COLLABORATIVE RESEARCH: Woody Encroachment into Desert Grassland: Experimental Asessment of the Critical Seedling Establishment Phase

近几十年来，干旱/半干旱草原和稀树草原上灌木和树木的繁殖得到了广泛的记录。这一世界性现象对畜牧业生产造成不利影响，威胁到农村经济的生计。它还被认为对北美、南美、澳大利亚和非洲的陆地碳循环产生了重大影响。木本植物入侵草原的能力在不同物种之间差异很大。为什么有些人如此成功，而另一些人则不是？这项研究将通过确定木本植物如何在关键的建立阶段在草原上站稳脚跟来解决这个问题。通过比较在一系列气候条件和干扰(落叶)下成功或不成功的木本入侵者的生存和生长情况，研究将确定a)在许多看似合理的特征中，哪些根和枝的生长特征与侵蚀潜力可靠相关；以及b)土壤性质(如粘粒含量)如何放大或缓解影响侵蚀潜力的环境因素。目标有两个：(1)制定准则，可用于确定潜在的问题物种，并描述它们可能建立的条件，以便采取适当的管理行动，最大限度地减少它们对草原的入侵；(2)产生必要的信息，使模拟模型参数化，可用于预测木本植物入侵可能发生的时间和地点，从而使土地管理者有时间制定和实施适当的预防措施。外联活动将是这项工作的组成部分。

The proliferation of shrubs and trees in arid/semiarid grasslands and savannas in recent decades has been widely documented. This worldwide phenomenon threatens the livelihood of rural economies through adverse impacts on livestock production. It is also thought to have had a significant impact on the terrestrial carbon cycle in North and South America, Australia and Africa. The ability of woody plants to encroach into grasslands varies widely among species. Why are some so successful and others not? The study will address this question by determining how woody plants gain their foothold in grasslands during the critical establishment phase. By comparing the survivorship and growth of more and less successful woody encroachers under a range of climatic conditions and disturbances (defoliation), the study will determine a) which root and shoot growth characteristics, of the many that seem plausible, are reliably associated with encroachment potential; and b) how soil properties (such at clay content) may amplify or mitigate environmental factors influencing encroachment potential. The goals are two-fold: (1) to develop guidelines that can be used to identify potential problem species and characterize the conditions under which they are likely to establish so that appropriate management actions can be taken to minimize their invasion into grassland; and (2) to generate information needed to parameterize simulation models that can be used to forecast when and where woody plant invasions are likely to occur, thus giving land managers time to develop and implement appropriate preventative measures. Outreach activities will be an integral part of this work.