The application of tree rings for monitoring urban forest change: A remote sensing perspective
Tree rings have long been used to monitor forest change by measuring differences in tree ring widths through time derived from a representative sample of forest trees. However, for many reasons, tree rings have only rarely been utilized to monitor urban forest change. Urban forest change monitoring has more commonly occurred with time-series of remote sensing imagery, such as yearly stacks of Landsat satellite imagery converted to some vegetation index or other proxy. Tree rings and remote sensing time-series are thus similar, providing temporal records of forest productivity change from different perspectives and processes. From an urban forest remote sensing perspective, tree rings represent a unique natural validation tool for detected changes that has not been utilized. In an urban-rural watershed west of Toronto, Canada, we explored the forest history information provided by both tree rings and overlapping Landsat time-series data at 16 sites. We directly compared the two information sources over the overlapping period (1972-2018) statistically and by temporally matching increase-decline trends. Stronger connections occur at coniferous forest sites, potentially driven by differential response to summer temperature change. We also identified how major events in the region, such as a recent ice storm and the pressures of suburbanization, influence change in both sources. Many of the results discussed here are based on a paper (“Temporal connections between long-term Landsat time-series and tree-rings in an urban-rural temperate forest”) published in 2021.