Effects of naphthalene on soil fauna abundance and enzyme activity in the subalpine forest of western Sichuan, China

Naphthalene has been widely used to study the role of soil fauna, but its potential non-target effects on soil enzyme activity remain unknown in subalpine forests. We added naphthalene for two years and determined the effect of such additions on the abundance of soil fauna and soil enzyme activities (β-glucosidase, cellobiohydrolase, invertase, peroxidase, polyphenol oxidase, N-acetyl-β-D-glucosaminidase, leucine arylamidase, urease, nitrate reductase and nitrite reductase) in a subalpine forest. Naphthalene could efficiently suppress the individual density and population of soil fauna in situ. The individual density and number of groups were decreased by 72.6–84.8% and 15.0–28.0%, respectively. Naphthalene significantly affected the activities of β-glucosidase, cellobiohydrolase, polyphenol oxidase, N-acetyl-β-D-glucosaminidase, leucine arylamidase and nitrite reductase and the activity increased in the first litter peak of naphthalene addition, and decreased at the later. The activities of β-glucosidase, cellobiohydrolase, polyphenol oxidase, peroxidase, N-acetyl-β-D-glucosaminidase, leucine arylamidase and nitrite reductase showed a negative correlation with the soil microbial PLFAs. Conversely, the activities of invertase, urease and nitrate reductase were positively correlated with the soil microbial PLFAs. Our results suggest that naphthalene is an effective method to reduce soil fauna in subalpine forest. The enzyme activity was influenced by soil fauna and microbial PLFAs.