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Significant forest loss in North America are due to several natural factors such as fire, insect outbreaks, diseases, drought, etc. They can have a significant impact on the economy of affected countries but also an environmental impact particularly in a context of climate change.
In Quebec (Canada) insect outbreaks including spruce budworm (SBW) outbreaks occur synchronously over large areas. Several studies show that climate and forest composition are significant factors in the development of epidemics. Climate directly affects the spruce budworm development cycle but also host trees for example droughts make them more vulnerable. Forest composition also directly affects the insects because they are specific in their choice of hosts: a high abundance of host trees promotes outbreaks while a large amount of non-host trees will decrease the available resource and could have a protective effect on host trees.
The main objective of this thesis is to better understand the mechanisms at work during a SBW outbreak in Quebec, including the impact of forest composition and climate. Furthermore, it will explore the use of different remote sensing tools to study the SBW. It will be organized around four main objectives: 1) to compare the previous SBW outbreak (70s-80s) with the current one(2000-2010), 2) to understand the relative importance of climatic factors and forest composition on the outbreak severity depending on the spatial scale and the time evolution of the outbreak (beginning, middle, end of the outbreak), 3) to provide more specific information on SBW defoliation and interannual variations, taking into account the entire growing season with almost daily data, 4) to compare the use of aerial surveys and satellite imagery (Landsat and MODIS) to map and study the defoliation caused by the SBW.
The study area for objectives 2 and 3 will cover areas affected by SBW outbreaks in southern Quebec through the use of Landsat and MODIS satellite data while the study area objectives 1 and 4 will focus on the Côte-Nord in Quebec, area affected by the two SBW outbreaks studied and where field data were collected. The approach will be based on the study of remote sensing data (aerial and satellite images) validated by field surveys. The analysis of vegetation data will be combined with climate data to see the influence of climate on SBW outbreaks.
This thesis will evaluate the silvicultural theory that looks at the effect of forest biodiversity on minimizing outbreaks but also provide information on the interaction between climate and insects outbreaks. It will help the development of silvicultural strategies to reduce the effect of outbreaks and early detection strategies of infected areas through remote sensing.