三峡库区消落带土壤酶活性特征

土壤酶驱动土壤生态系统养分的循环和控制生态系统的功能。选取三峡库区消落带三个海拔梯度的土壤，以从未淹没的样地作为对照，研究消落带土壤酶活性特征。结果表明，消落带区域土壤有机碳（OC）、微生物生物量碳（MBC）和所测定的四种酶[磷酸酶（PNP）、芳基硫酸酯酶（PNS）、N-乙酰-β-D-氨基葡萄糖苷酶（NAG）和β-糖苷酶（PAG）]的绝对活性（单位土壤干重的酶活性）和四种酶的几何平均数（GME）显著低于从未淹没的对照样地。在消落带区域，只有磷酸酶的绝对活性随着淹没持续时间的延长而降低，其他土壤三种酶的绝对活性在三个样地之间并无显著性的差异。土壤四种酶的几何平均数与有机碳、微生物生物量碳的变化相似，在海拔梯度较低的样地最低，其他两个较高海拔梯度的样地之间无显著性的差异。然而单位有机碳或微生物生物量碳的四种酶的具体活性的变化趋势与酶的绝对活性的变化并不一致。PNP的具体活性在所有测定的样地之间都无显著性的差异，而其他三个酶的具体活性是海拔最低的样地显著高于其他样地，其他样地之间并无显著性的差异。因而，这些结果意味着四种酶的几何平均数能够敏感指示三峡库区消落带水位消涨及其不同淹没持续时间对土壤质量的影响，是一个能够综合反映所有土壤酶活性对消落带水位消涨的响应的敏感指标。

Characteristics of the Activities of Soil Enzymes in Riparian Zone of Three Gorges Reservoir Area

Soil enzyme catalyzes soil nutrient cycles and controls the function of ecosystem. The results showed that soil organic carbon(SOC), microbial biomass carbon(MBC), absolute activities of soil four enzymes:phosphatase(PNP), arylsulfatase(PNS), N-acetyl-β-glucosaminidase(NAG) and β-glucosidase (PAG)) (i. e. activity per dry soil mass) and the geometric mean of enzyme activities (GME) were lower in riparian zone than those of the never inundation of uplands(NI). In riparian zone, although the absolute activity of PNP increased with the elevation, there was no significant difference for the absolute activities of other soil three enzymes. The change in GME which was similar to the change in SOC and MBC, was lower in LI than MI and SI which had no significant difference in riparian zone. However, the change in the soil specific enzyme activities expressed either per unit of SOC or MBC was different from absolute activities of soil enzymes. There was no significant for PNP specific activity among sites measured, whereas PNS, NAG and PAG specific activities were higher in LI than other sites which were no significant difference. Therefore, the results suggested that GME was a suitable index to condense the whole set of soil enzyme values in a single numerical value, which was sensitive to the extent of soil quality degradation resulted from elevation gradient in riparian zone of Three Gorges Reservoir Area.