Monteverde Cloud Forest Preserve Research Articles

Effects of Treefall Gap Disturbances on Ant Assemblages in a Tropical Montane Cloud Forest

AbstractThe study of gap dynamics and the effects of gaps on diversity has been at the center of tropical ecology for decades. While most studies have focused on the responses of plant species and communities to gap formation, in this study, we consider the effects of treefall gap disturbances on leaf litter ant assemblages in a Neotropical montane cloud forest. We sampled leaf litter ant assemblages and estimated a suite of abiotic parameters in 12 large (>80‐m2) treefall gaps across a chronosequence and in 12 paired adjacent intact forest sites in the Monteverde Cloud Forest Preserve in Costa Rica. No species were more common in gaps than in intact forests, and in fact, species that were common in gaps were also among the most common in forests. The Chao2 estimate of species richness, however, was higher in gap sites than in intact forest sites. In addition, ant assemblages in gap sites did not become more similar to those in adjacent intact sites as gaps aged. In contrast to other studies, our work demonstrates that ant assemblages in the Monteverde Cloud Forest Preserve are weakly affected by the formation of treefall gaps. Together, these results indicate that treefall gap dynamics probably play little role in promoting ant diversity at more regional scales, or coexistence among species at more local scales.

Complex spatial structure in a population of Didymopanax pittieri, a tree of wind-exposed lower montane rain forest

Didymopanax pittieri is a common shade-intolerant tree colonizing treefall gaps in the elfin forests on windswept ridgecrests in the lower montane rain forests of the Cordillera de Tilaran, Costa Rica. All D. pittieri taller than >0.5 m in a 5.2-ha elfin forested portion of a gridded study watershed in the Monteverde Cloud Forest Preserve were located, mapped, and measured. This local population of D. pittieri is spatially inhomogeneous, in that density increases with increasing wind exposure; D. pittieri are more abundant near ridge crests than lower on windward slopes. The important and ubiquitous phenomenon of spatial inhomogeneity in population density is addressed and corrected for in spatial analyses by the application of the inhomogeneous version of Ripley’s K. The spatial patterns of four size classes of D. pittieri ( 20 cm dbh) were investigated. Within the large-scale trend in density driven by wind exposure, D. pittieri saplings are clumped at the scale of treefall gaps and at the scale of patches of aggregated gaps. D. pittieri 5–10 cm dbh are randomly distributed, apparently due to competitive thinning of sapling clumps during the early stages of gap-phase regeneration. D. pittieri larger than 10 cm dbh are overdispersed at a scale larger than that of patches of gaps. Natural disturbance can influence the distribution of shade intolerant tree populations at several different spatial scales, and can have discordant effects at different life history stages.

Tourist Expansion and Development of Rural Communities

Central America harbors some of the most important remnants of tropical vegetation at a global level. Its rainforests, among the most representative tropical ecosystems, cover only 5% of the Earth's surface but are home to half of the world's biological diversity. Costa Rica, the second smallest country on the Central American isthmus, has been able to establish a national network of protected areas safeguarding tropical biodiversity on more than 25% of its territory. These areas serve educational purposes and attract scientists and tourists, with important implications for the development of the surrounding rural communities. The creation in 1972 of the Monteverde Cloud Forest Preserve brought important socioeconomic and environmental changes to adjacent communities. These changes were both positive (eg introduction of new rural production methods) and problematic (sudden urban development without prior land use planning).

<strong>Epiphytic bryophytes of Monteverde, Costa Rica</strong>

A survey of the literature and collections in the Monteverde Cloud Forest Preserve and adjacent pastureland yielded a total of 198 epiphytic bryophyte taxa (120 species of hepatics in 50 genera, 77 species of moss in 48 genera, and 1 hornwort): 178 in the primary forest, 63 in the secondary forest, and 84 in the pastureland.

Floating and fidelity in nest visitation byCrawfordapis luctuosa (Hymenoptera: Colletidae)

We studied nest visitation behavior of the ground-nesting beeCrawfordapis luctuosa (Colletidae) at the Monteverde Cloud Forest Preserve, Puntarenas Province, Costa Rica. Some females entered many nests, while others consistently entered only one nest. Multiple nest entry was exhibited by bees we called floaters, and those bees that consistently entered only one nest were provisioning bees. Provisioning bees abandoned their old nests after provisioning periods and became nonprovisioning bees that floated over the nesting area. Floating behavior was a nest-searching behavior typified by oscillating flights just above the ground (<15 cm). Floaters investigated available nests and were not observed to interact aggressively with nest owners. Upon establishing a new nest, floaters became provisioning bees.

