Invertebrate assemblages of hanging and container litter on conifer trees

Abstract

ABSTRACTArboreal litter provides a habitat patch for detritus-based invertebrates in the aboveground part of forest ecosystems and exists in two forms. Hanging litter (HL) remains attached to branches and tree trunks after foliage dies, or hangs as intercepted falling litter exposed to the surrounding air. In comparison, litter in container habitats (CL) is deposited in pocket-like structures, such as treeholes and trunk crevices, that are enclosed by woody substrates. In experiments using litter bags and artificial containers, we: (1) compared litter invertebrate assemblages among HL, CL, and forest-floor litter, and (2) evaluated the relative importance of patch size and resource quantity for litter invertebrate assemblages in HL on Japanese cedar (Cryptomeria japonica) trees. Our results showed that the moisture content of litter and collembolan density tended to be higher in arboreal container litter (i.e. CL) than in arboreal bag litter (i.e. HL). In the second experiment, the total abundance of invertebrates was influenced more by resource quantity (litter weight) than by patch size (litter bag area). Redundancy analysis (RDA) indicated that each major group (oribatid mites, collembolans, and Gamasida) was influenced by different environmental factors in the HL. Our findings indicate that: (1) HL and CL represent different habitat types for litter invertebrates; (2) the major invertebrate groups have different habitat preferences in the HL; and (3) the abundance of invertebrates in HL is influenced more by litter quantity than by litter density (litter weight per area).