中文摘要：

西土寒宪蚓（Ocnerodrilus occidentalis）为广东人工林和撂荒地内广泛分布的外来种蚯蚓,因其对水热、pH值及土壤有机质等的变化不敏感,其分布范围有逐渐扩大的趋势。研究西土寒宪蚓对人工林碳循环的影响过程,可以为如何减少外来蚯蚓影响下的人工林土壤碳排放提供思路。在广东鹤山大叶相思（Acacia auriculaeformis）人工林内设置外来蚯蚓和乡土植物野外控制实验,利用静态箱-气相色谱法对土壤CO2通量进行15天的原位测定。结果发现,单独添加西土寒宪蚓及单独种植三叉苦（Evodia lepta）,对土壤CO2通量的效应都不明显。植物物理过程（如遮阴作用等）、植物生物过程（如根际化学物质分泌过程等）及植物在未添加蚯蚓样方和添加蚯蚓样方中对土壤CO2通量的效应分别为–32.1%、40.9%、8.8%和–7.2%、30.7%、23.5%。植物的物理过程抑制了土壤CO2排放,但提高了蚯蚓对土壤CO2排放的促进作用（提高了39.3%）。植物的生物过程促进了土壤CO2排放,但减弱了蚯蚓对土壤CO2排放的促进作用（降低了23.5%）。试验期间蚯蚓对多数土壤理化性质的影响并不明显,但是蚯蚓的存在有增强土壤细菌活性的趋势,而且使土壤CO2通量与土壤理化性质的相关性更加密切了;同时,蚯蚓的存在也使土壤CO2通量与土壤水热因子的关系发生了变化。可见,森林土壤CO2通量不仅与水热条件有关,还受地上和地下生物过程的调控。如果只关注森林土壤CO2通量的大小,而忽略影响土壤CO2产生及释放的生物学过程,将无法找到减少森林土壤CO2排放的有效途径。减缓人工林中土壤碳的排放,必须综合考虑植物物理过程、植物生物过程以及蚯蚓对土壤CO2排放过程的独立效应和交互效应。

英文摘要：

Aims The exotic earthworm Ocnerodrilus occidentalis is widespread in plantation and abandoned areas in Guangdong,China.Its distribution is gradually expanding due to insensitivity to temperature,moisture,soil pH and soil organic matter.Study of the processes of soil carbon dynamics affected by O.occidentalis can provide new insights for the reduction of soil carbon emissions.Our objective was to investigate the short-term impacts of this exotic earthworm and native plants on soil CO2 fluxes.Methods A field experiment was conducted in an Acacia auriculaeformis plantation at the Heshan Hilly Land Interdisciplinary Experimental Station.CO2 fluxes were measured for 15 days in situ using the static chamber technique and analyzed with a gas chromatogram.Important findings Both O.occidentalis and Evodia lepta had no significant effects on soil CO2 fluxes.The effects of plant physical processes（such as shading）,plant biological processes（such as secretion of root exudates） and overall processes on soil CO2 fluxes were –32.1%,40.9% and 8.8%,respectively,in treatments without earthworm addition,and were –7.2%,30.7% and 23.5%,respectively,in treatments with earthworm addition.Plant physical processes inhibited soil CO2 emissions,but enhanced the effects of the earthworm on soil CO2 emissions（increased by 39.3%）.Plant biological processes enhanced soil CO2 emissions,but inhibited the effects of earthworms on soil CO2 emissions（decreased by 23.5%）.Earthworm addition showed almost no significant impacts on most soil physical and chemical properties,but enhanced the activity of soil bacteria and led to a closer correlation between soil CO2 fluxes and soil physical and chemical properties.Meanwhile,earthworm activities changed the relationships between soil CO2 fluxes and soil hydrothermal factors.Hence,soil CO2 fluxes were not only influenced by hydrothermal factors,but also regulated by above-and below-ground biological processes.Therefore,it was difficult to determine an effective way to reduce forest soil