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M.B. Horta & E. Keizer 2010. Assessment of human and physical factors influencing distribution of vegetation degradation
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The present study examined the vegetation degradation phenomenon in a protected area,
characterized by subtropical moderately humid climate, where degradation affects not only
forest, but also other vegetation types. The main objectives of this study were:
1. assess the variations of vegetation degradation;
2. investigate the association between spatial distribution of vegetation degradation and
human (roads network, rural settlements/village/city, tourist sites, mining sites,
agricultural areas) and physical factors (slope, geology, drainage).
2. Methodology
2.1 Study area and map data set
The Environmental Protection Area (EPA) Cachoeira das Andorinhas comprises an area of
18.700 ha. It is located in the north of the Ouro Preto Mountain Range, Minas Gerais state, in
the west extreme of the Brazilian Atlantic Forest dominion, setting bounds with the Savannah
dominion (Rizzini 1979). The climate is subtropical moderately humid. The mean annual
temperature varies from 19.5ºC to 21.8ºC.
The data sources utilized for the map data set composition comprehended: Landsat TM image
30m resolution; topographic map (for roads, rural settlements, villages, and city); contour map;
geology map; and drainage map. Data collection in the field was carried out for the ground truth
and localization of tourist and mining sites. The DEM (Digital Elevation Model) was obtained
from a digitized contour map aiming the creation of the slope map. The classification of the
Landsat TM image into land cover classes was carried out through a cluster of steps of
supervised classification. The overall classification accuracy obtained was 82%.
2.2. Data collection and analysis
Data collection in the field was carried out in a total of 47 sample plots (25 x 25m) using
stratified random sampling. For the establishment of vegetation degradation levels in the area 5
ecological indicators (I) were selected according to the literature (De Pietri 1992; De Pietri
1995; Hargyono 1993). The classes of vegetation degradation defined comprehended: not
degraded (0), low degraded (1), moderately degraded (2), highly degraded (3) and extremely
degraded (4). The direction of the influence of each indicator in the vegetation degradation
process was defined through the use of multivariate analysis (Principal Component Analysis).
Higher proportion of invasive species cover (%), lower estimation of canopy cover (%) and
lower proportion of understory cover (%) meant higher level of degradation in the forest areas.
The higher degradation condition in the savannah and rocky shrublands was determined
according to the higher proportion of invasive species cover (%), higher proportion of bare soil
(%) and higher percentage of dead shrubs. The invasive species considered were: Arundinaria
effusa, Eupatorium sp., Gleichenia sp., Lantana lilacina, Melinis minutiflora, Panicum sp.,
Pteridium aquilinuum, Rhynchospora exaltata, Solanum sp., Vernonia scorpiodes; Poaceae 1;
Poaceae 2.
Principal Component Analysis (PCA) was implemented for the definition of scores that
represented the vegetation degradation variations and for checking redundancy in the data. For
the forest areas the human factors distance to agricultural areas and distance to tourist sites
presented clustered to village/city/ rural settlements, and were removed from the analysis. For
the savannah and rocky shrublands the variable distance to village/city/ rural settlements was
clustered to mining sites and removed from the analysis.
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.