Tropical Semideciduous Forest Research Articles

Vertical stratification and defensive traits of caterpillars against parasitoids in a lowland tropical forest in Cameroon

Insect herbivores and their parasitoids play a crucial role in terrestrial trophic interactions in tropical forests. These interactions occur across the entire vertical gradient of the forest. This study compares how caterpillar communities, and their parasitism rates, vary across vertical strata and between caterpillar defensive strategies in a semi deciduous tropical forest in Nditam, Cameroon. Within a 0.1 ha plot, all trees with a diameter at breast height (DBH) ≥ 5 cm were felled and systematically searched for caterpillars. We divided the entire vertical gradient of the forest into eight, five-metre strata. All caterpillars were assigned to a stratum based on their collection height, reared, identified, and classified into one of three defensive traits: aposematic, cryptic and shelter-building. Caterpillar species richness and diversity showed a midstory peak, whereas density followed the opposite pattern, decreasing in the midstory and then increasing towards the highest strata. This trend was driven by some highly dense shelter-building caterpillars in the upper canopy. Specialisation indices indicated decreasing levels of caterpillar generality with increasing height, a midstory peak in vulnerability, and increasing connectance towards the upper canopy, although the latter was likely driven by decreasing network size. Both aposematic and shelter-building caterpillars had significantly higher parasitism rates than cryptic caterpillars. Our results highlight nuanced changes in caterpillar communities across forest strata and provide evidence that defences strategies are important indicators of parasitism rates in caterpillars and that both aposematic and shelter-building caterpillars could be considered a “safe haven” for parasitoids.

Melissopalynology of pot-pollen and pot-honey of the Mayan stingless bee Melipona beecheii Bennett, 1831 (Apidae, Meliponini) in Yucatan, Mexico

The Mayan bee Melipona beecheii is one of the most important and widely cultivated stingless bees in Mexico. In order to document pollen and nectar resources for M. beecheii during the dry season, 25 pot-pollen and 25 pot-honey samples were collected from February to May 2021 at eight villages in Yucatan, Mexico. All samples were acetolysed, and 500 pollen grains were counted randomly for each sample. A total of 21 taxa belonging to eight botanical families were observed in the pot-pollen samples; in contrast, 32 pollen types from 16 botanical families were recorded in the pot-honey samples. According to PCA analyses, the pollen types that explained the maximum variance among the pot-pollen samples were Senna racemosa var. racemosa, Lonchocarpus punctatum, Cochlospermum vitifolium, Bursera schlechtendalii and B. simaruba, while S. racemosa var. racemosa, C. vitifolium, Alternanthera ramosissima, Psidium guajava, B. schlechtendalii, B. simaruba, L. punctatum, Mimosa bahamensis and Solanum americanum explained the greatest variance among the pot-honey samples. Our results confirm that M. beecheii displays polylectic foraging and targets for the secondary vegetation of tropical deciduous and tropical semideciduous forests. Diversity in the pot-pollen was found to be lower than that of the pot-honey samples. Since some pot-honey samples were overrepresented by the pollen grains of S. racemosa var. racemosa, PCA and cluster analysis grouped those pot-pollen and pot-honey samples together.

Cubanthonomus, a new genus of Anthonomini (Coleoptera: Curculionidae: Curculioninae) from Cuba.

Cubanthonomus Anderson, new genus (Coleoptera: Curculionidae: Curculioninae: Anthonomini) is here described to accommodate the Cuban species Cleogonus grossulus Suffrian, which was previously placed as incertae sedis within Cleogonini. The genus is characterized by head constricted behind the eyes, globose form, compact antennal funicle of seven antennomeres, base of pronotum strongly produced posteriorly at middle, elytra with rows of punctures (striae effaced), tarsal claws with small basal tooth, profemora with two teeth, meso- and metafemora with single small tooth. Specimens have been collected in tropical semideciduous forest but no host associations are known.

Enhanced net CO2 exchange of a semideciduous forest in the southern Amazon due to diffuse radiation from biomass burning

Abstract. Carbon cycling in the Amazon fundamentally depends on the functioning of ecosystems and atmospheric dynamics, which are highly intricate. Few studies have hitherto investigated or measured the radiative effects of aerosols on the Amazon and Cerrado. This study examines the effects of atmospheric aerosols on solar radiation and their effects on net ecosystem exchange (NEE) in an area of semideciduous tropical forest in the north of Mato Grosso. Our results show that for a relative irradiance (f) 1.10–0.67, a decrease in incident solar radiation is associated with a reduction in the NEE. However, an average increase of 25 %–110 % in NEE was observed when pollution levels and aerosol optical depth (AOD) were above ≈ 1.25 and f < 0.5. The increase NEE was attributed to the increase of up to 60 % in the diffuse fraction of photosynthetically active radiation. The change in AOD and f was mainly attributable to biomass burning organic aerosols from fires. Important influences on vapor pressure deficit (VPD) as well as air temperature (Tair) and canopy (LCT), induced by the interaction between solar radiation and high aerosol load in the observation area, were also noticed. On average, a cooling of about 3–4 ∘C was observed for Tair and LCT, and a decrease of up to 2–3 hPa was observed for VPD. Given the long-distance transport of aerosols emitted by burning biomass, significant changes in atmospheric optical properties and irradiance will impact the CO2 flux of semideciduous forests distributed in the region.

