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ŠUMARSKI LIST 7-8/2018 str. 22     <-- 22 -->        PDF

birds as well as many lichen, mosses and fungi species (Dudley,Vallauri 2004).
In historical aspect, for many years the dead wood was removed from the stands as a measure for protection against insects and fungi, which are perceived as a threat for the healthy forest status. This leads to reduction of the quantity of the dead wood in the forest ecosystems to critical low levels, which are not enough for maintaining the vital populations of many forest species (Lazarov et al., 2012). The protection of these species and forest habitats became a priority and require a new perception of the dead wood meaning with the establishment of European ecological network Natura 2000.
Each group of organisms require different types and amount of dead wood. Characteristics of deadwood as size, tree species, type (standing or lying), duration and stage of decay are important to maintain their life cycle. It is assumed that the dead wood with larger sizes deliver more microhabitats and therefore habitats for more species. But studies show that smaller deadwood debris are important habitat for some species of fungi.
Deadwood as part of living trees (dead branches, rotten core, etc.), also has its residents. The availability of adequate supplies and diverse in their quality characteristics dead wood provides optimal conditions for the existence of organisms related to the functioning of ecosystems, but there are rare and endangered species of conservation importance, which are entirely dependent on its presence in the forests. The understanding of the importance of deadwood habitat for such organisms is constantly growing. However, the ecology of communities of dead wood is not yet well understood, making it difficult to formulate practical recommendations for their conservation.
About a third of plants and animals in the forest are directly related to the presence of dead wood and they are also the most endangered species group in Europe (Borisov 2006). By the studies in Germany, it was found that over half of inhabiting forests beetles are saproxylic (Köhler 2000 - in Schlaghamersky 2007). Despite its great importance, the dead wood is currently critically at low level in most European countries. This applies especially to the forests, in which logging is carried out. Often the dead wood was 20 times less than that of the natural (without or with minimal human intervention) forests (Dudley,Vallauri 2004).
The dead wood is included as one of the important parameters for defining the Favourable Conservation Status of forest ecosystems in the NATURA 2000 sites. It is defined by the „Guide for assessing favorable conservation status of species and habitat types in Natura 2000 in Bulgaria“ (Zingstra et al. 2009) regulations and it is an important step for the management planning of their maintaining or improving.
The need to assess the status of biodiversity, carbon stocks, and the risk of forest fires and calamities of diseases and pests have accelerated the need for an inventory of dead wood in forests. Depending on the goals, the assessment is made of different spatial levels, ranging from territory of states to individual habitats. In many countries the quantity and characteristics of dead wood is a part of the national forest inventories.
In the ongoing inventory, the largest volume of deadwood was reported in the forests of Switzerland (11 m3.ha-1), Czech Republic (6.5 m3.ha-1), Austria and Slovenia (6 m3.ha-1). Significantly lower volumes were recorded in Bulgaria and Slovakia (0.3 m3.ha-1), UK (0.4 m3.ha-1), Greece (0.7 m3.ha-1) and Spain (0.9 m3.ha 1) (UNECE/FAO 2000).
The evaluation of dead wood in smaller spatial scales is essentialy with conservation and scientific interest.
Many authors focus their attention on dead biomass. It is accepted as essential stock of biomass and carbon pool (Arthur, Fahey 1992; Bradford et al. 2009; Domke et al. 2011) that need to be considered in inventories and evaluated under the Framework Convention for UN climate change. Kueppers et al. (2004) studied the dead wood biomass and the rate of decay in altitude gradient. According to Oswalt, Brandeis (2008), the dead wood is an important part of the total biomass and should be also considered when assessing carbon stocks. In Bulgaria investigations on quantity and distribution of dead wood in representative forest plant communities are insufficient. Currently, the measurements were made within the project „Biodiversity Conservation rid of Maglenik, Eastern Rhodopes“ and „State and perspectives of the population of plain chestnut in Belasitza“ (Velichkov et al. 2011).
Zlatanov et al. (2013) suggest as an index for a complex assessment of old age forests, the „accumulation of dead wood“ to be used as an indicator. It consists in the presence of standing and fallen dead trees in varying degrees of decomposition of wood in an amount at least 80 m3.ha-1 for spruce and fir, 60 m3.ha-1 for common beech and European oak and 40 m3.ha-1 for the remaining oaks and pines. Lower quantities around 50 m3.ha-1 are typical for many old oak and beech forests in Bulgaria.
The information about the amount of dead wood in coniferous stands are found in publications of Panayotov et al. (2011), Rangelova, Panayotov (2013).
In 2013 within the project „Mapping and determination of the conservation status of habitats and species“, the amount of dead wood in some natural habitats in areas included in the Natura 2000 network was assessed.
During the past years, the new settings in the national legislation, especially these related to the Natura 2000 development and management, require the quantity information about this component for the forest habitats assessment of favorable nature conservational status. The inventory and dead wood monitoring are encouraged as instruments for sustainable forest management as the forest certification.