Estimating Fuel Quantity and Moisture

Estimating Fine Fuel Quantities and Moisture

There are several ways to estimate the standing crop of fine fuel. Experience, photo guides and clipping are the most common way to estimate the more reliable and the only way to estimate the percent moisture.

Method for Clipping:
Build a ¼ meter square plot frame out of round stock, rebar, or PVC tubing. A ¼ meter square plot frame dimension is 50 cm(1/2 meter) on each side as measured on the inside of the frame.

Place the plot frame at several locations in the pasture. The objective is to determine the standing crop and moisture of the fine fuel, so place the frame in representative areas (some with high fuel loads and some with light fuel loads). Use clippers or a knife and remove all vegetation at just above the crown of the plant. Place the clipped sample into a numbered paper bag and label it so that you will know what it represents. Weight (grams) the bag and sample as soon as possible and write the weight on the bag.

The sample can then be dried in a microwave oven at 30 second intervals until the weight does not change from one drying cycle to the next. Record the weight of the bag and sample after drying. Calculate % moisture by:

Estimating Live Juniper

To have an idea of the effectiveness of the prescribed burn on Juniper, it is a good idea to estimate the % moisture. Strip Juniper leaves (about 100 grams) at about shoulder height, taking only the green leaves, with no brown stems.

Place these in bags as in the previous example and dry them in the microwave oven, Calculate % moisture in the same way.

(Wet weight – Dry weight / Dry Weight) X 100 = % moisture.

Weigh 10 empty paper bags together and divide the total weight by 10 to get an average bag weight. Calculate standing crop (lbs/acre) by subtracting the bag weight from each sample weight and then multiplying the weight in grams * 40 to get the standing crop in kg/ha. Lbs./acrea+kg/ha * .89