The landscape scale of effect on the alpha and beta diversities of woody species in a semideciduous tropical forest

ContextMost tropical forest landscapes are highly fragmented, have habitat patches varying in size and shape, and display different degrees of perturbation, but with high conservation values. Therefore, a major goal of landscape ecology is to discover the actual spatial scale at which landscape composition and structure affect biological processes and biodiversity.ObjectiveThis study aimed to determine the landscape scale of effect governing the α and β diversities of woody species in a highly fragmented, semideciduous tropical forest.MethodsWe recorded the diversity of woody species in 19 plots scattered across a highly fragmented, semideciduous tropical forest landscape. Then, we used CART algorithms to evaluate the effects of landscape attributes on the α and β diversities of such species across 100 scales (10–1000 m) and tested continuous effects with generalized additive models.ResultsThe shape and size of habitat patches in the range of 250–470 m determined α diversity. As for β diversity, nestedness was affected by the shape of forest patches at 510 m, whereas landscape heterogeneity affected species turnover within 100 m buffers.ConclusionWhile a previous study in a similar habitat reported effects at 800 m, the number, size, and shape of habitat patches in the current study accounted for the diversity of the focal plots within 100–510 m. Furthermore, CART effectively screened 100 scales, revealing which landscape attributes correlated the most with the diversity of woody plants. The findings provide valuable guidelines for conservation, restoration efforts, and public policies.

Assessing Forest Species Diversity in Ghana’s Tropical Forest Using PlanetScope Data

This study utilized a remotely sensed dataset with a high spatial resolution of 3 m to predict species diversity in the Bobiri Forest Reserve (BFR), a moist semi-deciduous tropical forest in Ghana. We conducted a field campaign of tree species measurements to achieve this objective for species diversity estimation. Thirty-five field plots of 50 m × 20 m were established, and the most dominant tree species within the forest were identified. Other measurements, such as diameter at breast height (DBH ≥ 5 cm), tree height, and each plot’s GPS coordinates, were recorded. The following species diversity indices were estimated from the field measurements: Shannon–Wiener (H′), Simpson diversity index (D2), species richness (S), and species evenness (J′). The PlanetScope surface reflectance data at 3 m spatial resolution was acquired and preprocessed for species diversity prediction. The spectral/pixel information of all bands, except the coastal band, was extracted for further processing. Vegetation indices (VIs) (NDVI—normalized difference vegetation index, EVI—enhanced vegetation index, SRI—simple ratio index, SAVI—soil adjusted vegetation index, and NDRE—normalized difference red edge index) were also calculated from the spectral bands and their pixel value extracted. A correlation analysis was then performed between the spectral bands and VIs with the species diversity index. The results showed that spectral bands 6 (red) and 2 (blue) significantly correlated with the two main species diversity indices (S and H′) due to their influence on vegetation properties, such as canopy biomass and leaf chlorophyll content. Furthermore, we conducted a stepwise regression analysis to investigate the most important spectral bands to consider when estimating species diversity from the PlanetScope satellite data. Like the correlation results, bands 6 (red) and 2 (blue) were the most important bands to be considered for predicting species diversity. The model equations from the stepwise regression were used to predict tree species diversity. Overall, the study’s findings emphasize the relevance of remotely sensed data in assessing the ecological condition of protected areas, a tool for decision-making in biodiversity conservation.

Age matters: variations in parasitoid diversity along a successional gradient in a dry semi-deciduous tropical forest.

Parasitoids are an important group of insects because their species number is among the highest. Multiple studies have addressed the relationships between forest successional age and insect diversity by focusing on herbivorous organisms, but changes in diversity of parasitoids are still poorly known. This work analyses the diversity of parasitoids in tropical forests representing three successional stages. A total of 30 traps were placed, ten in each forest successional stages. We estimated true diversity of Ichneumonidae species and guilds and explored the relationship between their diversity and the abundance of plant species using an Indicator Species Analysis; the relationship between parasitoid species and plant richness and abundance was tested using a Redundancy Analysis. A total of 1522 individuals and 168 morpho-species were captured in four months. Species richness showed no differences; however, parasitoid abundance was higher in young forest, while intermediate forest had the highest true diversity values (1D) with 71.6 effective species. According to insect guilds, richness, abundance, and diversity were similar in the three vegetation successional stages. This finding may be explained based on the intermediate disturbance hypothesis, which postulates that moderate disturbance levels favor the highest diversity. In conclusion, successional age matters, i.e., diversity is the highest in intermediate stages, while the old forests harbors guilds unique to that successional stage, such as parasitoids of melitophagous larvae of bees. Other successional stages were characterized by a single species of parasitoid, belonging to the genera Eiphosoma and Anomalon, which may indicate altered and preserved forests, respectively.

