Investigating the effects of invading earthworms on soil properties and seedling growth in forest ecosystems.

土壤-植物相互作用在陆地生态系统的功能中起着重要作用。由于植物向土壤提供的凋落物和根系分泌物的数量和质量不同，植物群落组成和多样性对土壤性质和生物群有重要影响。同样，土壤生物群可以通过对土壤性质和过程（如凋落物分解和养分循环）的影响来影响植物群落的组成和生产力。此外，人们普遍认为，在北美北部，本地蚯蚓没有在最近的冰川期存活下来。尽管如此，大约400年前，欧洲殖民者在北美引进了外来的蚯蚓，这些蚯蚓已经占领了包括森林生态系统在内的大多数陆地生态系统。当它们扩展到林分时，它们改变了土壤性质，影响了林下植物群落的组成和树苗的生长。尽管由于沙质和酸性土壤被认为对蚯蚓的入侵更有抵抗力，但外来蚯蚓最近在北方森林的几个地方定居。结果表明，针叶林中阔叶树（如白杨和桦树）的存在可能有助于它们在北方针叶林中扎根。在加拿大东部的北方森林，机械化采伐的引入导致了硬木的入侵，特别是颤抖的白杨。由于硬木的入侵，人们可能会假设外来蚯蚓将扩大其在北方森林中的范围或种群规模，这种扩张可能会改变土壤性质和影响树木的更新，并最终改变上层的组成。虽然蚯蚓可能对陆地生态系统的功能产生重大影响，但我们对外来蚯蚓对土壤性质和植物群落的影响以及人为干扰（如伐木）对土壤-植物系统的影响如何受到外来蚯蚓的影响知之甚少。在这种情况下，本项目的主要目标是了解在天然林中，外来蚯蚓的存在如何影响土壤性质和植物群落，以及它们如何调节伐木对土壤性质和幼苗生长的影响。最终，我们寻求制定考虑到外来蚯蚓对土壤和植被影响的造林指南。

Soil-plant interactions play a major role in the functioning of terrestrial ecosystems. Because plant species differ in the amount and quality of litter and root exudates they supply to the soil, plant community composition and diversity have important effect on soil properties and biota. Likewise, the soil biota can influence the composition and productivity of plant communities through their effects on soil properties and processes, such as litter decomposition and nutrient cycling. Furthermore, it is widely accepted that in northern North America indigenous earthworms did not survive the most recent glacial period. Nonetheless, some 400 years ago European settlers introduced exotic earthworms in North America which have since colonized most terrestrial ecosystems, including forest ecosystems. As they expanded into forest stands, they modified soil properties and influenced the composition of understory plant communities and the growth of tree seedlings. Despite being considered more resistant to earthworm invasion because of sandy and acidic soils, exotic earthworms have recently colonized several parts of the boreal forests. It is suggested that the presence of hardwood tree species (e.g. aspen and birch) in conifer-dominated stands may have facilitate their establishment in the boreal forest. In the eastern Canadian boreal forest, the introduction of mechanised logging led to hardwood encroachment, notably trembling aspen. As a result of hardwood encroachment, one may hypothesize that exotic earthworms will expand their range or population size in the boreal forest, and that this expansion may modify soil properties and influence tree regeneration, and ultimately alter overstory composition. Although earthworms may exert a major influence on the functioning of terrestrial ecosystems, we know little about the effects of exotic earthworms on soil properties and plant communities, and how the effects of anthropogenic disturbances (e.g. logging) on soil-plant system may be influenced by exotic earthworms. In this context, the main objective of this project is to understand how in natural forest the presence of exotic earthworms influences soil properties and plant communities, and how in logged stands they modulate the effects of logging on soil properties and seedling growth. Ultimately, we seek to develop silvicultural guidelines that take into account the effects of exotic earthworms on soils and vegetation.