Radovi, Vol. 47 No. 1, 2019.
Izvorni znanstveni članak
Dieback of Aleppo Pine and Outbreak of Bark Beetle Orthotomicus erosus in Forest Park Marjan
Milan Pernek
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Nikola Zorić
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Marta Matek
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Ivan Lukić
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Sanja Novak Agbaba
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Boris Liović
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Ivana Mihaljević
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Nikola Lacković
; Hrvatski šumarski institut, Jastrebarsko, Hrvatska
Sažetak
The intensive dieback of pine trees on Marjan was observed in 2017, and it probably began in 2016 with dieback of individual Aleppo pine trees. Given the very serious extent and spread of drying of trees in the Forest Park Marjan, the aim of this study is to determine the possible causes of Aleppo pine dieback with the focus on identification of the cause, the age and the thickness of the dead trees, as well as the effect of the climate on this event. In 2017, several infested pine trees were cut down from which samples of symptomatic needles and branches were collected. Samples were marked and transported to the Croatian Forest Research Institute laboratory, where they were incubated and stored for further analysis. The infested material from all parts of the tree has been collected and infestation was recorded. The infested material was incubated in cages at controlled temperature conditions (20 ° C ± 2 ° C) and day and night regime (L : D = 18 : 6). Thus, the emerging insects were collected from the cages, where upon stored in alcohol or immediately determined. Bark beetles Orthotomicus erosus and Pityogenes calcaratus emerged from all parts of the trees in the climate chamber. Both species are harmful pests, but more attention here is given to the Mediterranean bark beetle, which is in the gradation phase and probably started to attack
healthy trees. In the whole forest area of Marjan sample stripes have been laid out, diagonally throughout each compartment/subcompartment in 2017, 2018 and 2019. To each encountered tree the diameter and height was measured, and a certain category of health condition was determined by visual inspection and using of the binoculars for each pine tree, dividing them into one of the 5 categories of drying stage. The largest number of infected and dried trees are about 25 cm in diameter. In 2017, about 7,500 pine trees were showing symptoms of dieback on Marjan, representing 13% of all trees, and drying continued in the following years, reaching cumulative 17% in 2018 and 23% in 2019. Seasonal deviations of temperature and precipitation in percentile indicate the perennial shift of normal to hotter and drier. Higher temperatures and extreme droughts create cumulative stress on the trees. On the other hand, insects are poikilotherm animals, they react quickly to temperature changes which in species with high biological potential such as some types of bark beetles can lead to rapid population and spatial expansion, i.e. gradation. The observed phenomenon suggests that the cause of the pine trees dieback on Marjan lies in
chaining of the several unfavorable factors (drought, the prolongation of vegetation due to climate changes), resulting in the gradation of the bark beetle O. erosus. Climate changes enabled a higher number of generations and an increase in population that led to the attack of healthy trees and their drying in groups in 2017, i.e. the gradation of bark beetles. New findings emerged from this research show that the Mediterranean bark beetle first appears in the tree crown and then in the trunk and lower parts of the tree. It is suggested that the lower uninfected parts of the tree are used as trap trees. Gradation of bark beetle O. erosus that was observed in this study has never been recorded so far and it is possible that this pest, in case that aridifi cation changes continue, will become a permanent problem in Mediterranean forests.
Ključne riječi
Pinus halepensis; climate change; aridifi cation; Mediterranean bark beetle
Hrčak ID:
305401
URI
Datum izdavanja:
1.7.2019.
Posjeta: 221 *