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

Abstract

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 CO 2 , 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 (d 13 C), 13 CO 2 discrimination (D 13 C) and intracellular carbon concentration (C i ) are also reported.Our results indicate an age effect on D 13 C 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 CO 2 . Nevertheless, in both forest and grassland sites A. angustifolia has had growth limitations corresponding to low precipitation and high temperatures observed in the 1940s.

New insights into vegetation, climate and fire history of southern Brazil revealed by a 40,000 year environmental record from the State Park Serra do Tabuleiro

“…Taking Araucaria angustifolia as an indicator species for moist and cold forest, since it can neither tolerate temperatures lower than -10°C nor an annual precipitation lower than 1,400 mm or a marked dry season (Hueck 1966), climate was cold on the Serra do Tabuleiro during the last glacial. Lower precipitation and higher temperature levels can affect Araucaria angustifolia growth (Silva et al 2009). According to Leonhardt and Lorscheitter (2010), a warmer climate affects the reproductive capacity of Araucaria forest taxa.…”

1982–2010 Trends of Light Use Efficiency and Inherent Water Use Efficiency in African vegetation: Sensitivity to Climate and Atmospheric CO2 Concentrations

“…We found from satellite and climate observations that iWUE* increased significantly over the last three decades over the northern savannas and central African forest biomes (10%-20% per decade), consistent with the long-term increase in WUE observed at forest sites elsewhere [32,64,[74][75][76][77][78][79][80]. The ORCHIDEE model only succeeded to reproduce a significant and positive iWUE* trend in the central African forest and not in savannas.…”

Conifer demography in forest–grassland mosaics: a landscape-scale study over a 24-year period

“…Only a minority of studies have carried out demographic monitoring for more than a few years, while long-lived groups like conifers may experience negligible growth and mortality over short time scales (Beckert et al 2014, Paludo et al 2016. Dendrochronological analyses (e.g., Silva et al 2009) allow for long-term assessment of growth patterns, but cannot provide information on survivorship or on ecological determinants of growth other than climatic variables.…”