Microarthropod colonization of litter in arboreal and soil environments of a Japanese cedar (Cryptomeria japonica) plantation

摘要

We used leaf-litter and bark-litter bags to examine the colonization patterns of microarthropods in arboreal and soil microhabitats of a Cryptomeria japonica plantation. The mass loss of leaf-litter was slower in the arboreal environment than in the soil environment. The variation in leaf-litter mass among litter bags increased markedly with increasing decomposition in the soil, and was smaller in the arboreal environment. The colonization processes of microarthropods differed between the arboreal and soil leaf-litter bags. In the arboreal bags, Collembola, Gamasida, and Prostigmata had a peak density in the summer of the second year after establishing the bags whereas Oribatida maintained relatively constant densities until 15 months. In the soil bags, Collembola colonized the litter first, and Gamasida and Prostigmata subsequently colonized the more decomposed litter. The vertical colonization patterns of the major microarthropods were consistent at all heights on the tree trunk. Slow decomposition in arboreal litter reflected severe conditions for most decomposers throughout the experimental study. In contrast, severe conditions of arboreal litter may lead to a relatively stable resource for limited microarthropods that have physiological tolerance for unfavorable conditions. Because of the traits of these fauna, the arboreal litter may thus be utilized seasonally by Collembola and Gamasida, but continuously by Oribatida. We suggest that soil microarthropods would be more affected by successional changes than by seasonal changes, because of faster decomposition of the litter, whereas arboreal microarthropods would be more affected by seasonal changes because of slow decomposition processes in the arboreal environment.