Temperature data are fundamental measurements to study the phenology of biocoenosis; the temperature, in fact, is the primary factor that controls bio-geochemical cycles and therefore the speed with which fauna and flora develop. This can be observed in particular in Alpine ecosystems, due to the snowfall and cold, which reduce the period of vegetation. The species present in these contexts are particularly sensitive to the temperature, so that they have sufficient time to complete their cycle of reproduction, which is essential for the survival of the populations. The network of temperature stations in the PhenoAlp project will enable scientists to study the phenology of Alpine flora and fauna, as a function of climatic variations.
Temperature data enable us to understand the variations in the climate throughout the year, but also to compare different years with each other. In the three years of readings, we have been able to note particularly high temperatures in the spring and autumn of 2011, as compared to 2009 and 2010 (see figure 1). Thus, it will be possible to visualize the evolution of temperatures through the various decades, follow the impact of these variations on the development of Alpine biocoenosis and to understand the relationship between the phenology and climatic change.
Figure 1: daily mean temperature (2 m) , recorded in Loriaz (1,921 m asl) from 2009 to 2011.
The network of PhenoAlp stations enables recording of the air temperature at different altitudes, but also the temperature in the first horizons of the soil. The latter measurement also enables us to indirectly calculate the duration of the snow season in the observation sites. In effect, when present,snow protects the ground from freezing and creates a buffer effect, whereby the temperature remains stable at around 0° C (see figure 2). The ground remained covered in snow for 131 days during the winter of 2009-2010 and for 95 days during the winter of 2010-2011.
Figure 2: daily soil temperature recorded in Loriaz (1,921 m asl) from 2009 to 2011
The decrease of temperature with altitude is an important process to be taken into consideration during phenological studies in mountainous areas. With six degrees less on the average, every 1,000 malpine ecosystems have little time, with respect to plains areas, to carry out their annual phenological cycle, due to the lower temperature throughout the year, but also due to more consistent and long lasting snow. These two phenomena are visible on the gradient situated in the Mt. Avic Regional Natural Park (see figure 3). The four stations record the temperature on an altitude gradient of 850 m asl. The difference in temperature between the highest and lowest station, in 2011, was 3° C on the average, in the springtime (2.4° C on the average during the period without snow). Additionally, the snow melted 10 days earlier at the lowest station.
Figure 3: Average daily temperatures at 2 m above the ground, recorded by the 4 stations in the Mt. Avic regional natural park (1,921 m asl) in 2011.