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Approximately 8000 km$^2$ of Brazilian Amazon forest are selectively logged each year. Although virgin forest in eastern Amazonia is generally immune to fire, selectively logged forests are susceptible to fire. In eastern Amazonia we employed permanent-plot studies, forest fuel moisture measurements, and hemispheric canopy photographs to study the impacts of fire on a selectively logged forest, the microclimatic conditions that foster forest fires, and the measures that loggers might take to reduce fire incidence. Significant tree mortality followed a typical ground fire in a selectively logged forest. Forty-four percent of all trees $\\geq$ 10 cm in diameter at breast height died in a burned plot while only 3% died in an unburned plot. In large logging gaps the density of regenerating pioneer species increased by $>$60% in burned plots 15 mo after the fire, while it decreased by $>$40% in unburned plots. The rate of fuel drying in selectively logged forest was influenced by photon flux density (PFD), time since logging, and logging techniques. There was a significant $(P = 0.005)$ negative correlation between PFD and the number of days fuel sticks required to reach the point where fire could spread. In a recently logged forest, large logging gaps ($>700$ m$^2)$ reached fire susceptible after 6 d, and medium-sized logging gaps ($\\approx$ 200-700 m$^2$) reached fire susceptibility after 15 d. But fires susceptibility declines over time as logging gaps become densely packed with saplings; fuel moisture conditions in large gaps of forest selectively logged 4 yr earlier were similar to those found in virgin forest, thus reducing the likelihood of fire. Careful logging also can reduce the likelihood of fire. Special low-impact logging techniques remove the same amount of timber as do the more typical high-impact logging techniques, but fire is significantly less likely because the more careful operation avoids the creation of large logging gaps, the most fire susceptible areas.

Despite the growing concern over reptile population declines, the effects of modern industrial silviculture on reptiles have been understudied, particularly for diminutive and often overlooked species such as small-bodied snakes. We created 4 replicated forest-management landscapes to determine the response of small snakes to forest harvesting in the Coastal Plain of the southeastern United States. We divided the replicated landscapes into 4 treatments that represented a range of disturbed habitats: clearcut with coarse woody debris removed; clearcut with coarse woody debris retained; thinned pine stand; and control (unharvested second-growth planted pines). Canopy cover and ground litter were significantly reduced in clearcuts, intermediate in thinned forests, and highest in unharvested controls. Bare soil, maximum air temperatures, and understory vegetation all increased with increasing habitat disturbance. Concomitantly, we observed significantly reduced relative abundance of all 6 study species (scarletsnake[Cemophora coccinea], ring-neck snake[Diadophis punctatus], scarlet kingsnake[Lampropeltis triangulum], red-bellied snake[Storeria occipitomaculata], southeastern crowned snake[Tantilla coronata], and smooth earthsnake[Virginia valeriae]) in clearcuts compared with unharvested or thinned pine stands. In contrast, the greatest relative snake abundance occurred in thinned forest stands. Our results demonstrate that at least one form of forest harvesting is compatible with maintaining snake populations. Our results also highlight the importance of open-canopy structure and ground litter to small snakes in southeastern forests and the negative consequences of forest clearcutting for small snakes.

We studied physiognomy-specific (i.e., gaps vs. understory) responses of birds to low harvest (18.7 m³/ha), reduced-impact logging by comparing 3500 mist net captures in control and cut blocks of an Amazonian tena firme forest in Brazil at 20-42 mo postharvest. Species richness did not differ significantly between control (92 species) and cut (85) forest based on rarefaction to 1200 captures. Fifty-six percent of all species were shared between control and cut forest, compared to the 64 percent shared between control blocks. Higher captures of nectarivores and frugivores in cut forest likely occurred as a consequence of postharvest resource blooms. Higher captures of some insectivores in cut as compared to control forest were unexpected, attributable to increased wandering or shifts from association with midstory to understory as a consequence of habitat alteration. Logging influenced capture rates for 21 species, either consistently, or via positive interaction with physiognomy or time (13 species higher in cut forest and 8 species higher in control forest). Cut understory sites had lower diversity (H') and scaled dominance than understory and gap sites in control forest. Temporal changes in captures may have resulted from successional dynamics in cut forest: two guilds and three species increased in abundance. Increases in abundances of guilds and particular species were more prevalent in control than in cut forest, suggesting that logging displaced birds to control forest. In general, the effects of logging were relatively minor; low harvest rates and reduced-impact methods may help to retain aspects of avian biodiversity in Amazon forest understories. /// Nós estudamos as respostas fisionômico-específicas (ou seja, clareiras vs. sub-bosque) das aves à exploração madeireira de impacto-reduzido (18.7 /ha) comparando 3,500 capturas com redes em parcelas controle e exploradas de uma floresta de terra firme na Amazonia Brasileira entre 20 a 42 meses após a exploração. A riqueza de espécies não diferiu significativamente entre a floresta controle (92 espécies) e a floresta explorada (85), com base na rarefação de 1,200 capturas. Cinqüenta e seis por cento das espécies eram compartilhadas entre a floresta controle e a floresta explorada, enquanto que 64% das espécies eram compartilhadas entre as parcelas controle. A maior incidência de aves nectarívoras e frugívoras na floresta explorada provavelmente ocorreu em conseqüência da proliferação temporária de recursos após a exploração. As maiores taxas de captura de alguns insetívoros em floresta explorada em relação à floresta controle foram inesperadas, e são atribuídas ao incremento da mobilidade das aves ou a um deslocamento de espécies associadas ao médio-bosque para o sub-bosque em resposta às alterações de hábitat. A exploração madeireira influenciou as razões de captura de 21 espécies, tanto diretamente como através da interação positiva com a fisionomia ou com o tempo (13 espécies foram mais comuns na área explorada e 8 espécies foram mais comuns na área controle). Os sítios em sub-bosque explorado apresentaram diversidade (H') e dominância menores do que os sítios em sub-bosque e clareira da floresta controle. Mudanças temporais nas taxas de captura podem ter resultado da dinâmica de sucessão da floresta explorada: duas guildas e três espécies incrementaram em abundância. Incrementos na abundância das guildas e de algumas espécies em particular foram mais freqüentes na floresta controle do que na floresta explorada, sugerindo que a exploração madeireira deslocou aves para dentro da floresta controle. Em geral, os efeitos da exploração madeireira foram relativamente pequenos; exploração de baixa intensidade e métodos de baixo impacto podem ajudar a manter aspectos importantes da diversidade avifaunística do sub-bosque da floresta Amazônica.

