Cloud Forest Site Research Articles

Floral phenology of an Andean bellflower and pollination by buff-tailed sicklebill hummingbird.

The Andean bellflowers comprise an explosive radiation correlated with shifts to specialized pollination. One diverse clade has evolved with extremely curved floral tubes and is predicted to be pollinated exclusively by one of two parapatric species of sicklebill hummingbirds (Eutoxeres). In this study, we focused on the floral biology of Centropogon granulosus, a bellflower thought to be specialized for pollination by Eutoxeres condamini, in a montane cloud forest site in southeastern Peru. Using camera traps and a pollination exclusion experiment, we documented E. condamini as the sole pollinator of C. granulosus. Visitation by E. condamini was necessary for fruit development. Flowering rates were unequivocally linear and conformed to the “steady‐state” phenological type. Over the course of >1800 h of monitoring, we recorded 12 E. condamini visits totaling 42 s, indicating traplining behavior. As predicted by its curved flowers, C. granulosus is exclusively pollinated by buff‐tailed sicklebill within our study area. We present evidence for the congruence of phenology and visitation as a driver of specialization in this highly diverse clade of Andean bellflowers.

Anfibios del bosque nuboso de El Silencio de Los Ángeles, San Ramón de Alajuela, Costa Rica

We present the list of amphibians for the El Silencio de Los Ángeles Cloud Forest (Villa Blanca Hotel and Reserve) in San Ramón de Alajuela, Costa Rica, Central America. We performed nocturnal visual and acoustic surveys in the trail system, mainly from 2013 to 2014. We also received data from the local guides up to 2019. We compared the similarity of amphibian richness of our site against other premontane reserves in Costa Rica with a cluster analysis (Jaccard index, single linkage). We recorded 26 species distributed in 16 genera, eight families and two orders. Notrotiton gamezi was the only threatened species detected. The El Silencio de los Ángeles Cloud Forest site is around 80 % similar to San Lorencito River Station and 55% to Nectandra Reserve. Containing 12% of the Costa Rica’s amphibian richness, this premontane woodland should be considered among the most important clouded forest in Central Costa Rica for amphibian conservation.

Arboreal Epiphytes in the Soil-Atmosphere Interface: How Often Are the Biggest “Buckets” in the Canopy Empty?

Arboreal epiphytes (plants residing in forest canopies) are present across all major climate zones and play important roles in forest biogeochemistry. The substantial water storage capacity per unit area of the epiphyte “bucket” is a key attribute underlying their capability to influence forest hydrological processes and their related mass and energy flows. It is commonly assumed that the epiphyte bucket remains saturated, or near-saturated, most of the time; thus, epiphytes (particularly vascular epiphytes) can store little precipitation, limiting their impact on the forest canopy water budget. We present evidence that contradicts this common assumption from (i) an examination of past research; (ii) new datasets on vascular epiphyte and epi-soil water relations at a tropical montane cloud forest (Monteverde, Costa Rica); and (iii) a global evaluation of non-vascular epiphyte saturation state using a process-based vegetation model, LiBry. All analyses found that the external and internal water storage capacity of epiphyte communities is highly dynamic and frequently available to intercept precipitation. Globally, non-vascular epiphytes spend <20% of their time near saturation and regionally, including the humid tropics, model results found that non-vascular epiphytes spend ~1/3 of their time in the dry state (0–10% of water storage capacity). Even data from Costa Rican cloud forest sites found the epiphyte community was saturated only 1/3 of the time and that internal leaf water storage was temporally dynamic enough to aid in precipitation interception. Analysis of the epi-soils associated with epiphytes further revealed the extent to which the epiphyte bucket emptied—as even the canopy soils were often <50% saturated (29–53% of all days observed). Results clearly show that the epiphyte bucket is more dynamic than currently assumed, meriting further research on epiphyte roles in precipitation interception, redistribution to the surface and chemical composition of “net” precipitation waters reaching the surface.

