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- Elberling, Bo, et al.
(author)
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Soil and Plant Community Characteristics and Dynamics at Zackenberg
- 2008
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In: High-arctic ecosystem dynamics in a changing climate - Ten years of monitoring and research at Zackenberg Research Station, Northeast Greenland (Advances in Ecological Research). - 0065-2504. - 9780123736659 ; 40, s. 223-248
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Book chapter (other academic/artistic)abstract
- Arctic soils hold large amounts of nutrients in the weatherable minerals and the soil organic matter, which slowly decompose. The decomposition processes release nutrients to the plant-available nutrient pool as well as greenhouse gases to the atmosphere. Changes in climatic conditions, for example, changes in the distribution of snow, water balance and the length of the growing season, are likely to affect the complex interactions between plants, abiotic and biotic soil processes as well as the composition of soil micro- and macro-fauna and thereby the overall decomposition rates. These interactions, in turn, will influence soil-plant functioning and vegetation composition in the short as well as in the long term. In this chapter, we report on soils and. plant communities and their distribution patterns in the valley Zackenbergdalen and focus on the detailed investigations within five dominating plant communities. These five communities are located along an ecological gradient in the landscape and are closely related to differences in water availability. They are therefore indirectly formed as a result of the distribution of landforms, redistribution of snow and drainage conditions. Each of the plant communities is closely related to specific nutrient levels and degree of soil development including soil element accumulation and translocation, for example, organic carbon. Results presented here show that different parts of the landscape have responded quite differently to the same overall climate changes the last 10 years and thus, most likely in the future too. Fens represent the wettest sites holding large reactive buried carbon stocks. A warmer climate will cause a permafrost degradation, which most likely will result in anoxic decomposition and increasing methane emissions. However, the net gas emissions at fen sites are sensitive to long-term changes in the water table level. Indeed, increasing maximum active layer depth at fen sites has been recorded together with a decreasing water level at Zackenberg. This is in line with the first signs of increasing extension of grasslands at the expense of fens. In contrast, the most exposed and dry areas have less soil carbon, and decomposition processes are periodically water limited. Here, an increase in air temperatures may increase active layer depth more than at fen sites, but water availability will be critical in determining nutrient cycling and plant production. Field manipulation experiments of increasing temperature, water supply and nutrient addition show that soil-plant interactions are sensitive to these variables. However, additional plant-specific investigations are needed before net effects of climate changes on different landscape and plant communities can be integrated in a landscape context and used to assess the net ecosystem effect of future climate scenarios.
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| 3. |
- Tritsaris, Katerina, et al.
(author)
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IL-20 is an arteriogenic cytokine that remodels collateral networks and improves functions of ischemic hind limbs
- 2007
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In: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 104:39, s. 15364-15369
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Journal article (peer-reviewed)abstract
- Successful therapeutic angiogenesis for the treatment of ischemic disorders relies on selection of optimal proangiogenic or arteriogenic agents that are able to promote establishment of functional collateral networks. Here, we show that IL-20, a pleiotropic inflammatory cytokine, displays an imperative effect on vascular remodeling. Stimulation of both large and microvascular endothelial cells with IL-20 leads to activation of receptor-dependent multiple intracellular signaling components, including increased phosphorylation levels of JAK2/STAT5, Erk1/2, and Akt; activation of small GTP-binding proteins Rac and Rho; and intracellular release of calcium. Surprisingly, IL-20 significantly promotes endothelial cell tube formation without affecting their proliferation and motility. These findings suggest that the vascular function of IL-20 involves endothelial cell organization, vessel maturation, and remodeling. Consistent with this notion, delivery of IL-20 to the ischemic muscle tissue significantly improves arteriogenesis and blood perfusion in a rat hind-limb model. Our findings provide mechanistic insights on vascular functions of IL-20 and define therapeutic implication of this cytokine for the treatment of ischemic disorders.
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