akar.earthWood density: Definition
What is wood density? Definition of basic wood density, why it matters in allometric biomass models, and typical ranges for Indonesian tree species.
Wood density is the oven-dry mass of wood divided by its green (fresh) volume, usually expressed in g/cm³. In carbon accounting it is often called basic wood density or wood specific gravity, and it tells you how much biomass is packed into each unit of stem volume.
Why it matters
Two trees of the same diameter and height can hold very different amounts of carbon if one has light wood and the other dense wood. Pantropical allometric equations such as Chave et al. (2014) therefore use wood density as a direct input. Volume-based methods also multiply stem volume by wood density to get biomass. A wrong density value biases every tree in the inventory.
How it is measured and sourced
Wood density is measured by taking a core or disc, measuring its green volume (often by water displacement), then oven-drying and weighing it. Most projects do not measure it themselves. They take species values from the Global Wood Density Database or national compilations, and fall back to genus or family means when species data is missing. See our allometric equations guide for how this feeds the calculation.
Indonesia angle
Indonesian species cover nearly the full tropical range. Fast-growing pioneers such as sengon have light wood, often around 0.3 g/cm³, while ironwood (ulin) is among the densest timbers, close to or above 1.0 g/cm³. Values vary with site, age and growth rate, so plantation-grown trees can be lighter than literature values from natural forest. Mixed agroforestry plots with fruit trees, coffee and shade trees need species-by-species values rather than one average.
Common mistakes
- Using air-dry density (at about 12% moisture) from timber trade tables instead of basic density. Air-dry values are higher and overstate biomass.
- Applying a single default density to a mixed-species plot.
- Using natural-forest values for young, fast-grown plantation trees without checking.
Related terms
Wood density connects to allometric equation, above-ground biomass and carbon fraction. Test the effect with our tree CO2 calculator, or see the ARR hub for the wider context.
Frequently asked questions
What units is wood density given in?
Basic wood density is usually given in grams per cubic centimetre (g/cm³) or tonnes per cubic metre, which are numerically the same.
Where can I find wood density values?
The Global Wood Density Database is the most common source. Species values vary, so use a regional value or a genus mean if a species value is missing.