兴安落叶松林型对土壤氮素含量的影响

Nitrogen distribution in soils of different Larix gmelinii forest types

为了揭示大兴安岭地区土壤氮素含量的变化规律,探讨草类-兴安落叶松林、杜鹃-兴安落叶松林、溪旁-兴安落叶松林、真藓-兴安落叶松林、柴桦-兴安落叶松林、杜香-兴安落叶松林、赤杨-兴安落叶松林等7种林型对土壤氮素含量的影响,文中采用野外取样结合室内分析土壤全氮及碱解氮含量。结果表明:1)不同的森林类型中土壤的全氮及碱解氮含量具有明显差别,全氮含量以真藓-兴安落叶松林最大,其值为15.76g/kg,溪旁-兴安落叶松林最小,其值为6.83g/kg;碱解氮含量以赤杨-兴安落叶松林最大,其值为916.28mg/kg,杜鹃-兴安落叶松林最小,其值为475.27mg/kg。2)不同森林类型腐殖质层全氮含量与淀积层的比值也存在较大差异,以草类-兴安落叶松林最大,比值为4.49;真藓-兴安落叶松林最小,比值为1.08;其他类型的比值在1.14-4.45之间,兴安落叶松林土壤氮素含量随土壤深度增加而减少,且主要分布在腐殖质层中。3)生长在阴坡的真藓-兴安落叶松林等林型利于全氮的积累,而腐殖质层全氮含量与淀积层的比值较小,生长在阳坡的赤杨等林型利于全氮的分解,腐殖质层全氮含量与淀积层的差异较大。保护兴安落叶松赖以生存的冻土环境,对维持目前土壤氮素水平具有重要意义。

The study focused on the distribution of total nitrogen and alkali - hydrolyzable nitrogen in soil of the Larix gmelinii forests. The results showed that ： （ 1 ） The total nitrogen content of the soil changed with different forest types, which varied from 6.83 to 15.76 g/kg. Among the seven forest types, Bryaceae - Larix gmelinii forest had the greatest content of total nitrogen, while the stream - Larix gmelinii forest had the lowest. （2） The alkali - hydrolyzable nitrogen content of the soil also changed with different forest types, which varied from 475. 27 to 916.28mg/kg. Among the seven forest types, Alder - Larix gmelinii forest had the greatest content of al- kali- hydrolyzable nitrogen, while the Cuckoo - Larix gmelinii forest had the lowest. （3） Forests growing in shady such as Bryaceae - Larix grnelinii forest types are favorable for nitrogen accumulation, and total nitrogen difference between humus layer and deposited layer is small; forests growing in sunny such as Alder - Larix grrtelinii forest types are conducive to decompose nitrogen, and total nitrogen difference between humus layer and deposited layer is larger. It is important to protect permafrost environment which can keep low temperatures and high humidity conditions and to maintain the current level of soil nitrogen.