growth and wood characteristics of acacia mangium grown in kerala

4. RESULTS AND DISCUSSION4.1. EXTENT OF ACACIA MANGIUM IN KFRALAf the total 1065 agricultural offices contacted through the proforma0 survey, 155 responded (Table 3). The results presented in Table 3, basedon 14.6% returns (district-wise returns vary between 2.2% and 48.7%)provide a rough picture about the extent of A. mangium plantations in Kerala.In India, this low elevation species was probably introduced in the eighties.However, it was only in the early 1990’s that farmers had started plantingthem, either interplanted with farm crops or as pure plots. In 1997, trees upto an age of 13 years are present in some plots. Mangium timber has not yetreached the market. Unfortunately, data on the extent of planting in Keralais not available. There is no plantation of this species at State Governmentlevel, particularly by the Kerala Forest Department. Mature trees are availablein the State only in a private plantation at the Trivandrum Archbishop’sPalace and in Bethany Estate, near to the Mar Ivanios College, Trivandrum.The extent of both these plantations amounts to a few hectares only.District-wise data show that A. mangium has been introduced in all thedistricts of Kerala. The state average shows presence of A. mangium in 43%of the Panchayats. Farmers have taken up plantations of above 400 m 2 in8 districts. The largest block has an area of 3.24 ha. Even though blockplanting is not reported from Malappuram District, we are aware of cultivationof the species in plots above 400 m 2 in Nilambur of Malappuram.Our dependence on 155 returns is certainly a limitation of this survey, andtherefore the data on block planting of A. mangium may be understood withinthis limitation.4.2. GROWTH RATETable 4 and Appendix 3 gives the details of variation of GBH with age asrecorded from various plantations. It can be seen that the mean annualincrement (MAI) of GBH vanes from 11.1 to 17.9 cm. The GBH graduallyincreased as the age increased and reached a mean value of 100.0 cm at theage of 7 years. The slightly low value of GBH observed for the 8-year-old treesmay be due to the limited number of trees available for measurement andthat too, from only one plantation. The influence of soil factors on growth maybe another reason for the slightly low growth observed in this case. After8 years, again the mean GBH was found increasing. A GBH of around 1 1 1 cm18