Cryptic diversity and ranavirus infection of a critically endangered Neotropical frog before and after population collapse

AbstractMesoamerican amphibian declines in apparently pristine and protected habitats have been severe, especially at elevations above 500 m sea level and have been linked to emerging diseases and a changing climate. The Craugastor punctariolus species series of direct developing frogs is endemic to the region and used to be comprised of 33 species, seven of which have known populations at present. One of these, C. ranoides, endemic to southern Nicaragua and Costa Rica, was historically found in cloud forest sites of Área de Conservación Guanacaste (ACG) in north‐west Costa Rica and extended into dry forest sites 20 km distant. Here, C. ranoides declined and disappeared from high elevation sites between the mid‐1980s and early 1990s, but populations persisted in the lowland dry forest. We compared the genetic richness and ranavirus infection status of C. ranoides from extant dry forest populations to historic museum specimens of now extinct ACG cloud forest populations using DNA sequence diversity at two mitochondrial loci and molecular screening for ranavirus. Extant dry forest populations of C. ranoides formed a monophyletic group which included historic specimens sampled at cloud forest sites. However, the extirpated ACG cloud forest population contained additional diversity: samples formed a divergent clade with unknown spatial distribution. Ranavirus was detected in both current and museum samples of C. ranoides and sequences from a 267‐nucleotide region of the major capsid protein gene shared 100% sequence identity with one another and with Frog virus 3. Our findings document cryptic diversity within an endangered species that has demonstrated no recovery in cloud forests and raises questions about Ranavirus and its potential link to the amphibian declines in this system. The presence of the same C. ranoides clade within present day and historical samples suggests a potential for effective translocation and repopulation of extirpated cloud forest populations.

Preserving butterfly diversity in an ever‐expanding urban landscape? A case study in the highlands of Chiapas, México

We examined the relationship between landscape structure and composition, geographic ranges, microhabitat characteristics and the diversity of butterflies (Papilionidae, Nymphalidae, Pieridae, Hesperiidae, Lycaenidae) in an expanding urban landscape in the highlands of Chiapas, Mexico. Between 2001 and 2016, mountain wetlands, secondary forest, and agro-pasture land, have declined significantly in area covered due to increasing housing activities and expansion of roads and conversion of land for cattle activity. Cloud forest exhibited a minor positive expansion in area, mostly through forest regeneration. In total, we recorded 3630 individuals from 90 species at key sites spanning natural, semi-natural and urban areas. A rarefaction curve analysis for local richness indicated that mountain wetland sites recorded the highest butterfly diversity. Logistic regression analyses suggested that species with narrow geographic ranges could be associated to cloud-forest sites, and that species with relatively more widespread distributions in the Neotropics were more likely to be classified as occurring in mountain wetland habitats. This was confirmed by IndVal analyses from which we identified 39 butterfly species as potential reliable land-cover indicators. Furthermore, canonical correspondence analyses suggested significant associations for the values of butterfly abundance and microhabitat variables such as canopy cover, open areas, presence of grasses, bare soil or rocks. It is a matter of urgency that should put in place monitoring schemes to assess occupancy and change so we can assess changes in the status of butterfly species in rapidly-expanding urban landscapes in tropical Mexico.

Fog Water Chemical Composition on Ailaoshan Mountain, Yunnan Province, SW China

ABSTRACT Between December 2015 and March 2016, fog water was collected at the subtropical mountain cloud forest site Ailaoshan in SW China at 2476 m above mean sea level. An active fog collector was employed to collect 117 samples during more than 140 hours of fog, covering 6 major fog events. The chemical analysis included acidity and inorganic ion concentrations. The median pH values of the fog events varied between 3.7 and 4.2, characterizing the fog water as acidic (pH < 5.0) to very acidic (pH < 4.0). The ion composition was dominated by H+, NH4+, SO42– and NO3–, which made up more than 86% of the total ionic concentration (TIC). The generally rather high ion concentration levels cannot be explained by nearby emission sources but rather by long-range transport of air pollutants from various sources in East Asia. During one event on February 8, 2016, it is evident that it was the emissions from a large coal-fired power plant in Myanmar that led to high concentrations of sulphuric acid. This pilot study of fog chemistry in rural, mountainous SW China should be complemented by studies spanning the moist summer monsoon season and covering more chemical species.

Rediscovery of the Endangered frog Phrynopus montium (Shreve, 1938) Amphibia, Anura, Craugastoridae) in the cloud forest of central Peru.

