Global Change Abstracts The Swiss Contribution - SCNAT

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106 08.1-179 An improved canopy integration scheme for a land surface model with prognostic canopy structure Thornton P E, Zimmermann N E USA, Switzerland Modelling , Forestry , Plant Sciences , Ecology A new logical framework relating the structural and functional characteristics of a vegetation canopy is presented, based on the hypothesis that the ratio of leaf area to leaf mass (specific leaf area) varies linearly with overlying leaf area index within the canopy. Measurements of vertical gradients in specific leaf area and leaf carbon:nitrogen ratio for five species (two deciduous and three evergreen) in a temperate climate support this hypothesis. This new logic is combined with a two-leaf (sunlit and shaded) canopy model to arrive at a new canopy integration scheme for use in the land surface component of a climate system model. An inconsistency in the released model radiation code is identified and corrected. Also introduced here is a prognostic canopy model with coupled carbon and nitrogen cycle dynamics. The new scheme is implemented within the Community Land Model and tested in both diagnostic and prognostic canopy modes. The new scheme increases global gross primary production by 66% (from 65 to 108 Pg carbon yr(-1)) for diagnostic model simulations driven with reanalysis surface weather, with similar results (117 PgC yr (-1)) for the new prognostic model. Comparison of model predictions to global syntheses of observations shows generally good agreement for net primary productivity (NPP) across a range of vegetation types, with likely underestimation of NPP in tundra and larch communities. Vegetation carbon stocks are higher than observed in forest systems, but the ranking of stocks by vegetation type is accurately captured. Journal of Climate, 2007, V20, N15, AUG 1, pp 3902-3923. 08.1-180 Fitness-related parameters improve presenceonly distribution modelling for conservation practice: The case of the red-backed shrike Titeux N, Dufrene M, Radoux J, Hirzel A H, Defourny P Belgium, Switzerland Modelling , Biodiversity , Ecology , Zoology The red-backed shrike (Lanius collurio L.) is a bird living in human- altered agricultural areas that are managed by extensive farming techniques. This passerine species has declined significantly in Western Europe over the last 30-40 years. The Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems development of efficient species-specific conservation strategies relies on fine- grained information about the ecological resources and environmental conditions that constitute its reproductive habitat in this agricultural landscape. Species distribution models are used increasingly in conservation biology to provide such information. Most studies investigate the environmental pattern of species distribution, assuming that species records are reliable indicators of habitat suitability. However, ecological theory on source-sink dynamics and ecological traps points out that some individuals may be located outside the environmental bounds of their species’ reproductive niche. Those individuals could reduce model accuracy and limit model utility. Parameters related to the reproductive success of this shrike in Southern Belgium were integrated into a fine-scale presence-only modelling framework to demonstrate this problem and to address critical habitat requirements of this species relative to conservation management. Integrating reproductive parameters into the modelling framework showed that individuals occurred, but did not reproduce successfully, above a certain environmental threshold. This indicated that the reproductive niche of the shrike is ecologically narrower than standard practice in species distribution modelling would suggest. The major resources (nest sites availability, distance to human settlements, suitable perching sites, foraging areas and insect abundance) required for the reproduction of the red-backed shrike were quantified and ranked to offer concrete species -specific conservation management guidelines Biological Conservation, 2007, V138, N1-2, AUG, pp 207-223. 08.1-181 Response of Pinus leucodermis to climate and anthropogenic activity in the National Park of Pollino (Basilicata, Southern Italy) Todaro L, Andreu L, D’alessandro C M, Gutirrez E, Cherubinic P, Saracino A Italy, Spain, Switzerland Forestry , Plant Sciences , Ecology , Biodiversity Pinus leucodermis (=P. heldreichii var. leucodermis) is widespread in the Balkan Peninsula and is present as a post-glacial relict in Southern Italy. The oldest Italian populations of this species are located at high elevation in the National Park of Pollino, where grazing and logging had endangered their survival, especially during the 20th century. In 1993 the National Park was founded and anthropogenic activities were restricted. To understand the response of P. leucodermis at the upper tree-line to climatic and anthropogenic ac-
Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems 107 tivity variations, we developed a tree-ring width chronology (1464-2003). For the period 1804-2003 separate chronologies for the earlywood and latewood were built, and resin duct density was assessed on total ring, earlywood and latewood. Age structure of saplings was also determined. After 1950 a steep decline in tree-ring width was followed by a recovery since 1981. During the 20th century radial growth response to climate was not strong and not stable. In the period 19532000 P. leucadermis radial growth seemed to take advantage of high temperatures and low precipitation. Resin duct density chronologies were not a reliable dendroecological variable, but they documented a metabolic trade-off between growth and differentiation processes. The gap in the age structure between long- lived trees (over 200 years old) and saplings around 40 years old, which mainly grow in protected microsites between rocks, could indicate a negative influence of grazing and related human activities. We suggest that the protection strategies introduced by the National Park could play a positive role in the recruitment of new saplings and in the ring growth recovery of old trees of P. leucodermis. Biological Conservation, 2007, V137, N4, JUL, pp 507-519. 08.1-182 Regional assessment of climate change impacts on maize productivity and associated production risk in Switzerland Torriani D S, Calanca P, Lips M, Ammann H, Beniston M, Fuhrer J Switzerland Agriculture, Soil Sciences , Modelling , Ecology , Plant Sciences A simple model of yield was used along with climate scenarios to assess the impact of climate change on grain maize productivity and associated economic risk in Switzerland. In a first application, changes in the precipitation regime alone were shown to affect the distribution of yield considerably, with shifts not only in the mean but also in the standard deviation and the skewness. Production risk was found to respond more markedly to changes in the long-term mean than in the inter-annual variability of seasonal precipitation amounts. In a further application, yield projections were generated with respect to a full climate scenario, with the emission pathway as specified in the IPCC A2 scenario. Anticipation of the sowing date was found to reduce the negative impact of climate change on yield stability, but was not sufficient to ensure average productivity levels comparable to those observed at present. We argued that this was caused by the reduction in the duration of the growing season, which had a stronger impact than suggested by previous studies. Assuming no change in price relations, the results also revealed a strong increase in production risk with climate change, with more than a doubling in the probability of yield falling short of a critical threshold as compared to today’s situation. Regional Environmental Change, 2007, V7, N4, DEC, pp 209-221. 08.1-183 Potential effects of changes in mean climate and climate variability on the yield of winter and spring crops in Switzerland Torriani D S, Calanca P, Schmid S, Beniston M, Fuhrer J Switzerland Modelling , Meteorology & Atmospheric Sciences , Agriculture, Soil Sciences , Ecology , Biodiversity Climate change is expected to affect both the average level and the variability of crop yields. In this modelling study, we quantified mean and inter-annual variability of grain yield for maize Zea mays L., winter wheat Triticum spp. L. and winter canola Brassica napus L. for climatic conditions corresponding to current and doubled atmospheric CO 2 concentrations. Climate scenarios with and without taking into account changes in the inter-annual variability of climate were developed from the output of a regional climate model for the time window 2071 to 2100. Climate change effects on the mean yield of maize and canola were consistently negative, but a positive impact was simulated for mean yield of winter wheat for elevated CO 2 concentration. The coefficient of yield variation increased in the scenarios for maize and canola, but decreased for wheat. Higher thermal time requirements increased mean yield and reduced yield variability for all crops. Shifts in the sowing dates had a beneficial impact on the yield of maize, but not on the yield of canola and wheat. It is concluded that in the Alpine region, the potential effect of climate change is crop-specific. However, the introduction of new cultivars may provide means by which to maintain or even increase current productivity levels for most of the crops. Climate Research, 2007, V34, N1, JUN 14, pp 59-69.
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