Mountain Cloud Forest Research Articles

Spatiotemporal distribution of organochlorine pesticides in the upper La Antigua watershed, Veracruz Mexico

Even though the use of organochlorine pesticides has been prohibited since the last century their presence is still being recorded around the world. In the upper La Antigua watershed, Veracruz, Mexico we have reported concentrations of these contaminants in different compartments of the riverine ecosystems. This is of relevance due to their potential disruptive endocrine effect on the vertebrates drinking the water or feeding in the riverine area. In this study we evaluated concentrations of organochlorine pesticides (OCPs) in streams running throughout mountain cloud forest and two different types of land use, pasture lands and coffee plantations. Water and periphyton samples were collected during the wet and the dry seasons from streams located in independent micro-basins. Spatial explicit analyzes show that the concentrations measured are independent of the distribution of the streams in the geographical area sampled. However seasonal differences were found during the dry season in the water and during the rainy season in periphyton. While OCPs in water support the idea that micro-basins can be used as independent monitoring units, OCPs in periphyton can be indicators of the effect of different land use. Some concentrations of all the OCPs registered had values above the limits for tap water.

Implementing ITS1 metabarcoding for the analysis of soil microeukariotic diversity in the Mountain Cloud Forest

PurposeIn threatened diversity hotspots, such as mountain cloud forests, microbiome studies have focused essentially on bacteria. Unlike prokaryotic microbiomes, the study of the microeukaryotes has largely been restricted to the visual identification of specific groups. Herein, microeukaryotic edaphic diversity from a pristine mountain cloud forest (MCF) of Mexico was analyzed via the metabarcoding of the ITS1 region of ribosomal DNA.Materials and methodsAn exploratory triangular sampling was conducted in the mountain cloud forest located in El Relámpago Mount, Santiago Comaltepec, Oaxaca, Mexico. Each vertex was located adjacent to a dominant plant species in the ecosystem (Oreomunnea mexicana and Alsophila salvinii). After DNA extraction the ITS1 region (rDNA) was amplified. Microeukaryotic sequences were filtered by computational subtraction against the ITS2 Database. Next, alpha and beta diversity indexes were calculated, and the relationship between abiotic variables and diversity patterns were inferred by means of a Canonical Correspondence Analysis.ResultsOverall, 138 inferred sequence variants were identified, including 87 protists, 35 animals (microfauna), and 16 algae. Within the animals, the nematodes were the dominant group, chlorophytes dominated algae, and in Protista, no dominance patterns were observed given the high diversity and equitability of this group. Soil available carbon, carbon degrading enzymes and the pH play a key role in modeling the community structure. Remarkably, high beta diversity levels were obtained, evidencing a strong spatial heterogeneity at the small scale.ConclusionsThe ITS metabarcoding proved to be a useful tool to conduct multi-taxa diversity assessments for microeukaryotes, allowing the identification of alpha and beta diversity patterns and overcoming limitations of sampling and the direct observation of individuals. The results presented in this work evidenced high microeukaryotic diversity levels in the soil of MCF and encourage future studies aiming to explore the taxonomic diversity of individual taxa.

Population genetics of the endemic Large-crested toad (Incilius cristatus): a declining and critically endangered species

Abstract The Large-crested toad is an endemic species of the mountain cloud forests of the Sierra Madre Oriental in Mexico. It is listed as endangered, and the population trend is decreasing. We used mitochondrial fragments 12S (450 bp) and cytochrome b (410 bp) from four toads’ populations from remnant fragments of mountain cloud forest in Puebla and Veracruz to estimate the genetic’ structure, gene flow, and demographic history. The 12S gene had a single haplotype and null nucleotide diversity. The cytochrome b fragment showed 4 haplotypes, intermediate nucleotide diversity (), and strong genetic structuring (). Demographic history suggests that there is a low effective population size (), possibly due to post-bottleneck expansion and contraction events in some populations. Current difficulty finding individuals at localities where they had been previously documented suggests that the population continues to decline, resulting in low diversity and gene flow. Habitat fragmentation and loss, as well as water pollution at breeding sites, increases the probability of extinction of this species. The importance of establishing conservation strategies for the habitat and genetic diversity of the remaining populations is highlighted.

