engleski

The state of health and intensive monitoring of forests in Croatia

The state of forests in Croatia have been monitored since 1987 according to the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) at 87 bioindicative level 1 plots, located according to a 16 x 16 km network. It has been established that their state of health has, since monitoring began, continually declined. That is, the falling of needles and leaves and changes in their colour has increased since 1995, after which period there has been major improvement. In 1987, there was considerable damage of 7, 9 % in Croatian forests, 27.7 % in 1995 and 19.6 % in 1998. Intensive monitoring of the state of forests is also undertaken according to ICP-Forest methods on 7 permanent level II plots, which are located in various regions in Croatia in various phytocenoses. On the plots, the state of the crowns is assessed and the electric resistance of the tree`s translocation system measured. Trees that do not have any visual signs of crown damage, i.e. healthy trees that fall into the class 0 of damage, have lower electric resistance than trees that fall into classes 1, 2, 3 of damage. For example, the Fir species (Abies Alba Mill.), healthy trees (defoliation 0 class, needle loss up to 10 %, degree of defoliation “none”) have an average electric resistance of 9.2 KW, class 1 trees (10-25 %, slight defoliation) have 9.8 KW, class 2 trees (25-60 % moderate def.) have 12.4 KW, while class 3 trees (>60 %, severe def.) have 17.3 KW. Measurements were undertaken in August 1997 and 1998. For class 4 trees (dead) electric resistance was not measured, as the translocation system was inactive. To determine the state of crowns in level II plots, besides the ICP Forests methods, a unique method of the Forestry Institute is utilised. This method is the interpretation of aerial photographs of top crown details. Aerial photographs are taken with a special portable device, by which a capsule with a mounted camera is launched vertically from the ground, and within the scope of the upper point of movement, automatically photographs a particular motif and returns to the ground in a free fall. On aerial photographs, the degree of defoliation and discolloration in the upper isolated section of the tree crown is assessed, rather than being measured. Through the use of this method, objectivity of research as well as visibility of the most physiologically active crown parts that are not visible from the ground is attained. Aerial photos show fir trees on Medvednica mountain on permanent sample plot No 103 (in proximity to the city of Zagreb) with different scales of damage and an oak tree on plot No 102 (in proximity to the city of Jastrebarsko).

The state of Health of forests; defoliation class; intensive monitoring.

nije evidentirano