Effects of microclimatic variation of snowmelt and temperature on subarcticalpine and Arctic plants
Year: 2019
Type: dissertation
Abstract: Climate change will be most pronounced at high latitudes where it will affect autumn, winter and spring disproportionally more than the growing season. Increasing or decreasing precipitation as snow, rising temperature and more frequent freeze-thaw cycles raise uncertainties about how the timing of snowmelt and the length of the growing season will change for northern plants. The timing of plant developmental stages (phenophases) in relation to snowmelt timing is important for avoiding harsh weather conditions in spring and ensuring a long growing season. In this doctoral dissertation, I investigate the effect of snowmelt timing and temperature conditions on plant phenology and plant stress. The first objective was to determine the natural variation in snowmelt timing on a small spatial scale in subarctic-alpine Finland. Such variation in the microclimate is created by the landscape topography and show the range of conditions plant populations are currently adapted to. Snowmelt timing varied by up to seven weeks within a few metres distance, so that early-melting plots were exposed to more frequent and more severe spring freezing events. This implies that plant populations are already exposed to the kind of climatic conditions which would be predicted from climate change. Secondly, I studied how the physiology of Vaccinium vitis-idaea and the phenology of seven subarctic-alpine plant species are affected by this natural variation in microclimate. The higher numbers of freezing events in early-melting plots were related to a higher reduction in the quantum yield of photosystem II (ΦPSII) in V. vitis-idaea, but not to increases in frost damage. This species therefore does not suffer substantial damage from the natural climatic variation in this habitat, implying that in this location it is likely highly resistant to the predicted changes in climate. Differences in snowmelt timing also led to three distinct patterns of phenological timing in subarctic-alpine plant species along the snowmelt gradient. These patterns can raise ideas about the mechanisms underlying the rate of plant development and can help researchers classify past and future phenological responses. Lastly, I compare the effect of natural versus experimental gradients of snowmelt timing on the timing of autumn senescence in High Arctic plants. The results show that the two gradients lead to different conclusions regarding the effect of snowmelt timing on the timing of autumn senescence. Selective warming only in the beginning of autumn had a delaying effect on autumn senescence in Dryas octopetala, despite the short duration of the warming treatment. Previous studies have commonly employed a warming treatment over the entire growing season. The results of this dissertation highlight that we need to integrate different approaches to studying climate change effects on plants. Natural gradients, although often disregarded, can give additional insight into plants’ adaptation to climate variation and therefore complement experiments. Experimental treatments simulating climate change need to be very selective in which period of the plant life cycle they are applied as expected changes in climate strongly depend on the season. Due to the variable sensitivity of different phenophases and plant species to climate and the importance of plants in the ecosystem carbon balance, further detailed research is needed to understand the drivers and mechanisms underlying plant phenology.
Source: Työväentutkimus Vuosikirja
Author: Friederike Gehrmann
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W2948819754