Temperatures in the Life Zones of the Tyrolean Alps

Abstract

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 below 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 ...

Temperature Microclimates of Plants in a Tropical Alpine Environment: How Much does Growth Form Matter?

“…Height aboveground and aspect are of primary importance and during the day they override the effect of the 300 m elevational difference between the lower and higher sites, in agreement with Diemer (1996). The typical daytime vertical temperature profile, with a narrow boundary layer of warm air above heated topsoil and overlaid with cooler air (Geiger, 1965;Meinzer et al, 1994a;Jordan and Smith, 1995;Larcher and Wagner, 2011), was observed only on the leeward, western side. On the windward, eastern side, low radiation input along with very high air humidity due to permanent cloudiness (Sklenář et al, 2015) produced very gentle vertical temperature profiles that lacked the layer of substantially warmer air near the ground.…”

“…The two sites were about 200 elevational meters below the distributional limit of Azorella on the Antisana volcano, which suggests that the uppermost cushion plants might grow at even lower mean temperatures. In contrast, Saxifraga bryoides, a cushion plant from a glacier foreland (2880 m) in the Austrian Alps experienced a mean temperature of 8.5 °C during 105 days of the temperate alpine growing season (Larcher and Wagner, 2011;Larcher, 2012). This difference suggests that the growing season mean temperature correlated with the occurrence of alpine treelines worldwide (Körner, 2003;Körn-er and Paulsen, 2004;Scherrer and Körner, 2011) may not be easily applicable to explain upper distributional limits of alpine plant growth forms, at least in the tropics.…”

“…These leaves are heated many degrees above the air temperature, that is, they decouple from the ambient air, which provides the plant with "extra heat" (Salisbury and Spomer, 1964;Körner, 2003;Larcher and Wagner, 2011;Larcher, 2012). In the tropical alpine environment, for instance, the heat accumulated by inflorescences and leaves of some species during the day can help to outbalance rapid cooling after sunset (Miller, 1986(Miller, , 1994Beck, 1994).…”

Trends in Population Size of Rare Plant Species in the Alpine Habitats of the Ukrainian Carpathians under Climate Change

“…Some of them belong to specialized life forms, for instance, cushions that accumulate heat [15,29], e.g., Saxifraga bryoides and S. oppositifolia. Physiological and morphological adaptations of the cold-specialized species, particularly in the leaves, enable efficient gas exchange in cold environment [15,30], but are disadvantageous in the warmer climate and cause overheating and withering of plants that cannot tolerate the increase of temperature above certain levels.…”

Application of heat stress in situ demonstrates a protective role of irradiation on photosynthetic performance in alpine plants

“…Many alpine plant species have evolved prostrate growth forms that promote the decoupling of plant body temperature from ambient air (Körner & Larcher 1988) in response to the decrease in mean air temperature with increasing elevation. This decoupling allows canopy temperature (Larcher & Wagner 2010) and leaf temperature to become significantly greater than ambient air temperatures (Salisbury & Spomer 1964;Körner & Cochrane 1983). For example, in the cushion plant Silene acaulis, a maximum dif-ference of 22 (Neuner et al 2000) and 24.5 K (Gauslaa 1984) between leaf and ambient air temperatures was measured on calm summer days that were characterized by little wind and high solar irradiation.…”