Landscapes Forest and Global Change - ESA - Escola Superior ...

J. Gaspar et al. 2010. Visibility analysis and visual diversity assessment in rural landscapes
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being occupied by Eucalyptus (Eucalyptus globulus) (Table 1). However, forest fires are a
major driver of change of the landscape.
The results of the visibility analysis for each of the land cover classes were combined to derive
the values of visual diversity (Figure 1).
Figure 1 Landscape visual diversity: number of land cover types visible for 1954, 1974 and
1995.
The changes in visual diversity through time shows a comparatively small change between 1954
and 1974, but more significant changes by 1995, with an increase of the higher diversity values
(7, 8 and 9), and a decrease of the lower diversity values. These changes will be influenced by
the reduction in the overall number of patches of land cover classes between 1954 and 1974, but
an increase in the area and patches of Maritime pine and Other land uses. The combination of
these changes has led to an increase in the mean patch size, and the increase in the distance
between patches of the same land cover classes having a significant influence on the distribution
of the visual diversity.
The period between 1974 and 1995 shows a significant increase in higher visual diversity values,
which can be explained by the increase of fragmentation, but also the new patches of Eucalyptus
and Broadleaved species in highly visibile areas. The effect of forest fires also had a srong
effect in terms of patch fragmentation, and provided conditions to increase the visibility of
abandoned agriculture areas.
Table 2 Landscape content.
Land cover class visibility
1954 1974 1995
30% 50% 70% 30% 50% 70% 30% 50% 70%
Dry cropland 1.0 1.2 0.6 0.3 0.6 0.5
Irrigated crops
Maritime pine 59.4 68.9 38.2 81.3 86.7 55.4 21.3 14.5 4.6
Eucalyptus 0.6 0.8 9.2 6.9 1.5
Broadleaved species 0.5 0.5
Other conifers
Water
Other land uses 14.2 17.8 10.7 4.2 7.0 3.3 41.1 40.7 26.8
Social areas
Maritime pine + Dry cropland 1.9 1.4 0.3
Maritime pine + Irrigated crops 0.5
Maritime pine + Eucalyptus 1.1 4.6
Other land uses + Maritime pine 21.3 10.6 13.3
Other land uses + Eucalyptus 4.6
Other land uses + Broadleaved species 0.4
Other land uses + Water 0.3
Total 98.3 87.9 49.6 99.3 94.8 58.8 96.2 63.1 32.9
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.