半干旱黄土区水平阶整地人工油松林地土壤水分和养分状况

Soil Moisture and Nutrient Levels in Artificial Pinus Tabulaeformis Forest by Level Terracing in Semiarid Loess Plateau

水平阶整地是半干旱黄土高原丘陵沟壑区普遍应用的一种抗旱造林措施。为研究水平阶整地措施对人工油松林的影响,对20a高密度人工油松林样地的土壤水分和养分状况进行了研究。结果表明,雨季末各样地0—160cm土层的平均土壤含水量为5.43%,其中0—60cm土层为6.94%,60—160cm土层为4.53%,雨季对各样地的土壤水分补给量很小;碱解氮、速效磷、速效钾、有机质和全氮具有表聚性,尤其是0—10cm土层表聚性显著,全磷和全钾表聚性不明显;各样地pH值均大于8;0—100cm土层的全磷、速效磷、全钾和速效钾平均含量为中等水平,有机质、全氮、碱解氮为低或很低水平。结果说明在半干旱黄土区降水量不足的情况下,人工植被密度如果过大,会恶化土壤水分和养分的状况,所以人工疏伐就成了人工林后期管理和经营中必要的环节。

Level terracing is a common forestation practice in the semiarid hilly-gully area of the Loess Plateau in China.To study the impacts of the practice on artificial forests,soil moisture and nutrient condition in a 20-year-old dense artificial Pinus tabulaeformis forest was evaluated.The average soil moisture content at the end of rainy season was found to be 6.94% in the 0—60 cm layer and 4.53% in the 60—160 cm layer,while it was 5.43% in the whole soil profile（0—160 cm）.This indicates that the soil moisture level is not replenished significantly during rainy season.Alkali solution N,available P and K,organic matter,and total N were significantly concentrated within 10 cm of soil surface,while total P and K showed insignificant surface accumulation.The pH values at all sites were higher than 8.The average contents of total P and K and available P and K in the 0—100 cm layer were all in middle level,but the average contents of organic matter,total N,and alkali-solution N were low or very low.Result from the study suggests that in the semiarid Loess Plateau with insufficient precipitation,dense artificial forest may lead to soil moisture and nutrient condition deteriorating and that artificial thinning is an important work in later stage management of artificial forests.