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|ŠUMARSKI LIST 1-2/2017 str. 9 <-- 9 --> PDF
THE IMPACT OF ENVIRONMENTAL DRIVERS ON NARROW-LEAVED ASH (Fraxinus angustifolia Vahl) BUDBURST DATES
UTJECAJ KLIMATOLOŠKIH PARAMETARA NA POČETAK OTVARANJA PUPOVA POLJSKOG JASENA (Fraxinus angustifolia Vahl)
Ivan ANDRIĆ, Davorin KAJBA
Narrow-leaved ash (Fraxinus angustifolia Vahl) is a fast growing and light demanding forest tree species. In Croatia, the largest complexes of this species can be found along the Sava River. The main objective of research was to determine the influence of environmental drivers on budburst dates. Research was carried out in the clonal seed orchard of Nova Gradiška through four vegetation seasons (2012, 2014, 2015 and 2016). In total, 42 clones were involved in this study. The target phase of phenology monitoring was the phase with distinct budburst and partial segregation of bud scales. Three environmental drivers were selected (temperature, precipitation and insolation) with three different summing dates (1st November, 1st December and 1st January). Statistical data processing included the following analyses: Spearman Rank Correlation, Linear Regression, Multiple Regression and Stepwise Multiple Regression. Among three tested environmental drivers in all of the analyses performed in the study, insolation proved to be the most important factor in the description of budburst dates in narrow-leaved ash.
KEY WORDS: climate change, temperature, insolation, precipitation, phenology
Narrow-leaved ash (Fraxinus angustifolia Vahl, Oleaceae) is a fast growing and light demanding forest tree species, which covers central-southern Europe and northwest Africa up to the Caucasus (San-Miguel-Ayanz et al. 2016). It is a hygrophilic and predominantly thermophilic tree species that favours deep, clayed and moist soils exposed to occasional seasonal flooding. The largest complexes of narrow-leaved ash in Croatia are located along the Sava River (Fukarek 1983; Anić 1999, 2001). One of the major problems in natural narrow-leaved ash stands is the absence of regular seed yield. The background of this problem is still unexplained, but it could be the result of the synergy of several biotic and abiotic factors, as well as of silvicultural treatments. The greatest threat to the stability of forest ecosystems of narrow-leaved ash is currently posed by the phytopathogen Hymenoscyphus fraxineus T. Kowalski (Kowalski 2006). Just like in common ash (Fraxinus excelsior L.), it first causes necroses, then defoliation, and finally tree dieback (Kowalski 2006).
The two critical priorities regarding future climate is the management of water resources and the understanding of impacts of climate change on the vegetation cover (Zeppel et al. 2014), where phenology represents the best instrument for the detection and appraisal of climate changes