Past century changes in Araucaria angustifolia (Bertol.) Kuntze water use efficiency and growth in forest and grassland ecosystems of southern Brazil: implications for forest expansion

• Published in: Global change biology Vol. 15; no. 10; pp. 2387 - 2396
• Main Authors: SILVA, LUCAS C.R, ANAND, MADHUR, OLIVEIRA, JULIANO M, PILLAR, VALÉRIO D
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.10.2009; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: age; Animal and plant ecology; Animal, plant and microbial ecology; Araucaria; Araucaria angustifolia; basal area increment; Biological and medical sciences; Brazil; carbon; Carbon dioxide; carbon isotope; Carbon isotopes; Climate change; Coniferous trees; conifers; Ecology; Ecosystems; ecotones; forest expansion; forest growth; forest trees; Forestry; Forests; Fundamental and applied biological sciences. Psychology; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Grasslands; growth rings; High temperature; isotopes; southern brazil; stand basal area; temperature; tree-rings; Vegetation; Water use; Water use efficiency; South America; Brazil; America; Grassland; Forests; Forest zone; Growth; basal area increment; Water use efficiency; Carbon; Araucaria; Dynamical climatology; ecotones; Climate change; Basal area; Tree ring; Ecotone; grasslands; carbon isotope; southern brazil; forest expansion; tree-rings; Expansion; Isotopes
• DOI: 10.1111/j.1365-2486.2009.01859.x
• ISSN: 1354-1013

Araucaria angustifolia (Bertol.) Kuntze is an indigenous conifer tree restricted to the southern region of South America that plays a key role in the dynamics of regional ecosystems where forest expansion over grasslands has been observed. Here, we evaluate the changes in intrinsic water use efficiency (iWUE) and basal area increment (BAI) of this species in response to atmospheric CO₂, temperature and precipitation over the last century. Our investigation is based on tree-rings taken from trees located in forest and grassland sites in southern Brazil. Differences in carbon isotopic composition (δ¹³C), ¹³CO₂ discrimination (Δ¹³C) and intracellular carbon concentration (Ci) are also reported. Our results indicate an age effect on Δ¹³C in forest trees during the first decades of growth. This age effect is not linked to an initial BAI suppression, suggesting the previous existence of nonforested vegetation in the forest sites. After maturity all trees show similar temporal trends in carbon isotope-derived variables and increasing iWUE, however, absolute values are significantly different between forest and grassland sites. The iWUE is higher in forest trees, indicating greater water competition or nutritional availability, relative to grassland, or both. BAI is also higher in forest trees, but it is not linked with iWUE or atmospheric CO₂. Nevertheless, in both forest and grassland sites A. angustifolia has had growth limitations corresponding to low precipitation and high temperatures observed in the 1940s.