FOREST COVER ANALYSIS THROUGH THE WEIGHTS OF EVIDENCE METHOD IN THE CAMPANHA OCIDENTAL REGION - RS (BRAZIL)

ABSTRACT The uncontrolled expansion of human activities may lead to a reduction in vegetation cover, an increase in erosion processes and soil sealing. The aim of this study is to examine forest cover using the Weights of evidence method based on land use maps between the years of 1996 and 2011 in the micro-region of the Campanha Ocidental located in the state of Rio Grande do Sul (Brazil). The spatial database was constructed in SPRING software (version 5.2.1) based on LANDSAT 5 images, which were georeferenced and classified. Geophysical and socioeconomic variables were included in the database for further analysis in Dinamica EGO software (version 2.2.8). In order to parameterize the probabilistic model for the analysis of the dynamics of forest cover change, we calculated the percentage of class change through transition matrices; calculated the intervals for discretization of continuous variables; calculated the weights of evidence (W+); analyzed the correlation between the weights of the input variables for all transitions; simulated future scenarios and; validated the simulated final map based on the historical map. This model was adequate for understanding the variables that most contribute to forest cover change in the region. The results showed that the emergence of new forest areas was influenced by hypsometry, distance to sandy lands and per capita income, while deforestation by rural population and distance to the sandy lands.

摘要
人类活动的无节制扩张可能引发植被覆盖缩减、侵蚀过程加剧与土壤封闭问题。本研究以巴西南里奥格兰德州（Rio Grande do Sul）西坎帕尼亚（Campanha Ocidental）微区域为研究对象，基于1996年至2011年的土地利用图，采用证据权重法（Weights of evidence method）开展森林覆盖相关研究。空间数据库依托经过地理配准与分类的LANDSAT 5影像，在SPRING软件（版本5.2.1）中构建完成。本研究将地球物理与社会经济变量纳入数据库，以供Dinamica EGO软件（版本2.2.8）开展后续分析。为参数化用于森林覆盖变化动态分析的概率模型，本研究依次完成以下工作：通过转移矩阵计算各类别变化占比、确定连续变量离散化区间、计算证据权重（W+）、分析所有转移情景下输入变量权重间的相关性、模拟未来情景，并基于历史地图对模拟生成的最终地图进行验证。该模型可有效阐明该区域内驱动森林覆盖变化的核心变量。研究结果显示，新增森林区域的形成受高程因素、距沙地距离以及人均收入的影响，而森林砍伐活动则受农村人口规模与距沙地距离的影响。