Phrynopus montium (Shreve, 1938) was described from Cascas, Junín Department, Peru, at an undetermined elevation between 3000 and 4000 m a.s.l. in the Cordillera Central. With the exception of the type specimens used in the original description, no additional sightings of P. montium had been reported for 76 years. Additionally, its coloration in life, microhabitat use, and precise elevational distribution remained unknown. During a field expedition conducted in 2014, two individuals of P. montium were found at an upper cloud forest site in central Peru, 8.7 km south from Hacienda Cascas. Here, I describe the coloration in life, microhabitat use, and elevation of these individuals.

Home Range Size and Nocturnal Roost Locations of Western Chat-Tanagers (Calyptophilus tertius)

Western Chat-Tanagers (Calyptophilus tertius) are a rare and globally vulnerable songbird endemic to the island of Hispaniola. We conducted a radio-telemetry study of non-breeding Western Chat-Tanagers at two adjacent cloud forest sites in Sierra de Bahoruco in southwestern Dominican Republic during March and April of 2010. Male home ranges averaged 2.18 ± 0.25 ha in size (n = 4) and were significantly larger than those of females (0.88 ± 0.04 ha; n = 2). However, core use areas did not differ significantly between the sexes. We assumed that males and females with overlapping home ranges were mated pairs. At night, two putative pairs roosted an average distance apart of 15.8 ± 3.5 m (n = 7 observations).

A method for quantifying cloud immersion in a tropical mountain forest using time-lapse photography

Quantifying the frequency, duration, and elevation range of fog or cloud immersion is essential to estimate cloud water deposition in water budgets and to understand the ecohydrology of cloud forests. The goal of this study was to develop a low-cost and high spatial-coverage method to detect occurrence of cloud immersion within a mountain cloud forest by using time-lapse photography. Trail cameras and temperature/relative humidity sensors were deployed at five sites covering the elevation range from the assumed lifting condensation level to the mountain peaks in the Luquillo Mountains of Puerto Rico. Cloud-sensitive image characteristics (contrast, the coefficient of variation and the entropy of pixel luminance, and image colorfulness) were used with a k-means clustering approach to accurately detect cloud-immersed conditions in a time series of images from March 2014 to May 2016. Images provided hydrologically meaningful cloud-immersion information while temperature-relative humidity data were used to refine the image analysis using dew point information and provided temperature gradients along the elevation transect. Validation of the image processing method with human-judgment based classification generally indicated greater than 90% accuracy. Cloud-immersion frequency averaged 80% at sites above 900m during nighttime hours and 49% during daytime hours, and was consistent with diurnal patterns of cloud immersion measured in a previous study. Results for the 617m site demonstrated that cloud immersion in the Luquillo Mountains rarely occurs at the previously-reported cloud base elevation of about 600m (11% during nighttime hours and 5% during daytime hours). The framework presented in this paper will be used to monitor at a low cost and high spatial resolution the long-term variability of cloud-immersion patterns in the Luquillo Mountains, and can be applied to ecohydrology research at other cloud-forest sites or in coastal ecosystems with advective sea fog.

Winter habitat disturbance influences density and territory size of a Neotropical migratory warbler

Migratory birds face population declines attributed to habitat loss and modification in the wintering grounds, which may influence body condition, time of arrival to breeding grounds, and future reproductive opportunities. Despite this, very little is known of the wintering ecology of migratory birds. During three winter seasons, we assessed Wilson’s Warbler (Cardellina pusilla) density, territory size, and body condition at three cloud forest sites in southeast Mexico, with differing degrees of habitat disturbance and forest cover: preserved 125 ha of cloud forest actively protected for 40 years; moderately disturbed site of 67.5 ha of cloud forest under protection for 29 years; and highly disturbed unprotected site with 6.5 ha of cloud forest. We determined warbler density using 20 unlimited-radius point-counts at each site. We also captured and measured birds (n = 74) over three years, to obtain a body condition index, and re-sighted color-banded birds to determine individual territory size at each site. Bird densities were two times greater and territory size was smaller in the conserved forest site compared to disturbed sites with lower forest cover. However, there was no significant difference among sites in the body condition index of territorial birds. Furthermore, territory size and body condition were relatively constant among years for birds in conserved forest, but exhibited high inter-annual fluctuations at disturbed forest sites. Considering the higher bird density, smaller territory size, and inter-annually consistent body condition at the conserved cloud forest site, we propose that this represents higher quality wintering habitat for Wilson’s Warblers.

