The bioclimatic temperatures that mountain plants experience are very different from the macroclimatic temperatures and vary according to the exposition, relief, and growth form. This is shown in the example of boundary layer temperatures recorded in the Tyrolean Alps between the timberline and the nival zone over several years. Microsite temperatures were compared to the air temperatures provided by meteorological stations of the official weather service nearby. In winter plant temperatures

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... ow the snow are largely uncoupled from the free air temperatures. During the growing season, across all zones, plant temperatures diverge to differing degrees from free air temperatures depending on the growth form of plants and the canopy structure. In Vaccinietum communities and in closed grassland, average temperature differences between the free air and plant canopy were 0.5 K in July and August. Prostrate mats of the Loiseleuria heath, rosette and cushion plants, however, heat up much more than erect plants during sunny periods, and mean plant temperatures were about 2-3 K warmer than the free air temperatures. As a result, the adiabatic lapserate for bioclimatic temperatures of the life zones in the Alps does not parallel the adiabatic lapse rate of free air temperatures. Sitzungsber. Abt. I (2010) 213: 31-51 high mountain climate is defined by a small-scale, terrain-dependent and short-term changeability [1, 42] . Sunny slopes and windy ridges are fairly dry and show rather little snow in winter whereas sheltered depressions are relatively wet in summer and permanently covered with snow during winter. Above the timberline, the duration of snow cover not only depends on the altitude but also on topography. With incomplete snow cover, characteristic patterns of snow patches and snowmelt areas develop for a given terrain. In these patches, which can be covered by winter snow as late as mid June and August, the growing season is very short and thus unfavourable for growth and development of high mountain plants. The bioclimate, which is the microclimate from the upper surface of the vegetation down to the deepest roots in the soil is more balanced, warmer and wetter than the surrounding air [31] . Among the different climatic factors, temperature is of crucial importance to the life processes of plants. The thermal climate that mountain plants experience is very different from free-air temperatures. The boundary layer temperatures in micro-habitats demonstrate that weather services data are unable or not relevant [37] . In the night, plant temperatures are similar to the free-air temperatures or, due to radiation cooling, are even lower. During the daytime hours, plants can considerably heat up above the air temperature on clear days with low wind, whereas in periods with clouds, wind and precipitation plant temperatures approximate to the air temperatures [4, 24] . Plant architecture and thus the canopy structure additionally affects the thermal bioclimate. Generally, prostrate growing plants as prostrate dwarf shrubs, rosettes and cushions decouple their climate stronger from the ambient than erect plant forms in that they accumulate more heat during daytime at high irradiation, but may also lose more heat by thermal re-radiation at clear sky during the night [17] . In the last 50 years of mountain research in the Tyrolean Alps comprehensive microclimatic and ecological studies have been carried out. In this contribution, representative examples of plant temperatures in diverse habitats between timberline (1950 m a.s.l.) and glacier regions (subnival and nival zone up to 3450 m a.s.l.) are presented and compared to the air temperatures recorded by the nearest meteorological stations of the official weather service. Study sites were in a treeline ecotone [2, 41, 46] , in dwarf-shrub communities of the lower alpine zone [4, 23] , in closed alpine grassland (e.g. [6, 40] ), in open alpine vegetation and in the alpine-nival ecotone (e.g. [22, 30, 35] ), and in a nival area with scant patchy vegetation [32, 44] . 32