Distribution of Picea rubens and global warming
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For half a century the commercially and ecologically important tree species red spruce (Picea rubens) has been in decline over its entire range. For understanding the causes of declines at the Great Smoky Mountains National Park (GSMNP), the objectives of this study were: first, to develop a foundation for systematic and comprehensive understanding of the red spruce growth system through interdisciplinary synthesis; second, to investigate the causes of growth decline and the effects of global warming on Picea rubens growth from a tree growth model in systems modeling studies; third, to estimate suitable habitat conditions for red spruce from the tree growth model and predict the distribution range of red spruce and the effects of global warming on this range in GIS studies. Based on three study objectives, this study was divided into three main modeling sections: Envirogram of Annual Radial Increment of Red Spruce (ARIRS), a conceptual model; the red spruce Annual Radial Increment Models (ARIMs), which are systems models; and Red Spruce Habitat Model (RSHM), a spatial landscape GIS model. The ARIRS envirogram well conceptualized complex interactions affecting red spruce growth and offered a conceptual model for ARIMs. ARIMs significantly showed that air pollution disturbance was the dominant cause of red spruce growth decline at high elevation, and red spruce growth had significant positive relationships with water availability and radiation and a negative relationship with the air pollution disturbance at low elevation. ARIMs predicted red spruce growth was more affected by air pollution than global warming at high elevation and more by global warming than air pollution at low elevation. The ARIM results were applied to RSHM to find suitable habitat conditions for red spruce. RSHM significantly predicted spatiotemporal distribution of geographical range and habitat suitability of red spruce. RSHM also predicted that global warming would cause red spruce distribution to shrink by degradation of habitat suitability. Overall, this study showed significance and importance of comprehensive modeling for better understanding of tree systems by linking a conceptual modeling effort, the ARIRS envirogram, to a systems modeling effort, ARIMs, and the latter to a spatial landscape modeling effort, RSHM.