Long term impacts of grass invasions and fire on community change and plant soil feedbacks

在过去的二十年里，科学家、土地管理者和公众已经开始认识到物种入侵的严重后果。尽管认识到这一点，但很少有研究记录了当入侵不受控制时，入侵对生态系统的长期影响。这项拟议的研究评估了在夏威夷季节性干燥林地中促火草的长期影响。这些草最初是作为牧草引进的，后来逃到了荒地，助长了火势的蔓延。这些地点的本地物种不适应火灾，导致本地物种急剧减少，营养循环发生强烈改变，包括氮的损失，氮是植物生长的关键资源。拟议的研究使用观察和实验来评估入侵引起的生态系统氮循环变化，这些变化在20世纪90年代被充分记录下来，自入侵以来随着时间的推移而变化，以及当前生长条件对本地物种的影响。实验将评估氮随时间的损失率、土壤碳库的变化以及这些变化对本地和非本地物种的影响。在干旱和半干旱生态系统中，促进火灾的非原生草是一个重要的管理问题。这项研究的结果将使我们更好地了解不管理这些入侵的长期后果，无论是在燃料负荷和土壤营养条件方面，还是在被烧毁的入侵地点，本地物种最终是否会在火灾压制下恢复。最后，研究结果将提供在因火和草入侵而退化的地点可以使用哪些本地物种和恢复措施的具体信息。

Over the past twenty years, scientists, land managers and the public have come to recognize the dramatic consequences of species invasions. Despite this recognition, few studies have documented long-term ecosystem consequences of invasions when those invasions go unchecked. The proposed research evaluates long-term impacts of fire-promoting grasses in seasonally dry woodlands in Hawai'i. These grasses, originally introduced as pasture forage, escaped into wildlands where they promote the spread of fire. Native species in these sites are not fire-adapted resulting in a dramatic loss of native species and strongly altered nutrient cycling including losses of nitrogen, a critical resource for plant growth. The proposed research uses observations and experimentation to evaluate how invader-induced changes in ecosystem nitrogen cycling that were well documented in the 1990s, have changed over time since invasion and what the consequences of current growth conditions are for native species. Experiments will evaluate nitrogen loss rates over time, changes in soil carbon pools and the consequences of these changes for native and non-native species. Fire-promoting non-native grasses are a significant management concern in arid and semi-arid ecosystems. The results of this research will provide greater understanding of the long-term consequences of not managing these invasions both in terms of fuel loads and soil nutrient conditions and in terms of whether native species will eventually recover in burned invaded sites under fire suppression. Lastly, results will provide site specific information regarding which native species and restoration treatments can be used in sites degraded by fire and grass invasion.