黄土高原不同降水类型区林地、草地与农田土壤干燥化效应比较

SOIL DESICCATING EFFECTS OF FORESTLANDS,GRASSLANDS AND CROPLANDS IN ZONES DIFFERENT IN RAINFALL PATTERN ON THE LOESS PLATEAU

黄土高原人工林草地和旱作农田土壤干燥化问题十分突出,严重威胁着人工植被建设成效和旱作农业可持续发展。通过对黄土高原半湿润区、半干旱区和半干旱偏旱区53类林地、草地和农田深层土壤湿度的观测,分析比较了各类型区各类林地、草地和农田土壤湿度、土壤水分过耗量、土壤干燥化指数、土壤干层厚度等土壤干燥化效应指标。结果表明:(1)林地、草地和农田土壤湿度平均值依次为6.46%～12.57%、6.49%～11.52%和9.32%～16.00%,均以半湿润区最高,半干旱区居中,半干旱偏旱区最低,林地、草地和农田土壤水分过耗量平均值分别为521mm、491mm和30mm,林地土壤水分过耗量以半干旱区最高,草地以半湿润区和半干旱偏旱区最高,农田以半干旱偏旱区最高;(2)林地、草地和农田土壤干燥化指数平均值依次为39%、42%和96%,分别属于严重干燥化、严重干燥化和轻度干燥化强度,林地土壤干燥化程度以半干旱区和半干旱偏旱区最严重,草地以半湿润区和半干旱偏旱区最严重,农田以半干旱偏旱区最严重,林地、草地和农田土壤干层厚度平均值依次为881cm、836cm和336cm,林地土壤干层厚度以半干旱区和半干旱偏旱区最厚,草地和农田以半干旱偏旱区最厚。

Soil desiccation is a prominent in artificial forestlands, grasslands and croplands on the Loess Plateau, seriously threatening the effects of revegetation and sustainable development of dryland farming. Based on observation of soil moisture in deep soil layers in 53 different kinds of forestlands, grasslands and croplands in semi-humid zone, semi-arid zone and semi-arid/arid zone of the Loess Plateau, soil moisture contents, soil water overuse rate, soil desiccation indexes and thickness of desiccated soil layers in these areas various forestlands, grasslands and croplands were calculated, analyzed and compared. Results show as follows： 1） Mean soil moisture contents of forestlands, grasslands and croplands were in the range of 6.46% - 12.57%, 6.49% - 11.52% and 9.32% - 16.00%, respectively; with the highest in the semi-humid zone, and the lowest in the semi-arid/arid zone. The average soil water overuse rate of forestlands, grasslands and croplands was 521 mm, 491 mm, and 30 mm, respectively, and the highest among the forestlands was in the semi-arid zone, and the highest among the grasslands in the semi-humid zone and semi-arid/arid zone, and the highest among the croplands in the semi-arid/arid zone. 2） The average soil desiccation index of the forestlands, grasslands and croplands was 39%, 42 % and 96%, respectively, falling into the category of severely desiccated, severely desiccated and slightly desiccated, separately. The most severely desiccated forestland soils were in the semi-arid zone and semi-arid/arid zone, the most severely desiccated grassland soils in the semi-humid zone and semi-arid/arid zone, and the most severely desiccated cropland soils were in the semi-arid/arid zone. The average thickness of the desiccated soil layers in forestlands, grasslands and croplands was 881 cm, 836 cm and 336 cm, respectively. The thickest desiccated soil layers of forestlands were in the semi-arid zone and semi-arid/arid zone, and of grasslands and croplands in the semi-arid/arid zone.