Girth growth of rubber (Heyea brasiliensis) trees during the immature phase

摘要

Growth and performance of rubber trees (Hevea brasiliensis) during the immature phase were studied in a tropical humid climate. Monthly girth growth of the main stem from 25 clones, between ages three and eight years, was monitored. Monthly girth increments, seasonal and annual absolute and relative girth rates were the analysis parameters. Three seasons, viz. S1 (April till July), S2 (August till November) and S3 (December till March) were demarcated for seasonal comparisons. All clones followed a broadly similar pattern of growth. Monthly girth increment varied from 0 to 2 cm month(-1). Girth growth began in April/May, peaked in July/August, declined from October and terminated by December. In the subsequent period up to March, no growth was observed. Most of the growth occurred in S1 and S2 with values of 43 and 53% respectively. Based on growth attributes, four groupings of clones were obtained. The results indicated an annual growth period of seven to eight months with an annual mean girth increment of 6.5 cm annum(-1) and a mean relative increment rate of 2.5 mm cm(-1) annum(-1).