Riparian zones are vital components of the landscape. Much attention has been focused on the question of how wide a buffer is needed to protect the original riparian environment. We sampled five streams 2-4 m wide and associated riparian ecosystems before and after clearcutting in western Washington. Buffers ranging from 17 to 72 m wide were left intact at all sites when harvesting. Our objectives were: (1) to characterize pre-harvest microclimatic gradients across riparian ecosystems, from the stream to the upland; (2) to identify effects of harvesting on these gradients; and (3) to describe effects of buffer width and near-stream microclimate on stream microclimate. Six weather stations measuring air temperature, soil temperature, surface air temperature, relative humidity, short-wave solar radiation, and wind speed were installed along transects running across the stream and into the upland, and two reference stations were established, one in an upland clearcut and one in an upland interior forest. Pairwise comparison tests were used to evaluate statistical differences between stations along transects for determination of gradient extent. Pre-harvest riparian gradients existed for all variables except solar radiation and wind speed, and values generally approached forest interior values within 31-62 m from the stream. After harvesting, microclimate values at the buffer edge and each subsequent location toward the upland began to approximate clearcut values instead of forest interior values, indicating an interruption or elimination of the stream-upland gradient. In addition, regression analyses showed that stream microclimate was affected to some degree by buffer width and microclimate in the surrounding area. We conclude that a buffer at least 45 m on each side of the stream is necessary to maintain a natural riparian microclimatic environment along the streams in our study, which were characterized by moderate to steep slopes, 70-80% overstory coverage (predominantly Douglas-fir and western hemlock), and a regional climate typified by hot, dry summers and mild, wet winters. This buffer width estimate is probably low, however, since it assumes that gradients stabilize within 30 m from the stream and that upslope edge effects extend no more than 15 m into the buffer (a low estimate based on other studies). Depending on the variable, required widths may extend up to 300 m, which is significantly greater than standard widths currently in use in the region (i.e., ∼10-90 m). Our results indicate that even some of the more conservative standard buffer widths may not be adequate for preserving an unaltered microclimate near some streams. Additional site-specific data are needed for different site conditions in order to determine whether generalizations can be made regarding near-stream microclimate.

Amphibians share several biological characteristics that may cause them to be sensitive to abrupt transitions in microhabitat and microclimate that occur across forest edges. To better understand the importance of edge effects on amphibians in a forested landscape, we sampled the distribution of populations along drift fences placed perpendicular to silvicultural edges of varying contrast in central Maine. Within the community of amphibians sampled (14 species), salamanders generally were more sensitive to even-aged harvesting and associated edge effects than were anurans, but forest habitat generalists and specialists were identified within both groups. We conservatively estimated the depth of edge effects at 25-35 m for a subset of management-sensitive species (Plethodon cinereus, Ambystoma maculatum, A. laterale, and Rana sylvatica). An index of edge contrast, calculated using ambient light penetration levels, was valuable in predicting the magnitude of edge effects among sites that included silvicultural edges of different age and origin (old field plantations versus recent clearcuts). Some structural microhabitat variables relevant to forest management were identified as potentially limiting to amphibians near forest edges, including canopy cover, litter cover, and a measure of stumps, snags, and their root channels. Our observations are consistent with the results of other work on biotic edge effects in the eastern United States and suggest that impacts from intensive forest management practices extend beyond the boundaries of harvested stands.