Belowground carbon stored in a tropical mountain cloud forest of east-central Mexico

Abstract Carbon stocks in root biomass and soil organic carbon (SOC) were analysed in tropical mountain cloud forest (TMCF) of Mexico. Additionally, the hypothesis that the concentration of roots in the forest is not homogeneous but that they are concentrated near the trunks of the trees was evaluated. Root biomass was 707.68 ± 150.41 g·m−2, which stores ∼353.85 ± 75.21 g·C·m−2. Coarse roots contributed 36.8%, fine roots 35.5%, and very fine roots 27.7% of the total biomass. The results did not support the hypothesis that fine roots are concentrated near the trunks of the trees. On average, SOC was 108.23 ± 33.21 Mg·C·ha−1. Mean C stored in the soil (C in roots + SOC) was 111.77 ± 32.97 Mg·C·ha−1. The TMCF is an ecosystem with a high potential for soil carbon storage, with similar C values reported to those in other tropical forests.

Functional traits and adaptive capacity of cloud forest Ternstroemia species in response to climatic variation

Tropical Mountain Cloud Forests (TMCFs) produce distinct climatic gradients that can both constrain and facilitate the presence of tree species and/or specific combinations of functional traits. Local climatic adaptation allows for maximum fitness under hydric stress, resulting in specific morphological adaptations to the TMCF tree species. In this study, we assessed the hypothesis that the functional traits of two uncommon TMCF species (Ternstroemia huasteca and T. sylvatica) would show similar morpho-anatomical adjustments to climate variation. Our research questions were: how do the Ternstroemia functional traits vary interspecifically between TMCFs? Which of these two species is the most climatically vulnerable? To answer these questions, we examined differences in wood anatomical traits and leaf vascular tissues between both species. For this, we assessed the effects of temperature, precipitation, and evapotranspiration on the functional traits of Ternstroemia in different TMCFs. Our analyses suggested that, not all climatic factors considered affected the functional traits of Ternstroemia at the same magnitude. These findings provide insights into the ecophysiological functional trait adaptation mechanisms in response to hydraulic deficit in TMCF understory tree species.

Taxonomic Novelties in Sapranthus (Annonaceae): a new large-sized species endemic to the mountain cloud forest of Central America

Sapranthus (Annonaceae) is a Neotropical genus comprising ten small tree species, most of which inhabit the tropical dry forests of Mexico and Central America. Morphological characteristics of these species are quite variable and taxonomically informative, but the morphological affinities among them have not been studied. A multivariate cluster analysis was carried out to infer the morphological affinities among all species of Sapranthus, and to establish the position of a new species, S. pinedai, a shade tree used in the coffee plantations of Guatemala and El Salvador. This new species, illustrated and described herein, is recognized by a unique combination of features identified through comparisons with morphologically similar taxa, and a preliminary assessment of the conservation status of the new species was calculated. The results presented here show that Sapranthus forms four morphological groupings in two main clusters. The new species is more similar to S. microcarpus and S. campechianus, but differs from both species by its essentially glabrous leaves, short pedicels, fewer carpels, greater number of ovules per carpel, biseriate ovules, larger sessile fruits with a thick testa, and by its several lunate to wedge-shaped seeds. These morphological groupings provides new insights into the understanding of the sectional classification of the genus Sapranthus, the geographic distribution of its species, and the morphological affinity of the new species.

Predation of oak acorns by Baird's tapir in one of the last remnants of mountain cloud forest in Southern Mexico

