DEVELOPING AN INDEX FOR FOREST PRODUCTIVITY MAPPING - A CASE STUDY FOR MARITIME PINE PRODUCTION REGULATION IN PORTUGAL

ABSTRACT Productivity is very dependent on the environmental and biotic factors present at the site where the forest species of interest is present. Forest site productivity is usually assessed using empirical models applied to inventory data providing discrete predictions. While the use of GIS-based models enables building a site productivity distribution map. Therefore, the aim of this study was to derive a productivity index using multivariate statistics and coupled GIS-geostatistics to obtain a forest productivity map. To that end, a study area vastly covered by naturally regenerated forests of maritime pine in central Portugal was used. First, a productivity index (PI) was built based on Factorial Correspondence Analysis (FCA) by incorporating a classical site index for the species and region (Sh25 - height index model) and GIS-derived environmental variables (slope and aspect). After, the PI map was obtained by multi-Gaussian kriging and used as a GIS layer to evaluate maritime pine areas by productivity class (e.g., low, intermediate and high). In the end, the area control method was applied to assess the size and the number of compartments to establish by productivity class. The management compartments of equal productivity were digitized as GIS layer and organized in a temporal progression of stands’ age regularly available for cutting each year during a 50-year schedule. The methodological approach developed in this study proved that can be used to build forest productivity maps which are crucial tools to support forest production regulation.

摘要 森林生产力高度依赖于目标森林物种所在立地的环境因子与生物因子。当前森林立地生产力通常借助应用于清查数据的经验模型开展评估，此类模型仅能输出离散的预测结果；而基于地理信息系统（GIS，Geographic Information System）的模型则可生成立地生产力空间分布图。为此，本研究旨在通过多元统计方法结合GIS-地统计学方法构建生产力指数，进而生成森林生产力地图。基于此，本研究选取葡萄牙中部广泛分布天然更新海岸松（maritime pine）林的区域作为研究对象。首先，结合该物种与区域的经典立地指数模型（Sh25——树高指数模型）以及GIS提取的环境变量（坡度与坡向），通过因子对应分析（Factorial Correspondence Analysis, FCA）构建生产力指数（Productivity Index, PI）。随后，通过多高斯克里金法生成生产力指数分布图，并将其作为GIS图层，依据生产力等级（低、中、高）对海岸松林地进行分类评估。最终，采用面积控制法对各生产力等级对应的经营小班规模与数量进行测算。将生产力均等的经营小班数字化为GIS图层，并按照林分年龄构建时间序列，确保在50年的经营周期内，每年均可定期开展采伐作业。本研究开发的方法学框架证实，其可用于生成森林生产力地图，而此类地图是支撑森林生产调控的关键工具。