Naphthalene exerts substantial nontarget effects on soil nitrogen mineralization processes in a subalpine forest soil: A microcosm study

Abstract

Naphthalene has been widely used to test the functional roles of soil fauna, but its nontarget effects remain uncertain in various soils. To determine whether there is a potential nontarget effect on soil biochemical properties in subalpine forest soil, soils in a subalpine forest on the western Qinghai-Tibet Plateau were treated by naphthalene in microcosms. The responses of soil microbial activity and nutrients to naphthalene were studied following 52 days of incubation. The results showed that the naphthalene application obviously decreased the microbial respiration rate in the first 10 days of the incubation and then increased the rate in the following days of the incubation. Moreover, the naphthalene application did not significantly affect the microbial activities overall, measured as soil microbial phospholipid fatty acid (PLFA) abundances and biomasses, or most enzyme activities (invertase, nitrate reductase and nitrite reductase) during the whole incubation period. However, naphthalene suppressed increases in the DON, NH4+-N and NO3--N contents and urease activity and led to the net mineralization of inorganic N (NH4+-N + NO3--N), in contrast to the net immobilization result in the controls. These results suggest that naphthalene can exert direct nontarget effects on soil microbial respiration and N mineralization processes in subalpine soils. Caution should be taken when using naphthalene to repel soil animals in field experiments.