| Summary: | Tree growth is mechanistically linked to the global water and carbon (C) cycles and is thus a key area of research. As part of this research studies have explored linkages between remote sensing data products and tree growth, but the majority of this research has focused on tracking photosynthesis and inter-annual tree growth. Only a fewstudies have explored intra-annual stem radial growth, which provides information on long term carbon sequestration. The following chapters explore new remote sensing-based approaches for monitor intra-annual stem radial growth in North American forests. Chapter 1 outlines some of the previous work that has used remote sensing approaches to monitor tree growth, as well as some of the potential challenges that exist. Chapter 2 explores possible connections between remotely sensed snow disappearance date and the onset of stem radial growth in conifers at the forest-tundra ecotone (FTE) in North America. Specifically, we posed two hyphotheses: 1) that satellite based SDD estimates from the Moderate Resolution Imaging Spectroradiometer (SDDMODIS) are not significantly (p < 0.05) different than in situ measurements of SDD from soil temperature probes (SDDST), thereby suggesting that SDDMODIS is a reliable proxy for in situ SDD, and; 2) that estimates of SDD are not significantly different than the onset of tree radial growth, implying that SDDMODIS could reliably detect the start of tree wood growth at the FTE. To test our hypotheses, we used data from two field sites at the FTE - one located in Alaska (AK) and one in the Northwest Territory (NWT). SDDMODIS and SDDST were synchronous at AK, while they were asynchronous at NWT. Both SDD estimates were significantly different from tree growth onset at AK in both years but were similar in NWT. These results highlight the ecological heterogeneity of the FTE and the key knowledge gaps remaining in our understanding of environmental factors driving tree growth at this ecotone. However, our finding that remote estimates of SDD were ...
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