Growth litter yield and litter nutrient composition of Casuarma oligon in the Papua New Guinea Highlands.

Abstract

Casuarina Oligodon is the most common planted tree species in Papua New Guinea Highlands. A growth study of C. oligodon was carried out at the three sites at different altitudes (2000, 1750 and 1300 m above sea level). Another unreplicated observation study examined litter yield and nutrient composition of C. Oligodon using a three year old stand (4444 trees/ha) over a three year period. At the 2000 m site, the height and diameter growth was slower initially but reached 4.5 m and 47 mm respectively at 33 months. The site also recorded 100% survival of seedlings. At the 1750 m site, the height growth slowed after 12 months which was mainly due to the continuous die back of growing apical tips. The diameter showed almost positive linear growth. About 69% of the plants had dead apical growing tips with 6% mortality. At the site at 1300 m, height and diameter at 12 months were 3.0 m and 34 mm respectively. The results of the litter yield study show that monthly average ranges between 200 and 400 kg/ha (dry matter) from a three-year-old plot. Although the nutrient content in dry leaf litter was low, it returned to the topsoil 45.6, 2.4 and 9.6kg/ha of N, P and K respectively.