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Interannual variation in vegetation activity at continental scales: Analysis of patterns, processes and change
Abstract
Vegetation and climate interact at different spatio-temporal scales. As a consequence, analyses of inter-relationships between vegetation and climate must be scale-dependent and site- specific. In this dissertation, multi-temporal satellite data are used to examine climate-vegetation relationships at different scales in order to detect the most important changes occurring in the landscape surface as related to inter-annual climate variability. Patterns have been identified as forms of spatial variation, processes have been studied as climate-vegetation relationships, and change has been (statistically) evaluated as significant departures from indicators of reference. Several research questions have been addressed in this dissertation. This resulted in (a) the application of change-vector analysis for characterization of inter-annual land cover changes in the conterminous United States; (b) deriving measures of seasonal and interannual variation in vegetation activity from remotely-sensed observations; (c) and the analysis of inter-annual changes in the onset of greenness as a function of thermal variables and water budget. Changes occurring in the landscape can be basically of two types: (a) Archetypes or similar inter-annual changes that are repeated every year and that occur at local scales (i.e., for specific land cover types); and (b) Anomalous deviations from archetypes or inter-annual changes that produce regional vegetation responses. Several seasonal measures can be used for inter-annual comparisons of satellite imagery. The total variability contained in satellite imagery can be reduced to three forms of temporal and spatial variation interpretable as seasonal vegetation signals. Different combinations of water-use and energy variables determine the different onset dates in the growing seasons, i.e., there is no a single factor responsible for triggering photosynthetic activity. Generally, thermal variables (such as growing degree-days and surface temperatures) are more important than water use variables to determine the onset dates.
Subject Area
Geography|Ecology|Remote sensing
Recommended Citation
Mora Flores, Franz Eduardo, "Interannual variation in vegetation activity at continental scales: Analysis of patterns, processes and change" (1999). ETD collection for University of Nebraska-Lincoln. AAI9951303.
https://digitalcommons.unl.edu/dissertations/AAI9951303