Timberline Paleoecology in the Alps

Holocene Timberline Fluctuations and Climate Variability Alpine life and landscapes are exposed to extreme environmental conditions. Avalanches, landslides and floods, due to extreme climatic events such as heavy snow and rain storms, can impact both wild and managed landscapes. Above timberline, climatic conditions are so harsh that they impede the growth of trees. According to one recent hypothesis (the “growth-limitation hypothesis”), low temperatures reduce production of plant tissues (Körner, 1999). Therefore, trees become victims of their strategy to accumulate large amounts of biomass in order to overgrow other vegetational life forms. Because the upper boundary of tree growth is temperature controlled, it can be used as a proxy for estimation of past temperatures, assuming that today’s occurrence of trees is in equilibrium with local climate. Similar assumptions are made to derive paleo-temperature estimations from other organisms. Many recent paleoecological studies in the Alps have focused on climate reconstruction, but relatively few studies have addressed basic past relationships between organisms and their biotic and abiotic environments. One of the reasons for avoiding the latter topic may be that accurate studies require independent environmental proxies and high temporal resolution (years to decades), especially if the goal is to reconstruct past responses of short-lived organisms to climatic change. Moreover, concerns about global warming have focused much effort on the reconstruction of past climatic changes and their forcing mechanisms, but the response of organisms and biomes seems at least from an ecological and economical point of view of similar relevance (e.g. collapse, migration or adaptation of boreal and alpine life). The above-mentioned assumption that today’s distribution of trees is in equilibrium with climate may not necessarily be true. Over the past several thousands years, human activities in the Alps have resulted in lowering of timberlines by 200-300 altitudinal meters. Nevertheless, single trees in remote