Neutral landscape models (NLMs) with 30% woodland cover
Land cover thresholds have played an influential role in describing the pattern of landscapes, particularly the 30% cover rule.
A number of landscape metrics (number of patches, total edge, largest patch, total core area) which exhibit land cover thresholds were applied to a range of neutral landscape models, which varied in their degree of spatial clustering and ‘actual’ Welsh woodland landscapes.
Applying simple thresholds
The concept of simple landscape thresholds, derived from random landscapes, is very appealing to aid the development of such plans and strategies. However, our results indicate there are considerable differences between random landscape elements and the Welsh landscapes, highlighting the likely problems of practically applying simple thresholds derived from the former.
The results confirm that the distribution of Welsh woodland is spatially clustered and not random, and associated with a combination of factors including topography, hydrology and land use:
Welsh woodland has greater similarity with the highly clustered landscape models. Interestingly, such models do not exhibit the same clear thresholds as the random landscapes.
Ordnance Survey maps: © Crown copyright. All rights reserved. Forestry Commission PGA 100025498 - 2004.