LTREB: Rapid Ecotonal Shifts, Pest Outbreaks, and Mortality of a Dominant Tree Species in Response to Record Drought

LTREB的研究将检验四个关键预测。首先，植物对草食动物的抗性影响群落和生态系统水平的过程。从1982年开始，对转基因抗、感虫树种进行了鉴定，并在1/2的感虫树种上，每年消灭2种常见害虫。研究涉及树健身慢性草食动物，菌根群落的反应，一个神秘的基石草食动物的社会后果，并利用抗性和易感树木重建过去的气候。正在进行的土壤细菌、养分循环和抗性成本的研究使得这些长期实验非常重要。第二，干旱导致生态区迅速转移，改变了群落结构和生态系统动态。1996年，一场创纪录的干旱导致60个地点的树木死亡率达到30-70%，估计有75，000棵成熟的树木死亡。这些网站经历了一个快速的生态过渡从松，杜松林地杜松林地或草地。其中11个地点与邻近的低死亡率地点配对，是一种宝贵的资源，因为它们是气候变化事件的直接结果。这些地点对于研究气候变化对菌根共生体、微生物分解者、节肢动物和脊椎动物群落的原因和后果，以及环境压力如何不同地影响生物多样性和生态系统功能至关重要。第三，重复干旱事件比单一干旱事件具有不同的影响。今年，2002年，已经被确定为有史以来最干旱的一年。继1996年干旱之后的这场新的干旱使我们能够确定同一地点是否遭受重复的死亡和选择，这可能比单一死亡事件产生非常不同的长期后果。第四，草食动物与环境的相互作用影响昆虫的爆发，改变群落结构和生态系统过程。自1982年以来，我们一直在监测蛾和介壳虫的分布情况，这些昆虫仅限于长期紧张的地点。但为了应对1996年创纪录的干旱，规模从这些震中扩大到西南部最大的爆发。我们已经绘制了它们的扩张图，并正在研究抗旱和易感树木如何受到干旱的影响。更广泛的影响：美国西南部正处于干旱之中，类似于许多气候变化模型预测的美国大部分地区的干旱。通过研究松及其相关社区所学到的原则可以用来对这些预测的气候变化的后果做出明智的决定。此外，由于NAU位于一个人口多样化的地区，包括42个美洲原住民部落，我们建议培训和指导来自代表性不足的群体的学生。我们这样做的能力将通过已经实施的计划得到加强，包括NSF赞助的环境生物学大学导师资助，针对代表性不足的群体和促进本科生研究的NAU赠款计划。

This LTREB research will examine four key predictions. First, plant resistance to herbivory affects community and ecosystem-level processes. Beginning in 1982 genetically resistant and susceptible trees were identified, and on 1/2 of the susceptible trees, 2 species of common insect have been removed each year. Studies involve tree fitness responses to chronic herbivory, mycorrhizal community responses, the community consequences of a cryptic keystone herbivore, and the use of resistant and susceptible trees in reconstructing past climates. Ongoing studies of soil bacteria, nutrient cycling, and costs of resistance make these long-term experiments very important tocontinue. Second, drought results in rapid ecotonal shifts, which alter community structure and ecosystem dynamics. In 1996 a record drought occurred that resulted in 60 sites that suffered 30-70% tree mortality and killed an estimated 75,000 mature trees. These sites underwent a rapid ecotonal shift from pinyon-juniper woodland to juniper woodland or grassland. Eleven of thesesites, paired with adjacent low mortality sites, represent a valuable resource because they are the direct result of a climate change event. These sites are crucial for studying the causes and consequences of climate change on mycorrhizal mutualists, microbial decomposers, arthropod and vertebrate communities, and how environmental stress differentially affects biodiversity andecosystem function. Third, repeated drought events have different effects than single drought events. This year, 2002, is already identified as the driest year in recorded history. This new drought following the 1996 drought allows us to determine if the same sites suffer repeated mortality and selection, which is likely to have very different long-term consequences than a single mortality event. Four, herbivore x environmental interactions affect insect outbreaks to alter community structure and ecosystem processes. Since 1982 we have been monitoring the distribution of moth and scale insects that were restricted to sites of chronic stress. However, in response to the record drought of 1996, scales have expanded from these epicenters to become the largest outbreak in the southwest. We have mapped their expansion and are studying how resistant and susceptible trees are affected by drought. Broader Impacts: The southwestern US is in the midst of a drought similar to those predicted to increase throughout much of the US by many climate change models. The principles learned by studying pinyon pine and its associated community can be used to make informed decisions regarding the consequences of these predicted climate changes. In addition, because NAU is located in an area with a diverse population including 42 Native American tribes, we propose totrain and mentor students drawn from a diversity of under-represented groups. Our ability to do so will be enhanced by programs already in place, including an NSF-sponsored University Mentoring in Environmental Biology grant targeting under-represented groups and an NAU grants program that promotes undergraduate research.