.With increasing scale,nugget-to-sill ratio of the geo-statistical analysis model decreases,and related distance,self-correlation and impact of structural factors increase,but the influence of random factors weakens.On the contrary with declining research scale,spatial distribution becomes more explicit,and the impact of random factors intensifies.【Conclusion】For those relatively seriously salinized areas,it is advisable to employ the nested multi-scale root-zone sampling strategy so as to get a full knowledge about characteristics of the spatial distribution and variability of soil salinity in the drip-irrigated cotton fields under film mulch.