Global Change Abstracts The Swiss Contribution - SCNAT

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100 ing geographic distance among parcels, and a differentiation among grazed and mown parcels, and among sexually and vegetatively reproducing populations. Band richness of sampled plants per village was higher for villages where parcels represented more different land-use types. Within populations, microsatellite band diversity was higher in grazed than in mown parcels. Conclusions The diversity of human land use in the Alps was associated with genetic diversity of P. alpina. Therefore, the ongoing socio-economically motivated land-use changes, which reduce the number of different land-use types, will affect the genetic diversity of P. alpina negatively. Annals of Botany, 2007, V100, N6, NOV, pp 1249-1258. 08.1-164 Recent decline in precipitation and tree growth in the eastern Mediterranean Sarris D, Christodoulakis D, Körner C Greece, Switzerland Meteorology & Atmospheric Sciences , Plant Sciences , Forestry We present evidence of a recent drying in the eastern Mediterranean, based on weather and tree-ring data for Samos, an island of the eastern Aegean Sea. Rainfall declined rapidly after the late 1970s following trends for the entire Mediterranean and was associated with reduced tree-ring width in Pinus brutia. The most recent decline led to the lowest annual radial stem increment after the last 100 years (as far as records reach). As moisture availability decreased best correlations of tree growth with rainfall were obtained for progressively longer integration periods (1-2 years in moister periods, 5-6 years during the severe dryness of 20th century’s last decades), suggesting increasing dependency in deep soil water. Such long-term integration periods of tree-growth responses to precipitation have not been reported before. They may reflect a tree- rooting pattern adapted to cope with even several successive dry years. In late summer 2000, moisture reserves became exhausted, however, and a substantial fraction of low altitude pines died, including some 80-year-old trees, which underlines the exceptional extent this trend had reached. Our findings provide empirical support for Intergovernmental Panel on Climate Change projections derived from global circulation models that the Mediterranean, its eastern basin in particular, should become drier as temperature rises, as was the case in the recent past. Global Change Biology, 2007, V13, N6, JUN, pp 1187-1200. Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems 08.1-165 Modeling the forest transition: Forest scarcity and ecosystem service hypotheses Satake A, Rudel T K Switzerland, USA Modelling , Forestry , Social Sciences , Ecology , Economics An historical generalization about forest cover change in which rapid deforestation gives way over time to forest restoration is called “the forest transition.” Prior research on the forest transition leaves three important questions unanswered: (1) How does forest loss influence an individual landowner’s incentives to reforest? (2) How does the forest recovery rate affect the likelihood of forest transition? (3) What happens after the forest transition occurs? The purpose of this paper is to develop a minimum model of the forest transition to answer these questions. We assume that deforestation caused by landowners’ decisions and forest regeneration initiated by agricultural abandonment have aggregated effects that characterize entire landscapes. These effects include feedback mechanisms called the “forest scarcity” and “ecosystem service” hypotheses. In the forest scarcity hypothesis, forest losses make forest products scarcer, which increases the economic value of forests. In the ecosystem service hypothesis, the environmental degradation that accompanies the loss of forests causes the value of ecosystem services provided by forests to decline. We examined the impact of each mechanism on the likelihood of forest transition through an investigation of the equilibrium and stability of landscape dynamics. We found that the forest transition occurs only when landowners employ a low rate of future discounting. After the forest transition, regenerated forests are protected in a sustainable way if forests regenerate slowly. When forests regenerate rapidly, the forest scarcity hypothesis expects instability in which cycles of large- scale deforestation followed by forest regeneration repeatedly characterize the landscape. In contrast, the ecosystem service hypothesis predicts a catastrophic shift from a forested to an abandoned landscape when the amount of deforestation exceeds the critical level, which can lead to a resource degrading poverty trap. These findings imply that incentives for forest conservation seem stronger in settings where forests regenerate slowly as well as when decision makers value the future. Ecological Applications, 2007, V17, N7, OCT, pp 2024-2036.
Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems 101 08.1-166 Ecological niche modelling of two cryptic bat species calls for a reassessment of their conservation status Sattler T, Bontadina F, Hirzel A H, Arlettaz R Switzerland Modelling , Ecology , Biodiversity , Zoology It is difficult to establish conservation priorities for cryptic species when their ecological requirements are confounded by problems with species identification. In some cases, such as Chiroptera, cryptic taxa may actually consist of both widespread, abundant species and localized, rare species. Discrimination between these species may be facilitated by phenotypic, species-specific traits such as echolocation calls. Echolocation studies supported by genetic data have revealed that one of the most abundant bat species in Europe actually consists of two cryptic species: Pipistrellus pipistrellus and P. pygmaeus. We recorded echolocation calls from both species along road transects in Switzerland to study their distribution and abundance. Using Ecological Niche Factor Analysis and discriminant analysis, we characterized species-specific habitat requirements, built habitat suitability maps and examined interspecific differences in niche parameters. The presence of P. pygmaeus was associated with landscape matrices comprising large rivers and lakes, human settlements and open woodland. P. pipistrellus utilized similar habitat matrices but was far more tolerant to deviations from its optimal habitat. P. pygmaeus occupied a much narrower ecological niche, encompassed mainly within that of its sister taxon. Synthesis and applications. P. pipistrellus is ranked as ‘not threatened’ in Switzerland. The results from this study indicate an abundance approximately 30 times higher than that of P. pygmaeus. In contrast, P. pygmaeus is distributed patchily and occurs at comparatively low densities. We recommend reclassification of P. pygmaeus as ‘rare and potentially threatened’. Conservation of P. pygmaeus should focus on the management of riparian woodland in areas with a high probability of occurrence. This study emphasizes the need to recognize the potential existence of cryptic taxa so that effective conservation management of rare species can be put into place before they are seriously endangered. Journal of Applied Ecology, 2007, V44, N6, DEC, pp 1188-1199. 08.1-167 Use of integrated modeling to enhance estimates of population dynamics obtained from limited data Schaub M, Gimenez O, Sierro A, Arlettaz R Switzerland, Scotland, France Modelling , Zoology , Ecology , Biodiversity Demographic data of rare and endangered species are often too sparse to estimate vital rates and population size with sufficient precision for understanding population growth and decline. Yet, the combination of different sources of demographic data into one statistical model holds promise. We applied Bayesian integrated population modeling to demographic data from a colony of the endangered greater horseshoe bats (Rhinolophus ferrumequinum). Available data were the number of subadults and adults emerging from the colony roost at dusk, the number of newborns from 1991 to 2005, and recapture data of subadults and adults from 2004 and 2005. Survival rates did not differ between sexes, and demographic rates remained constant across time. The greater horseshoe bat is a long-lived species with high survival rates (first year: 0.49 (SD 0.06); adults: 0.91 (SD 0.02)) and low fecundity (0.74 (SD 0.12)). The yearly average population growth was 4.4% (SD 0.1%) and there were 92 (SD 10) adults in the colony in year 2005. Had we analyzed each data set separately, we would not have been able to estimate fecundity, the estimates of survival would have been less precise, and the estimate of population growth biased. Our results demonstrate that integrated models are suitable for obtaining crucial demographic information from limited data. Conservation Biology, 2007, V21, N4, AUG, pp 945-955. 08.1-168 Tree species richness affects litter production and decomposition rates in a tropical biodiversity experiment Scherer Lorenzen M, Bonilla J L, Potvin C Switzerland, Panama, Canada Forestry , Plant Sciences , Biodiversity , Ecology We report data on leaf litter production and decomposition from a manipulative biodiversity experiment with trees in tropical Panama, which has been designed to explore the relationship between tree diversity and ecosystem functioning. A total of 24 plots (2025 m(2)) were established in 2001 using six native tree species, with 1-, 3-, and 6-species mixtures. We estimated litter production during the dry season 2005 with litter traps; decomposition was assessed with a litter bag approach during the following wet season. Litter
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