On the biology of Holopothrips chaconi sp.n. (Thysanoptera: Phlaeothripinae) from leaf-vein galls on Piper species (Piperaceae) in Costa Rica

&lt;p&gt;La mayoría de las especies del género neotropical &lt;em&gt;Holopothrips &lt;/em&gt;se asocian a las agallas de plantas pero se sabe muy poco de su biología. Aquí, se provee observaciones sobre la biología de una nueva especie de &lt;em&gt;Holopothrips&lt;/em&gt; que se asocia a las agallas de venas foliares en cuatro especies de &lt;em&gt;Piper &lt;/em&gt;en un bosque nuboso (Zurquí de Moravia) de Costa Rica. Esta especie coloniza las agallas luego de que el cecidómido inductor o un parasitoide del mismo emerge, y aparentemente varias generaciones de trips ocupan las agallas vacías. Un total de 175 agallas vacías en 34 hojas fueron recolectadas, llevadas al laboratorio para disección bajo el microscopio y se cuantificó su contenido. &lt;em&gt;Holopothrips&lt;/em&gt; ocupaba aproximadamente el 75 % de las hojas con agallas y en ellas el 40 % de las agallas. Se encontró toda combinación de adultos, ninfas y huevos, lo cual implica que los trips adultos entran y salen y posiblemente no defienden sus agallas de la invasión de otros miembros de su especie. Sin embargo, adultos y ninfas, levantan la punta del abdomen al ser perturbados, emitiendo un olor distintivo que sugiere una reacción defensiva ante posibles depredadores. La evidencia preliminar indica que se alimentan del tejido interior de la agalla y pasan muy poco tiempo fuera de la misma. Se describe la especie nueva y es una de sólo cuatro especies conocidas de &lt;em&gt;Holopothrips &lt;/em&gt;que poseen dos pares de setas epimorales en el pronoto. Al compararla con estas otras especies surge una marcada variación en la espermateca de la hembra y en las placas del poro esternal en el macho, los cuales se ilustran. Se requiere más investigación para confirmar la sugerencia que varias generaciones de trips ocupan las agallas vacias, para determinar si es cierto que los trips adultos se mueven entre agallas, y para explorar en más detalle la supuesta defensa química.&lt;/p&gt;

Applications of geographic information systems and remote sensing techniques to conservation of amphibians in northwestern Ecuador

The biodiversity of the Andean Chocó in western Ecuador and Colombia is threatened by anthropogenic changes in land cover. The main goal of this study was to contribute to conservation of 12 threatened species of amphibians at a cloud forest site in northwestern Ecuador, by identifying and proposing protection of critical areas. We used Geographic Information Systems (GIS) and remote sensing techniques to quantify land cover changes over 35 years and outline important areas for amphibian conservation. We performed a supervised classification of an IKONOS satellite image from 2011 and two aerial photographs from 1977 and 2000. The 2011 IKONOS satellite image classification was used to delineate areas important for conservation of threatened amphibians within a 200 m buffer around rivers and streams. The overall classification accuracy of the three images was ≥80%. Forest cover was reduced by 17% during the last 34 years. However, only 50% of the study area retained the initial (1977) forest cover, as land was cleared for farming and eventually reforested. Finally, using the 2011 IKONOS satellite image, we delineated areas of potential conservation interest that would benefit the long term survival of threatened amphibian species at the Ecuadorian cloud forest site studied.

The tip of the iceberg: a distinctive new spotted-wing Megaselia species (Diptera: Phoridae) from a tropical cloud forest survey and a new, streamlined method for Megaselia descriptions.

A new Megaselia species, M. shadeae, with a large, central, pigmented and bubble-like wing spot and a greatly enlarged radial wing vein fork, is described from Zurquí de Moravia, Costa Rica. As part of the Zurquí All Diptera Biodiversity Inventory (ZADBI) project, it represents the first of an incredible number of new phorid species to be described from this one Costa Rican cloud forest site. A new, streamlined method of description for species of this enormous genus of phorid flies is presented.

