Cross-Site: Earthworms and Soil Processes In North American Ecosystems

蚯蚓对农业和牧业系统中土壤过程的影响已得到充分认识，但关于蚯蚓在森林、草原和稀树草原等荒地生态系统中的重要性的信息却相当少。此外，人们对北美本土蚯蚓物种的生态学知之甚少，尽管它们在一些不受更新世冰川影响的地区很普遍。现有的少数研究表明，在它们丰富的地方，这些微生物可以对土壤结构特性和养分转化产生重大影响。然而。本土和外来入侵蚯蚓物种的相对重要性几乎仍然未知。这项提案要求提供资金，对本地和外来蚯蚓进行跨地点调查，以确定在未受干扰的生态系统中，本地物种是否比外来物种更有效地处理营养。他们还将确定干扰是否为外来蚯蚓的入侵奠定了基础，外来蚯蚓可能比本地蚯蚓更具竞争力，但在营养循环方面效率较低。这些想法将在三个LTER地点(Coweeta水文实验室、Konza草原研究自然区和Luquillo实验森林)和一个非LTER地点(阿帕拉契科拉国家森林)分两个阶段在三年内进行检验。他们将在各种栖息地进行实地调查和采集，并将使用富含13C和14N的底物启动野外围栏实验。这两个阶段的工作共同优化了稳定同位素在实地研究中的使用--首先，作为调查工具，以确定重要物种和跨地点资源利用模式；然后，作为生物地球化学示踪剂，阐述蚯蚓与微生物的相互作用，并量化各种蚯蚓物种对碳和氮动态的影响。这项研究的结果将极大地扩大他们对蚯蚓生态学、本地物种和外来物种之间的相互作用以及这两个群体对广泛生态系统中土壤养分过程的影响的了解。

Influences of earthworms on soil processes in agricultural and pastoral systems are well recognized but there is considerably less information about their importance in wildland ecosystems such as forests, grasslands and savannas. Furthermore, very little is known about the ecology of native earthworm species in North America, even though they are prevalent in a number of areas unaffected by Pleistocene glaciations. The few existing studies indicate that where they are abundant, these organisms can have significant effects on soil structural properties and on nutrient transformations. However. the relative importance of native versus invasive exotic earthworm species remain virtually unknown. This proposal requests funding for a cross-site investigation of native and exotic earthworms, to determine if native species are more efficient than exotic species in nutrient processing in undisturbed ecosystems. They also will determine if disturbance sets the stage for invasion by exotic earthworms, which may be more competitive than natives but less effective in nutrient cycling. Th ese ideas will be tested in two phases over a three year period at three LTER sites (Coweeta Hydrologic Laboratory, Konza prairie Research Natural Area and Luquillo Experimental Forest) and one non-LTER site (Apalachicola National Forest). They will undertake field surveys and collections in a variety of habitats, and will initiate field enclosure experiments using 13C- and 14N- enriched substrates. Together, these two phases of work optimize the use of stable isotopes in field studies--first, as survey tools to characterize and identify important species and patterns of resource utilization across sites; and then as biogeochemical tracers to elaborate earthworm-microbial interactions and to quantify influences of various earthworm species on C and N dynamics. Results from this study will greatly expand their understanding of earthworm ecology, interactions between native and exotic species, and influences of both groups on soil nutrient processes across a broad range of ecosystems.