The consumption of fruits and seeds by mammals can have a strong impact on the regeneration of tropical forests. Our knowledge of this biotic interaction has steadily increased recently but it remains fragmentary. This is largely due to most of the studies focusing on a small proportion of the diverse mammals and plants involved in these interactions and to the fact most commonly used methods provide just partial information about the whole seed dispersal/predation process. The use of camera traps has opened the opportunity to greatly improve our knowledge of the intricacies of frugivory and seed predation by increasing the likelihood to record very secretive animal species and providing detailed accounts of their behavior. Based on camera trap data we report acorn consumption of Quercus benthamii and Q. sapotifolia by the threatened Baird's tapir (Tapirus bairdii). This study was conducted in the largest remnant of Mountain cloud forest in Mexico, located in El Triunfo Biosphere Reserve (ETBR) in the state of Chiapas. Despite the fact that ten mammal species were recorded in the focal trees, only two of them (T. bairdii and Sciurus deppei) were documented exhibiting acorn consumption. We obtained 82 videos showing the consumption of Q. benthamii acorns by tapirs (sampling effort = 133 camera trap days, n = 8 trees) with an average of 6.04 ± 3.56 (± sd) minutes spent on this activity. In comparison, we only obtained one video of a tapir consuming Q. sapotifolia acorns (sampling effort = 264 camera trap days, n = 5 trees) during 35 s. Consumption of these Quercus species by tapir was not previously reported. Moreover, our study is the first (to our knowledge) to show video-recorded evidence of the interaction between tapirs and Quercus trees. Due to tapirs' large body size, the consumption of acorns might be an important source of mortality for some Quercus species (e.g., Q. benthamii).

Distinct epiphyte responses to drought in tropical mountain cloud forests

AbstractEpiphytes are often considered to be significantly impacted by precipitation changes because their lack of direct access to soil water. However, few in situ studies have examined how reduction in water availability may affect epiphyte growth. Using a unique stemflow collection and diversion device, we examined the effects of stemflow reduction of 25% and 50% on the growth and leaf traits of two common but distinct epiphyte species in a subtropical forest. One species (Asplenium nidus) has a large substrate, and another (Haplopteris zosterifolia) without known water storage structure. The 25% stemflow reduction had limited effects on the growth and leaf traits of the two epiphytes, indicating that 25% stemflow reduction did not reach the water stress threshold for the two epiphytes. It is also possible that the actual reduction in water availability was less than 25% since epiphytes do not use all available stemflow and there could be other sources of water such as fog and throughfall. The 50% stemflow reduction reduced leaf number and leaf area of H. zosterifolia, but not A. nidus, likely because water stored in the large substrate of A. nidus mitigated the impact of stemflow reduction. The thinner leaves, smaller leaf dry matter content, and lower δ13C of A. nidus than H. zosterifolia support the role of water storage of the substrate of A. nidus on mitigating water stress. The 50% stemflow reduction increased leaf thickness, leaf dry matter content of H. zosterifolia, and thickness of abaxial cuticle layer of both epiphytes but had no effect on δ13C. Stemflow reduction had no effects on nutrient concentration and nutrient ratios of both epiphytes suggesting that the epiphytes were able to maintain stoichiometry. Our results indicate that the epiphytes minimized nonstomatal water loss when environmental dryness increased but maintained stomata conductance, which could be important in minimizing the impacts of drought on plant growth and quickly resuming growth once drought ends. Our study highlights that not all epiphytes are similarly vulnerable to drought and precipitation reduction may change the relative abundance of epiphytes with and without water storage structure.

Land use scenarios, seasonality, and stream identity determine the water physicochemistry of tropical cloud forest streams.

Land use is a major factor determining stream water physicochemistry. However, most streams move from one land use type to another as they drain their watersheds. Here, we studied three land use scenarios in a tropical cloud forest zone in Mexico. We addressed three main goals, to: (1) assess how land use scenarios generate different patterns in stream physicochemical characteristics; (2) explore how seasonality (i.e., dry, dry-to-wet transition, and wet seasons) might result in changes to those patterns over the year; and (3) explore whether physicochemical patterns in different scenarios resulted in effects on biotic components (e.g., algal biomass). We studied Tropical Mountain Cloud Forest streams in La Antigua watershed, Mexico. Streams drained different three scenarios, streams with (1) an upstream section draining forest followed by a pasture section (F-P), (2) an upstream section in pasture followed by a forest section (P-F), and (3) an upstream forest section followed by coffee plantation (F-C). Physicochemistry was determined at the upstream and downstream sections, and at the boundary between land uses. Measurements were seasonal, including temperature, dissolved oxygen, conductivity, and pH. Water was analyzed for suspended solids, alkalinity, silica, chloride, sulfate, magnesium, sodium, and potassium. Nutrients included ammonium, nitrate, and phosphorus. We measured benthic and suspended organic matter and chlorophyll. Streams presented strong seasonality, with the highest discharge and suspended solids during the wet season. Scenarios and streams within each scenario had distinct physicochemical signatures. All three streams within each scenario clustered together in ordination space and remained close to each other during all seasons. There were significant scenario-season interactions on conductivity (F = 9.5, P < 0.001), discharge (F = 56.7, P < 0.001), pH (F = 4.5, P = 0.011), Cl- (F = 12.2, P < 0.001), SO42- (F = 8.8, P < 0.001) and NH4+ (F = 5.4, P = 0.005). Patterns within individual scenarios were associated with stream identity instead of land use. Both P-F and F-C scenarios had significantly different physicochemical patterns from those in F-P in all seasons (Procrustes analysis, m12 = 0.05-0.25; R = 0.86-0.97; P < 0.05). Chlorophyll was significantly different among scenarios and seasons (F = 5.36, P = 0.015, F = 3.81, P = 0.42, respectively). Concentrations were related to physicochemical variables more strongly during the transition season. Overall, land use scenarios resulted in distinctive water physicochemical signatures highlighting the complex effects that anthropogenic activities have on tropical cloud forest streams. Studies assessing the effect of land use on tropical streams will benefit from assessing scenarios, rather than focusing on individual land use types. We also found evidence of the importance that forest fragments play in maintaining or restoring stream water physicochemistry.