Bromeliad rain: An opportunity for cloud forest management

Large numbers of epiphytic bromeliads are regularly harvested from the canopy of cloud forests for traditional uses and illegal trade, with detrimental effects on the viability of populations. Since a significant proportion of natural mortality in epiphytes is caused by detachment from the support trees, harvesting of fallen plants represents a potential supply for commercial use that would have no impact on bromeliad population dynamics. We evaluated the potential of four cloud forest sites in southern Mexico to supply epiphytic bromeliads for commercialization. Bromeliad diversity and abundance was determined by sampling eight trees in each forest site and the number of fallen plants from these trees was recorded over three years. To determine the size of the potential harvest from the forest floor, the rate of bromeliad fall, and the species, condition and size of fallen individuals were recorded monthly in 10 plots (10×10m) at each site over a period of five months. Bromeliad fall rate varied from 26,910 to 92,712 rosettes ha−1 y−1. Of these, ca. 60% (16,770 to 55,992 rosettes ha−1 y−1) of the 18 species identified were in a suitable condition for commercialization. Diversity and abundance in the canopy were positively related to that of the fallen rosettes (P<0.05), indicating that the harvesting rate can be estimated from population densities in the host trees and that the fallen plants could therefore be used to indirectly evaluate the epiphyte community. Assessment revealed that the forest canopy could act as a nursery to supply a constant “rain” of bromeliads with minimum production costs. Even one ha of cloud forest can supply thousands of marketable bromeliads every year. Harvesting of fallen epiphytic bromeliads could add to the diversification of cloud forest management, contribute to the reduction of excessive canopy harvesting pressure and supply plants for forest enrichment programs. The results of this study are discussed in the context of the local stakeholder participation and national conditions.

The impact of grazing on dung beetle diversity depends on both biogeographical and ecological context

AbstractAimWe analysed the effects of grazing on the diversity and structure of dung beetle communities to see whether the biogeographical and ecological contexts influence dung beetle responses. We hypothesized that the responses of dung beetle communities are modulated by both the ecological conditions resulting from the transformation of native vegetation into grazing areas, and the history of the species inhabiting different biogeographical provinces.LocationThe state of Hidalgo, in the Mexican Transition Zone, central Mexico.MethodsWe used a standardized hierarchical sampling procedure in three biogeographical provinces located in Hidalgo. Within each province, we identified the dominant vegetation types, and within these we identified the sites with native vegetation and those modified by grazing. The design included 800 baited pitfall traps, and allowed us to study the response of dung beetle communities with different biogeographical histories to ecological context.ResultsWe captured 8707 beetles belonging to 37 species and 17 genera in the subfamily Scarabaeinae. We found that grazing areas only had a negative effect on dung beetle diversity in tropical forest; conversely, in dry environments (pine–oak forest and xerophilous scrubland) diversity in grazing areas was higher than in the native vegetation sites. We did not detect a clear effect in cloud forest sites. Species turnover between the native vegetation and pastures was high locally, and low over larger spatial scales (vegetation type or biogeographical province). In all four vegetation types grazing was associated with differences in dung beetle community composition.Main conclusionsThe impact of grazing on dung beetle diversity is dependent to a considerable degree on the local ecological conditions and the biogeographical context that has shaped the composition of communities over time.

Diversity and phylogenetic community structure of ants along a Costa Rican elevational gradient

The diversity and phylogenetic community structure of many organisms is negatively affected by factors that covary with elevation. On the Pacific slope of the Cordillera Guanacaste within Area de Conservación Guanacaste (ACG) in northwestern Costa Rica we found a negative relationship between elevation and ant diversity on each of three volcanos. This pattern was evident when diversity was measured through molecular operational taxonomic units (MOTU) or by phylogenetic diversity (PD) based on DNA barcodes or a multi‐gene phylogeny. We observed an asymmetrical mid‐elevation peak at approximately 600–800 m and we found high species turnover between sites on the same mountain and among the three mountains. At the highest elevation cloud forest sites we found evidence of significant phylogenetic clustering, the expected result of environmental filtering. The narrow elevational range of each species, coupled with the high diversity at each sampling point, emphasizes that climate change will bring strong changes in the location and composition of biodiversity on these mountains. The structure and composition of the hyperdiverse communities present at any one elevation is extremely vulnerable to a changing climate.

