Dead wood profile of a semi-natural boreal forest - implications for sampling

Abstract

Dead wood profile of a forest is a useful tool for describing forest characteristics and assessing forest disturbance history. Nevertheless, dead wood profiles, including both coarse and fine dead wood, are rare as well as studies on the effect of sampling intensity on the dead wood estimates. In a semi-natural boreal forest, we measured every dead wood item over 2 cm in diameter from 80 study plots. From eight plots, we further recorded dead wood items below 2 cm in diameter. Based on these data we constructed the full dead wood profile, i.e. the overall number of dead wood items and their distribution among different tree species, volumes of different size and decay stage categories. We discovered that while the number of small dead wood items was immense, their number dropped drastically from the diameter below 1 cm to diameters 2-3 cm. Different tree species had notably different abundance-diameter distribution patterns: spruce dead wood comprised mainly of the smallest diameter fractions, whereas aspen dead wood had larger share of large-diameter items. Considering volume, most dead wood was large (>10 cm in diameter), out of which 62% was birch. We also observed that the variation in the dead wood estimates was small for the numerically dominant tree species and smallest diameter categories, but high for the sub-dominant tree species and larger size categories. In conclusion, the more the focus of the dead wood inventory is on rare tree species and large dead wood items, the more comprehensive should the sampling be.