Plant-plant interactions and environmental change

Natural systems are being subjected to unprecedented rates of change and unique pressures from a combination of anthropogenic environmental change drivers. Plant–plant interactions are an important part of the mechanisms governing the response of plant species and communities to these drivers. For example, competition plays a central role in mediating the impacts of atmospheric nitrogen deposition, increased atmospheric carbon dioxide concentrations, climate change and invasive nonnative species. Other plant–plant interaction processes are also being recognized as important factors in determining the impacts of environmental change, including facilitation and evolutionary processes associated with plant–plant interactions. However, plant–plant interactions are not the only factors determining the response of species and communities to environmental change drivers – their activity must be placed within the context of the wide range of factors that regulate species, communities and ecosystems. A major research challenge is to understand when plant–plant interactions play a key role in regulating the impact of environmental change drivers, and the type of role that plant–plant interactions play. Although this is a considerable challenge, some areas of current research may provide the starting point to achieving these goals, and should be pursued through large-scale, integrated, multisite experiments

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