The diversity of moths (Erebidae: Arctiinae: Arctiini) from threatened mountain cloud forests in the Mesoamerican biodiversity hotspot

The diversity of moths (Erebidae: Arctiinae: Arctiini) from threatened mountain cloud forests in the Mesoamerican biodiversity hotspot

Pattern of post-dispersal fruit removal of Persea hintonii C.K. Allen by vertebrates in mountain cloud and pine-oak forests in western Mexico

Background: High post-dispersal fruit-seed removal can be a bottleneck for successful propagation to new areas of plant populations with fragmented distribution, as in cloud forest. Therefore, it is important to know how vegetation and fruit-eating behavior will influence the spatial removal pattern. Questions and/or Hypotheses: How do vegetation structure and density influence fruit removal of Persea hintonii in potential propagation areas? Study site and dates: Las Joyas Scientific Station, Sierra de Manantlán Biosphere Reserve, Jalisco, Mexico. April-May 2015. Methods: The number of fruits removed were recorded in treatments excluding of different size vertebrates, in areas with a dense or sparse understory within two forest types plus open areas with shrub cover. To identify vertebrate fruit-removing species, camera-traps were placed under the canopy of P. hintonii trees with high fructification amounts. Results: Fruit removal was lower in areas of low understory density at pine-oak forests (11.17 ± 5.30 %) and gap areas (25.5 ± 2.39 %), compared to subtropical cloud forests (72.51 ± 0.60 %). The number of days to start the fruit removal was lower in the cloud and pine-oak forests with dense understory than in those with a sparse understory. We identified six mammal and three bird species as removers of P. hintonii fruits, among which Pecari tajacu and small mammals were the most important fruit removers. Conclusions: Low density understory in pine-oak favor less fruit removal of P. hintonii, probably associated with the behavior of its consumers.

Responses of Surface Evaporative Fluxes in Montane Cloud Forests to the Climate Change Scenario

Abstract Fog plays a vital role in maintaining ecosystems in montane cloud forests. In these forests, a large amount of water on the surface of leaves and canopy (hereafter canopy water) evaporates during the morning. This biophysical process plays a critical factor in regulating afternoon fog formation. Recent studies have found that alterations in precipitation, temperature, humidity, and CO2 concentrations associated with future climate changes may affect terrestrial hydroclimatology, but the responses in cloud forests remain unclear. Utilizing numerical experiments with the Community Land Model, we explored changes in surface evaporative fluxes in Chi-Lan Mountain cloud forests in northeastern Taiwan under the RCP8.5 scenario with changes in the aforementioned various atmospheric variables. The results showed that increased rainfall intensity in climate change runs decreased the accumulation of canopy water, while larger water vapor concentrations led to more nighttime condensation on leaves. Elevated CO2 concentrations did not greatly impact canopy water amounts, but photosynthesis was enhanced, while transpiration was reduced and contributed to decreased latent heat fluxes, implying the importance of forest plant physiology in modulating land evaporative fluxes. Evapotranspiration decreased in Chi-Lan due to multiple combined factors, in contrast to the expected intensification in the global water cycle under global warming. The study, however, is restricted to an offline land surface model without land–atmosphere interactions and the interactions with adjacent grids, which deserves further analyses for the water cycle changes in the montane cloud forest regions.