Response of soil microbial biomass and enzyme activity in coffee-based agroforestry systems in a high-altitude tropical climate region of Brazil

Soil microbial communities are key indicators of changes in soil quality caused by cropping systems. Although there are studies that prove that coffee agroforestry systems increase or maintain soil organic matter levels, the effect of microbial biomass and enzymatic activity in tropical regions, especially in places with high altitude and mild temperatures, is still poorly understood. Thus, the present study aimed to evaluate the influence of two agroforestry systems (AFS-G: coffee intercropped with Grevillea robusta, AFS-C: coffee intercropped with Toona ciliata) and Coffea arabica monoculture on soil microbial biomass and activity and on the arylsulfatase and β-glucosidase enzyme activities, taking a native forest (Semi-deciduous tropical forest, with a predominance of the genera Parapiptadenia and Anadenanthera) as the control system. This study was performed in Oxisol soil areas located in the municipality of Barra do Choça, Bahia, Brazil. Litter (L, F and H layers) and soil topsoil (0–10 cm depth) samples were collected. Both were collected with four repetitions (four composite samples) in each system, litter with a 0.0625 m2 template and soil using a Dutch auger. The carbon microbial biomass, microbial activity (CO₂ released), arylsulfatase and β-glucosidase enzyme activities, organic carbon (SOC) and total nitrogen were also analyzed in the soil samples. The coffee with Grevillea robusta agroforestry system (AFS-G) did not reduce SOC compared to native forest, but the coffee with cedar agroforestry system had SOC losses at a rate of 0.56 Mg ha−1 year−1. The AFS-C cultivation system presented more MB-C (468.43 µg g−1) when compared to the other coffee systems. The AFS-G maintained the microbial activity levels and β-glucosidase and arylsulfatase enzyme activities in relation to the native forest. Coffee agroforestry systems (both AFS-G and AFS-C) in a tropical high-altitude climate region in Brazil are more favorable to maintain microorganisms and their activity in the soil, and therefore should be encouraged in order to more sustainably manage coffee growing.

Accelerated Soil Erosion and Sedimentation Associated with Agricultural Activity in Crater-Lake Catchments of Western Uganda

Intensifying agricultural activity associated with rapid population growth in rural western Uganda exerts immense pressure on natural resources, threatening not only soil fertility in the uplands but also water quality of the region’s many small crater lakes. To assess the relative risk of excess sediment and nutrient loading to individual lakes due to (inter) rill erosion within the catchments, we used the revised universal soil loss equation (RUSLE) and sediment delivery distributed model (SEDD) to estimate soil loss and sedimentation in 75 crater-lake catchments with diverse types and intensities of land use, including 17 catchments situated partly or entirely in national parks. We found that variation in potential soil loss (Ap) among all studied catchments was strongly related to differences in mean slope within each catchment. We also found substantial seasonal variation in vegetation cover, and thus, estimated actual soil loss (Am), on both cultivated land and protected savanna grassland, whereas the vegetation cover of protected semi-deciduous tropical forest was seasonally stable. Lacking detailed field data to validate model output, we used the ratio between estimated actual soil loss (Am) and potential soil loss (Ap) to evaluate the relative influences of land-use intensity and type, as well as the impact of protective measures. Our results showed that due to their characteristically steep slopes (21% on average), all crater catchments were highly susceptible to soil loss, and because most of them were small (203 ha on average), a large portion of the eroded material was transported to and deposited in the lakes. Given the strong dependence of the local population on these crater lakes as source of water and fish protein, and on the surrounding land for crop production, increased effort by environmental planners and managers is required to safeguard or restore the long-term availability of these natural resources. Avoiding bare soil conditions by restoring natural vegetation or employing agricultural techniques that provide high vegetation cover throughout the year are likely to result in considerable improvements.

