A 700-year paleoecological record of boreal ecosystem responses to climatic variation from Alaska

Copyright by the Ecological Society of America © 2008. Willy Tinner, Christian Bigler, Sharon Gedye, Irene Gregory-Eaves, Richard T. Jones, Petra Kaltenrieder, Urs Krähenbühl, and Feng Sheng Hu 2008. A 700-YEAR PALEOECOLOGICAL RECORD OF BOREAL ECOSYSTEM RESPONSES TO CLIMATIC VARIATION FROM ALASKA. Ecology 89:729–743. http://dx.doi.org/10.1890/06-1420.1Recent observations and model simulations have highlighted the sensitivity of the forest–tundra ecotone to climatic forcing. In contrast, paleoecological studies have not provided evidence of tree-line fluctuations in response to Holocene climatic changes in Alaska, suggesting that the forest–tundra boundary in certain areas may be relatively stable at multicentennial to millennial time scales. We conducted a multiproxy study of sediment cores from an Alaskan lake near the altitudinal limits of key boreal-forest species. Paleoecological data were compared with independent climatic reconstructions to assess ecosystem responses of the forest–tundra boundary to Little Ice Age (LIA) climatic fluctuations. Pollen, diatom, charcoal, macrofossil, and magnetic analyses provide the first continuous record of vegetation–fire–climate interactions at decadal to centennial time scales during the past 700 years from southern Alaska. Boreal-forest diebacks characterized by declines of Picea mariana, P. glauca, and tree Betula occurred during the LIA (AD 1500–1800), whereas shrubs (Alnus viridis, Betula glandulosa/nana) and herbaceous taxa (Epilobium, Aconitum) expanded. Marked increases in charcoal abundance and changes in magnetic properties suggest increases in fire importance and soil erosion during the same period. In addition, the conspicuous reduction or disappearance of certain aquatic (e.g., Isoetes, Nuphar, Pediastrum) and wetland (Sphagnum) plants and major shifts in diatom assemblages suggest pronounced lake-level fluctuations and rapid ecosystem reorganization in response to LIA climatic deterioration. Our results imply that temperature shifts of 1–2°C, when accompanied by major changes in moisture balance, can greatly alter high-altitudinal terrestrial, wetland, and aquatic ecosystems, including conversion between boreal-forest tree line and tundra. The climatic and ecosystem variations in our study area appear to be coherent with changes in solar irradiance, suggesting that changes in solar activity contributed to the environmental instability of the past 700 years

INTEGRATION: youth welfare and sustainable development in Switzerland

In Switzerland with its 7.3 million inhabitants, about 200,000 people are working in the agricultural sector managing 66,000 farms. Between 1990 and 2000, the number of agricultural employees shrunk by 50,000 and more than 22,000 agrarian businesses were abandoned – mostly smallscale farms with less than 3 ha. The Emmental region is a part of Switzerland characterized by a high share of agriculture. Compared to other regions the proportion of rural inhabitants is still relatively high, the decline of farms is therefore below the figures of the rest of Switzerland. Nevertheless, as an effect of the structural change also in rural regions, the remaining farmers depend more and more on additional incomes and are looking for extra work in different branches. Although the Emmental region is one of the economically poor marginal regions of Switzerland, it has a multitude of strengths: besides the intact landscape and numerous natural resources the inhabitants have a strong liaison to their culture and traditions. The family structures are essentially still in good order and the social network is functioning. Based on these strengths, the project INTEGRATION aims at three main targets: * Providing space for living and developing on a qualified farm with system-therapeutic and socialpedagogic support for socially deprived children and adolescents from urban centres such as Berne, Basel and Lucerne. * Offering places of care creates innovative and sustainable supplementary earnings for the farming families in an economically unfavourable mountain area. * At the political level, a new quality of the relation between ‘city’ and ‘country’ evolves by bringing together different cultures and exchanging ideas and experiences. INTEGRATION is a social youth-welfare project with a strong liaison with the economic sector. The well-being of the involved children, adolescents and partner families comes first but with its connections to economic and ecological aspects INTEGRATION has also become a typical project in the field of sustainable rural development. This may have led to the invitation of the representatives of the project to participate in the preparatory workshop in Vorden (The Netherlands), April 2004. They had the opportunity to present and discuss the philosophy of the project INTEGRATION and its results during the last eight years. As an innovative project in the field of social youth welfare in Switzerland, INTEGRATION was also asked for a contribution to the publication ‘Farming for Health’. Although there are quite a lot of activities in this field, the term ‘Farming for Health’ is neither widely known nor used in Switzerland yet. After the preparatory workshop, the project team discussed an appropriate translation into (Swiss) German: the best working title was found in ‘Landwirtschaft und soziale Wohlfahrt’. It will be a challenge for the future to determine a term that meets most of the requirements of the then involved organizations. The first part of this contribution gives a short overall description of activities in Switzerland, while the project INTEGRATION with its targets, activities and results is described in the second par

Changes in fire regimes since the last glacial maximum: an assessment based on a global synthesis and analysis of charcoal data

Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ?11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ?19,000 to ?17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ?13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ?3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load