Stand dynamics and basal area change in a tropical dry forest reserve in Nicaragua

Stand dynamics and basal area change were determined in deciduous and gallery forest types at the Chacocente Wildlife Reserve, Nicaragua. All stems ≥10 cm dbh in 4 ha were tagged and identified by species and measured in 1993 and 2000. In year 2000 totally 519 stems ha−1 with a basal area of 15.62 m2 ha−1 were recorded in the deciduous forest type and corresponding figures were 308 stems ha−1 and 23.13 m2 ha−1 for the gallery forest type. Comparison of stem diameter and basal area distribution during this study period revealed no changes. Both forests types had a reversed J-shape diameter distribution dominated (>80%) by small stems (<30 cm dbh). In the deciduous forest small stems contributed to more than half of the basal area, whereas in the gallery forest large stems (>70 cm dbh) contributed to almost half the basal area. Based on a logarithmic model the mortality and recruitment rates were calculated at 4.5 and 2.5% year−1, respectively, in the deciduous forest type and 4.2 and 4.0% in the gallery forest type. The decrease in stand density in the deciduous forest type was significant whereas it was not the case for the gallery forest type. There was also a significant decrease in basal area of 1.2% year−1 in the deciduous forest and no change in the gallery forest. The recorded median diameter (dbh) increment was 0.14 cm year−1 with a range of 1.21 cm year−1 in the deciduous forest type and corresponding figures for the gallery forest were 0.24 cm year−1 and 0.71 cm year−1. Three of the five most common species in the deciduous forest, Lonchocarpus minimiflorus, Gyrocarpus americanus and Stemmadenia ovovata had mortality rates above 9%. Although L. minimiflorus and S. ovovata had recruitment rates above average the net balance was negative. Among the five most common species only Tabebuia ochracea a timber species had an annual recruitment higher than its mortality rate. Non-timber species as a group had the largest calculated negative balance between mortality and recruitment as well as between loss and gain of basal area indicating a possible anthropogenic influence. In the gallery forest Capparis pachaca was the only species, out of the most common, with a positive annual balance. In both forest types there was a higher than average calculated recruitment and basal area growth for species with no local use.