Tree recruitment above the treeline and potential for climate-driven treeline change

• Questions   How do population structure and recruitment characteristics of Betula   saplings beyond the treeline vary among climatic regions, and what is   the potential for development into tree-sized individuals with   interacting grazing pressure?   Location   Scandes Mountains.   Methods   Sapling characteristics of Betula pubescens subsp. tortuosa, their   topographic position above the treeline, growth habitat and evidence of   recent grazing was investigated in three areas with a long continuous   grazing history, along a latitudinal gradient (62-69 degrees N).   Results   Saplings were common up to 100 m above the treeline in all areas. The   northern areas were characterised by small (< 30 cm) and young (mean 14   years old) saplings in exposed micro-topographic locations unfavourable   to long-term survival. In the southern area, broad height (2-183 cm)   and age (4-95 years; mean 32 years) distributions were found in   sheltered locations. Age declined with altitude in all areas. Sapling   growth rate varied within and between areas, and the age x height   interaction was significant only in the southern area. Growth rates   decreased from south to north and indicated a considerable time   required to reach tree size under prevailing conditions.   Conclusions   Regional differences can be attributed to climatic differences,   however, interacting biotic and abiotic factors such as   micro-topography, climate and herbivory, mutually affect the   characteristics of birch saplings. In view of the long time needed to   reach tree size, the generally expected evident and fast treeline   advance in response to climate warming may not be a likely short-term   scenario. The sapling pool in the southern region possesses strongest   potential for treeline advance.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Alpine zone

Browsing

Climate change

Mountain birch

Saplings

Treeline dynamics

Biology

Biologi

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