Recent Consequences of Climate Change Have Affected Tree Growth in Distinct Nothofagus macrocarpa (DC.) FM Vaz &amp; Rodr Age Classes in Central Chile

Alejandro Venegas-González,Isabella Aguilera-Betti,Fidel A Roig,Ariel A Muñoz,Karen Peña-Rojas,Martín A Hadad

doi:10.3390/f10080653

Abstract

Forests play an important role in water and carbon cycles in semiarid regions such as the Mediterranean ecosystems. Previous research in the Chilean Mediterranean forests revealed a break point in 1980 in regional tree-ring chronologies linked to climate change. However, it is still unclear which populations and age classes are more affected by recent increases in drought conditions. In this study, we investigated the influence of recent variations in precipitation, temperature, and CO2 concentrations on tree growth of various populations and age classes of Nothofagus macrocarpa trees in Central Chile. We sampled 10 populations from five sites of N. macrocarpa through its whole geographic distribution in both Coastal and Andes ranges. We used standard dendrochronological methods to (i) group populations using principal component analysis, (ii) separate age classes (young, mature, and old trees), (iii) evaluate linear growth trends based on the basal area increment (BAI), and (iv) analyze the link between BAI and atmospheric changes using linear mixed-effects models. Results showed that young trees are more sensitive to climate variability. Regarding population grouping, we observed that all population clusters were sensitive to winter-spring precipitation, but only the Andes and Coastal populations were negatively correlated with temperature. The results of CO2 fertilization analyses were controversial and unclear. Since young trees from all population clusters reacted positively in the phase with an increase of atmospheric CO2 between 1980 and 2014, this behavior was not translated into growth for the last 15 years (2000–2014). However, it should be noted that the young trees of the highest elevation populations did not have a negative growth trend, so it seems that CO2 counteracted the negative effect of recent regional climate change (increase in temperature and precipitation decrease) in these population trees. Further studies are needed to assess the effects of climate variability over other ecological and physiological processes.

Highlights

Atmospheric CO2 is the principal contributor to global warming [1]
Concerning physiological reactions according to ontogeny, increases in atmospheric CO2 and air temperature during the 20th century have been related to increments in the internal water use efficiency (iWUE) and the intercellular CO2 concentration, with adult trees showing higher iWUE values than young trees, which broadly indicates the incidence of climatic, environmental, and ontogenetic variability in the tree responses [13]
We concluded that the growth of N. macrocarpa populations from Mediterranean deciduous forests of Central Chile (MDFC) are being strongly affected by recent climate change in the region, as expressed by decreasing precipitations and increasing temperatures, but not due to the influence of rising atmospheric CO2 on stem biomass, regardless of the age of trees

Summary

Introduction

Atmospheric CO2 is the principal contributor to global warming [1] This increase has been indicated as an impact factor on plant growth and function, as reflected in the 20th century increases of the internal water use efficiency (iWUE) [2] and as an inducer of changes in the health and dynamics of different forest ecosystems in multiple regions [3]. Concerning physiological reactions according to ontogeny, increases in atmospheric CO2 and air temperature during the 20th century have been related to increments in the iWUE and the intercellular CO2 concentration, with adult trees showing higher iWUE values than young trees, which broadly indicates the incidence of climatic, environmental, and ontogenetic variability in the tree responses [13]. Understanding the response and forest resilience to atmospheric changes (i.e., temperature, precipitation, and CO2 concentration) has become an important topic for its conservation [14]

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Discussion

Conclusion