Hypsometric stratification by site and total height classes of Eucalyptus clonal plantations

Abstract

The employment of hypsometric relation in the forest inventory processing is a very common activity, which must be performed so that results in accurate and unbiased estimations. An attempt to increase the estimate accuracy of height is to adopt variables for stratification. The aim was to test stratification criteria of hypsometric relation in Eucalyptus sp. clonal stands. Database came from plots of continuous forest inventory of Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla S. T. Blake hybrid planting, located in northwest of Bahia state, Brazil, whose ages ranged from 27 to 78 months, measured from year 2007 up to 2010. Tree heights were estimated employing the database without stratification and after, we estimated the heights considering site classes and height within each site as stratification criteria. Scolforo’s hypsometric model was the most appropriate to estimate the total height either without stratification or with stratification of data. The modelling at data without stratification generated accurate and reasonably unbiased estimations, while the stratifications provided accurate estimates close to the fitting without stratification. Considering the whole database and regarding to accuracy issues, the modelling by height classes at each site provides the best results.