Tree-site index and soil-site index methods in developing growth and yield prediction models for Leucaena leucocephala (Lam) de Wit
1988
Uriarte, M.T.
A comprehensive study to determine the relationship between age and dominant height (tree-site index method) and between site properties and dominant height (soil-site index method) was conducted for Leucaena leucocephala (Lam) de Wit. The resulting site equations were used to determine the yield models using ordinary least squares and systems of equations. Using the Chapman-Richards model, the tree-site index was found to be more reflective of the site quality properties. It was also more preferable because of easy data gathering and no laboratory analyses are needed. However, soil-site index can be used in areas where there are no standing trees. Based on 121 sample plots, it was found that the dominant height of Leucaena leucocephala was strongly correlated with elevation, depth of A-horizon, pH, phosphorus, rainfall, magnesium and nitrogen. Three hundred eighty-three (383) sample plots were used for yield prediction. The selected models showed that age, site index and spacing significantly affect yield. The system of equations model was composed of the stand diameter, stand basal area and yield equations. Using three-stage least squares, the models accounted for 66% of the variation in yield. The predicted yield models developed were statistically sound and valid relative to the basic concepts of stand development such as: sigmoid shape through time approaching an asymptote at the carrying capacity of the site and differentiation properties with respect to site quality, age and stand density. The models were also statistically verified against real world data, hence, they are considered valid for prediction purposes within the ranges of data used.
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