Aim Species ranges are confined by environmental parameters such as minimum temperatures. Beyond correlations of ranges and climatic parameters, however, physiological tolerances (here: cold tolerance) have rarely been linked to the climate of species' ranges. We hypothesize that natural range shifts due to climate warming and proactive-assisted colonization may each be constrained by limits to the tolerance of species to rare frost events.Location Bayreuth, Germany, and the Northern Hemisphere.Methods We quantified cold tolerance (LT50 obtained by relative electrolyte leakage method) of 27 native and exotic (Northern Hemisphere) tree species in the autumn, mid-winter and spring of 2011-12 at the Ecological Botanical Garden of the University of Bayreuth, Germany, and linked observed cold tolerances as well as changes in cold tolerance between sampling dates to the climate of the native ranges of the species.Results Observed cold tolerance was strongly related to the climate of the native ranges of the species (cross-validated correlations between climate and expressed cold tolerance determined by boosted regression trees were 0.50 in autumn, 0.49 in mid-winter, and 0.65 in spring). Cold tolerance was generally greater for species that experienced colder temperatures and lower levels of precipitation in their native ranges. Changes in cold tolerance between the three sampling dates over the winter, however, were not linked to the climate of the native ranges.Main conclusions Our results demonstrate the evolutionary importance of cold tolerance, which should be acknowledged in assisted colonization trials and projections of range shifts by considering absolute minimum temperature as an important ecological factor.

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.KEY WORDS: Climate change · Climate scenario · Inter-annual variability · Crop yield · Maize · Winter wheat · Winter canola Resale or republication not permitted without written consent of the publisherClim Res 34: [59][60][61][62][63][64][65][66][67][68][69] 2007 increase in mean temperature. Enhanced climate variability may lower mean yields because of a higher incidence of years with adverse conditions (Southworth et al. 2000), but sign and magnitude of the impacts will likely vary from region to region and depend on the crop (Porter & Semenov 2005). In Europe, productivity is likely to increase in northern Europe but decrease in southern Europe, unless adaptive measures are implemented to cope with the negative impact of climate change (Olesen & Bindi 2002).The specific response of crops to climate change will depend on how growth and yield formation are stimulated by elevated CO 2 concentrations. Direct stimulation of photosynthesis and increase in transpiration and water use efficiencies both play a role (Fuhrer 2003). The potential for a direct effect is larger in C3 than C4 crops, because ribulose-1, 5-bisphosphate carboxylaseoxygenase (RuBisCO) in the latter is already CO 2 saturated at current atmospheric levels (Long et al. 2004).The overall objective of our study was to examine the effects of climate change on productivity for 3 of the main crops grown in Switzerland and Europe, namely Zea mays L. (maize), a C4 crop, Triticum spp. L. (winter wheat) and Brassica napus L. (winter canola), both C3 crops. Specific aims were to (1) develop a climate change scenario that accounts not only for the change in mean conditions but also in year-to-year variability; (2) compare mean yield levels an...

The impact of climate change on Swiss maize production is assessed using an approach that integrates a biophysical and an economic model. Simple adaptation options such as shifts in sowing dates and adjustments of production intensity are considered. In addition, irrigation is evaluated as an adaptation strategy. It shows that the impact of climate change on yield levels is small but yield variability increases in rainfed production. Even though the adoption of irrigation leads to higher and less variable maize yields in the future, economic benefits of this adoption decision are expected to be rather small. Thus, no shift from the currently used rainfed system to irrigated production is expected in the future. Moreover, we find that changes in institutional and market conditions rather than changes in climatic conditions will influence the development of the Swiss maize production and the adoption of irrigation in the future.

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