| Summary: | 碩士 === 國立成功大學 === 生命科學系碩博士班 === 97 === Invasive species is an important cause for changes of ecosystem structure and function. However, researches on invasive species often ignore the belowground invasive species, for example, the earthworms. In recent years, an invasive earthworm, Pontoscolex corethrurus, originated from South America has been found widely distributed in Taiwan, but its effects on local forest ecosystems are not known. A microcosm study in the laboratory with 3 soil types from Fushan (FS, high organic matter, clay-loam), Nanjenshan (NJS, low organic matter, clay-loam), and Taichunggang (TCG, low organic matter, sand) demonstrated that the earthworm significantly increased CO2 efflux in all 3 soils, but did not change microbial biomass-C at the end of experiment. The degree of CO2 increase by earthworm was highest in FS soil, but were not significantly different between NJS and TCG soils. During the experimental period, earthworms grew in weight in all 3 soils and reproduced in FS and TCG soils, with the largest increases in FS soil. The earthworm might increase soil CO2 efflux by its own respiration as well as by stimulation of microbes or alteration of microbial community. The earthworm did not change soil total carbon, total nitrogen and extractable total organic carbon significantly, but increased extractable total nitrogen in all 3 soils. P. corethrurus increased ammonium in clay-loam soil and nitrate in sandy soil, but decreased microbial biomass-N in sandy soil. The results suggest the invasion of P. corethrurus may have significant consequences on CO2 efflux and nutrient cycles in local forest soils, and the effects should not be overlooked.
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