engleski

Relations between habitat factors and dieback of Narrow-leaved ash in Croatian Posavina

Extraordinarily intensive tree dieback is indicator of disorder in forest ecosystem functioning. Tree dieback is consequence of negative effect of different biotic and abiotic factors i.e. decreased vitality and physiological activity of trees. In this study was analysed effect of some factors i.e. like climate, hydrological and structural factors on narrow-leaved ash trees. Considering crown defoliation, narrow-leaved ash is the most endangered forest tree species in Croatia. Narrow-leaved ash tree dieback is constantly increasing, especially during last few years. Research of relationship between some habitat and structual factors and narrow-leaved ash tree dieback was done in the area of Croatian Posavina. From management plans were taken data considering growing stock dieback of narrow-leaved ash trees (m3), as well as areas of forest compartment were dieback and number of sanitary cuttings was found during period from 1998 till 2014 (N=874 sections, N=1100 sanitary cuttings). Tree dieback intensity was shown as volume of tree volume dieback per area unit (m3/ha). In Posavina area average intensity of narrow-leaved ash dieback was 8.13 m3/ha, minimal was 0.02 m3/ha, and maximal 314.5 m3/ha. Average dieback considering micro-relief type was in wet microdepressions, microdepressions and lower at microelevations. According to conducted researches it can be concluded that climate, hydrological and structural factor have effect on narrow-leaved ash tree dieback. Between climate elements, precipitations and potential evapotranspiration significantly affect narrow-leaved ash tree dieback, while this is not case for air temperature. Narrow-leaved ash dieback is affected by decreased annual amount of precipitations, increased potential evapotranspiration, reduced River Sava level, and decrease of underground water level especially in deeper layers of pedosphere. Drought and floods as two extremes also have significant effect on narrow-leaved ash trees dieback: ecological drought when appearing in ecosystem, and flood water with its long absence. Intensity of dieback was higher in stands with larger number of trees and intensive stocking. This partially can be attributed to between- species and within-species competition. Correlations of habitat and structural factors considering tree dieback were low to moderate. Beside economical forest functions, tree dieback results in decrease of non-wood forest functions.

dieback, habitat, narrow-leaved ash, Posavina

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