An analysis of tree mortality in southern California using high spatial resolution remotely sensed spectral radiances: a climatic change scenario: Fid-Bau Portal

An analysis of tree mortality in southern California using high spatial resolution remotely sensed spectral radiances: a climatic change scenario

Hope, Allen S. / Stow, Douglas A.

Abstract

Abstract The value of remotely sensed data for ecological monitoring and modeling studies that address landscape changes due to climatic change is widely recognized. However, these data can be collected at a variety of spatial resolutions which was significant implications in terms of the information that can be derived from the data. Most readily available remotely sensed data tend to have ground resolutions substantially greater than the size of individual plants so pixels may contain a mixture of vegetation types, background cover, illumination intensity and shadow. These mixtures make it difficult to evaluate fine-scale vegetation dynamics. This paper examines the potential utility of high spatial resolution remotely sensed data for assessing vegetation condition within a climatic change context. The drought in southern California that started in 1987 and the associated increase in tree mortality due to bark beetle infestations, provided the climatic change scenario for the study. A possible consequence of anthropogenically induced climatic change is the occurrence of more intense and prolonged droughts in some regions leading to greater mortality rates for susceptible vegetation species. Studies of present-day patterns and processes of vegetation mortality associated with droughts may help to identify future consequences of hypothesized climatic changes. High spatial resolution (0.5 m) reflected spectral radiances were collected over the Cuyamaca State Park in southern California and related to levels of bark beetle infestations that increased during the drought years. The results from this demonstration project indicated that high spatial resolution remotely sensed data allow investigators to isolate individual plants from the scene background and are likely to provide valuable information for assessing vegetation condition. The characteristics of the reflected spectral radiances and their geostatistical properties may be potential indicators of differences in vegetation condition. These data are also likely to be valuable for determining biophysical quantities required in models of ecosystem function and for monitoring key species that may be particularly sensitive to climatic change (indicator species).