Fragmentation is a disruption in the connectivity of landscapes. The aims of this paper are (i) to quantitatively assess the fragmentation rates in three landscape units located in a hydrocarbon basin, and (ii) to model their behavior between 2001 and 2013 using landscape metrics at different scales of resolution. The following metrics were selected using principal component analysis (PCA): The Clumpiness Index (CLUMPY), patch density (PD), perimeter-area fractal dimension (PAFRAC) and effective mesh size (MESH). Results from our investigations pointed out that hydrocarbon activity increased the fragmentation at the sites. In particular, the CLUMPY index increased in all three landscape units, the average of PD decreased from 60 to 14 patches per 100 hectares, whereas the mean of MESH was quite constant, however, due to oil production, it decreased mainly in the coastal valleys. Finally, the PAFRAC also decreased at sites with oil production, being more evident in the plateau and coastal canyons. As a whole, outputs from our analyses clearly pointed out that the monitoring of landscape fragmentation trends in arid and semi-arid zones can be successfully achieved using metrics derived from satellite spectral information.
The Geography has provided the greatest theoretical body for the study of the configurations that occur over the geographical space. The generation of cartography that represents ground cover is one of the most important uses of remote sensing. Polygons were selected, with oil and livestock activity, in the landscape units: coastal canyons, plateaus and western valleys. The polygons were used to evaluate multi-temporal changes in land cover and plant communities over a period of 15 years. Supervised classifications and analysis of landscape metrics were made to examine the possible causes of these changes by comparing: i) polygons without oil or livestock activity (control), ii) polygons with oil and livestock activity, iii) polygons with oil activity and without livestock activity, and iv) polygons without oil activity and livestock activity. The results obtained indicated that the density of patches, the total edge, the edge density and the division index of the fragments increased in the three landscape units, between 2001 and 2016. The contagion index, however, decreased. An increase in bare soil was observed in the plateaus and in the western valleys, with a regression of the dominant plant communities. The density of patches in the sites without disturbance was the lowest, and in the sites with both disturbances acting simultaneously was maximum. In the sites without disturbance the effective mesh size was maximum, while in the sites with some disturbance it was smaller. When analyzing the effect of the disturbance on the elements of the landscape it was observed that the presence of the disturbance generates the highest density of patches and the minimum connectivity. The results show that there was a process of fragmentation in the coverage of the soil directed by the oil exploitation and sheep farming, which decrease the size of the patches and, therefore, the density of the same per unit area.
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