Dead wood stocks of Beech forests in Ograzhden and Osogovska Mountains in Bulgaria.

Dead wood is a key element in forests as it plays a role in maintaining biodiversity, carbon sequestration, element cycling and fire risk. Amounts and ratios of dead wood fractions are now monitored in many countries to assess forest ecological status. In this regard, the aim of the present study is to determine the stocks of dead woody biomass in the Ograzhden and Osogovska mountains (Bulgaria) and to assess their quantity from a nature conservation point of view. The standing biomass was calculated using height rates tables, the lying biomass - using the method of intersecting lines, and the stumps - by height and diameter. Degrees of decomposition are on standard scales. The stock of dead biomass varies from 11.52 m³.ha^-1 in Mountain Ograzhden to 5.45 m³.ha^-1 in Mountain Osogovo. Stump biomass predominates (61-39%), and standing biomass is least in amount (14-22%). Coarse debris are absent in two of the sample areas. In the standing biomass, one of the initial stages of decomposition prevails - stage 1 (54%) and stage 2 (58%). In the lying biomass, that which decomposed to a lesser extent also prevails - A (30-50%), B (53-36%). Among the stumps, those in a more advanced stage of decomposition C (39-50%), D (26-52%) prevail. The sample plot in Ograzhden mountain is in good condition in terms of the amount of dead biomass in it. In the Osogovo mountain, the total amount of dead biomass is insufficient from an ecological point of view. [ABSTRACT FROM AUTHOR]