RESISTANCE AND RESILIENCE IN A DIRECTLY REGENERATING RAIN-FOREST - NICARAGUAN TREES OF THE VOCHYSIACEAE AFTER HURRICANE-JOAN

Two trees of the family Vochysiaceae, Vochysia ferruginea and Qualea paraensis, were abundant in a Nicaraguan rainforest which was heavily damaged by Hurricane Joan in 1988, and both had recovered their previous densities by 1993. However, their regeneration followed quite different paths. Vochysia suffered complete mortality of adult trees in the hurricane, but rapid growth and high survivorship of its abundant seedlings and sprouts of saplings, restored its population density (though not yet its mean diameter at breast height) and indeed led to spatial expansion. Qualea, however, showed 100% survival of trees during the hurricane but substantial mortality in the following years. Although seedlings and sprouts of Qualea are quite rare, ingrowth is sufficient to maintain the population so far. However, vine growth on Qualea (unlike Vochysia) is substantial. These two species are thus contrasting elements of the 'direct regeneration' which has been observed in this rainforest. The Vochysia pattern of death and recovery can be described as 'resilience', while the Qualea pattern of survival can be called 'resistance'. The regenerating Vochysia population is mostly seedlings and saplings, while that of Qualea is mostly adult trees. Depending on the pattern of regeneration, different management strategies will be appropriate for maintaining tree species subject to natural disturbances such as hurricanes and/or artificial ones such as logging.