The weight of a tree stump, which consists of the remaining base of the trunk and the attached root system, is highly variable and depends on a few major physical factors. Estimating this weight is often necessary for practical purposes, such as determining the right heavy machinery for removal, calculating disposal fees, or planning transportation logistics.
Key Variables Affecting Stump Weight
The three inputs that overwhelmingly determine a stump’s weight are its size, the species of the tree, and the amount of water held within its wood. Size is defined by the diameter of the cut surface and the height of the remaining trunk section above ground.
The tree species is a major variable because wood has an inherent density, categorized as either a heavier hardwood or a lighter softwood. For example, a maple stump will naturally weigh far more than a pine stump of the exact same size. Furthermore, the stump’s moisture content dictates the bulk of its final weight, as freshly cut or “green” wood is significantly heavier than wood that has been left to dry or “seasoned” for an extended period.
Calculating the Volume of a Stump
Determining the total volume of the wood material is challenging due to the irregular, flared shape of the stump and the unseen root mass. The visible, above-ground section of the stump can be approximated using a simple geometric formula, such as treating it as a short cylinder. This approximation involves measuring the diameter across the top and the height from the ground to the cut surface.
A more accurate volume calculation must account for the root flare, which is the wider, tapering section where the trunk meets the ground, and the extensive underground root system. Since excavating and measuring the entire root mass is impractical, forestry professionals often use a multiplier to estimate the total volume based on the visible stump volume.
Depending on the tree species and soil conditions, the total woody volume, including major roots, can be estimated by multiplying the calculated above-ground volume by a factor that often falls between 1.25 and 2.0. This accounts for the unseen mass that is integral to the stump structure.
Wood Density and Moisture Content
Converting the calculated volume into a weight requires knowing the wood’s density, which is directly related to its specific gravity. Specific gravity is a unitless measure that compares the density of wood to the density of water. For weight calculations, this specific gravity is multiplied by the density of water (approximately 62.4 pounds per cubic foot) to find the wood’s density in pounds per cubic foot.
The weight of a stump changes dramatically based on its moisture content. “Green weight” refers to a freshly cut stump, which can have a moisture content ranging from 30% to over 100% of its dry weight. Conversely, a stump that has been dead or cut for several years will approach “air-dry weight,” typically corresponding to a moisture content of around 12% to 20%, resulting in a much lighter mass.
A 24-inch diameter, 1-foot tall stump from a dense hardwood like Red Oak, which has a high specific gravity and high initial moisture, might weigh over 600 pounds when green, while a similarly sized stump from a less dense softwood like White Pine, with a lower specific gravity, might weigh only 300 to 400 pounds.