Forests play a key role in the carbon balance in terrestrial ecosystems. One of the main uncertainties in climate change predictions focuses on how the spatio-temporal dynamics of forest productivity will be affected by rising temperatures. However, tree growth ring sequences provide a type of high resolution file on biological responses to the impact of climate change.
A multidisciplinary research team made up of Russian and Spanish researchers, in which a researcher from the UPM School of Forestry, Forestry and Natural Environment has participated, has analyzed the patterns of the growth rings in thickness of different species of conifers in Spain and Siberia.
The study, published in PNAS, has verified that there is an increase in spatial synchrony in these patterns in both regions, which represents a warning sign of the impacts of climate warming on forest ecosystems on a subcontinental scale. The concept of spatial synchrony in tree growth refers to coincidences of changes between geographically disjoint tree populations.
“The study carried out wanted to verify whether this phenomenon was local or rather extends over large regions on a subcontinental scale. For this purpose, two highly contrasted terrestrial ecosystems were selected: the extremely cold taiga of continental Siberia and the comparatively warm and dry Mediterranean montane forests ”, explains Mar Génova, a researcher at UPM. Ninety-three growth ring timelines of six different species of conifers were used: 45 timelines from central Siberia and 48 from various Iberian mountain systems.
New methodology for the study of rings
To cope with the treatment of the large volume of data, a new methodological framework has been developed, capable of coping with large sets of ring width sequences dating back several centuries in time. These new methods have made it possible to demonstrate that the synchrony between growth patterns in coniferous forests whose main limiting factor is, in the case of the taiga, the cold, and in the case of the Mediterranean forests, the drought, has been increasing in the last 120 years to a peak in the early 21st century.
This coherence unprecedented in the recent past, on a large geographical scale, indicates that the synchrony of growth between distant forests up to almost a thousand kilometers is very similar to that of trees that inhabit the same forest mass.
This more synchronous growth of forests caused by climate warming is a global phenomenon, but the particular mechanisms that act in each case are regionally dependent. In particular, they are related to the increase in drought stress in late spring in Spain and to a greater impact of year-on-year fluctuations in summer temperatures in Siberia. In addition, all this is related to an earlier onset of wood formation, which has been shown to be induced by a warmer climate.
Increasing the synchrony in thickness growth may be useful to establish climatic thresholds for tree survival and to anticipate local and regional forest decay phenomena.
Photo: Sampling of a centenary Scots pine with Pressler's bit, Navarredonda de Gredos, Spain. / Sea Genoa
Shestakova, TA, Gutiérrez, E., Kirdyanov, AV, Camarero, JJ, Génova, M., Knorre, AA, Linares JC, Resco de Dios, V., Sánchez-Salguero, R. & Voltas, J. (2016) . "Forests synchronize their growth in contrasting Eurasian regions in response to climate warming". Proceedings of the National Academy of Sciences, 113 (3), 662-667.