George L. Vourlitis

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The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state(More)
The Pantanal is the largest wetland in the world with extremely high plant and animal diversity, but large areas have been invaded by Vochysia divergens Pohl (Vochysiaceae), a tree that is native to the Amazon Basin, and Curatella americana L. (Dilleniaceae), a tree that is native to the Brazilian savanna (cerrado). V. divergens is reportedly floodadapted,(More)
The recent and widespread expansion of the pioneer tree species Vochysia divergens Pohl into western Brazil has the potential to significantly alter the structure and function of the Pantanal—a UNESCO World Heritage Site and the World’s largest tropical wetland. Here we assess the seasonal pattern of evapotranspiration (ET) and micrometeorological variables(More)
Anthropogenic nitrogen (N) deposition is a globally important source of N that is expected to increase with population growth. In southern California, N input from dry deposition accumulates on vegetation and soil surfaces of chaparral and coastal sage scrub (CSS) ecosystems during the summer and fall and becomes available as a pulse following winter(More)
Nitrogen (N) deposition in heavily polluted southern Californian shrublands is estimated to be 20-45 kg N x ha(-1) x yr(-1), but more exposed locales can receive as much as 145 kg N x ha(-1) x yr(-1). This large anthropogenic N input has the capacity to alter the composition of plant communities. We conducted N-fertilization experiments in chaparral and(More)
Recently reported high-latitude warming has the potential to affect arctic ecosystem structure and function in the short and long term. Arctic ecosystems are known sources of atmospheric CH(4), and recent CO(2) flux measurements indicate that these ecosystems are now, at least regionally, net sources of atmospheric Co(2). It appears that over the short term(More)
Tropical savanna ecosystems are extremely diverse and important for global carbon storage. In the state of Mato Grosso, tropical savanna (locally known as the Cerrado), turns from well-drained, upland areas into seasonally flooded areas within the Pantanal; however, the Cerrado and the Pantanal share many common tree species, such as Vochysia divergens, a(More)
Leaf area index (LAI) is a key driver of forest productivity and evapotranspiration; however, it is a difficult and labor-intensive variable to measure, making its measurement impractical for large-scale and long-term studies of tropical forest structure and function. In contrast, satellite estimates of LAI have shown promise for large-scale and long-term(More)
Brazilian savanna (known as cerrado) has highly seasonal variation in rainfall yet trees have widely different phenological strategies ranging from evergreen to fully deciduous. While qualitative patterns of canopy phenology are well-known, few studies have quantitatively measured schedules of leaf and branch phenology. We measured the leaf and vegetative(More)