| Soil moisture is the main environmental factor to constrain vegetation growth. This study took the patch vegetation area on Desert-oasis Ecotone in the middle reaches of Heihe River as the study area, the soil moisture data was collected in 0~100 cm soil layer of samples(340 m×300 m) and the strip(1050 m) in before and after rainy season in 2014~2015. Firstly, we analyzed the distribution of soil moisture and total variation characteristics. Secondly, the spatial variation characteristics and apatial distribution of soil moisture were analyzed with the method of geo-statistical methods. Thirdly, using the grey correlation analysis analyzed the influences between the factors(such as soil particle, soil organic matter, vegetation coverage, altitude the meteorological factors etc al.) and soil moisture in sampling. Finally, discussing the chang of soil moisture under these kinds of Nitrarias phaerocarpa, Calligonum chinense, Haloxylon ammodendron, vegetation patches, bare patches. The main results are as follows:(1) On the vertical distribution, the average soil moisture in 0~10cm soil layer in depth was minimum; the average soil moisture in 80~100cm soil layer in depth was maximum; and the average soil moisture in 0~100cm soil layer increased with soil depth increasing—it presented a fast increasing trend.(2) The soil moisture of the patch vegetation area was mostly characterized by strong spatial variation, maximum error of variation coefficient of soil moisture appeared in 10~20cm soil layer.(3) The variogram models of soil moisture in 0~100cm soil layer were exactly the same before rainy season in 2014~2015. These models were linear model, index model, index model, spherical model, spherical model and spherical model respectively. But the variogram models of the soil layer in 10~100cm were different after the rainy season in 2014~2015. These models after the rainy season in 2014 were respectively the linear model, spherical model, spherical model, exponential model, spherical model and exponential model, these models after the rainy season in 2015 were linear model.(4) About 75.6% ~99.7% of spatial variance of soil moisture in 10~100cm soil layer was caused by spatial autocorrelation within 64.2~145.3m before rainy season in 2014. About 76.9%~92.9% of spatial variance of soil moisture in 10~100cm soil layer within 79.9~154.2m was caused by spatial autocorrelation after rainy season in 2014. About 85.7%~99.7% of spatial variance of soil moisture in 10~100cm soil layer within 57.0~131.1m was caused by spatial autocorrelation before rainy season in 2015. Within 131.3m, about 67.8%~100% of spatial variance of soil moisture in 0~10 cm soil layer before and after rainy season in 2014~2015, and about 42%~100% in 10~100cm soil layer after rainy season in 2015 was caused by random factors.(5) In the patchy vegetation region, soil moisture in 0~10cm soil layer was low, and its spatial distribution was consistent after rainy season in 2014 and 2015. The soil moisture in 10~20cm soil layer change abruptly, and its spatial distribution was inconsistent after the rainy season in 2014 and 2015. The soil moisture in 20~60cm soil layer was active, which was higher in north and southwest and lower from southeast to the northwest. The soil moisture in 60~100cm soil layer was relatively stable, its spatial distribution was consistent before and after rainy reason in 2014 and 2015.(6)Soil moisture of upper soil(0~40cm) closely linked with organic matter, vegetation coverage, grade(> 1 mm, 0.5 ~ 1 mm, 0.25 ~ 0.5 mm, 0.1 ~ 0.25 mm, 0.25 ~ 0.1 mm and 0.075 mm), elevation and sediment deposition, the influence degree was high. Soil moisture of below soil(40 ~ 100cm) closely linked with organic matter, graded(particle size, particle size of 0.5 mm or 0.075), but such as vegetation coverage, elevation had a litter influence on soil water. In addition, coarse sand particle size(>0.5mm) almost had greastest influence on soil water in 100 cm soil layer.(7) The main meteorological factors affecting soil moisture in the different periods were different. The major meteorological factors were wind speed, evaporation and soil temperature before the rainy season in 2014; these were rainfall and evaporation capacity after the rainy season in 2014; these were the relative humidity and soil temperature before the rainy season in 2015; these were the accumulated temperature and wind speed after the rainy season in 2015.(8) Bubble thorn had a strong impact on soil moisture, the changing tread of soil moisture within 5m almost the same on the vertical distribution. Soil moisture in Nitrarias phaerocarpa from 0m, 1m, and 2m to 5m was present a "wave type" change. The variation trend of soil moisture of Calligonum chinense from 0m, 1m to 2m was almost the same, the soil moisture content increased rapidly as the deepening of the soil. The soil moisture of Haloxylon ammodendron within10 m in 0~120cm soil layer was low, the soil moisture content increased slowly as the soil layer respectively. Soil water in the Bare patches increased rapidly with soil deepen, soil water in the vegetation patches increased rapidly with soil deepen at first(20~80 cm), then it remained unchanged(80 ~ 120 cm). |
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