长白山不同海拔梯度森林土壤中性糖分布特征

2010年7月,采集长白山北坡5个典型植被带(阔叶红松林、明针叶林、暗针叶林、岳桦林和高山苔原)林下土壤,研究了不同海拔梯度下森林土壤的中性单糖分布、数量及其影响因素,并结合中性糖来源差异探讨土壤有机质的生物化学积累机制.结果表明: 在长白山不同海拔梯度下,森林土壤的中性糖差异显著,中性糖来源碳在土壤有机碳(SOC)中的相对含量为80.55～170.63 mg·g^-1,并且随海拔升高呈递增的趋势.采用多元线性拟合分析发现,生长季平均气温是影响土壤中性糖相对含量的主要因素,低温有助于中性糖的积累.土壤中(半乳糖+甘露糖)/(阿拉伯糖+木糖)为1.62～2.28,且随海拔升高呈增加趋势,说明土壤中微生物来源中性糖的贡献随海拔升高逐渐增加.微生物熵随海拔升高而降低,说明低温条件下微生物活性下降而对外源碳的利用效率提高,植物残体被微生物分解转化后,以微生物同化物的形式固存于土壤中,从而增加了微生物来源中性糖的比例.

Distribution pattern of neutral sugar in forest soils along an altitude gradient in Changbai Mountains, Northeast China

In July 2010, soil samples were collected from five typical forests (Pinus koraiensis and broadleaved mixed forest, Picea and Abies forest, Larix and Abies forest, Betula ermanii forest, and alpine tundra) along an altitude gradient on the northern slope of Changbai Mountains to investigate the distribution and quantity of neutral sugar in the soils and related affecting factors. The origins of the neutral sugar were differentiated to probe into the biochemical accumulation mechanisms of soil organic matter. There was a significant difference in the neutral sugar content among the forest soils. The relative content of soil neutral sugar’s carbon to soil organic carbon ranged in 80.55-170.63 mg C·g^-1, and tended to be increased with elevated altitude. The multiple regression analysis showed that the mean temperature in growth season was the main factor affecting the relative content of soil neutral sugar, and low temperature was conducive to the accumulation of neutral sugar. The ratio of (galactose + mannose) / (arabinose + xylose) in the five soils was around 1.62-2.28, and had an increasing trend with elevated altitude, illustrating that the contribution of soil microbial neutral sugar to soil organic matter increased with elevated altitude. Soil microbial metabolic quotient declined significantly along elevated altitude, suggesting that in low temperature environment, soil microbial activity decreased but the carbon utilization efficiency enhanced. As a result, a significant portion of decomposed plant residues was transformed into microbial neutral sugar and accumulated stably in soil, and thus, increased the proportion of soil microbial neutral sugar.