宁南黄土高原不同土地利用模式对土壤的影响研究

Effects of land use pattern on soil in the Loess Plateau of south Ningxia

宁南黄土高原采取退耕、还林、还草措施5年后,区域局部生态环境发生了较大变化。文章针对退耕后的典型土地利用方式,阐述了自然撂荒坡地、柠条(CaraganakorshinskiiKom.)灌木林地、坡耕地产生的土壤水热、养分效应,其结果对减少宁南黄土高原土壤养分流失、提高土地生产力和合理农业布局具有重要的意义。利用径流小区试验方法,研究结果表明:不同土地利用方式下土壤储水量的变化为单峰型,与雨量峰值相比,对应储水量略有滞后现象。土壤储水量整体表现为农耕地>自然荒坡>柠条林地。受植被类型影响,坡面土层温度为荒坡草地>柠条林地>农地。随坡度增加,自然荒坡土壤有机质有降低的趋势,相同坡度下(25°)自然荒坡土壤有机质平均为12.76g/kg,是农耕地、柠条林地的1.2倍和1.94倍。在3种土地利用方式下,全磷含量没有明显差异,坡耕地土壤速效磷、速效钾含量较高,柠条林地和自然荒坡速效磷、速效钾含量没有明显差异。不同土地利用方式下,Ca-P(钙结合态的磷酸盐)占无机磷总量的比例,达29.6%～59.07%,O-P(闭蓄态磷酸盐)最少,仅占4.73%～22.45%。土壤过氧化氢酶、与土壤全氮、有机质、碱解氮呈显著正相关。

Aider the measure of reverting farmland to forest or grassland was carried out for 5 years, the great change in local environment and ecology had taken place. We studied the effect of three kinds of land use patterns on soil nutrients and soil temperature and moisture under the different slope gradients by using runoff plot. The results showed that the changing trend of soil water storage capacity was single peak, and the trend was not harmonious with rainfall in the same season, It was described as following： farmland 〉 barren rangeland 〉 Caragana korshinskil Kom, bushland, Soil temperature was described as following： barren rangeland 〉 farming land 〉 Caragana korshinskii Kom .bushland, Both were affected by vegetation type, Organic matter in the barren rangeland gradually decreased with slope gradient increasing, and the average value was 12.76 g/kg at 25°gradient. It was 1.2 times as that of farmland and 1.94 times as that of Caragana korshinskii Kom, bushland. Total phosphorus didn＇t have significant difference under three kinds of land use patterns. The available phosphorus and the available potassium were higher in farmland, but neither had significant difference in Caragana korshinskii Kom .bushland and barren rangeland. The proportion of Ca-P was the most in the fraction of inorganic phosphorus, which could reach to 29.6% - 59.07%. The proportion of O-P was the fewest, only about 4.73% - 22.45%.There was an obvious correlation relationship between the Catalase, Urease activity, the total Nitrogen, organic matter and the available Nitrogen. Once the changing trend of soil temperature and moisture and soil nutrient under the different kinds of land use patterns were found, the most effective way of rational allocation of agriculture could be used to improve soil fertility and reduce soil nutrient loss in the Loess Plateau in south Ningxia.