运用自制微型蒸发器,测定了古尔班通古特沙漠2013年4-10月原生荒漠区梭梭(Haloxylon ammodendron)群落土壤蒸发量;结合降水量资料,分析了梭梭灌丛、裸地、梭梭冠层下不同方位、与梭梭基部不同距离处、不同坡位(东坡、西坡、坡顶和丘间地)及雨后的土壤蒸发特征;模拟了土壤蒸发量与土壤含水率的关系。结果表明:土壤蒸发量表现出与降水量相似的季节变化趋势;植被对土壤蒸发量的影响并非简单的"促进"或者"抑制",在萌发期(4-5月),梭梭冠层下土壤蒸发量大于裸地,在生长旺盛期(6-9月),梭梭冠下土壤蒸发量小于裸地,在枯落期(10月)梭梭冠下土壤蒸发量与裸地土壤蒸发量差别不大;梭梭冠层下不同方位的土壤蒸发量为西、北向 > 东向 > 南向;距梭梭基部越近土壤蒸发量越小;不同坡位土壤蒸发量差异显著,西坡的土壤蒸发量最大,东坡和丘间地的土壤蒸发量次之,坡顶的土壤蒸发量最小,4-10月西坡、丘间地、东坡的累计土壤蒸发量分别是坡顶累计土壤蒸发量的1.26、1.09、1.14倍;雨后土壤蒸发量随时间推移近似呈负指数消减;土壤蒸发量与土壤含水率呈指数函数关系,当土壤含水率较低时,可用表层土壤含水率推测土壤蒸发量。
Soil evaporation is an ineffective loss of rainfall, it directly determines the amount of rainfall that will eventually become soil water,which is available to plants.In the desert area where soil water is rare and valuable, study of soil evaporation is more important than that in other regions. Haloxylon ammodendron community of native desert was selected to quantify the mechanism of soil evaporation in Gurbantunggut Desert. To evaluate the soil evaporation pattern, we examined field soil evaporation experiment from April to October in 2013 using micro-lysimeter with precipitation data, analyzed the soil evaporation characteristic of H. ammodendron shrub and naked land, the different directions, slope positions (eastern slope, western slope, top of slope and inter-dune) were away from shrub base and after rain. Simulate the relationship between soil evaporation and soil water content was done by yield control experiment. Results showed that the soil evaporation presented the similar pattern with seasonal precipitation. The influences of vegetation on soil evaporation are not absolutely only either promotes or inhibits, compared with naked land, the soil evaporation of land under H. ammodendron canopy was higher in the germination period (April to May), less in the exuberant period (June to September), and little differences in the litter period (October). The intensity of soil evaporation under H. ammodendron canopy in different directions following the order: west, north > east > south, the shorter the distances to H. ammodendron base, the less the soil evaporation. The soil evaporation was between the different slope positions. For soil evaporation, the greatest value occurred in western, followed by inter-dune and eastern slope, top of slope's is smallest. Compared with the top of slope, the cumulative seasonal soil evaporation of western slope, inter-dune and eastern slope were 1.26 times, 1.09 times, 1.14 times throughout the growing season, respectively. Soil evaporation over time after the rain approximate negative presented exponential reduction, soil evaporation and soil water content showed exponential relationship, and the topsoil water content could be used to infer soil evaporation when topsoil water content is low.
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