Tree growth on a compacted Oxisol

Abstract

For a site at Barora, Solomon Islands, assessment was made of survival and growth of Gmelina arborea and Terminalia brassii planted on a heavy clay soil degraded by crawler tractor logging of primary forest and other processes. Experimental paired plots were established in 1981 on six classes of degraded soil and in undisturbed forest as a control. Owing to tree fall on site, the data from the “Uncleared” plots was unsatisfactory. On trafficked land, tree survival was poor and basal areas were about half those on the “Least Disturbed” soil class. Gmelina arborea performed better than T. brassii. Field pedological investigations and bulk density measurements were found to be of use in identifying sites of poor and better growth. Physical and chemical status were established for a representative profile under primary forest and for the experimental plots. Comparison of degraded areas with the baseline profile suggested that fertility had been reduced and that there were few signs of soil recovery in the plots after 7 years. Problems related to control of soil compaction and the need for sustainable cropping systems are discussed.