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

M.B. Horta et al. 2010. Landscape Structure of a Conservation Area and its Surroundings in Minas Gerais State, Brazil
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4. Discussion
The landscape structure results for the conservation site showed that the area to be preserved
comprises a large amount of forest and grasslands. These findings increase the site importance
for nature conservation purposes especially considering that the area is set in the Brazil’s
Atlantic Forest Dominion, a highly threatened tropical ecosystem (Conservational International
2000), where conservation recommendations includes large areas, with elevate forest cover to
favor species maintenance (Metzger 2009).
Inside the conservation site the results of low patch number and high average area for the forest
cover indicated the preservation of more continuous areas whereas in the surroundings the
findings suggested concerns regarding fragmentation, especially for those areas located at the
east side, closer to Itabira county. Valente (2001) found as more fragmented, in a landscape
structure study of river basins, the sites with lower mean patch area and higher patch density. As
pointed out by Ji at al (2008), patch number and average area can reflect the fragmentation of a
certain landscape in some degree. Landscapes comprising lower mean patch area tend to be
more fragmented (Mac Garigal and Marks 1995).
The mean shape index results inside and outside the conservation area for the various land cover
classes indicated a prevalence of irregular patches. Valente (2001) and Jorge and Garcia (1997)
found similar results for the mean shape index in forest and savannah environments. Patches
characterized by larger areas tends to present more irregular shapes (Mac Garigal and Marks
1995) and irregular patches with lower areas interact in a higher degree with the surrounding
matrix being more susceptible to the edge effect (Valente 2001). In the present study, the
characteristics of the core area might be compensating the shape. The land cover majority inside
and outside the conservation area presented high proportion of core area suggesting a larger
proportion of natural vegetation with low influence of the edge effect. This is the case of the
largest forest patch found inside the area to be preserved (1.529,20ha). Regarding conservation
purposes, the forest patch exceeds the 250ha core area criterion suggested by Jongman (1995),
for nature conservation planning in Europe.
The mean distance among patches of the same land cover inside the conservation area was
highest for forests and in the surroundings for grasslands. Considering that approximately half
of the patches of natural vegetation inside the conservation area presented low mean distances, a
relative aggregation and low isolation among patches is occurring. Low isolation enables a
better influx of animals, seeds and pollen improving dispersion and biological diversity (Forman
& Godron 1986).
The highest interspersion and juxtaposition index inside the conservation area was found for the
pastures. This land cover type showed consequently a higher adjacency to the other patch types
indicating a potential impact risk, since inappropriate fencing system coupled with free grazing,
may favor invasive species colonization and damages to the seed bank.
The surrounding area may work well as a buffer zone and enhance the flux among patches,
given the richness in patches found. Nevertheless, the fragmentation trend especially on the east
side and the large amount of pastures has to be considered. As pointed out by Jongman (1995)
nature conservation sustainability must be supported by policies on buffering external
influences and integrating functions, where possible.
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.