北京九龙山不同林分土壤肥力诊断与综合评价

Diagnosis and comprehensive evaluation on soil fertility of different stands in Beijing Jiulong mountain

以北京九龙山辖区13种林分的土壤为研究对象,分别测定土壤p H值、有机质、全氮、有效磷、速效钾、碱解氮等肥力指标,按照不同林分对土壤肥力指标进行诊断,并用修正的内梅罗综合指数法对土壤肥力进行综合评价。结果表明:土壤p H值呈弱酸性,土壤有机质含量丰富,其中有约一半的林分处于Ⅰ级,但土壤全氮与有效磷含量较低,几乎所有林分都处于Ⅲ级和Ⅳ级,土壤速效钾与碱解氮含量中等偏下,几乎所有林分都处于Ⅱ级和Ⅲ级;土壤综合肥力系数(Pj)变幅为0.87~1.85,平均为1.20±0.30,其中肥力属于一般(0.9<Pj<1.8)林分占总林分的76.29%,白蜡丁香混交林土壤肥力系数较高,而樟子松纯林和白蜡与华北落叶松混交林的肥力系数较低,表明九龙山林分土壤肥力总体处于一般水平,且土壤有效磷和全氮含量是影响综合肥力系数的主要指标,因此,在加强林地土壤的改良方面,提高土壤有效磷和全氮含量是关键。

Based on the soil data of 13 forest types in Beijing Jiulong mountain, indexes of soil fertility, including soil p H-value, organic matter, total nitrogen, available phosphorus, available potassium and alkali hydrolysable nitrogen, were determined. Soil fertility of different forest types were diagnosed and comprehensively evaluated through modified Nemerow comprehensive index method. Results showed that： the p H value of forest types was in weak acid; the content of soil organic matter was rich, about 50% of the total number of forest types belonged to grade Ⅰ; but the soil total nitrogen and available phosphorus were deficient to some extent, all forest was almost of grade Ⅲ and Ⅳ; the soil available potassium and alkali hydrolysable nitrogen were lower than the average, all forest was almost of grade Ⅱ and Ⅲ. The range of comprehensive fertility coefficient（Pj） of forest soil was 0.87 ~ 1.85, the mean value was 1.20±0.30, and 76.29% of forest types was in the middle level（0.9〈 Pj〈 1.8）, the Fraxinus chinensis- Syringa mixed forest was comparatively high, while that the pure forest of Pinus sylvestris and the Fraxinus chinensis- Larix principis-rupprechtii mixed forest were just the opposite. It is concluded that soil fertility of forest in the Jiulong Mountain is not good and effective measures should be taken to improve it. Among that, it is the key to improve the content of total nitrogen and available phosphorus.