Effects of acid deposition on the avoidance behavior of Folsomia candida (Collembola, Isotomidae)

Excessive acid deposition causes soil acidification, and changes the soil microhabitat, thus affecting the survival and reproduction of soil organisms. Folsomia candida (Collembola, Isotomidae), as a model organism, is widely used to assess the chemical toxicity in soil, and its avoidance response can indicate the environmental changes. In this study, we used Folsomia candida to assess the risks of acid deposition on soil ecosystems. Different pH (3.0, 3.5, 4.0, 4.5, 5.0, and 5.5) treatments were set up in petri dish experiments, and the avoidance behavior of Folsomia candida was measured after 12, 24, and 48 h exposure to the pH conditions. The results indicated that (1) both the exposure duration and pH level influenced avoidance behavior of collembolan. (2) After 12 h exposure, most of the individuals showed avoidance behavior but without significant differences among the treatments. (3) After 24 h exposure, significant avoidance behavior was observed at pH 3.0, 3.5, and 4.0. (4) After 48 h exposure, avoidance behavior was found in all treatment conditions except for pH 5.5. This study clarified the direct responses of soil fauna to acid deposition, and indicated that both pH and length of exposure influenced the avoidance behavior of Folsomia candida. During the experimental period, the collembolan reacted negatively and showed consistent avoidance behavior at pH 3.0, 3.5, and 4.0. Reversed avoidance behavior was apparent between pH 4.5 and 5.0 and not observed at pH 5.5, indicating that the latter was the preferred pH environment.