Fog and coffee: a new species of Tridimeris (Annonaceae) endemic to the mountain cloud forest of Mexico

Tridimeris is the only genus of Annonaceae endemic to Mexico. Despite this, the genus has been largely ignored and very little is known about it; specifically its diversity and distribution in Mexico are not well studied. Here a new species of Tridimeris, T. huatuscoana, is described and illustrated. The most general characteristics of the new species confirm that dimerous flowers (two sepals and four petals) and the large, and fleshy fruits are the most obvious synapomorphies for the Mexican genus Tridimeris. With respect to the other two species described so far (Tridimeris hahniana and T. chiapensis), the new species can be easily distinguished by the unique combination of 2-flowered inflorescences, large petals pubescent outside, food bodies present at the base of its inner petals, setose leaf domatia, and fruits shortly pedunculate and stipitate. The new species expands the richness of the genus to three species, all endemic to Mexico and restricted to montane cloud forests.

High nitrogen‐fixing rates associated with ground‐covering mosses in a tropical mountain cloud forest will decrease drastically in a future climate

Abstract Tropical mountain cloud forests (TMCF) harbour a high bryophyte (mosses and liverworts) biomass and diversity. Furthermore, the high air humidity makes these forests well suited for bryophyte‐associated nitrogen (N2) fixation by cyanobacteria, providing a potentially important source of N input to the ecosystem. However, few studies have assessed bryophyte‐associated N input in these ecosystems, and these have focused on epiphytic bryophytes, whereas abundant ground‐covering bryophytes have not been included. In this study, we quantified N2 fixation rates associated with bryophytes, focusing on ground‐covering mosses in a neotropical mountain cloud forest. Furthermore, we identified the effects of climate change (higher temperature 10 vs. 20° and lower bryophyte moisture level 50% vs. 100%) on N2 fixation across bryophyte species and groups (mosses and liverworts). Nitrogen fixation rates associated with ground‐covering moss species were up to 2 kg N ha−1 year−1, which is comparable to other N inputs (e.g. N deposition) in tropical cloud forests. Furthermore, changes in temperature showed little effect on N2 fixation, but low moisture levels significantly suppressed N2 fixation activity. We found low N2 fixation activity associated with the investigated liverworts. Our results demonstrate the importance of ground‐covering, moss‐associated N2 fixation as a N source in tropical cloud forests and suggest that predicted future declines in precipitation in these systems will reduce N inputs from bryophyte‐associated cyanobacteria. Read the free Plain Language Summary for this article on the Journal blog.

Study on the Water and Heat Fluxes of a Very Humid Forest Ecosystem and Their Relationship with Environmental Factors in Jinyun Mountain, Chongqing

The high-humidity mountain forest ecosystem (HHMF) of Jinyun Mountain in Chongqing is a fragile ecosystem that is sensitive to climate change and human activities. Because it is shrouded in fog year-round, illumination in the area is seriously insufficient. However, the flux (energy, water) exchanges (FEs) in this ecosystem and their influencing factors are not clear. Using one-year data from flux towers with a double-layer (25 m and 35 m) eddy covariance (EC) observation system, we proved the applicability of the EC method on rough underlying surfaces, quantified the FEs of HHMFs, and found that part of the fog might also be observed by the EC method. The observation time was separated from day and night, and then the environmental control of the FEs was determined by stepwise regression analysis. Through the water balance, it was proven that the negative value of evapotranspiration (ETN), which represented the water vapor input from the atmosphere to the ecosystem, could not be ignored and provided a new idea for the possible causes of the evaporation paradox. The results showed that the annual average daily sensible heat flux (H) and latent heat flux (LE) ranged from −126.56 to 131.27 W m−2 and from −106.7 to 222.27 W m−2, respectively. The annual evapotranspiration (ET), positive evapotranspiration (ETP), and negative evapotranspiration (ETN) values were 389.31, 1387.76, and −998.45 mm, respectively. The energy closure rate of the EC method in the ecosystems was 84%. Fog was the ETN observed by the EC method and an important water source of the HHMF. Therefore, the study area was divided into subtropical mountain cloud forests (STMCFs). Stepwise regression analysis showed that the H and LE during the day were mainly determined by radiation (Rn) and temperature (Tair), indicating that the energy of the ecosystem was limited, and future climate warming may enhance the FEs of the ecosystem. Additionally, ETN was controlled by wind speed (WS) in the whole period, and WS was mainly affected by altitude and temperature differences within the city. Therefore, fog is more likely to occur in the mountains near heat island cities in tropical and subtropical regions. This study emphasizes that fog, as an important water source, is easily ignored in most EC methods and that there will be a large amount of fog in ecosystems affected by future climate warming, which can explain the evaporation paradox.

