Measuring Litterfall and Branchfall

Abstract

Trees capture CO2 from the air, return a large fraction to the atmosphere via autotrophic respiration, produce five tissues from assimilated carbon, and return expired tissues to the soil via the process of senescence. Methods described in this chapter deal with the measurements of the flow of above-ground solid carbon-based material to the forest floor as litterfall and branchfall. The measurement methods are rather simple and non-technological yet functional. They require an understanding of the scale and dynamics of the processes under study as well as the use to which these data will be put.. Back calculation of net primary productivity for example requires not only the mass of foliage captured by litter traps, but also the loss in mass of the leaf between the time it was produced to the time it was captured in the trap. Similarly, the proper capture of ground-area-based large woody debris requires an appropriate spatial sampling design that is tailored to the expected size of the debris to be captured. Stands with a finer branch structure such as fir and spruce will provide a well-distributed rain of twigs and small branches whereas stands of temperate hardwoods will provide small twigs as well as irregular inputs of litterfall in the form of large branches or even tree boles. Alternative methods based on estimation of branch production and retention may also be used to estimate the flux of larger dead material.