In order to understand the impacts of forest management on biodiversity at the forest landscape scale, it is first necessary to have tools for quantifying changes in the landscape pattern, due to the predicted relationship between landscape pattern and the ecological processes that underpin biodiversity.
Evaluation of landscape pattern metrics
An aerial photograph showing an area of Glen Affric in the Scottish Highlands, with large areas of single aged plantation.
An aerial photograph of Clipstone Forest in Nottinghamshire, with smaller areas of each age class of trees which are mixed more intimately.
(Both photographs show an area of one square kilometre).
An evaluation of some of the landscape pattern metrics that have been previously used to measure landscape pattern was undertaken, in order to assess their effectiveness at characterising UK forest landscapes. Over 40 different pattern metrics were reviewed, in a range of different forest types and complexities. The following four were found to characterise UK forest landscapes most effectively:
- Patch size
- Aggregation of patches
- Patch shape (edge-to-interior ratio)
- Mixture of patches.
Clipstone, the smallest landscape in the comparison, features towards one extreme of each of the factors, with small, aggregated patches. At the opposite end of the scale is Glen Affric, which generally has large patches of older stands and open areas. However, younger stands tend to be smaller and, in the case of the latter, highly dispersed.
The shape of patches appears to be related to their age, with many younger stands (restock and thicket) having compact shapes. This may reflect forest management constraints, e.g. ease of working and cost-effectiveness. At the other extreme, the more complex, elongated shapes are associated with over-mature stands, suggesting that a substantial proportion of these may be strips retained for aesthetic reasons, or belts along riparian corridors, for example (they may also be related to the species present, e.g. semi-natural broadleaved remnants).
The mixture of patches differs from the spatial pattern explained by aggregation in that it reflects the mixture of adjacent patches, i.e. the degree of contrast between associated stands. The New Forest and Glen Affric show surprisingly little of this mixing, which may reflect past history (Acts of inclosure, areas of open forest) and topographic influences (elevation, accessibility), respectively. In contrast, Coed-y-Brenin and Clocaenog show much greater intimacy of age classes, which may be the consequence of these resulting from large-scale afforestation, where forest establishment would have been phased.
An introduction to new landscape ecology research to enhance biodiversity in British forests (PDF-192K)
Forestry Commission Information Note 34
This project was completed in 2001.