Luisumaoppia molinoensis gen. nov., sp. nov. (Acari, Oribatida, Oppiidae) from Peru.

A new oribatid mite genus, Luisumaoppia gen. nov. (Oribatida, Oppiidae, Oppiinae), with Luisumaoppia molinoensis sp. nov. as type species, is described from soil and leaf litter in primary mountain cloud forest in Andes, Peru. It differs from the other genera of Oppiidae by the presence of modified (nearly straight), directed backwards leg claws located on bent pretarsi. The relationships of Luisumaoppia gen. nov. with the related genera in Oppiinae are presented.

Characteristics of Central American brocket deer resting sites in a tropical mountain cloud forest in eastern Mexico.

The Central American brocket deer is a vulnerable species. Geographically isolated populations have been affected by poaching and habitat fragmentation, leading to local extinctions. It is therefore important to understand this species’ habitat characteristics, particularly of resting sites, which play a crucial role in survival and fitness. We describe the characteristics and distribution patterns of Central American brocket deer resting sites at the microhabitat and landscape scales in San Bartolo Tutotepec, Hidalgo, México. We conducted eight bimonthly field surveys between November 2017 and March 2019, consisting of 32 transects of 500 m length to search for fecal pellets, footprints, scrapes, and browsed plants. At each resting site we identified, we measured canopy closure, horizontal thermal cover, protection from predators for fawns and adults, escape routes, slope from the ground, presence of scrapes, cumulative importance value of the edible plant species, and distance from the resting site to the nearest water resource to characterize the site at the microhabitat scale. At the landscape scale, we identified the type of biotope, elevation, aspect, and slope. We compared all of these parameters from resting sites with a paired randomly selected site to serve as a control. We performed a multiple logistic regression to identify the parameters associated with the resting sites and a point pattern analysis to describe their distribution. We characterized 43 resting sites and their corresponding control plots. At the microhabitat scale, resting sites were associated with higher vertical thermal cover, more concealment cover, more escape routes, more edible plant species, higher slope from the ground, and closer distance to water resources. At the landscape scale, resting sites were associated with beech forest, oak forest, secondary forest, and ravine biotopes and negatively associated with pine forest, houses, and roads. Resting sites had an aggregated spatial pattern from 0 to 900 m, but their distribution was completely random at larger scales. Our study revealed that Central American brocket deer selected places with specific characteristics to rest, at both microhabitat and landscape scales. We therefore suggest that existing habitat be increased by reforesting with native species—particularly Mexican beech forest and oak forest—to improve the deer’s conservation status in the study area.

FINE ROOT DENSITY ACROSS SOIL PROFILES IN TROPICAL MOUNTAIN CLOUD FOREST AND ADJACENT MANAGED FIELDS IN VERACRUZ (MEXICO): INFLUENCE OF SOIL PROPERTIES

