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认识到物种入侵的严重后果。尽管认识到这一点，很少有研究记录了长期的生态系统后果的入侵时，这些入侵不受控制。这项拟议中的研究评估了夏威夷季节性干旱林地中促火草的长期影响。这些草最初是作为牧草引入的，它们逃到了荒地上，在那里它们促进了火灾的蔓延。这些地点的本地物种不适应火灾，导致本地物种的急剧损失和营养循环的强烈改变，包括氮的损失，这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者引起的生态系统氮循环变化，这些变化在20世纪90年代得到了很好的记录，自入侵以来随着时间的推移发生了变化，以及当前生长条件对本地物种的影响。实验将评估随着时间的推移氮损失率，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。在干旱和半干旱的生态系统中，非原生的促火草是一个重要的管理问题。这项研究的结果将提供更好的了解长期的后果，不管理这些入侵无论是在燃料负荷和土壤养分条件方面，并在本地物种是否会最终恢复在火灾下被烧毁的入侵网站。最后，结果将提供网站特定的信息，关于本地物种和恢复治疗可以用于火灾和草入侵退化的网站。

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.