title: Long tree-ring chronologies provide evidence of recent tree growth decrease in a Central African tropical forest.
abstract: It is still unclear whether the exponential rise of atmospheric CO2 concentration has produced a fertilization effect on tropical forests, thus incrementing their growth rate, in the last two centuries. As many factors affect tree growth patterns, short -term studies might be influenced by the confounding effect of several interacting environmental variables on plant growth. Long-term analyses of tree growth can elucidate long-term trends of plant growth response to dominant drivers. The study of annual rings, applied to long tree-ring chronologies in tropical forest trees enables such analysis. Long-term tree-ring chronologies of three widespread African species were measured in Central Africa to analyze the growth of trees over the last two centuries. Growth trends were correlated to changes in global atmospheric CO2 concentration and local variations in the main climatic drivers, temperature and rainfall. Our results provided no evidence for a fertilization effect of CO2 on tree growth. On the contrary, an overall growth decline was observed for all three species in the last century, which appears to be significantly correlated to the increase in local temperature. These findings provide additional support to the global observations of a slowing down of C sequestration in the trunks of forest trees in recent decades. Data indicate that the CO2 increase alone has not been sufficient to obtain a tree growth increase in tropical trees. The effect of other changing environmental factors, like temperature, may have overridden the fertilization effect of CO2.
authors: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy; Ecole Pratique des Hautes Etudes, Centre for Bio-Archaeology and Ecology, Institut de Botanique, University of Montpellier 2, Montpellier, France.
authors: Giovanna
authors: G
authors: Battipaglia
authors: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy.
authors: Enrica
authors: E
authors: Zalloni
authors: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy.
authors: Simona
authors: S
authors: Castaldi
authors: Department of Mathematics and Physics, Second University of Naples, Caserta Italy.
authors: Fabio
authors: F
authors: Marzaioli
authors: Department for Innovation in Biological, Agro-food and Forest Systems. Università della Tuscia (DIBAF), Viterbo, Italy.
authors: Roberto
authors: R
authors: Cazzolla-Gatti
authors: Department of Biosciences and Territory, University of Molise, Pesche, Italy.
authors: Bruno
authors: B
authors: Lasserre
authors: Department of Biosciences and Territory, University of Molise, Pesche, Italy; The EFI Project Centre on Mountain Forests (MOUNTFOR), San Michele all'Adige, Italy.
authors: Roberto
authors: R
authors: Tognetti
authors: Department of Biosciences and Territory, University of Molise, Pesche, Italy.
authors: Marco
authors: M
authors: Marchetti
authors: Department for Innovation in Biological, Agro-food and Forest Systems. Università della Tuscia (DIBAF), Viterbo, Italy.
authors: Riccardo
authors: R
authors: Valentini
mesh_terms: D000350:Africa, Central; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000032:analysis; D065928:Forests; D012044:Regression Analysis; D014197:Trees / Q000254:growth & development*; D014329:Tropical Climate
chemical_list: D002245:Carbon Dioxide; D002244:Carbon