&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;. Fine roots play a crucial in ecosystem functioning as they supply nutrients and water to plants and represent one of the main pathways for carbon transfer to the soil. &lt;strong&gt;Objective.&lt;/strong&gt; This study assessed the vertical distribution of fine root density and analyzed its relationship with soil properties from a land use change perspective in three vegetation cover types (tropical mountain cloud forest, grassland, coffee crop). &lt;strong&gt;Methodology.&lt;/strong&gt; Soil samples of known volume per horizon were extracted from the soil profile. In laboratory, fine roots (≤ 2 mm in diameter) were tweezers picked, rinsed with water and subsequently oven-dried (70 °C), and weighed. While, the soil was air-dried for chemical analysis. &lt;strong&gt;Results&lt;/strong&gt;. In all soil profiles, average fine root density was greater in grassland (16.06 kg m&lt;sup&gt;-3&lt;/sup&gt; ± 3.5, average ± SE) than in tropical mountain cloud forest (8.45 kg m&lt;sup&gt;-3&lt;/sup&gt; ± 1.3), and coffee crop (2.73 kg m&lt;sup&gt;-3&lt;/sup&gt; ± 0.44). On average, grassland, tropical mountain cloud forest, and coffee crop showed 78.4%, 73.2%, and 65%, respectively, of fine root density on the first soil horizon. &lt;strong&gt;Implications&lt;/strong&gt;. Soil properties were strong predictors of fine root density variation. For example, there was a significant positive correlation between fine root density and soil organic carbon, total soil nitrogen, and effective cation exchange capacity (nutrient availability) in all vegetation covers. A significant negative correlation was observed between fine root density and pH in tropical mountain cloud forest but was not correlated in grassland and coffee crop. In all vegetation covers, there was a significant negative correlation between fine root density and soil bulk density and a strong positive correlation between it and soil water content at field capacity. &lt;strong&gt;Conclusion.&lt;/strong&gt; This research contributes data that will improve our understanding of fine root density-soil interactions in a changing regional environment.&lt;/p&gt;

A new species of Dixella, the first Mexican record of Dixella shannoni, and a summary of dixid records from Mexico (Diptera: Dixidae).

We describe a new species of the genus Dixella Dyar Shannon of Mexico. Specimens were collected in Lagunas de Santo Domingo, Municipality of Huatusco, Veracruz, a small vegetation-lined lake within an increasingly relictual mountain cloud forest. This species is most closely related to Dixella cumbrica Peters Cook, 1966, based upon the shape of the apical lobe of the gonocoxite and flattened gonostylus. Also, we include the first record of Dixella shannoni (Lane, 1942), in Mexico, based upon specimens collected in Santiago Yaveo, Oaxaca. Additionally, we present a list of all localities in which dixids have been collected in Mexico.

A new fog and low stratus retrieval for tropical South America reveals widespread fog in lowland forests

Fog-driven epiphyte-rich tropical cloud forests were long believed to be restricted to mountainous regions. Recent studies have shown the occurrence of such forest types in the lowlands of French Guiana, where early morning radiation fog was shown to modify the water and energy cycles at the canopy level of the tropical lowland rain forest (Gehrig-Downie et al., 2012; Obregon et al., 2011). Since this newly discovered Tropical Lowland Cloud Forest (TLCF) harbours a unique biodiversity comparable to mountain cloud forests, knowledge of its spatial distribution across tropical lowland forests is of large ecological interest, but so far fully unknown. A prerequisite to detect potential TLCF stands is knowledge on the spatial occurrence of fog/low stratus clouds (FLS) over longer time scales, indicating fog frequency. We address this need on a continental scale by presenting the first spatially-explicit, high-resolution product on nocturnal FLS occurrence over the entire tropical lowland rain forest area of South America. The product is based on a new FLS retrieval scheme that uses brightness temperature (BT) information of night-time satellite images acquired by the Aqua Moderate Imaging Spectroradiometer (Aqua MODIS). Since landforms substantially influence small-scale FLS development, we used a dynamic threshold technique depending on the spatially variable subpixel information on landform suitability for FLS generation. The product was successfully validated against in-situ visibility measurements combined with a plausibility analysis based on the published but scarce fog observations over the Amazon. The independence of the new algorithm from measured total precipitable water (TPW) is an improvement over existing procedures that are limited to the availability of these ancillary data. The FLS frequency map for the entire tropical lowland forest of South America derived from over 52,000 scenes (18 years from 2003 to 2020 inclusive) indicates that FLS is widespread, though spatially differentiated, throughout the tropical lowland forests of South America, providing suitable environmental conditions for the TLCF. This knowledge on the spatial distribution of potential TLCF is of major importance for conservation efforts. The new FLS scheme is applicable to all tropical lowland forests and can therefore support global conservation efforts of the valuable TLCF ecosystems.