Comparison of sonic anemometer performance under foggy conditions

A sonic anemometer comparison was performed at a mountain cloud forest site in Taiwan to evaluate the effect of fog on sonic anemometers performance, with particular emphasis to their employment in eddy-covariance applications. Four sonic anemometers (Campbell CSAT3, Gill R3-50, METEK USA-1, and R.M. Young 81000VRE) were tested for 15 consecutive days with an overall fog duration of 86h.Four aspects were analyzed: (1) spike statistics during foggy and non-foggy conditions, (2) spectral and co-spectral analyses before, during, and after 16 fog events, (3) correlations between turbulence characteristics of wind and temperature, and (4) flux error estimations.All sonic anemometers produce more spikes when the visibility is below 1000m, compared to conditions with visibilities above 1000m. However, the overall number of spikes caused by fog is generally low and therefore of no concern for any of the tested sonic anemometers.Spectral analyses showed that for most anemometers fog mostly affects spectra of the sonic temperature. Here, the high frequency range is either damped or amplified. These effects worsen with increasing duration and density of fog. In case of the 81000VRE and the USA-1, all three wind component spectra, sonic temperature spectra as well as the co-spectra of w’T’ and w’u’ show white noise in the high frequency range during dense fog. The CSAT3 shows noise only in the high frequency range of the sonic temperature and the co-spectra of w’T’. Smallest sensitivity to fog was observed for the R3-50. Nevertheless, differences in resulting fluxes are usually smaller than the flux error of the measurements. Due to the results of the spectral analysis and small flux errors the R3-50 seems to be suited best for eddy covariance measurements and process studies under dense foggy conditions.

Does canopy wetness matter? Evapotranspiration from a subtropical montane cloud forest in Taiwan

Evapotranspiration (ET) and canopy wetness were measured over a 2-year intensive field campaign at the Chi-Lan Mountain cloud forest site in Taiwan. Eddy covariance and sap flow methods were applied to measure ET and tree sap flow of the endemic yellow cypress (Chamaecyparis obtusa var. formosana). ET was 553 mm yr−1 over the study period with an annual rainfall and fog deposition of 4893 and 288 mm yr–1, respectively. The duration of canopy wetness exceeded actual fog or rain events (mostly in the afternoon), and the intercepted water was evaporated later in the following dry morning. The cumulative wet duration accounted for 52% of time over the study period, which was longer than the duration of rainfall and fog altogether (41%). As it adapted to the extremely moist environment, the yellow cypress behaved in a wet-enhanced/dry-reduced water use strategy and was sensitive to short periods of dry atmosphere with high evaporation potential. During dry days, the sap flow rate rose quickly after dawn and led to conservative water use through midday and the afternoon. During periodically wet days, the canopy was mostly wetted in the morning, and the interception evaporation contributed largely to the morning ET. The initiation of morning sap flow was postponed 1–3 h, and the sap flow rate tended to peak later at midday. The midday canopy conductance was higher in the periodically wet days (10.6 mm s–1) as compared with 7.6 mm s−1 in the dry days. Consequently, the dry-reduced water use strategy led to much lower annual ET with respect to the available energy (~46%) and high precipitation input (~11%). The moist-adapted ecohydrology we report reveals the vulnerability of montane cloud forests to prolonged fog-free periods. More research is urgently needed to better understand the resilience of these ecosystems and formulate adaptive management plans. Copyright © 2012 John Wiley & Sons, Ltd.

