STAND DENSITY INDICES FOR FOREST PLANTATIONS

Abstract

Stand density can be defined as the quantitative measure of stocking expressed either absolutelyin tenus of number of trees, basal area, or volume per unit area or relative to some standcondition. It is an important measure to schedule thinning regimes especially in the even-agedstands. There are a number of indices available toquantify the stand density. However, matchingdensity indices are mostly depends on species and its growth behaviour. In this study fourdifferent stand density indices were compared on Eucalyptus grandis stands grown in theNuwara-Eliya division

The first index is the basal area, which is a conventional method to measure stand density. Inmanaged plantations due to the lack of continuity, it is not so widely used among the even agedstands, though it is the major tool to measure the density in natural forests. The maximumobserved basal area was 74.6m2/ha and the minimum was 3.6m2/ha. The second index is therelative spacing (RS). Plantations are more suitable to indicate their stand density by measuringrelative spacing .The minimum observed relative spacing was 0.088 and the maximum was0.458.The third index Crown Competition Factor (CCF), describes the relationship betweencrown surface area and the stand area. This can be interpreted; as when the crown surface areafor a unit land area is high then the stand density is high .It is a good measure to interpret thestand density situation for a dense crown species. The fourth popular stand density measure isStand Density Index (SOl). Under the proper management system, it produces a basal area of75m2/ha with 195 stems/ha and mean diameter of 70 em

There is no unique density index available for a particular tree species. The suitability of densityindices depends not only on species but also on their growth behaviour. In this study, crowncompetition factor showed very less accessibility especially for E. grandis. Stand basal area ismore descriptive and regardless of age, for the comparison of stands, it is inferior. Relativespacing is more appropriate for the stands where no thinning takes place. This explains how thenumber of stems/ha affects the RS with the age. This method is good to use in the spacing trialrather than to quantify the thinning. Stand density index (SOl) appeared to be the most prolificdensity index for this species.