Sustainable ecotourism in Costa Rica: the Monteverde Cloud Forest Preserve

The paper discusses the sustainability of the Monteverde Cloud Forest Preserve in the context of Costa Rican ecotourism. While the history of the Preserve is somewhat unique, the analysis of visitation, financial, ecological and economic factors provides a convincing case that tourism at the Preserve is sustainable. The experience of the Preserve is also put in the context of Costa Rican ecotourism, particularly to the national parks. The paper concludes that the Preserve has played a very important role in the development of Costa Rica as an ecotourism destination. Nonetheless, the failure of experience at the Preserve to inform recent changes in national park pricing policy reveal that Costa Rica has yet to fully capitalize on the experience gained and lessons learned at the Preserve.

Valuation of non-priced amenities provided by the biological resources within the Monteverde Cloud Forest Preserve, Costa Rica

To quantify the economic benefits of the Monteverde Cloud Forest Preserve and to test the contingent valuation method in a third world setting, a contingent valuation survey was designed with five experimental treatments. These determined an overall expected value per visitor; determined and compared two ways of eliciting value, single versus annual lump-sum payments; and compared average values of Costa Rican versus non-Costa Rican visitors. Visitors were willing to pay to prevent the Preserve's conversion to agricultural uses. Monteverde's value as a cloud forest preserve appears much higher than any value it might have in agricultural use. Despite lower incomes, Costa Rican visitors valued the Preserve more highly than non-Costa Rican visitors. Visitors may have differentiated only weakly between greatly differing bid amounts. Expected values derived from econometric analysis of the differing experimental treatments suggest that further methodological adaptation of the contingent valuation method may be required (1) when it is applied in third world settings, and (2) when precision is critical in estimating WTPs.

Amphibian Declines and Climate Disturbance: The Case of the Golden Toad and the Harlequin Frog

The endemic golden toad (Bufo periglenes) was abundant in Costa Rica’s Monteverde Cloud Forest Preserve in April–May 1987 but afterwards disappeared, along with local populations of the harlequin frog (Atelopus varius). We examine the possible relationship between these sudden declines and unusually warm, dry conditions in 1987. For our analyses of local weather patterns, we define a 12‐month (July–June) amphibian moisture‐temperature cycle consisting of four periods: (1) late wet season; (2) transition into dry season; (3) dry season; and (4) post‐dry‐season (early‐wet‐season) recovery. The 1986–1987 cycle was the only one on record (of 20 analyzed) with abnormally low rainfall in all four periods, and temperature anomalies in 1987 reached record highs. Flow in local aquifer‐fed streams during the dry season and post‐dry‐season recovery period reached a record low. This climate disturbance, associated with the 1986–1987 El Niño/Southern Oscillation, was more severe than a similar event associated with the 1982–1983 El Niño, though this earlier oscillation was the strongest of the past century. Demographic data for one harlequin frog population, gathered during these two climatic events, support the hypothesis that in 1987, shortly before the population collapsed, the frogs underwent an unprecedented shift in distribution within the habitat in response to desiccating conditions. The juxtaposition of these rare demographic events suggests they were causally linked yet sheds little light on mechanisms underlying the sudden decline. While desiccation or direct temperature effects may have been factors leading to high adult mortality, moisture‐temperature conditions may have interacted with some other, unidentifted agent. We discuss two hypotheses concerning possible synergistic effects: In the climate‐linked epidemic hypothesis, microparasites are the additional agent. In the climate‐linked contaminant pulse hypothesis, atmospheric contaminants scavenged by mist and cloud water in montane areas reach critical concentrations when conditions are abnormally warm and dry.

