Global Change Abstracts The Swiss Contribution - SCNAT

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72 in climate niche modelling. A simulation model is developed which incorporates three key features that have been largely overlooked in studies of range shifting dynamics: the form of intraspecific competition, density dependent dispersal and the transient dynamics of habitat patches. The results show that the exact shape of the response depends critically on both local and patch dynamics. Species whose intraspecific competition is contest based are more vulnerable than those whose competition is scramble based. Contesters are especially sensitive when combined with density dependent dispersal. Species living in patches whose carrying capacity grows slowly are also susceptible to rapid shifts of environmental conditions. A complementary analytic approach further highlights the importance of intraspecific competition. Oikos, 2007, V116, N9, SEP, pp 1531-1539. 08.1-92 Drought induces lagged tree mortality in a subalpine forest in the Rocky Mountains Bigler C, Gavin D G, Gunning C, Veblen T T Switzerland, USA Plant Sciences , Forestry , Ecology Extreme climatic events are key factors in initiating gradual or sudden changes in forest ecosystems through the promotion of severe, treekilling disturbances such as fire, blowdown, and widespread insect outbreaks. In contrast to these climatically-incited disturbances, little is known about the more direct effect of drought on tree mortality, especially in high-elevation forests. Therefore projections of drought-induced mortality under future climatic conditions remain uncertain. For a subalpine forest landscape in the Rocky Mountains of northern Colorado (USA), we quantified lag effects of drought on mortality of Engelmann spruce Picea engelmannii, subalpine fir Abies lasiocarpa, and lodgepole pine Pinus contorta. For the period 1910-2004, we related death dates of 164 crossdated dead trees to early-season and late-season droughts. Following early- season droughts, spruce mortality increased over five years and fir mortality increased sharply over 11 years. Following late-season droughts, spruce showed a small increase in mortality within one year, whereas fir showed a consistent period of increased mortality over two years. Pine mortality was not affected by drought. Low pre- drought radial growth rates predisposed spruce and fir to drought- related mortality. Spruce and fir trees that died during a recent drought (2000-2004) had significantly lower pre-drought growth rates than live neighbour trees. Overall, we found large inter- Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems specific differences in drought-related mortality with fir showing the strongest effect followed by spruce and pine. This direct influence of climatic variability on differential tree mortality has the potential for driving large-scale changes in subalpine forests of the Rocky Mountains. Oikos, 2007, V116, N12, DEC, pp 1983-1994. 08.1-93 Conservation of high-altitude wetlands: 368 experiences of the WWF network Biksham G Switzerland Biodiversity , Ecology Mountain Research and Development, 2007, V27, N4, NOV, pp 368-371. 08.1-94 Restoration of montane fen meadows by mowing remains possible after 4-35 years of abandonment Billeter R, Peintinger M, Diemer M Switzerland Ecology , Biodiversity , Agriculture, Soil Sciences , Plant Sciences The abandonment of management in Swiss fen meadows has reduced their plant species diversity and the fitness of some typical fen species. We examined whether the resumption of mowing can reverse these effects, and if so, which mechanisms are responsible for community change; we also tested whether restoration success depends on the duration since abandonment. Experimental mowing was applied to 15 montane fen meadows of NE Switzerland that had been abandoned for 4-35 years. After two years of mowing, plant species richness was 11 % higher in mown plots (2 m(2)) than in fallow plots, approaching levels of neighbouring continuously managed fen meadows. In particular, experimental mowing significantly increased the number of fen indicator species (+15 %) as well as herbs and woody species (seedlings and saplings), while grass, sedge and rush species richness was not affected. Mowing had little effect on aboveground biomass, but strongly reduced litter mass (-50%) and canopy height (-20%). Seedling densities of two common species showed opposite responses to mowing: they increased in Carex davalliana and decreased in Succisa pratensis, approaching values of continuously mown fen meadows. Duration since abandonment had no significant effect on any of the variables. Our results demonstrate a rapid recovery of montane fen plant communities irrespective of the duration since abandonment (up to 35 years). We conclude that the restoration of pre-fallow plant
Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems 73 community composition is likely to be successful if site conditions (hydrology, nutrient status) remain intact and if common habitat specialists are still present in the vegetation and/or seed bank. Botanica Helvetica, 2007, V117, N1, JUN, pp 1-13. 08.1-95 Dynamics in debris-flow activity on a forested cone - A case study using different dendroecological approaches Bollschweiler M, Stoffel M, Schneuwly D M Switzerland Forestry , Plant Sciences , Geomorphology Dendrogeomorpho logical analyses of trees affected by debris flows have regularly been used to date past events. However, this method has always been limited to forested cones where trees registered the impact of previous events. The minimum age dating of trees growing in the debris deposits can, in contrast, provide information on the latest possible moment of past activity. In this paper, we report on results obtained from a combination of these two approaches on a forested cone in the Valais Alps (Switzerland). A detailed geomorphic map in a scale of 1: 1000 served as a basis for the sampling strategy. Disturbed Larix decidua Mill. and Picea abies (L.) Karst. trees growing in the deposits allowed reconstruction of 49 events between AD 1782 and 2005 as well as the determination of the spatial extent of events. In the debris-flow channels where survivor trees are missing, we selected the oldest post-event trees and assessed their age by counting their growth rings. Missing rings due to lack of center as well as to sampling height were added so as to determine real tree age. The combination of the dendrogeomorphological event reconstruction with the assessment of germination dates of successor trees allowed realistic approximation of the minimum time elapsed since the last debris-flow activity in 23 of the 29 channels present on the current-day cone surface. In general, channels in the northern part of the cone and those close to the currently active channel generally show signs of (sub-) recent activity with one last overbank sedimentation event in the 1980s, whereas signs of debris-flow activity are absent from the channels in the outermost part since the late 19th century. As a consequence of the deeply incised channel and the stabilization measures undertaken along the banks, signs of debris flows are missing in the tree-ring record for the past two decades. Catena, 2008, V72, N1, JAN 1, pp 67-78. 08.1-96 Methanol exchange between grassland and the atmosphere Brunner A, Ammann C, Neftel A, Spirig C Switzerland Agriculture, Soil Sciences , Plant Sciences , Meteorology & Atmospheric Sciences , Ecology Concentrations and fluxes of methanol were measured above two differently managed grassland fields (intensive and extensive) in central Switzerland during summer 2004. The measurements were performed with a proton-transfer-reaction mass-spectrometer and fluxes were determined by the eddy covariance method. The observed methanol emission showed a distinct diurnal cycle and was strongly correlated with global radiation and water vapour flux. Mean and maximum daily emissions were found to depend on grassland species composition and, for the intensive field, also on the growing state. The extensive field with a more complex species composition had higher emissions than the graminoid-dominated intensive field, both on an area and on a biomass basis. A simple parameterisation depending on the water vapour flux and the leaf area index allowed a satisfying simulation of the temporal variation of methanol emissions over the growing phase. Accumulated carbon losses due to methanol emissions accounted for 0.024 and 0.048% of net primary productivity for the intensive and extensive field, respectively. The integral methanol emissions over the growing periods were more than one order of magnitude higher than the emissions related to cut and drying events. Biogeosciences, 2007, V4, N3, pp 395-410. 08.1-97 A standardized procedure for surveillance and monitoring European habitats and provision of spatial data Bunce R G H, Metzger M J, Jongman R H G, Brandt J, de Blust G, Elena Rossello R, Groom G B, Halada L, Hofer G, Howard D C, Kovar P, Mucher C A, Padoa Schioppa E, Paelinx D, Palo A, Perez Soba M, Ramos I L, Roche P, Skanes H, Wrbka T Netherlands, Denmark, Belgium, Spain, Slovakia, Switzerland, England, Czech Republic, Italy, Estonia, Portugal Ecology , Biodiversity Both science and policy require a practical, transmissible, and reproducible procedure for surveillance and monitoring of European habitats, which can produce statistics integrated at the landscape level. Over the last 30 years, landscape ecology has developed rapidly, and many studies now require spatial data on habitats. Without rigorous rules,
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