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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。
Octelodrilus occidentalis, a widely distributed exotic species of earthworm in the plantation and abandoned land of Guangdong Province, is not sensitive to changes in water and heat, pH and soil organic matter, and its distribution range is gradually expanding. Studying the process of Eclipta imprisalus on carbon cycling in plantations can provide ideas for how to reduce soil carbon emissions under planted earthworms. Field control experiments of alien earthworms and native plants were set up in Acacia auriculaeformis plantation, and the soil CO2 fluxes were determined by in situ box-gas chromatography in situ for 15 days. The results showed that the effects of soil CO2 fluxes were not obvious when either alone or in combination with Evodia lepta alone. The effects of plant physical processes (such as shading, etc.), plant biological processes (such as rhizosphere chemical processes, etc.) and plant CO2 fluxes on soil without or with earthworm samples were -32.1% , 40.9%, 8.8% and -7.2%, 30.7% and 23.5% respectively. Phytoecological processes inhibited soil CO2 emissions, but increased the contribution of earthworms to soil CO2 emissions by 39.3%. Plant biological processes promote soil CO2 emissions but reduce the contribution of earthworms to soil CO2 emissions (down 23.5%). The influence of earthworms on the physico-chemical properties of most soils during the experiment was not obvious, but the existence of earthworms tended to increase the activity of soil bacteria, and the correlation between soil CO2 flux and soil physical and chemical properties was closer. At the same time, the presence of earthworms The relationship between soil CO2 flux and soil hydrothermal factors has changed. It can be seen that the soil CO2 fluxes are not only related to hydrothermal conditions, but also regulated by above and below biological processes. If we only focus on the amount of CO2 fluxes in forest soils and ignore the biological processes that affect the production and release of soil CO2, we will find no effective way to reduce CO2 emissions from forest soils. The mitigation of soil carbon emissions from plantations must take into account plant physical processes, plant biological processes and the independent and interactive effects of earthworms on soil CO2 emissions.