大兴安岭北部森林土壤微生物量碳和水溶性有机碳特征研究

Characteristics of Soil Microbial Biomass Carbon and Dissolved Organic Carbon in Northern Forest Region of Daxing'an Montains

为揭示大兴安岭北部不同森林类型土壤微生物量碳和水溶性有机碳变化特征，选择大兴安岭北部典型植被类型白桦林、山杨林、兴安落叶松林、樟子松林和白桦一山杨林为研究对象，分析不同月份及不同土层间土壤微生物量碳和水溶性有机碳变化规律。结果表明：大兴安岭北部5种主要森林类型0—32cm土壤微生物量碳和水溶性有机碳含量波动范围分别为220．40～909．54mgkg-1和21．22～211．93mgkg-1，不同林型之间差异显著，微生物量碳表现出阔叶林大于针叶林的趋势，水溶性有机碳则表现为落叶松林〉白桦一山杨林〉山杨林〉白桦林〉樟子松林。5种森林类型微生物量碳和水溶性有机碳有着明显的季节动态，微生物量碳总体表现为在6月或10月达到较高值，在7—9月出现较低值。水溶性有机碳总体表现为在6、8、10月的含量较高，7月和9月较低。两种活性碳均表现为随土壤深度的加深而逐渐降低。不同林型各月份微生物量碳和水溶性有机碳占总有机碳的比例范围分别为0．64％～7．60％和0．08％--0．67％，微生物量碳分配比例随土壤深度加深表现出上升趋势，水溶性有机碳则波动性较大。土壤蔗糖酶、脲酶、碱性磷酸酶和总有机碳与两种活性碳的相关关系均达极显著水平（P〈0．01），表明这些指标可以对活性碳预测起到指示性作用。

To reveal the effect of forest types on characteristics of soil microbial biomass carbon （MBC） and dissolved organic carbon （DOC）, five representative forest types were selected in north of Daxing＇anling. They were birches forest dominated by Betula platyphylla, poplar forest dominated by Populus davidiana, larch forest dominated by Larix gmelinii, mongoliea forest dominated by Pinus sylvestnis var. Mongolica and birch-poplar mixed forest dominated by Populus davidiana and Betula platyphylla. We analyzed the contents of MBC and DOC in various months and at various soil depths. The contents of MBC and DOC in different soil layer varied from 220.40 mg kg-1 to 909.54 mg kg-1, and from 21.22 mg kg-l to 211.93 mg kg-1, respectively. The content of soil labile organic carbon was significantly different among different forests. The content of soil MBC under hardwood forest was significantly higher than that under coniferous forest, and the content of soil DOC ranged in the order as follows： larch forest 〉 birch-poplar mixed forest 〉 poplar forest 〉 birches forest 〉 mongolica forest. The contents of MBC and DOC in five forest types had obvious fluctuation with time. In five forest types, the contents of soil MBC and DOC decreased with increase in soil depth. The ratios of MBC/TOC and DOC/TOC separately varied in the range of 0.64% to 7.60% and 0.08% to 0.67%. The ratio of MBC/TOC had a rising trend with increase in soil depth, not so with DOC/TOC. There was a significantly positive correlation （P 〈 0.01） between two kinds of soil labile organic carbon and soil invertase, urease, alkaline phosphatase and soil total organic carbon, which suggests that these variables could play indicative roles in predicting labile organic carbon.