The forest cycle: grow
Growing a forest follows the age of the trees.
- Plant (year 0): seedlings in rows.
- Tend (years 1 to 10): weed, replace dead seedlings, protect from animals.
- Thin (years 10 to 30): cut weak trees, sell the small poles, give room to the best.
- Prune to get clean logs.
- Harvest (about year 40 to 50 for many conifers; many tropical trees grow faster, some teak slower).
Keep a record book: planting date, species, thinning dates, growth. It guides the next job.
Using forest products
Wood has many uses, and the best use depends on log size and quality.
- Big straight logs: house beams, planks, furniture, plywood.
- Small logs and thinnings: poles, boards, fence posts, pulp for paper.
- Branches and waste: wood chips and pellets for fuel, and mulch.
- Other products: honey, mushrooms, fruit, resin, bamboo and medicinal plants.
Use wood in a cascade: first make long-lasting products, then reuse or recycle them, and only at the end burn the wood for energy. Wood in a building keeps its carbon locked away for decades.
Sustainable use: cut no more than grows
A forest keeps adding new wood every year, called the annual increment, measured in cubic metres per hectare per year (m³/ha/yr). If the owner cuts less than or equal to the increment, the forest stock stays the same or grows. This is sustainable yield.
Simple rule: yearly cut ≤ yearly growth. A forest of 100 ha that grows 8 m³/ha/yr can give at most 800 m³ each year. Cutting more would use up the stock, like spending savings.
Also replant after cutting, protect the soil, and keep part of the forest as natural area.
Key formulas and definitions
- Sustainable yearly cut ≤ annual increment × area
- Annual increment = total growth (m³) / years / area (ha)
- Cycle: plant → tend → thin → harvest → use → replant
- Cascade use: product → reuse/recycle → energy
Worked examples
1. A 50 ha forest grows 6 m³/ha every year. What is the most that can be cut sustainably each year?
Yearly growth = 6 × 50 = 300 m³. Sustainable cut ≤ 300 m³ per year.
2. A stand holds 280 m³/ha at age 40. What is the average yearly growth?
280 / 40 = 7 m³/ha per year.
3. A 60 ha forest is cut in 6 equal blocks, one per year, on a 6-year rotation of cutting. How many ha are cut each year?
60 / 6 = 10 ha each year.
4. Which use of a thick straight log is better: beams for a house or burning as fuel? Why?
Beams. Wood in use locks carbon away for decades and earns more. The log can be reused or recycled later, and burned only at the end (cascade use).
Common mistakes
- Thinking a forest is "used up" when trees are cut. If replanted and cut within growth, it renews.
- Burning good logs for fuel when they could be beams or furniture.
- Cutting all the forest in one year and having nothing to cut later.
- Forgetting to replant after harvest.