抚育间伐强度对大兴安岭落叶松次生林土壤肥力的影响

Effect of thinning intensity on soil fertility of Larix gmelinii secondary forest in Daxingan mountains

为改善大兴安岭落叶松天然次生林的生态环境,观测间伐后林地土壤肥力的变化情况,探讨最有利于林地土壤改良的间伐强度。在大兴安岭设置间伐强度分别为9.43%、16.75%、29.00%、40.01%、53.09%、67.25%的实验样地和未间伐的对照样地,样地分别栽植兴安落叶松Larix gmelinii、兴安樟子松Pinus sylvestris、红皮云杉Picea koraiensis Nakai、西伯利亚红松Pinus sibirica促进林分更新。选取能够反映土壤肥力的化学性质指标和物理性质指标共13项,利用改进层次分析法和熵权法相结合的方法确定指标权重,同时运用灰色关联法,对各间伐样地的土壤肥力进行综合评价。结果表明:土壤有效磷(0.222)、有机质(0.145)在所有评价指标中所占权重偏高,灰色关联度(间伐强度)由大到小排序为0.73(40.01%)> 0.70(29%)> 0.65(16.75%)> 0.64(9.43%)> 0.63(53.09%)> 0.60(0)> 0.55(67.25%)。说明土壤有效磷、有机质是土壤肥力的重要影响因素,间伐强度40.01%的改造样地土壤肥力最佳,间伐强度9.43%～53.09%的落叶松次生林土壤肥力优于对照样地。适当的间伐强度能够改善林地内的土壤肥力,为大兴安岭落叶松次生林的改造提供参考。

In order to improve the ecological environment of Larix gmelinii natural secondary forest in the forest zone of Daxingan mountains,the changes of soil fertility in the woodland after thinning were observed,and the thinning intensity that is most conducive to soil improvement in the forest land were explored.The experimental plots of thinning intensity were 9.43%,16.75%,29.00%,40.01%, 53.09%,67.25% respectively,and the unthinned control plots were set.And Larix gmelinii,Pinus sylvestris,Picea koraiensis Nakai and Pinus sibirica were cultivated there so as to promote the forest stand renewal.By selecting a total of 13 chemical and physical indexes which can reflect the soil fertility,using the improved analytic hierarchy process and the entropy weight method to determine the index weights,and adopting the grey correlation method,the soil fertility of different thinning plots was evaluated comprehensively.The results are as follows.Soil available phosphorus (0.222) and organic matter (0.145) accounted for a higher weight in all evaluation indicators, and the order of grey correlation degree (thinning intensity) from big to small was 0.73(40.01%) > 0.70(29%) > 0.65(16.75%) > 0.64 (9.43%) > 0.63(53.09%) > 0.60(0) > 0.55(67.25%).It was found that soil available phosphorus and organic matter were important factors affecting soil fertility,the soil fertility of the improved sample plot with thinning intensity of 40.01% was the best,and the soil fertility of the secondary L.gmelinii forest with thinning intensity of 9.43%-53.09% was better than that of the control sample plot. Appropriate thinning intensity can improve soil fertility in the forest land and this provides a reference for the transformation of L. gmelinii secondary forest in Daxing’an mountains.