Planting (regeneration)
A new forest can come from planted seedlings or from natural regrowth (seeds or stumps that sprout). In planting, people choose tree kinds that suit the soil and rain, dig small pits and set seedlings in rows with equal spacing. Equal rows make weeding, thinning and cutting easy. The best time is the start of the rains.
Tending: weeding, thinning and pruning
Weeding: clearing weeds and climbers that compete for light, water and food while trees are small.
Thinning: removing some trees so that the rest have room. Trees that are too close grow tall and thin. After thinning, trunks grow thicker and the wood is worth more. The trees removed are the weak, bent or diseased ones, and often can be sold as small wood.
Pruning: cutting the low side branches close to the trunk. It gives a clean, straight log without knots. It is done in dry weather and only on the lower part of the tree.
Other care: protect from fire, grazing and pests.
Harvesting and replanting (rotation)
Harvesting is cutting trees that have reached the size we want. Two ways: clear-felling (cut all trees on a small plot, then replant) and selection felling (cut a few trees here and there, so that the forest never looks bare). Small plots, stumps left to sprout, and keeping a few big trees help wildlife.
The time from planting to harvest is the rotation. After harvest the plot is planted again. By planting a different plot each year, a forest gives wood every year for ever.
Safe working matters: helmets, gloves, chainsaw training, clear warnings before a tree falls, and moving logs with care so soil is not damaged.
Try it: how many trees to keep?
In the 3D, move the slider from 16 down to 4 trees. Read the trunk thickness and the wood score (number of trees x thickness squared, divided by 100). Which number keeps the highest score? At home: plant 8 bean seeds in a row, then 16 in the same row. After three weeks, compare how thick the stems are.
Key formulas and definitions
- Cycle: plant > weed > thin > prune > harvest > replant
- Rotation = years from planting to harvest
- More room per tree = thicker trunk
- Wood score (model) = trees x thickness^2 / 100
Worked examples
1. A plot has 16 trees with trunks of 10 cm. Find the wood score = trees x thickness^2 / 100.
16 x 10 x 10 / 100 = 1600 / 100 = 16. The 3D shows 16 for 16 trees.
2. After thinning to 8 trees, trunks reach 20 cm. Find the wood score in the same model. Is it better?
8 x 20 x 20 / 100 = 3200 / 100 = 32. 32 is more than 16, so thinning to 8 gives more good wood.
3. A forest has 30 equal plots and a rotation of 30 years. How many plots are cut each year for steady wood?
30 plots / 30 years = 1 plot a year.
4. Why do we prune in dry weather?
Cuts heal faster and disease and fungus spread less in dry weather.
Common mistakes
- Thinking thinning is a loss. The trees taken out make room, and the rest give more valuable wood.
- Pruning high up on the tree. Prune only the lower branches; the top crown makes food for growth.
- Planting in random places. Rows with equal spacing make later work easy.
- Forgetting to replant after harvest. Without replanting the forest is not sustainable.