Mercury concentrations in tropical resident and migrant songbirds on Hispaniola

Despite growing concerns over mercury (Hg) exposure to humans and wildlife on a global scale, little is known about Hg bioaccumulation in the New World tropics. From 2005 to 2011, we monitored Hg concentrations in blood of nine avian species occupying a geographic range of tropical wet broadleaf sites on the island of Hispaniola, including eight passerines (two Nearctic-Neotropical migrant and six resident species) and one top order predatory accipiter. Invertivorous songbirds were further differentiated by foraging guild, with six species of ground-foragers and two species of foliage-gleaners. Blood Hg concentrations were orders of magnitude higher in birds sampled in central and southern cloud forest sites (1,000-1,800 m elevation) than in northern and northeastern rainforest sites (50-500 m elevation), with migratory and resident species both showing 2-20× greater blood Hg concentrations in cloud forests than in rainforests. Within cloud forest sites, ground-foraging species had higher Hg concentrations than foliage-gleaning species. Top order predatory sharp-shinned hawks (Accipiter striatus) had the highest blood Hg concentrations among all species, suggesting that Hg biomagnification is occurring in terrestrial forests of Hispaniola. Two migrant songbird species overwintering on the island had higher blood Hg concentrations than have been recorded on their North American breeding grounds. Future studies should seek to elucidate sources of variation in atmospheric Hg deposition on Hispaniola and to quantify the dynamics of Hg cycling in tropical forest ecosystems, which may differ in important ways from patterns documented in temperate forest ecosystems.

Book review: Headwaters in the clouds

news and update book review Headwaters in the clouds Tropical Montane Cloud Forests, by L. A. Bruijnzeel, F. N. Scatena & L. S. Hamilton (editors), 2011, Cambridge University Press, 768 pp. £65 (Hardback) ISBN: 9780521760355; http:// www.cambridge.org/ Tropical Montane Cloud Forests (TMCFs) are gaining in scientific popularity since a first international symposium on this ecosystem was held in Puerto Rico in 1993. The promotion of the meeting by the UNESCO International Hydrological Programme illustrates a far-reaching effect of cloud forests: they act as water collectors for tropical forelands. TMCFs also harbour extraordinarily many plant species, contributing to outstanding positions in each of the five hottest spots of plant diversity. Why edit yet another comprehensive opus on TMCFs, after several previous fundamental works, despite their encompassing under 0.15% of the global terrestrial surface? The answer is clear to those who know this biome: there hardly exists a more fascinating environment than exuberant, moss-covered cloud forests, often called elfin forests due to their mystical appearance. They form highly complex ecosystems, which on different continents show divergent biocœnoses because of their fragmentation and isolated position within distinct tropical mountains in the Neotropics and, to a lesser degree, in the Paleotropics, and in a few cases even on Pacific islands. This book deals with general features of TMCFs (12 chapters) and contains examples from Middle America (21), South America (19), Southeast Asia (10), Africa (5) and Oceania / Australia (5). Most contributions result from a conference in Hawaii in 2004. A first glance reveals a nearly complete thematic spectrum. The book is subdivided into seven sections with a total of 72 chapters. The first part contains general features of TMCFs. Altitudinal distributions are presented in an introductory chapter, though integrative references to surrounding belts are missing. A useful GIS-based modelling approach provides instructive data on TMCF resources and losses including tables on their dimensions and distributions. Interestingly, Indonesia and Congo rank first in national extent, with neotropical countries falling lower down. A climate chapter is based on a dataset of 477 weather stations in cloud forest sites. Many graphs present vast dot clouds of data from stations between 200 and 5,000 m asl, which raises the confusing suspicion that TMCFs occur in regions of extremely dissimilar climates. A short but informative chapter on changes in fog precipitation should have been part of a later section, as also applies to one on epiphytism. Comments on global and local soil variations, as well as on nutrient cycling and limitation in TMCFs, provide convincing and compact estimations. Coloured maps of TMCF distribution highlight their restricted extent and natural fragmentation on a global scale. The subsequent and sadly brief section on regional aspects of floristic and faunistic diversity contains fascinating information from all TMCF- bearing continents. The range extends from research on epiphyte-diversity on solitary trees (up to 4,806 individuals of 114 vascular plant species on one single fig tree!) to potential and actual distribution patterns of the mountain tapir and Andean bear. The only point of criticism is that in a book on a biological realm this section could have been broader. The third section on hydrometeorology covers a broad remit since fog, rain and their interception are decisive triggers for the formation of TMCFs. Several parts display the importance of potential evaporation and irradiation as driving forces for the variable character of forests. Additionally, the degrees of litter mineraliation and soil acidity become crucial causes of ecological peculiarities. The contributions vary from rather specialist methodical content (e.g. measuring interception, usage of stable isotopes for diagnoses of precipitation origins) to comments on the water frontiers of biogeography 4.1, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society