土地利用方式对西藏东部河谷山地土壤肥力性质的影响

通过现场调查取样和室内理化分析,研究了西藏东部主要河谷地区不同土地利用方式下土壤肥力性质及其随土地利用方式变化的机制。结果表明:不同土地利用方式下土壤理化性质有明显的差异,耕地和裸地土壤砂粒含量高于其他利用方式,本区域土壤砂质特征明显;受有机质积累影响,乔木林地、灌丛地土壤具有相对较高N素养分;受施肥等因素影响,农耕地土壤具有相对较高P、K养分;在所有利用方式中,裸地土壤尽管具有相对较高的粉粒含量,但所有养分指标均最低,显著低于林地土壤。总之,对于西藏脆弱生境而言,耕作使得有机质更易于消耗。由于有机质与植被之间存在明显互相促进的作用,因此维持土壤有机质平衡对于恢复植被、保护青藏高原东缘生态屏障具有重要的意义。

Effect of land use on soil properties in river valleys of eastern Tibet

The Qinghai-Tibet Plateau is the most ecologically critical region as it is the source area of some large rivers, such as Yangtze, Huanghe, Lancang, and Yarlung Tsangbo rivers. Based on the field investigation and laboratory analysis of soil samples, this paper discussed the soil physical and chemical properties under different types of land use in main river valley areas in eastern Tibet. The results suggested that distinct differences of soil physical properties among soils under various types of land use were found, cropland and bare land had the higher content of sand compared with other types of land uses, while all the soils in this region tended to be desertified in texture; Due to the accumulation of organic matter, the soil in north-facing slopes contained higher nitrogen; While cropland soil contained higher P and K contents after the agricultural practices mainly owing to fertilization; Among all the types of land use, the bare land soil had the lowest nutrient contents, which were significantly lower than woodland soils despite of its relatively high silt content. The soil organic matter content influenced all the other N, P, K nutrients,which was positively correlated with total N, available N total P, available P and available K (R>0.527, N=97). The correlation between soil nutrients and silt content also disclosed the susceptibility of nutrient losses of disturbed soil by tillage, especially on steep hillslopes during rainfall events. Above all, organic matter management, in terms of land use scenario, is crucial for the significant protection of the regional ecology.