Forest Biomass

In addition to our measurements of soil and DDW respiration, we are also measuring forest biomass, and the composition of the biomass, around the tower. These results are particularly important when comparing results for the tower in intact forests to the towers in disturbed forests (see section on Disturbance ), and provide a measure of carbon accumulation in the trees when the plots are measured periodically. At each tower site, 48 circular subplots have been located systematically around the tower. In each plot, stem diameter is measured for each tree and the species is recorded. Individual trees are marked so that future plot inventories can quantify both the growth of individual stems and the death rate of individual stems through time.

 

Forest Biomass
Figure 1. Total biomass (live and dead, tree and roots) and biomass in standing-dead trees at the Howland Forest. Values for paper birch and black spruce are less than 0.1 Mg C ha-1.

Our results show that forest biomass is dominated by spruce and hemlock (Fig. 1). Total biomass (live and standing dead) is about 120 Mg C ha-1, of which about 75% is in aboveground biomass. Of the 120 Mg C ha-1, about 11 Mg C ha-1 is contained in standing-dead trees (includes both stems and roots). This represents just under 10% of total stand biomass. Down-and-dead wood contains about 4 Mg C ha-1.