Selcted Meteorological Stress Indices for 2013-2015

S. 65-75

Artikel aus einer Zeitschrift

200203807

Climatic conditions significantly affect forest ecosystems and the inherent biogeochemical processes and relationships in the system of soil, plant and atmosphere. Major meteorological variables are air temperature, precipitation and wind speed next to radiation and air humidity. In forest ecosystems, temperature affects most biogeochemical processes, as photosynthesis and respiration, microbial activity and evapotranspiration. Precipitation influences water supply for plants and microbes, state of soil aeration, nutrient leaching as well as wet deposition.
Regarding the considered plots in this study, most stress indicators showed an inter-annual variability between the years 2013 to 2015. 2013 featured the plots with the highest number in IceDays in the study period implying colder conditions in that year. Since 2013 also featured slightly higher values in MaxRain5, larger range and values between the lower and upper quartile of plots in HeavyRainDays, and higher numbers in NoRainPeriod, the stress indicators suggest that 2013 was in average characterised by a mixture of strong precipitation in winter and dry periods in summer. The year 2014 showed low (TropicalDays, IceDays, MaxRain5, NoRainPeriod) or average (HeavyRainDays) values in the stress indicator variables indicating less extreme weather conditions in that year. 2015 was characterised by the highest values as well as the largest range between the lower and upper quartile of plots in the temperature stress indicator TropicalDays and by lower values in HeavyRainDays. However, despite the much higher numbers in TropicalDays, NoRainPeriod in 2015 lay in the average range implying a lower potential of drought. To draw general conclusions on the annual weather conditions, the seasonal distribution and average values of air temperature, precipitation, humidity, radiation and wind speeds have to be studied and cannot be estimated based on the used stress indicator variables. However, it could be shown that these stress indicators can significantly vary between years and that forest ecosystems needed to adapt on this variability.