Large Wooden Debris’ Contribution into a Biogenic Carbon Cycle in Coniferous-Deciduous Forests of the Southern Regions of Russian Far East
Fallen trees stock and the carbon flux from its decomposition were assessed in two forests of Primorsky krai – on a forest plot of Primorsky State agricultural academy and in a national park “Bikin”. The fallen trees stock on testing plots varied from 10 to 120 m<sup>3</sup> ha<sup>–1</sup>, the carbon flux from the fallen trees decomposition varied from 0.06 to 0.59 t C ha<sup>–1</sup> year<sup>–1</sup>. Maximum fallen trees stock was detected in natural forest stands on special protected areas. Woodcutting heavily affect the fallen trees distribution by the decomposition stages, and local population’s activity results in a decrease of fallen trees stock. An seasonal contribution into the overall year carbon emission from the fallen trees surface was 3%, 20%, 55% and 22% for winter, spring, summer and autumn respectively. In overall heterotrophic breathing of a coniferous-deciduous forest ecosystem the carbon flux from the fallen trees makes up 2–7% but the absolute value of it is comparable with carbon stock in phytomass. Instrumental determination of the basic wood density on different decomposition stages has proven the correctness of the visual determination method.