floodplain forests gesamt
Growth limiting environmental factors and stand development in floodplain forests (2014-2018)

Annual rings of trees are most valuable and long-term climate proxy-data at an annual resolution. At the limits of tree growth like at the alpine treeline or within inner Alpine dry valleys, the year-to-year variability of ring widths reflects variation of climate conditions (e.g., Schuster and Oberhuber 2013). Likewise, trees growing along riversides may store information on hydrological parameters like streamflow, water level fluctuations, and precipitation in their growth rings (Polacek et al. 2006). Along the inner Alpine river Inn (Tyrol, Austria) several near-natural floodplain forests exist within the ‘Mieminger and Rietzer Innauen’. Alluvial terraces, which are only occasionally subject to flooding are dominated by deciduous stands dominated by grey alder (Alnus incana) and including white willow (Salix alba) and black poplar (Populus nigra). At some sites Scots pine (Pinus sylvestris) invades these stands, which is supposed to be due to periodic drought stress (low water level) occurring during the growing season.

Research Questions

This study is primarily aimed at determining long-term growth trends of co-occurring tree species and evaluating environmental influence (climate, water level fluctuation) on radial tree growth in several stands of the ‘Mieminger and Rietzer Innauen’. Furthermore, results of this dendroecological study will elucidate (i) spatio-temporal extent of growth variability and (ii) species-specific growth response to environmental extremes and (iii) will improve our understanding of forest development in floodplain forests within inner Alpine valleys.

References
Polacek D., W. Kofler and W. Oberhuber (2006) Radial growth of Pinus sylvestris growing on alluvial terraces is sensitive to water-level fluctuations. New Phytologist 169:299-308.
Schuster R, W Oberhuber (2013) Drought sensitivity of three co-occurring conifers within a dry inner Alpine environment. Trees 27:61-69

Funding
Tyrolean Government, Environmental protection department

Personnel involved
Franz Demar
Ines Aster
Oberhuber Walter