冀西北坝上地区土地利用方式对土壤化学性质的影响

为了解不同土地利用方式对冀西北坝上地区土壤化学性质的影响,对该地区4种土地利用方式(围封林地、围封采伐地、未围封林地和耕地)下的土壤化学性质进行了分析.结果 表明:耕地的pH在7.5～8.5之间,明显高于其他3种土地利用方式(在6.5～7.5之间)(P＜0.05);耕地土壤的有机质、全氮、全磷、全钾及速效氮、磷、钾都明显高于3种林地(P＜0.05);2种封育林地表层土壤(0～10 cm)各养分含量明显高于未封育林地(P＜0.05),但深层土壤差异不明显.土地利用方式对土壤养分的垂直分布有显著影响,耕地土壤养分,除速效磷外,均表现为先下降后上升的趋势,养分含量变化曲线呈"V"型;3种林地土壤养分随土层深度的增加而降低,拐点均在10～20 cm土层,养分含量变化曲线呈"L"型.由以上结果得出结论,土地利用方式对土壤养分含量及其空间分布具有明显影响,耕地因为人工施肥的原因各养分含量明显高于林地,但土壤有明显的盐碱化趋势;封育可明显提高林地表层土壤养分含量,但对深层土壤影响较小.

Influence of land use types on soil chemical properties in Bashang area northwest of Hebei Province

In order to understand the effects of different land use patterns on soil chemical properties in Bashang area, northwest of Hebei Province, the soil chemical properties of four land use patterns(enclosed forest land, enclosed deforested lands, unenclosed forest land and farmland) in this area were analyzed. The results showed that the pH of farmland was 7.5 to 8.5, which significantly higher than that of other three land use methods(6.5-7.5)(P<0.05). The farmland was significantly higher than the three forest lands in organic matter, total nitrogen, total phosphorus, total potassium and available nitrogen, phosphorus and potassium(P<0.05). The nutrient contents in the surface soil(0-10 cm) of the two closed forests were significantly higher than those in the unenclosed forests(P<0.05), but there was no significant difference in the deep soil. Land use types had a significant impact on the vertical distribution of soil nutrients. The soil nutrients in farmland decreased firstly and then increased along the soil depth like the V-shaped, except for available phosphorus. The soil nutrients of the three forest lands decreased with the increase of soil depth like the L-shaped, and the inflection point was in 10-20 cm soil layer. From the above results, it was concluded that land use types influences the soil nutrient content and its spatial distribution significantly. The farmland was obviously higher than three kinds of forest lands in different soil nutrients content because of fertilization, but salinization was happened in farmland. The enclosure could obviously improve the nutrients content of surface soil of forest lands, and had little effect on deep soil.