Anna J. Kwiatkowska-Falińska

Changes in spring and summer phenology in Poland - Responses of selected plant species to air temperature variations

ABSTRACT Many studies on the changes in the rhythm of nature (animate and inanimate) revealed that plants are good indicators of climate change, because they are responsive to air temperature variations. There is a clear trend towards earlier onset of plant development in Poland, especially for spring phenological events as flowering and leafing. The main objective of this study was to identify phenological tendencies of selected plant indicator species in Poland and to explore the statistical relationship between mean phenological onset date against mean monthly air temperature. Phenological observations of 9 plant species: Corylus avellana L., Tussilago farfara L., Padus avium L., Taraxacum officinale F.H. Wiggers coll., Betula pendula Roth, Syringa vulgaris L., Aesculus hippocastanum L., Robinia pseudoacacia L., Tilia cordata Mill. from 25 locations acquired in the period 1951–1990 were used. The results proved that phenological changes were the reaction of plants to air temperature variations. For spring and summer phenophases, the mean correlation coefficient was negative — higher air temperature was related to earlier onset dates. The advance of spring and summer phenology was estimated at -2.2 days per 1°C. Majority of phenological events were the most significantly correlated with mean monthly air temperature of the preceding months. Phenological trends observed in Poland were mainly negative (73% of analysed stations), significant (22%) but diversified between the selected species. Linear regression analysis of the onset dates against year (including regression coefficient) showed the highest values for Corylus avellana flowering: -0.24 days per year (20% significant) and Betula pendula leaf unfolding: -0.18 days per year (33% significant). Robinia pseudoacacia showed significant advances (72% of negative trends were significant) in a summer season with an average rate of -0.3 days per year. Whereas in case of Tilia cordata no tendencies to advance has been proved.

Effects of Wild Boar (Sus scrofa L.) Rooting on Seedling Emergence in Białowieża Forest

ABSTRACT The wild boar is an omnivorous animal, and by foraging (rooting) disturbs the top soil layer. In some regions of Poland and Europe seasonal fluctuations in rooting have been observed. Wild boars not only eat plants, but also strongly modify their habitat. In Białowieża National Park wild boar most frequently visit oak-hornbeam forests on fertile soil. On sites where the forest floor is covered with dense vegetation the germination of seeds is difficult, and wild boar rooting can promote the removal of diaspores from deeper layers of the soil seed bank. Within a 3-year observation on 30 subplots about 10,000 seedlings emerged representing 38 species. Our study revealed that rooted patches are characterised by a very rich and diverse flora of seedlings representing mostly forest species, but their density is low. The dominant species germinating in the disturbed ground vegetation is Urtica dioica, a species forming the persistent soil seed bank. There is a possibility that seedlings of herbaceous plants emerging on permanently rooted patches are of exogenous origin, since the seeds germinating there were in many cases damaged by repeatedly rooting animals and had no chance for further growth and reaching the generative phase. However, the soil seed bank in the rooted area has to be analysed to confirm this theory, that they have exogenous or endogenous origin. Seedling density in a repeatedly rooted oak-hornbeam forest is determined by factors other than those related to rooting. In this context the present study did not demonstrate a negative impact of rooting intensity on seedling emergence.