黄土丘陵区人工林典型林分土壤肥力综合评价

Comprehensive evaluation on soil fertility of typical plantations in loess hilly region

森林土壤肥力是供给森林植物生长所需水分和养分的重要基质。运用主成分分析、相关性分析两种评价方法,研究对比不同林分类型下人工林土壤肥力状况,以期为黄土丘陵区生态公益林和森林土壤资源的科学管理提供理论依据。以内蒙古自治区清水河县公益林区内的油松(Pinus tabuliformis Carr.)、落叶松[Larix gmelinii(Rupr.)Kuzen.]、山杏[Armeniaca sibirica(L.)Lam]、乔灌混交林、针阔混交林5种主要林分林下0~20 cm表层土壤为研究对象,选取土壤pH和有机质、全氮、全磷、有效磷、速效钾、碱解氮含量作为土壤肥力的评价指标。结果显示:1)pH变化范围为7.92~9.04,属于碱性土壤。2)根据全国第二次土壤普查分类标准,5种林分类型中,土壤全磷、有效磷含量5种林分均为三级,属于中上水平;碱解氮含量均为四级中下水平,整体含量偏低;落叶松林、山杏林的有机质、全氮含量为四级,油松林、乔灌混交林、针阔混交林为三级;针阔混交林的速效钾含量为二级较高水平,油松林、山杏林、乔灌混交林为三级,落叶松林为四级。3)两种评价方法最终得到的评价结果趋势一致,均表现为针阔混交林>乔灌混交林>油松林>落叶松林>山杏林,混交林整体肥力状况优于纯林。综上所述,在植被恢复和抚育管理人工林的过程中,于遵从自然规律以及因地制宜的原则上,建议适当增加混交林所占比例。

Forest soil fertility is an important substrate for supplying water and nutrients needed for forest plant growth.Using the correlation method and the principal component analysis method,two evaluation methods are used to study and compare the soil fertility status of artificial forests under different forest types,in order to provide a theoretical basis for the scientific management of ecological forests and forest soil resources in the loess hilly region.The study area locates in Qingshuihe county,Inner Mongolia,and the main research object is the 0~20 cm surface soils of Pinus tabulaeformis(Pinus tabuliformis Carr.),larch[Larix gmelinii(Rupr.)Kuzen.],mountain apricot[Armeniaca sibirica(L.)Lam],arbor-shrub mixed forest and coniferous broadleaf mixed forest.The soil pH,contents of organic matter,total nitrogen,total phosphorus,available phosphorus,available potassium and alkaline nitrogen are selected and used as indicators to evaluate soil fertility.The results show that 1)the soil pH is 7.92~9.04,which belongs to alkaline soil.2)According to the classification standard of the second national soil survey,among the 5 forest types,the total soil phosphorus and available phosphorus contents of the 5 forests are all at grade three,which belongs to the upper middle level.The alkali-hydrolysable nitrogen content is all at the lower level of grade four,and the overall content is low.The organic matter and total nitrogen content for larch forest and mountain apricot forest are at grade four,for Pinus tabulaeformis forest,arbor-shrub mixed forest and coniferous broad leaf mixed forest are at grade three.Coniferous broad leaf mixed forest with higher available potassium content is at grade two,and Pinus tabulaeformis forest,mountain apricot forest,and arbor-shrub mixed forest are at grade three,and the larch forest is at grade four.3)The comprehensive evaluation results of the two evaluation methods are consistent with the trend of comprehensive soil fertility,both showing as coniferous broad leaf mixed forest>arbor-shrub mixed forest>Pinus tabulaeformis forest>larch forest>mountain apricot forest.The overall fertility status of the mixed forest is better than pure forest.To sum up,in the process of vegetation restoration and tending and management of artificial forests,the proportion of mixed forests can be appropriately increased in accordance with the principles of natural law and local conditions.