Forests

In temperate climates, cockroaches are usually relegated to a minor role in soil biology because population densities can be low (e.g., Ectobius spp. in central Europe— Eisenbeis and Wichard, 1985). Similarly, in surveys of tropical forest litter, ants, mites, and springtails typically dominate in number, with cockroaches rating an incidental mention (e.g., Fittkau and Klinge, 1973). Cockroaches comprised just 3.0% of the arthropod biomass of the ground litter in a humid tropical forest in Mexico (Lavelle and Kohlmann, 1984), for example. On the other hand, cockroaches are very common in the leaf litter on the floor of the Pasoh Forest in West Malaysia, with 6.7 insects/m2 (Saito, 1976). They are very well represented in several forest types in Borneo. Leakey (1987) cites a master's thesis by Vallack (1981) in which litter invertebrates were sampled in four forest types at Gunung Mulu in Sarawak. Cockroaches contributed an impressive 43% of the invertebrate biomass in alluvial forest, 33% in dipterocarp forest, 40% in heath forest, and 2% in a forest situated on limestone. A specific decomposer role has been quantitatively established for Epilampra irmleri in Central Amazonian inundation forests (Irmler and Furch, 1979). This species was estimated to be responsible for the consumption of nearly 6% of the annual leaf litter input. Given that seven additional cockroach species were noted in this habitat, the combined impact on de-compositional processes may be considerable.

The ecological services of cockroaches are not limited to plant litter on the soil surface. Those species found in logs, treeholes, standing dead wood and branches, birds' nests, and plant debris trapped in epiphytes, lichens, mosses, and limb crotches in the forest canopy (i.e., suspended soils) are also members of the vertically stratified decomposer niche (Swift and Anderson, 1989). Cockroach species that feed on submerged leaf litter on stream bottoms and in tank bromeliads may have an impact in aquatic systems.

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