Once you have collected and processed the stand level data the next step is to use it to understand what is happening in the stand and then to specify silvicultural interventions. At a recent workshop in North West England Forest District a group of pioneers met to share their experience. This experience suggested that the main benefits from monitoring covers:
- Stand structure
Stand level data displayed by a GIS
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Objective information is produced on species composition, size, distribution and browsing damage on regeneration. This is useful because many forest managers:
- Over-estimate the amount of regeneration in a stand
- Under-estimate the level of browsing (often this will be one of the main reasons why there is little, or no, regeneration)
- Give emphasis to seedling regeneration, especially where there is a lot of it, rather than saplings that are much more likely to become part of the new stand
- Only focus on the preferred target species to regenerate instead of considering the wider species mix that will develop
- Have no way of assessing the distribution of regeneration (this can have important implications for thinning CCF stands). Some users linked their stand level data to a Graphical Information System (GIS) by using a handheld Global Positioning System (GPS). This has enabled them to examine the data spatially; an example is shown on the right.
Screenshot displaying diameter distribution
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Objective information is presented on species composition, basal area and diameter distribution of stands. This can be useful for two main reasons:
- The structure of a stand is critically important when deciding how to thin it.
The software allows the forest manager to test if the diameter distribution is ‘symmetric’ (similar to a normal distribution) or ‘skewed’ as shown in the example on the right. As can be seen, a skewed distribution would have a large number of small trees, a moderate number of medium trees and a low number of large trees, and is similar to the ‘reverse-j distribution’ much discussed as an option for managing continuous cover forests. If the stand has a symmetric diameter distribution this must be taken into account when thinning the stand, especially if the aim is to develop a structure with three or more canopy strata.
- It enables forest mangers to be objective about their approach to CCF management and record the results of their interventions.
At present we have some information concerning the correct range of basal areas to use when transforming stands (see Forestry Commission Information Note 40) but have little understanding of how this will vary with site and during different stages of transformation. It is imperative that we develop this experience and share it.
The results of monitoring can be used to present a professional approach to Continuous Cover Forestry management to potential or existing clients, team members or external contacts.
This information was first published in the January 2005 edition of Forestry and British Timber