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Arians, A.E., 1997

The impact of flood frequency, permafrost distribution, and climate variation on a northern treeline floodplain of Alaska

Bibliographic Reference

Arians, A.E., 1997, The impact of flood frequency, permafrost distribution, and climate variation on a northern treeline floodplain of Alaska: University of Colorado, Boulder, Ph.D. dissertation, 112 p., illust., map.

Abstract

Climate variation is an important determinant of change in the radial growth of white spruce trees on the Noatak River floodplain. However, climate variation may cause changes in local-scale phenomena that have an equally important influence on the variation in radial growth and distribution of white spruce (Picea glauca (Moench) Voss). The spatial variation of permafrost depth and flood recurrence interval was found to influence radial growth of treeline white spruce and their distribution along the Noatak River. Temporal changes in permafrost depth are likely causes of a change in the floodplain landscape that decrease the availability of suitable substrates for white spruce growth. Depth to permafrost, estimated by soil temperature, determines the location of treeline. Treeline forests along the Noatak River are associated with comparatively deep, warm substrates, while tundra grows on colder, shallower soil. Regeneration status is not influenced by soil characteristics, although seedling density varies with soil temperature. Stand-scale variation in radial growth of white spruce is influenced by local-scale variations in soil temperature. Although there is no direct correlation between local-scale flood recurrence interval and stand-scale radial tree growth, flood disturbance has an indirect effect on forest distribution through its effect on the local-scale soil texture mosaic. The frequency with which a site is flooded controls substrate texture, which in turn influences permafrost depth and soil temperature. Temporal variation in regional-scale temperature also influences stand-scale radial growth. White spruce at the Noatak treeline have significantly increased their growth in response to a 2o to 3o temperature increase in arctic Alaska since about 1850. In addition to a simple increase in growth correlated with temperature, however, the limiting factors on growth have changed. Temperature in arctic Alaska has not only increased, but the last 25 years have been unusually dry, so that recent tree growth has been limited by moisture as well as temperature. In this treeline floodplain forest, both regional temperature change and the influence of this change on local-scale environmental factors are important influences on the growth and distribution of white spruce.

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