Declining Amphibian Populations

W T tORLDWIDE DECLINES IN AMPHIBIAN POPULATIONS ATtracted wide attention following a workshop sponsored by the National Research Council (NRC) (1, 2). The declines seem to be general, but some regions and many taxa are apparently unaffected (1). Are the declines due to normal climatic fluctuations, which produce droughts and frosts that can severely reduce population size locally, or are there other, more insidious causes? The report of census data for four amphibians (three salamanders and a frog) gathered during a 12-year period of continuous (daily) monitoring at the Savannah River Site in South Carolina contributes importantly to this question (3). Substantial variation was found in breeding population sizes and juvenile recruitment. Population declines were found in some years, but these were coupled with increases; there is a complex dynamic associated with many factors, especially local moisture regimen. The new data, the most extensive available, raise the possibility that declines are the coincidental effect of population fluctuations. If so, the consequences will vary greatly from place to place. The southeastern United States is a veritable carpet of amphibians, from the abundant salamanders of the highest Appalachian peaks to dense lowland populations of both frogs and salamanders. Should populations decline to local extinction in this area, chances of recovery are high. However, local extinctions have more profound implications in other parts of the world, where species are specialists for habitats that are localized or badly fragmented; under such circumstances, opportunities for recolonization are low to nonexistent (4). It is significant that participants at the NRC workshop, who heard a brief summary of the new data, considered it unlikely that global declines were coincidental, because of the number and widespread distribution of the reports, but population fluctuations clearly must be taken into account. Concern about declines arises because amphibians are abundant, integral components ofmany diverse ecosystems. They are local top carnivores that are major consumers of invertebrates, especially insects. General declines would have widespread consequences and might indicate more general environmental problems (5). Some declines have been dramatic. Ranid frogs have all but disappeared from southern California (6). By the late 1980s a montane frog (Rana muscosa) had disappeared from 98% of the ponds in which it had been studied in the mid-1970s in SequoiaKings Canyon National Park (1, 4). In Oregon, populations ofRana cascadae, monitored since the mid-1970s, have suffered about an 80% disappearance (1, 7). The golden toad (Bufo periglenes), endemic to the Monteverde Cloud Forest Preserve in Costa Rica, has not bred in its traditional breeding sites since 1987; many other frog taxa in the region have experienced declines and local disappearance during this period (1, 8). The gastric-brooding frog (Rheobatrachus silus), which lived in rivers in relatively undisturbed regions of Queensland, Australia, has not been seen since 1979, and several other sympatric species offrogs also are thought to be extinct (9). Sometime after 1981, 8 of 13 species of frogs that had been present in Reserva Atlantica, Brazil, disappeared, including unusual diurnal hylodine frogs, whose birdlike calls were distinctive features

Notes on an army ant (Eciton burchelli) raid on a social wasp colony (Agelaia yepocapa) in Costa Rica

In this note we describe a raid by army ants (Eciton burchelli Westwood) on a colony of tropical swarm-founding wasps (Agelaia yepocapa Richards). The general features of such raids have been discussed elsewhere (Jeanne 1970, Naumann 1975, Young 1979). Army ants are a major predation force on social wasp colonies in many Neotropical areas (Chadab 19 79a, Jeanne 1975), and features of swarm-founding wasp behaviour indicate strong selection for dealing with army ant predation (Chadab 19 79b, Jeanne 1975). The raid described here involved a number of behavioural responses of the wasps to the ant attack which have not been reported before, and occurred at an unusually high elevation. The raid took place next to the dirt road leading to the Monteverde Cloud Forest Preserve in Puntarenas Province, Costa Rica. The wasp nest was located 4 m above the ground in a trunk cavity of a large (about 0.7 m DBH) broadleaf tree, several kilometres downhill from the Preserve headquarters. The surrounding habitat is a mixture of disturbed forest and pasture, at an elevation of about 1100 m. This is near the upper elevational limit for E. burchelli in the area (William Haber, pers. comm.) We first noticed the attack on 27 July 1988 late in the morning, but local residents claimed it had begun the previous afternoon. Army ants were entering the wasp nest cavity and extracting wasp brood (larvae and pupae) when we arrived, and continued to do so during our last observation at 1500 h that afternoon. The raid spanned a period of at least 24 h though it is uncertain whether it had continued through the night, when army ants usually bivouac (Franks 1989). The wasps were identified as Agelaia yepocapa (formerly Stelopolybia yepocapa). This is the first record of an A. yepocapa nesting site; like most