The effects of commercial logging on tree diversity in tropical rainforest are largely unknown. In this study, selectively logged tropical rainforest in Indonesian Borneo is shown to contain high tree species richness, despite severe structural damage. Plots logged 8 years before sampling contained fewer species of trees greater than 20 centimeters in diameter than did similar-sized unlogged plots. However, in samples of the same numbers of trees (requiring a 50 percent larger area), logged forest contained as many tree species as unlogged forest. These findings warrant reassessment of the conservation potential of large tracts of commercially logged tropical rainforest

If logging is to be compatible with primate conservation, primate populations must be expected to recover from the disturbance and eventually return to their former densities. Surveys conducted over 28 years were used to quantify the long-term effects of both low- and high-intensity selective logging on the density of the five common primates in Kibale National Park, Uganda. The most dramatic exception to the expectation that primate populations will recover following logging was that group densities of Cercopithecus mitis and C. ascanius in the heavily logged area continued to decline decades after logging. Procolobus tephrosceles populations were recovering in the heavily logged areas, but the rate of increase appeared to be slow (0.005 groups/km2 per year). Colobus guereza appeared to do well in some disturbed habitats and were found at higher group densities in the logged areas than in the unlogged area. There was no evidence of an increase in Lophocebus albigena group density in the heavily logged area since the time of logging, and there was a tendency for its population to be lower in heavily logged areas than in lightly logged areas. In contrast to the findings from the heavily logged area, none of the species were found at a lower group density in the lightly logged area than in the unlogged area, and group densities in this area were not changing at a statistically significant rate. The results of our study suggest that, in this region, low-intensity selective logging could be one component of conservation plans for primates; high-intensity logging, however, which is typical of most logging operations throughout Africa, is incompatible with primate conservation.

Fragmentation can alter the ecology of rain forest remnants in many ways, but its long-term effects on tree communities are poorly understood. One phenomenon that has received little attention is tree regeneration in fragmented forests. Patterns of regeneration are important because they will ultimately determine the floristic composition of the remnant. Janzen (1983) suggested that fragments of tropical dry forest in Costa Rica are prone to invasions of weedy, generalist plant species from the surrounding modified matrix, which could progressively alter the floristic composition of remnants. Laurance (1991, 1997) proposed that fragments in some tropical regions are chronically disturbed by winds and other factors and may exhibit a general shift toward successional trees, lianas, and vines adapted for recurring disturbance. Using data collected over 13 years, we describe patterns of tree recruitment in a fragmented landscape in central Amazonia. We ask three questions: (1) Do rates of tree recruitment differ between fragmented and continuous forests? (2) Are recruitment rates influenced by fragment area, age, and proximity of forest edge? (3) Are regenerating trees in fragments biased toward successional species or against old-growth species?

To evaluate the impact of fragmentation on forest regeneration, I measured the abundance of shade-tolerant, mature-phase tree seedlings (individuals 5-100 cm tall) in unfragmented and fragmented vegetation in three sites near Manaus, Brazil. The habitats studied were (1) continuous forest (control, n = 5); (2) 100-ha fragments (n = 2); (3) 10-ha fragments (n = 4); and (4) 1-ha fragments (n = 5). For 10- and 100-ha fragments, seedling density was measured in the center, the edge, and the corner of the fragments, and at 20-m intervals up to 100 m away from the fragment's edge. The density of seedlings declined significantly from continuous forest to forest fragments. Corners of 100-ha fragments had lower densities of seedlings than plots in centers and edges. In both 100- and 10-ha fragments, edge seedling density increased toward forest interior, but the increment was significant for only one site. Edge effects were more important than area effects per se in affecting seedling abundance. Overall, the centers of larger fragments (100 ha) did not have significantly higher densities of tree seedlings than smaller ones (10 and 1 ha). I suggest that a decrease in seed rain produced by increased tree mortality, reduced seed output and dispersal, high seed predation, and lower seedling establishment might explain the lower seedling numbers observed in forest fragments and fragment edges. These results suggest that forest fragmentation at Manaus may affect the regenerative potential of the forest.

Despite abundant evidence that both the environmental damage and the financial costs of logging can be reduced substantially by training workers, pre-planning skid trails, practicing directional felling, and carrying out a variety of other well-known forestry practices, destructive logging is still common in the tropics. Based on our collective experience with loggers in tropical forests, we discuss seven possible reasons for this seemingly irrational behavior. The principal reason poor logging practices persist is apparently that the widely heralded cost savings associated with reduced-impact logging relative to unplanned logging by untrained crews may not be realized under some conditions. In particular, where compliance with logging guidelines restricts access to steep slopes or prohibits ground-based timber yarding on wet ground, reduced-impact logging may be synonymous with reduced-income logging. Given that under such conditions loggers may not adopt reduced-impact logging methods out of self-interest, fiscal mechanisms for promoting sustainable forest management may be needed.