22.08.2014: Large volcanic eruptions can influence the climate from years to decades. Recently, scientists from the GFZ German Research Centre for Geosciences investigated the effects of large volcanic eruptions on tree growth. Based on tree-ring analysis they found a decreased growth in close to 60 percent of the examined trees over a period of four years after strong volcanic eruptions. However, positive growth responses were also identified in 32 percent of the trees. Furthermore this effect was less pronounced in central European lowlands compared to trees at altitudinal and alpine timberline sites.

It is well known that ashes, thrown out by volcanoes up to great heights, shield the solar radiation and can lead to a significant decrease of plant growth. In 1815 after the volcanic eruption of Tambora in Indonesia there was no summer the following year in the northern hemisphere with crop failures that led to famine at this time. In a recent study, a total of 52 large volcanic events during the last thousand years have been studied. The data set consisted of 1128 samples from oaks and pines that were taken at three different sites in northeast Germany (Greifswald, Eberswalde and Saxony). "For the first time tree growth responses were examined after volcanic eruptions in lowland temperate latitudes," says GFZ researcher Hagen Pieper. "Comparing tree growth from alpine sites with tree growth from lowland sites, the climatic impact after volcanic eruptions is stronger at the alpine sites compared to the lowlands sites."

Oaks seem to be more sensitive than pines: The tree-ring series of oaks show a stronger growth decrease (68%) than pines (53%). When comparing this data with other studies it suggests that volcanic eruptions from the last thousand years have had a stronger effect on northern hemisphere tree growth of the study sites than on southern hemisphere tree growth.

H. Pieper et al.,”The influence of volcanic eruptions on growth of central European lowland trees in NE-Germany during the last millennium”, Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 411, pp. 155-166, 1 October 2014,DOI: 10.1016/j.palaeo.2014.06.012