This is Section 7.3 of the Arctic Climate Impact Assessment
Lead Author: Terry V. Callaghan; Contributing Authors: Lars Olof Björn, F. Stuart Chapin III,Yuri Chernov,Torben R. Christensen, Brian Huntley, Rolf Ims, Margareta Johansson, Dyanna Jolly Riedlinger, Sven Jonasson, Nadya Matveyeva,Walter Oechel, Nicolai Panikov, Gus Shaver; Consulting Authors: Josef Elster, Heikki Henttonen, Ingibjörg S. Jónsdóttir, Kari Laine, Sibyll Schaphoff, Stephen Sitch, Erja Taulavuori, Kari Taulavuori, Christoph Zöckler
The individual of a species is the basic unit of ecosystems that responds to changes in climate and UV-B radiation levels. Individuals respond to environmental changes over a wide range of timescales: from biochemical, physiological, and behavioral processes occurring in less than a minute to the integrative responses of reproduction and death (Fig. 7.1). Reproduction and death drive the dynamics of populations while mutation and environmental selection of particular traits in individuals within the population lead to changes in the genetic composition of the population and adaptation.
Current arctic species have characteristics that have enabled them to pass various environmental filters associated with the arctic environment, whereas species of more southerly latitudes either cannot pass these filters or have not yet arrived in the Arctic. Changes in arctic landscape processes and ecosystems in a future climatic and UV-B radiation regime will depend upon the ability of arctic species to withstand or adapt to new environments and upon their interactions with immigrant species that can pass through less severe environmental filters.This section focuses on the attributes of current arctic species that constrain or facilitate their responses to a changingclimate and UV-B radiation regime.
Soil characteristics will determine to some extent the responses of vegetation to climate change. Arctic soils(and particularly moisture content) vary from the forest tundra to the polar deserts and within each of these vegetation zones.
In the high-arctic polar deserts, skeletal soils and stony ground predominate. Materials range from boulders to gravel and the dominant erosion process is physical weathering (e.g., freeze–thaw cracking)rather than chemical and biochemical weathering,which are strongly suppressed by lack of heat. Freeze–thaw cycles lead to a sorting of stones by size and formation of patterned ground consisting, for example, of stone nets. An organic layer is missing from the soil profile and organic material is restricted to small pockets under sparse plant cover or in cracks.The soils are neutral or only weakly acidic and the soil complexes are almost completely saturated with moisture although this differs between the polar deserts of Canada, Greenland,and the Russian Arctic. Gleys are almost absent and the active-layer depth is about 30 cm.
In the tundra biome, soil profiles are characterized by an organic layer that is often less than 10 cm deep on dry ridges, is deeper in moist and mesic habitats, and extends to deep deposits of peat in wet areas. Below the organic layer is a mineral layer.The active layer is deepest in the dry areas (~1 m) owing to the lack of summer insulation, and is shallowest in wet areas (~20 cm) due to efficient insulation by continuous vegetation cover and organic soil.The pH of tundra soils is generally acidic. Chemical and biochemical processe sare important but sorting of materials and patterned ground are still evident, leading to landscapes with larger polygons than those found in the polar deserts. In both polar-desert and tundra soils, the permafrost is generally continuous. In contrast, in soils of the forest tundra, the permafrost generally becomes discontinuous and the depth of the organic layer decreases except for waterlogged depressions where peat bogs are found.
Soil formation processes in the Arctic are slow and the type of soil is very likely to constrain potential rates of colonization by southern species.
Chapter 7: Arctic Tundra and Polar Desert Ecosystems
7.2 Late-Quaternary changes in arctic terrestrial ecosystems, climate, and ultraviolet radiation levels
7.3 Species responses to changes in climate and ultraviolet-B radiation in the Arctic
7.3.1 Implications of current species distributions for future biotic change
7.3.2 General characteristics of arctic species and their adaptations in the context of changes in climate and ultraviolet-B radiation levels
7.3.3 Phenotypic responses of arctic species to changes in climate and ultraviolet-B radiation
7.3.4 Genetic responses of arctic species to changes in climate and ultraviolet-B radiation levels
7.3.5 Recent and projected changes in arctic species distributions and potential ranges
7.4 Effects of changes in climate and UV radiation levels on structure and function of arctic ecosystems in the short and long term
7.4.1 Ecosystem structure
7.4.2 Ecosystem function
7.5 Effects of climate change on landscape and regional processes and feedbacks to the climate system
7.6 Synthesis: Scenarios of projected changes in the four ACIA regions for 2020, 2050, and 2080
7.7 Uncertainties and recommendations
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