Battipaglia Giovanna, Zalloni Enrica, Castaldi Simona, Marzaioli Fabio, Cazzolla-Gatti Roberto, Lasserre Bruno, Tognetti Roberto, Marchetti Marco, Valentini Riccardo
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.
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy.
PLoS One. 2015 Mar 25;10(3):e0120962. doi: 10.1371/journal.pone.0120962. eCollection 2015.
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.
在过去的两个世纪里，大气中二氧化碳浓度呈指数级上升是否对热带森林产生了施肥效应，从而提高了它们的生长速度，目前仍不清楚。由于许多因素会影响树木的生长模式，短期研究可能会受到几个相互作用的环境变量对植物生长的混杂效应的影响。对树木生长进行长期分析可以阐明植物生长对主要驱动因素的长期响应趋势。年轮研究应用于热带森林树木的长树轮年代学，能够进行这样的分析。在中非测量了三种广泛分布的非洲树种的长期树轮年代学，以分析过去两个世纪树木的生长情况。生长趋势与全球大气二氧化碳浓度的变化以及主要气候驱动因素（温度和降雨）的局部变化相关。我们的结果没有提供二氧化碳对树木生长有施肥效应的证据。相反，在上个世纪观察到所有这三个树种的总体生长都有所下降，这似乎与当地温度的升高显著相关。这些发现为近几十年来全球观察到的森林树木树干中碳固存放缓提供了额外支持。数据表明，仅二氧化碳的增加不足以使热带树木的生长增加。其他不断变化的环境因素（如温度）的影响可能已经超过了二氧化碳的施肥效应。
