ASSESSING THE QUALITY OF PERMANENT SAMPLE PLOT DATABASES FOR GROWTH MODELING IN FOREST PLANTATIONS

Informed plantation management requires a good database, since the qua lity of information depends on the quality of data, growth models and other planning tools. There are several importnat questions concerning permanent plots: how many plots, where to put them, and how to manage them. Plot measurement procedures are also important. This paper illu strates graphical procedures to evaluate existing databases, to identi fy areas of weakness, and to plan remedial sampling. Two graphs, one o f site index versus age, another with stocking versus tree size, may p rovide a good summary of the site and stand conditions represented in the database. However, it is important that these variables, especiall y site index, can be determined reliably. Where there is doubt about t he efficacy of site index estimates, it is prudent to stratify the dat abase according to geography, soil/geology or yield level (total basal area or volume production). Established permanent plot systems may sa mple a limited range of stand conditions, and clinical designs are an efficient way to supplement such data to provide a better basis for si lvicultural inference. Procedures are illustrated with three data sets : teak plantations in Burma, Norway spruce in Denmark, and a clinical spacing experiment in India.