In many countries, National Forest Inventory (NFI) data is used to assess the variability of forest growth across the country. The identification of areas with similar growths provides the foundation for development of regional models. The objective of the present study is to identify areas with similar diameter and basal area growth using increment cores acquired by the NFI for the three main Romanian species: Norway spruce (Picea abies L. Karst), European beech (Fagus sylvatica L.), and Sessile oak (Quercus petraea (Matt.) Liebl.). We used 6536 increment cores with ages less than 100 years, a total of 427,635 rings. The country was divided in 21 non-overlapping ecoregions based on geomorphology, soil, geology and spatial contiguousness. Mixed models and multivariate analyses were used to assess the differences in annual dimeter at breast height and basal area growth among ecoregions. Irrespective of the species, the mixed models analysis revealed significant differences in growth between the ecoregions. However, some ecoregions were similar in terms of growth and could be aggregated. Multivariate analysis reinforced the difference between ecoregions and showed no temporal grouping for spruce and beech. Sessile oak growth was separated not only by ecoregions, but also by time, with some ecoregions being more prone to draught. Our study showed that countries of median size, such as Romania, could exhibit significant spatial differences in forest growth. Therefore, countrywide growth models incorporate too much variability to be considered operationally feasible. Furthermore, it is difficult to justify the current growth and yield models as a legal binding planning tool.

中文翻译：

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基于国家森林清单增量核心的罗马尼亚主要树种生长的区域变异性

在许多国家/地区，国家森林清单（NFI）数据用于评估全国森林生长的变异性。确定增长相似的区域为发展区域模型提供了基础。本研究的目的是使用NFI为三种主要的罗马尼亚树种使用NFI获得的增量核心来识别具有相似直径和基础面积增长的区域：挪威云杉（Picea abies L.Karst），欧洲山毛榉（Fabus sylvatica L.），和无刺栎（Quercus petraea（太太）。我们使用了年龄小于100年的6536个增量岩心，共427,635个环。根据地貌，土壤，地质和空间连续性，该国被划分为21个非重叠的生态区。混合模型和多变量分析被用来评估生态区域之间乳房高度和基底面积增长的年径差异。不论物种如何，混合模型分析均显示出生态区域之间的增长存在显着差异。但是，一些生态区域在增长方面相似，可以汇总。多变量分析加强了生态区域之间的差异，并且没有显示云杉和山毛榉的时间分组。无橡树的生长不仅被生态区分开，而且还被时间分开，一些生态区更容易吃水。我们的研究表明，中等规模的国家（例如罗马尼亚）可能在森林生长方面表现出明显的空间差异。因此，全国范围内的增长模型包含了太多的可变性，以至于在业务上不可行。此外，很难证明当前的增长和收益模型是具有法律约束力的计划工具。