## 1 Introduction  
The interactions and feedback between aboveground and belowground communities play fundamental roles in controlling terrestrial ecosystem processes [1]. Aboveground communities can be both directly and indirectly affected by soil food web organisms, and, in turn, these plant community changes influence soil biota [2; 3]. Studies regarding litter decomposition have been conducted for decades. Recently, a greater number of scientists have focused on how this process is driven by complex soil food web interactions that alter soil biogeochemical cycles affected by climate change [4; 5; 6]. Exploration of the interrelationships between aboveground community and belowground decomposers can enhance our understanding of biogeochemical cycles in terrestrial ecosystems [1; 7; 8]. Soil fauna, an important group of belowground decomposers, plays a critical role in the litter decomposition process [9], and the interactions between soil fauna and fungal communities have received considerable attention worldwide [6; 10; 11]. Researchersoften employ physical (litterbags) and/or chemical (repellents) techniques to exclude soil fauna in order to elucidate the roles of soil fauna in decomposition experiments for decades [12; 13; 14; 15; 16]. Naphthalene, a commonly used soil fauna repellent, is either administered to the soil surface adjacent to litterbags or added into litterbags to the reduce the number of soil arthropods [15; 16; 17; 18]. Naphthalene application has proven to be easy to implement and effective for repelling soil arthropods [16; 19; 20; 21]. As the simplest polyaromatic hydrocarbon and a decomposable organic compound with two fused benzene rings, naphthalene may provide exogenous carbon for soil microbes [19], thereby directly effecting soil microbial communities. Research conducted in a tallgrass prairie concluded that the application of naphthalene was effective in reducing soil micro-arthropods and had negligible direct effects on soil microbial abundance and C dynamics [20]. However, studies from an alpine forest ecosystem located on the eastern Tibetan Plateau of China implied that naphthalene treatment might have affected active bacterial community abundance but not soil bacterial community structure [22]. Moreover, other researchers have demonstrated that naphthalene treatments not only significantly reduce the density and species richness of soil arthropods but also indirectly influence soil C-, N-, and P-degrading enzymes [16; 23]. The effects of naphthalene application on fungal communities and the related belowground ecological processes have not been thoroughly investigated. Furthermore, both graded mesh size litterbags and chemical treatments presented positive impacts of soil fauna on the litter decomposition process, for which the extent of the impacts varied. Some researchers have concluded that the effect of insecticide experiments (naphthalene) tends to be double that of the mean graded mesh effect (2.45 versus 1.19) on litter decomposition rate [24], and a similar result was also found in a recent meta-analysis [25]. This discrepancy between the two methods can result from either (1) the incomplete exclusion of animals when using the graded mesh bags or (2) the presence of enhanced microbial activity when using naphthalene with organic carbon additives [20; 22]. Thus, we do not have a quantitative and clear understanding of the effects of the application of naphthalene to the soil surface on soil fungal community composition. In this study, a field experiment was conducted to examine the effect of naphthalene on the soil fungal community in a poplar plantation, which represents the most widely distributed type of afforestation in Northern China owing to the tress' rapid growth, strong adaptability, and high yields [26; 27]. As a deciduous tree species, the decomposition of poplar leaf litter plays an important role in the carbon-cycling process [28; 29].