Role of Anisocentropus larvae in decomposition and leaching of riparian zone leaves

From our previous studies, it is necessary to examine multiple aspects of the natural system simultaneously to better mimic natural conditions. In this note, it was, therefore, evaluated that the leaching characteristics of leaves of several of the dominant plant species in the riparian zone of the Takeo River in Miyazaki Prefecture, Japan and examine the possible utilization of leachates from these leaves by larvae of shredder species, Anisocentropus (Trichoptera), as well as the effects of feeding and case building behaviors by these shredders on dissolved matter composition in streams. To replicate natural stream conditions, as found in the study site, litter packs consisting of leaves from the dominant plant species of Quercus glauca, Meliosma rigida and Styrax japonica leaves were placed into chambers filled with stream water with Anisocentropus larvae. Furthermore, in order to clarify the weight loss and leaching rates of leaves in the absence of larvae, Q. glauca, M. rigida, and S. japonica leaves were placed separately into each of three beakers filled with stream water, respectively. After 30 days of incubation, all of the remaining leaf materials and the larvae were removed from each chamber and the weight loss of leaves, the rates of growth and pupation of Anisocentropus larvae, and cation concentrations of water were measured. The order of weight loss rate among species was S. japonica > M. rigida > Q. glauca for every chamber. The growth of larvae cases was higher in the chambers that contained more leaves initially. NH4sup(+), Ksup(+), and Mgsup(2+) were present in the chamber water at higher concentrations than in the stream water (initial concentrations) due to leaching from leaves and biological activity of larvae. Ksup(+) was leached most abundantly in all samples. In the present study, it was demonstrated that leaching rate, weight loss rate, and the amount of cations released differ among three species that are dominant in the riparian zone and predominate the leaf litter along the investigated stream. Anisocentropus larvae in the stream selectively utilize leaves of different species according to purpose, such as a food source and for case building. In turn, the pupation and emergence rates of larvae are affected by the leachate from leaves of these species.