人为干扰下沙漠绿洲过渡带斑块状植被格局动态对其土壤水文特性的影响

The vegetation patch distribution pattern is a common type of vegetation landscape in desert oasis transition zone of arid area.This patchy vegetation has low coverage and its ecological function is also fragile in the zone, but this patchy vegetation can play an important role in resist wind sand hazards and maintain safe production of oasis. Nevertheless, in recent years, some unreasonable human activities make the vegetation patches of desert oasis ecotone appear flagging sign, and reduce its function of resisting wind and stabilizing sand. This project takes the patchy vegetation of desert oasis transition zone at the northern part of Linze County of Hexi Corridor as research object, by the continuous locating observation in disturbed plots and undisturbed plots of the patchy vegetation respectively, the spatial pattern characteristics of patchy vegetation and the spatial heterogeneity of soil hydrological elements were contrastively research in different plots, and the response mechanism of soil hydrological process to the evolution of patchy vegetation pattern was proved. Combined with the data of field sample plot monitoring and laboratory analysis of soil samples, to construct the simulation model between the change of patchy vegetation pattern and the disturbance factor and soil hydrological factor in different plots, and the mutual feedback relationship between the dynamics of patchy vegetation pattern and soil hydrological process under different human disturbance was revealed. At the same time, using interpretation data of Remote Sensing image of different time phases to explore the dynamic evolution law of patchy vegetation pattern in regional scale. The research results provide a scientific basis for the ecological management of the existing sand fixation vegetation and the spatial pattern configuration of the future sand fixation vegetation in other desert oasis transition zone in arid region.

植被斑块状格局是干旱区沙漠绿洲过渡带一种常见的植被景观类型。植被覆盖度低，生态功能脆弱，但对抵御风沙危害、维护绿洲安全生产发挥着重要作用。近年来，一些不合理的人为活动使沙漠绿洲过渡带斑块状植被出现衰退迹象，降低了其防风固沙功能。本项目以河西走廊临泽县北部沙漠绿洲过渡带斑块状植被为研究对象，通过对研究区不同干扰样地进行连续定位观测，对比研究不同样地斑块植被的空间格局特征及其土壤水文要素的空间异质性，探明土壤水文过程对斑块状植被格局演变的响应机理；结合野外样地监测和实验室土壤样品分析数据，构建不同样地斑块状植被格局变化与干扰因子、土壤水文因子之间的模拟模型，揭示人为干扰下斑块状植被格局动态与土壤水文过程之间的互馈关系；同时利用不同时相遥感影像解译数据，探讨区域尺度上斑块状植被格局的动态演变规律；研究结果可为干旱区其它沙漠绿洲过渡带现有固沙植被的生态管理和未来固沙植被的空间格局配置提供科学依据。

以临泽县北部的沙漠绿洲过渡带斑块状植被为研究对象，对人为干扰下不同斑块状植被的格局动态与土壤水文特性开展对比研究，旨在为干旱区防沙治沙工程实践中固沙植物种类选择及合理搭配提供科学依据。主要成果如下：.1、从2019-2022年，样地斑块状植被覆盖度由49.81%提高到51.18%，各覆盖类型的植被面积不断演替转移，其中，低覆盖度面积减小了10.88%，较低覆盖度面积减小了0.92%，中覆盖度面积增加了8.08%，较高覆盖度面积增加了19.38%，高覆盖度面积减小了14.81%。 .2、三种典型固沙植物的植株高度与其灌丛面积均呈幂函数关系，其中泡泡刺（PP）为y=0.0002x1.9888，R2=0.5699；沙拐枣（SG）为y=0.00002x2.2939，R2=0.5926；梭梭（SS）为y=0.0006x1.5194，R2=0.5067；但相关程度均呈不显著水平。.3、三种固沙植物根区的土壤总孔隙度和毛管孔隙度均与土壤持水性能指标存在极显著正相关关系。土壤容重与饱和持水量、毛管持水量、田间持水量均存在极显著负相关关系，其中梭梭根区土壤容重与饱和持水量的相关系数为-0.955；与毛管持水量相关系数为-0.949；与田间持水量相关系数为-0.945。说明梭梭根区土壤持水性能好。.4、三种固沙植物根区初始土壤含水率与土壤稳定入渗率均呈负相关，泡泡刺土壤初始含水率与土壤稳定入渗率相关程度最高，R2=-0.858。Kostiakov模型、Horton模型对三种固沙植物根区各土层土壤水分入渗模拟的效果差异较大，而Philip模型的模拟效果好，R2均在0.911以上。 .5、不同月份在距离根部2m处的蒸散发量始终大于0.5m处的蒸散发量。固沙植物根区的土壤水分蒸散发量与温度、辐射、水汽、风力等因子有关，相关性分析结果表明，对土壤水分蒸散发影响最大的因子依次为地表温度、太阳辐射、土壤热通量和10min平均风速。.6、三种格局的固沙植被根区土壤含水率垂向上表现出两种变化趋势，一是随深度增加而增大，二是随深度增加先增大后减小。三种格局的固沙植被根区的土壤含水率总体上为SS×PP>SG×PP>SG×SS，说明混交植被SS×PP根区的土壤持水能力显著高于其它两种混交方式的植被。 .7、三种固沙植物近地表阻沙效率梭梭为60.7%，泡泡刺为51.0%，沙拐枣为46.3%。