A Dendrochronological Analysis of Insect Outbreaks and Climate Effects on Tamarack from Indiana and Michigan.

摘要

Disturbances have a strong impact on tree stand dynamics across the world. In North America, the larch sawfly (Pristiphora erichsonii) and larch casebearer (Cleophora laricella) are two non-native species of insects affecting tamarack across much of their native range. The majority of research on the effects of larch sawfly on tamarack (Larix laricina) has been conducted in Canada with very little dendrochronological work in the United States along the geographical boundary of tamarack or on the effects of larch casebearer on radial growth. As a consequence, very little is known about the relationship between tamarack and these insects' outbreaks in the United States. The traditional model of Ecological Amplitude in biogeography explains that species are limited along their southern border by species interaction, so it is very important to start to understand the relationship between predator and prey. At the Pigeon River State Fish and Wildlife Area in northern Indiana, tamarack are stressed and dying out on the landscape and local naturalists believe insect outbreaks are a potential factor.;I use the traditional dendrochronological methods to develop and compare host and non-host chronologies from northern Indiana and central Michigan. I then compared these chronologies to each other, local climate variables, and insect outbreak information to better understand climate and outbreak signals in radial growth. I found that tamarack in Indiana showed a stronger negative response to temperature in Indiana than in Michigan which indicates warmer temperature play a role in limiting the southern margin of the species' range. Tamarack also provided a good record of local insect outbreak events. Using outbreak information collected from local naturalists, I developed a tree ring outbreak signature for larch casebearer. Continued work along the southern boundary of the species will determine the combined impacts of multiple species specific predators as climate changes.