Stratifying the area into blocks
The crucial first step to collect the data is to stratify the area into blocks that have common site factors and are to be managed as a single unit. In general the bigger the better as this will help reduce costs. Within each block, data are collected from fixed-area plots where the plot area is selected to assess a minimum number of trees.
Locating plots on a systematic grid within each block where data is to be collected
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Plots are located on a systematic grid covering the whole area and can be located using a compass and pacing.
The plots can be temporary or permanently marked depending on a number of factors; most people who have used the system so far feel that the advantages of permanent plots outweigh their disadvantages.
The main assessments in each plot are:
- Species
- Number and diameter of trees
- Species and number of saplings
- Species and number of seedlings
- Browsing damage
- Vegetation type and cover.
Saplings are woody plants at least 130 cm in height and less than 7 cm diameter at breast height. Saplings are important because given good silviculture there is a greater than 90% chance of them surviving to maturity.
| Diameter at breast height (cm) | Height (cm) | |
|---|---|---|
| Seedling | n/a | <130 |
| Sapling | <7 | ≥130 |
| Tree | ≥7 | ≥130 |
Processing the data
Once the data have been collected they can be processed and examined using the software developed by Forest Research.
In the development of the software, the opportunity has been taken to allow other information concerning the transformation of an area to be recorded alongside the monitoring data. Hence the system allows the transformation plan, diary notes, fixed-point photographs and information on stand location to be stored.
The software enables information on the following to be displayed:
- Species, number and size of trees
- Basal area per species
- Diameter distribution
- Sapling and seedling regeneration
- Vegetation type and cover.
For example:
Species, number and size of trees
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Diameter distribution
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Sapling and seedling regeneration
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The above screenshots illustrate data from a stand with an overstorey of Scots pine and Japanese larch in Wykeham Forest, Yorkshire. The stand has a good structure for immediate introduction of Continuous Cover Forestry and the density and species composition of the saplings will ensure good recruitment of trees over the next 10 years assuming appropriate thinning.
This information was first published in the January 2005 edition of Forestry and British Timber
