Tree biomass and tree indication

Aims follow the dynamics of the tree biomass in the whole catchment follow the dynamics of the tree populations including standing dead trees, logs and stumps Change in the tree biomass is closely related to the biogeochemical circulation in the catchment. Increase in the biomass is balanced by acidification in the root zone via release of protons and vice versa. It is impossible within IM to analyse the content of elements in all tree parts. Therefore the total amount of elements, including heavy metals, in the catchment is estimated on the basis of actual tree measurements and chemistry data in the literature. The trees and their remnants constitute important substrates and biotopes for a great number of organisms, both mammals, birds and soil mikroorganisms. Trees may also be regarded as long-term indicators of changes in the climate and acidification as examples. The trees are inventoried every five years on a number of circular plots distributed systematically over the site, the diameter of which are 10 m. Some environmental characteristics of the plot observed are slope, direction of slope, depth of soil, groundwater availability, soil type, thickness of soil horizons, texture.   Variables position of the individiual tree, log and stump (direction and distance from the plot centre), stem diameter at breast height (dbh) of all trees, tree height, crown diameter and lower crown limit of sample trees, tree dominance class, tree vitality, degree of decomposition of logs and stumps, biomass, amount of elements in biomass

	Circular plots for the subprogrammes Tree biomass and tree indication and Vegetation structure and species cover respectively are systematically distributed over the catchment. The vegetation plot lies tangentially to the south outside of the tree plot . Thus disturbance by trampling on the vegetation is avoided.
	The position and diametre of all trees, stumps and windthrows >5 cm diameter at breast-height (dbh) are measured within 10 m radius from the plot centre. On a selection of sample trees also height and crown size are measured (Ammarnäs)