Robert Bogdanić

Climate change and increasing climate extremes can jeopardise the stability of urban forest ecosystems, damage trees and cause their decline and death. The aim of this study was to analyse the intensity and causes of sanitary felling and their correlations with climate variables and age of sessile oak (Quercus petraea), common beech (Fagus sylvatica), European hornbeam (Carpinus betulus) and black locust (Robinia pseudoacacia) in urban forests in the City of Zagreb in the period 1994–2020. The intensity of sanitary felling was analysed based on the listed causes and correlated with temperature, precipitation, wind speed, drought indices and tree age. The results revealed species-specific differences in sanitary felling intensity and its associations with selected climatic variables and stand age. Statistically significant correlations were identified between sanitary felling intensity and precipitation anomalies in sessile oak and black locust and between sanitary felling intensity and mean annual air temperature in common beech. However, these associations should not be interpreted as evidence of direct climatic effects on tree mortality, as sanitary felling is also influenced by management decisions and local environmental conditions. The findings highlight the value of long-term sanitary felling records for identifying patterns of tree removal and their associations with climatic variability in urban forests.

Crown defoliation in trees is one of the indicators of forest tree vitality, and a primary criterion for selecting trees for sanitary felling. In Croatia, the selection of trees for sanitary felling includes all dead trees and those with crown defoliation greater than 60% (defoliation class 3a); in the past, the threshold for marking trees for sanitary felling was above 80% (class 3b). The aim of this study was to analyze tree mortality in pedunculate oak (Quercus robur), silver fir (Abies alba), and European beech (Fagus sylvatica), as well as crown regeneration, i.e., the reduction in defoliation. The analysis included a total of 7975 trees, comprising 1182 silver fir, 4221 European beech, and 2572 pedunculate oak trees, covering the period from 1998 to 2023. The mortality rate was 7.2% for silver fir, 2.16% for beech, and 9.6% for oak. The percentage of trees that regenerated their crowns or reduced defoliation to below 60% was 17.01% for fir, 4.33% for beech, and 12.51% for oak. Considering the proportion of silver fir and pedunculate oak trees whose defoliation decreased to below 60%, a defoliation threshold greater than 80% would be a more appropriate criterion for sanitary felling, except for European beech trees, for which there is a minimal difference between the recovery rates in classes 3a and 3b.

Analiza kretanja rasadničke proizvodnje šumskog sadnog materijala doprinosi kvalitetnijem planiranju proizvodnog programa kao i radova u uzgajanju šuma. Dostupnost sadnog materijala ključna je za mnoge dionike šumarskog sektora kako u šumarskoj znano...

The increased frequency of climate change-induced droughts poses a survival challenge for forest trees, particularly for the common beech (Fagus sylvatica L.). Drought conditions adversely affect water supply and nutrient uptake, yet there is limited understanding of the intricate interplay between nutrient availability and drought stress on the physiology, growth, and biomass accumulation in young trees. We aimed to address this knowledge gap by examining the effects of irrigation and fertilisation and their interaction with various parameters in common beech saplings, including foliar and root N, P, and K concentrations; height and diameter increments; and aboveground and belowground biomass production. Our findings revealed that a higher fertilisation dose increased nutrient availability, also partially mitigating immediate drought impacts on foliar N concentrations. Also, higher fertilisation supported the post-drought recovery of foliar phosphorus levels in saplings. Prolonged drought affected nitrogen and potassium foliar concentrations, illustrating the lasting physiological impact of drought on beech trees. While drought-stressed beech saplings exhibited reduced height increment and biomass production, increased nutrient availability positively impacted root collar diameters. These insights have potential implications for forest management practices, afforestation strategies, and our broader understanding of the ecological consequences of climate change on forests.