Biomass Production and Chemistry 

General Description

Biomass measurements near Toolik Lake, Alaska were first made in 1982. Since then additional measurements have been made, including harvesting several times through the growing season. The harvests have included several different tundra types (heath, wet sedge, acidic and non acidic mesic tussock, shrub), both treated and untreated plots, woody stem biomass, and across several different sites. Per cent carbon nitrogen and phosphorus were also measured for several of the harvests.

Table 1 lists the biomass harvests. It contains the following information for each harvest: date, site and  treatment.

Below is a description of the general method. Exceptions and modifications for a particular harvest are noted in the documentation for that harvest.

Method

Field: Samples are obtained by collecting all aboveground biomass and belowground stems and rhizomes in 20 x 20 cm quadrats, located randomly along line transects within the site. Normally, 4 or 5 quadrats are collected along each of 4 transects at each site or treatment. Aboveground biomass is considered "within" the quadrat if it is associated with a meristem that is within the quadrat. Details are given in Shaver and Chapin (Ecological Monographs, 61(1), 1991, pg. 1.)

Lab: Each quadrat is first sorted into species and then into tissue type. Depending on the harvest, tissue types can be broad categories, i.e. above and below, or more detailed, i.e. inflorescences, new growth, old growth, etc. The separated samples are dried for several days at approximately 65 ºC and then weighed. The dry weight for each quadrat, species and tissue type is recorded. Finally the samples from all quadrats in a transect are combined according to tissue type. Samples are then returned to Woods Hole for nutrient analysis.

Table 1: Biomass Harvests 1982-Present