Undamaged Forest Research Articles

Resiliency and response to hurricane disturbance in a tropical shrub, Ardisia escallonioides (Myrsinaceae), in south Florida

The resiliency to hurricane disturbance and the response toposthurricane environmental conditions were examined in the tropicalshrub Ardisia escallonioides (Myrsinaceae). Hurricane Andrewstruck three of four study sites in subtropical hardwood forests insouth Florida on 24 August 1992. Posthurricane understory light levelsin the disturbed sites ranged from 21 to 53% of full light in1993 and remained high in 1994; in contrast, light levels averaged only9% in the undisturbed forest. Significant differences inmortality, damage, and defoliation were observed among the threehurricane-damaged populations. Mortality was low, but adults sufferedhigh levels of damage and defoliation. Following the hurricane,populations in the most severely disturbed forests had more growth thanpopulations in lightly damaged or undamaged forests. Seed germinationand seedling growth were not associated with light availability. Nolong-term seed dormancy was observed. The observed response toposthurricane environmental conditions is consistent with understoryspecies that show release following canopy opening, but are able topersist under periods of canopy closure. The local dominance of thisspecies in many coastal forests in south Florida may be due to the highfrequency of hurricanedisturbance.

Fire in the tropical gallery forests of Belize

ABSTRACT. Historical records of burning, field observations, and a manipulation experiment were used to evaluate the extent and impact of fire in a system of gallery forests in the Mountain Pine Ridge savanna, Belize. The outer boundaries of gallery forests are fire‐prone zones, but fires rarely intrude into these forests. This is attributed to the existence of fire‐tolerant trees in the outer zone, which preserve a forest interior of low flammability. Occasional fire incursions are patchily distributed and partially inhibited by slope convexities. Intrusions consume litter and root mats and destroy seedlings and saplings, but create a wide variety of subsequent light regimes depending upon the degree of canopy destruction. At most sites, partial canopy cover persists and seedlings of a subset of forest tree species establish preferentially. Early survivorship of these seedlings is comparable to those established in undamaged forest. Where canopy opening is severe, a secondary succession is initiated, with large numbers of herbaceous plants deriving from the seed bank. Gallery forests contain core zones into which fire very rarely intrudes, and peripheral zones that experience fire incursions that are patchily distributed in space and time. In the latter zones fire incursions play a role comparable to that of canopy gaps in continuous forests, but also create a unique class of micro‐habitats to which a subset of tree species is specialized. The fire regime over the recent past in this gallery forest system appears to have had an enriching, rather than a depauperizing, effect on the forest communities, and such systems represent plausible refugia for forest species in fire‐prone landscapes.

Stand Structure and Dynamics of Pinus densiflora Forests Damaged by Pine Wilt Disease in the Southern Part of Okayama Prefecture.

In order to explore the effects of pine wilt disease on the stand structure of Pinus denszflora forests in urban fringe areas of Okayama City, we researched two damaged forest stands and one undamaged forest stand. In one of the damaged stands, selective felling of dead pine trees were conducted, and in the other damaged stand, no operations to protect pine treees were conducted. Stand structures varied in the studied stands. Biomass in the two damaged stands were reduced by pine wilt disese damage. In the damaged stand where the selective felling operation was conducted, biomass of the understorey was remarkably reduced. In both the undamaged stand and the damaged stand without protection, evergreen broad-leaved species were abundant in small size classes and were predominate in the understorey. In the damaged stand with the selective felling operation, deciduous broad-leaved species were abundant in small size classes and were predominate in the understorey. It was thought that the selective felling operation disturbed the understorey of the stand and this disturbance caused the establishment of shade intolerant species. From the analysis of diameter increments, it was presumed that the grawth of remnant trees had been accelerated after the outbreak of the disease. It was assumed that the remnant trees had been released from the suppression because the canopy trees of P.densiflora were dead and thus decreased by pine wilt disease. From our research we concluded that pine wilt disease accelerated the succession of the pine forests.However, selective felling operations disturbed the forest stand and decelerated the succession.

Conservation, biodiversity and european forestry

AbstractThe declining quality of Europe's forests is causing increasing concern. while the European Community is set to develop its policies for sustainable forest management later in 1993, the relatively undamaged forests of central and eastern Europe warrant particular attention. Nigel Dudley discusses the background to European forest decline and the likely elements that a sustainable forestry management plan should include in East and West.

Birds of a Severely Hurricane-Damaged Atlantic Coast Rain Forest in Nicaragua

On 22 October 1988 Hurricane Joan severely damaged 500,000 ha of lowland tropical rain forest in southeastern Nicaragua near Bluefields. An expedition in February 1989 detected virtually no birds in formerly forested sites, although standing trunks that had been snapped were resprouting and the forest appeared to be recovering. In March 1990 I observed birds along rivers and at a secondary forest site and surveyed and mist-netted birds at three sites reported to be largely mature forest before they were damaged by the hurricane. I recorded a total of 161 species throughout the hurricane-damaged region. In seven days at the regenerating forest sites, I recorded 113 species of birds, a species richness comparable to undamaged lowland forest I visited six months later near the Rio Santa Cruz, Nicaragua. Mist net capture rates at the damaged sites suggested overall bird abundance similar to that of a comparable lowland rain forest at La Selva, Costa Rica, but the typical habitats of mist-netted frugivores differed significantly between the two areas: the hurricane-damaged sites had proportionately fewer captures of species typical of the forest interior. Most of the birds encountered in the hurricane-damaged forest were species typical of forest edge, forest canopy, and second-growth habitats; only 19 species were birds typical of the forest interior, and only two were exclusively so. Woodcreepers, forest antbirds, and furnariids, families characteristic of lowland rain forest, were notably absent or under-represented. Overall forest structure appeared to be important in determining the species composition of the reappearing bird community.

Price and Welfare Effects of Catastrophic Forest Damage From Southern Pine Beetle Epidemics

Abstract Southern pine beetle (Dendroctonus frontalis) epidemics are periodically responsible for catastrophic levels of mortality to southern yellow pine forests. Traditional forest damage appraisal techniques developed for site specific economic analysis are theoretically weak since they do not consider aggregate impacts across ecosystems and related markets. Because the traditional model estimates losses only to producers with damaged forests, it provides misleading information from a distributional standpoint by ignoring impacts on producers with undamaged forests and timber consumers. An economic model of timber supply and demand is introduced and used to develop a new technique for estimating short-run market level impacts of catastrophic forest damages. The null hypothesis that catastrophic disruption of forest ecosystem production has no effect on timber markets is tested using intervention analysis and data on the recent Texas-Louisiana epidemic. Parameter estimates are used to compute short-run changes in economic welfare for producers on damaged forests, producers on undamaged forests, and timber consumers. Principal findings are: (1) changes in social welfare resulting from catastrophic damage to standing timber across forest ecosystems requires market-level analysis, and (2) the net change in economic welfare resulting from insect epidemics is unambiguously negative. For. Sci. 37(2):500-516.

An Aphid Population Explosion Induced by Chronic Gamma Irradiation of a Forest

A population explosion of the aphid, Myzocallis discolor, occurred on white oaks (Quercus alba) damaged by chronic gamma irradiation. Oaks exposed to 9.5 R/day during 18 months supported maximum aphid populations of 25 winged adults per leaf (350,000/m2 of forest). The aphid was not found in the undamaged forest. The irruption was correlated with changes in predator populations and with small changes in the sugar, total N and lipid content of white oak leaves. The relative importance of these two sets of factors could not be determined.