Effects of Solidago canadensis invasion on soil enzyme activities

As Solidago canadensis imposes great threats to native ecosystems in some areas of China, it has important ecological value to study invasive mechanism of S. canadensis. We selected five field areas in Zhejiang province, one of zones invaded heavily by S. canadensis in China. In each area, four invasive gradients were established according to the invasive density［including one control un-invaded by S. canadensis (Nat), and three gradients with different invasive densities (Ecot1, Ecot2 and Exot)］. Nine soil enzyme activities, associated individually with soil carbon, nitrogen and phosphorus cycling, were analyzed. The results show that compared with the soil un-invaded by S. canadensis, the activities of dehydrogenase, -glucosidase, invertase, urease and alkaline phosphatase are slightly increased, but are not statistically significant (p0.05). Inversely, the proteinase activity is slightly decreased, but is not statistically significant either (P0.05). Different from those enzymes mentioned above, both nitrate reductase and acid phosphatase activities are significantly increased with S. canadensis invasion (P 0.05), while the cellulase activity is significantly decreased (p0.05). The principal components analysis indicates that the aggregated shift of soil enzyme activities can be classified as three groups, such as the group un-invaded by S. canadensis, the Ecot1-Ecot2 group, and the Exot group covered only by S. canadensis. Redundancy analysis reveals that changes in soil enzyme activities are largely determined by interactions of S. canadensis invasion with soil physico-chemical properties.