The Influence of Recent Climate Change on Tree Height Growth Differs with Species and Spatial Environment

Tree growth has been reported to increase in response to recent global climate change in controlled and semi-controlled experiments, but few studies have reported response of tree growth to increased temperature and atmospheric carbon dioxide (CO2) concentration in natural environments. This study addresses how recent global climate change has affected height growth of trembling aspen (Populus tremuloides Michx) and black spruce (Picea mariana Mill B.S.) in their natural environments. We sampled 145 stands dominated by aspen and 82 dominated by spruce over the entire range of their distributions in British Columbia, Canada. These stands were established naturally after fire between the 19th and 20th centuries. Height growth was quantified as total heights of sampled dominant and co-dominant trees at breast-height age of 50 years. We assessed the relationships between 50-year height growth and environmental factors at both spatial and temporal scales. We also tested whether the tree growth associated with global climate change differed with spatial environment (latitude, longitude and elevation). As expected, height growth of both species was positively related to temperature variables at the regional scale and with soil moisture and nutrient availability at the local scale. While height growth of trembling aspen was not significantly related to any of the temporal variables we examined, that of black spruce increased significantly with stand establishment date, the anomaly of the average maximum summer temperature between May-August, and atmospheric CO2 concentration, but not with the Palmer Drought Severity Index. Furthermore, the increase of spruce height growth associated with recent climate change was higher in the western than in eastern part of British Columbia. This study demonstrates that the response of height growth to recent climate change, i.e., increasing temperature and atmospheric CO2 concentration, did not only differ with tree species, but also their growing spatial environment

Patterns of Tree Establishment Following Glacier-Induced Floods in Southern Patagonia

Whereas tree establishment after large-scale disturbances such as fires, avalanches, and landslides have been documented for Patagonian forests, information on forest recovery following floods is scarce. Glaciar Perito Moreno has remained stable throughout the twentieth century, reaching the Peninsula de Magallanes several times and embalming parts of Lago Argentino. Following each ice-dam flood, the Nothofagus forests along the flooded shores die. We combined dendrochronology and spatial statistics to describe forest recolonization following the episodic flood caused by this glacier in 1988. Four tree species recolonized the lakeshores after the flood. Tree establishment started during spring-summer 1988– 1989, the growing season following the break of the ice dam in February 1988. More than 60% of the trees were established between the years 1994–2000, suggesting a rapid colonization of bare shores after the ice-dam break. Using Ripley’s spatial analysis, a 100% significant association between species was recorded at sites where two or more species were present. Species dominance was largely modulated by the composition of neighboring non-flooded forests and the climatic conditions along the precipitation gradient. While rates of tree colonization are influenced by species and their seed dispersal capacities, the grouping patterns by site may be modulated by differences in substrate and microclimatic conditions.Fil: Guerrido, Claudia Marcela. Universidad Nacional de la Patagonia Austral; ArgentinaFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Amoroso, Mariano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. - Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; ArgentinaFil: Rodriguez Catón, Milagros Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

Tree-Growth Variations of Nothofagus antarctica Related to Climate and Land Use Changes in Southern Patagonia, Argentina

Isolated forest patches of Nothofagus antarctica (ñire) are frequent in the Patagonian forest-steppe ecotone. These remnants, also called relicts (R), are separate from the continuous forests (C). Over the past century, these ecotonal forests have been impacted by anthropogenic activities, including fires, logging, and cattle ranching. In order to identify in N. antarctica ring-width records the variations in tree growth associated with documented changes in land use, five sites were selected in Santa Cruz, Argentina. In each site, increment cores from R and C were collected. We developed individual chronologies, and the relationships between regional climate variations and N. antarctica growth were established for each forest type and site. The similarities/differences between site-paired chronologies (R-C) were estimated by calculating moving correlation coefficients lagged by 1 year. N. antarctica regional growth was directly related to precipitation during the current growing season (November–December; r = 0.34, n = 62, p < 0.01), and inversely related to temperature (December–March; r = −0.58, n = 62, p < 0.001). Since the middle of the twentieth century, a progressive decrease has been recorded in regional radial growth, consistent with an increase in summer temperature and a decrease in spring precipitation. In the context of this regional response of N. antarctica to climate, differences in growth patterns between R and C were associated with past changes in land use. Overall, the largest differences between R and C chronologies were concurrent with the settlement of cattle ranches and the associated use of forests. Conversely, similarities between R and C records increased after the establishment of protected areas and during the implementation of similar management practices in both forest types. Our research provides the first dendrochronological records from Nothofagus antarctica for the Argentinean Patagonia and represents one of the first efforts to identify in tree-rings past changes in livestock practices in southern South America.EEA Santa CruzFil: Vettese, Evangelina S. Consejo Nacional de Investigaciones Científicas y Técnicas. CIT Santa Cruz; Argentina.Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina.Fil: Orellana Ibáñez, Ivonne A. Universidad Nacional de la Patagonia San Juan Bosco. Facultad de Ciencias Naturales y Ciencias de la Salud; Argentina.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina.Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina