STAND DYNAMICS IN MPANGA-RESEARCH-FOREST-RESERVE, UGANDA, 1968-1993

Changes in the composition and structure of mid-altitude, semi-deciduo us tropical forest in Mpanga Research Forest Reserve, Uganda are descr ibed for a 25-year period between 1968 and 1993. Three surveys of a 0. 64 ha (80 m x 80 m) permanent plot were carried out in 1968, 1982 and 1993, during which a total of 397 trees with a dbh greater than or equ al to 9.5 cm were identified. Forty-nine species were identified in to tal, representing 19 families. Eight individuals remain unidentified. Dbh measurements were recorded for 359 non-buttressed trees, whilst th e equivalent measurement for 38 buttressed trees was the diameter of t he trunk immediately above the buttress. Basal area, diversity and den sity of trees increased within the plot during the survey period by, r espectively, 8% (from 39.2 to 42.2 m(2) ha(-1)), 7% (from 44 to 47 spe cies) and 11% (459 to 508 trees ha(-1)). The main compositional change s were increases in understorey trees and a decline in seral taxa. Gro wth rates (productivity) and turnover were lower during the period 198 2 to 1993 than the period 1968 to 1982. Rates of growth and mortality were generally highest in seral species and lowest in main canopy taxa . Mortality rates were also highest amongst the smallest trees enumera ted (dbh <30 cm). Changes in composition and structure over the survey period are believed to reflect forest recovery after low intensity pi t-sawing was curtailed from 1951. Forest recovery also may have caused the reduced growth rates and turnover recorded for the most recent su rvey period, by restricting the opportunities for light-demanding, fas ter-growing and relatively productive seral taxa, and to have outweigh ed any effects of externally-driven processes, such as changes in atmo spheric conditions.