Life after fire - Long-term responses of 20 timber species in semi-deciduous forests of West Africa

Understanding the response of commercial timber species to fire is fundamental to designing sustainable forest management strategies in West Africa. In this area of high deforestation for agriculture, semi-deciduous tropical forests have been reduced to a trickle in 50 years and are now subject not only to logging but also to increasingly frequent fires. This paper aims to study the long-term (37 years) demographic and growth responses of 20 timber species after a spatially heterogeneous fire in a West African semi-deciduous forest. We (i) inventoried, in 2020, 100 hectares of plots already established before the 1983 fire, (ii) built demographic and growth models, in a Bayesian framework, to estimate the vulnerability to fire of each species and (iii) linked this vulnerability to functional traits: wood density (WD) and bark thickness (BT). Our results show that most species have lower current abundances but higher growths in burnt areas than in fire-preserved areas. We identified three categories of vulnerability to fire: 1 non-vulnerable species, 16 species with vulnerable demography, and 3 highly vulnerable species. Species with high wood density or thin bark show higher demographic vulnerability to fire. Our results show that fire management is a top priority in West African semi-deciduous forests to maintain long-term populations of timber species and ultimately the forest industry. The differences in vulnerability observed, and the strong predictive power of the functional traits studied, should make it possible to (i) better define harvesting rates and adapt them to fire risk and (ii) better select commercial species to be promoted for reforestation or natural (assisted) regeneration.

Soil organic carbon stock under semi-deciduous tropical forests: case of the Téné protected forest (Oumé, Côte d'Ivoire)

Soil organic carbon stocks (SOCS) estimated from international databases are generally subject to uncertainties. These errors are more significant in developing countries where field studies are rare. To overcome this shortcoming, soil samples were collected in the experimental set-up of Téné protected forest (ES-TPF), located in central-western Côte d'Ivoire, to identify the soil types and the corresponding actual SOCS. The FAO soil classification guide was used to identify soil types. SOCS were determined from the carbon concentrations, bulk densities, and proportions of fine elements, in 0-30 cm, 30-60 cm and 60-100 cm thicknesses. The results showed three soil types, namely Plinthosols at top slope, Ferralsols at top and middle slope and Fluvisols at bottom slope. In the reference thicknesses 0-30 cm and 0-100 cm, the respective SOCS are on average 44.89±25% tC.ha-1 and 61.56±23% tC.ha-1 in Plinthosols; 49.16±26% tC.ha-1 and 93.40±16% tC.ha-1 in Ferralsols; 41.18±32% tC.ha-1 and 68.54±22% tC.ha-1 in Fluvisols. Almost all these values differed from those in the international databases, especially in the depths. Therefore, the results obtained are recommended for a better accounting and management of SOCS in the semi-deciduous tropical forests of West Africa.

Siembra directa de Brosimum alicastrum Sw. (Moraceae) y Enterolobium cyclocarpum (Jacq.) Griseb. (Mimosaceae) en diferentes habitats en el trópico seco del centro de Veracruz

Los acahuales (i.e. selvas secundarias) de zonas tropicales secas o estacionales, suelen ser pobres en especies arbóreas y dominados por unas cuantas especies de arbustos y árboles pioneros, usualmente dispersados por viento, siendo notable la ausencia de plantas arbóreas del dosel cuyas semillas relativamente grandes dependen de vectores animales para su dispersión. Varios estudios han encontrado que la siembra directa de especies arbóreas zoócoras con semillas grandes, en pastizales abandonados puede ser una práctica exitosa para enriquecer y acelerar la sucesión secundaria. Sin embargo, todavía no se conocen cabalmente las condiciones de hábitat o etapa sucesional óptima para realizar la siembra directa de semillas de árboles de fases sucesionales tardías. En este estudio seleccionamos dos especies arbóreas con semillas zoócoras relativamente grandes, que suelen formar parte del dosel de las selvas sub-caducifolias del centro de Veracruz: Brosimum alicastrum y Enterolobium cyclocarpum. Las sembramos en siete hábitats; seis de ellos representando un gradiente de menor a mayor complejidad estructural o desarrollo sucesional, desde pastizal activo hasta acahual de 10 años y el hábitat restante fue selva mediana sub-caducifolia bien conservada. Evaluamos experimentalmente la importancia de la depredación de semillas, protegiendo la mitad de ellas sembradas dentro de jaulas diseñadas para excluir a vertebrados granívoros. Durante un año monitoreamos la emergencia, supervivencia y crecimiento de plántulas, marcando a las que sobrevivieron su primer año, para ser registradas cuatro años y medio después. Un porcentaje relativamente alto de plántulas emergió de las semillas sembradas (75% en Brosimum, 60% Enterolobium). No detectamos diferencias significativas en la emergencia de plántulas entre los siete hábitats, ni entre los dos tratamientos de exposición a granívoros (dentro vs. fuera de exclusorios). Ninguna de las semillas sembradas fue removida por granívoros. La supervivencia y crecimiento deEnterolobium durante el primer año fue mayor en hábitats abiertos sin cobertura de plantas leñosas (ca. 60%) que en los sombreados por arbustos y árboles (<10%). En contraste, las plántulas de Brosimum sobrevivieron y crecieron mucho mejor bajo la sombra de plantas leñosas (>80%) que en hábitats abiertos (0%). Nuestros resultados muestran que los pastizales abandonados y los acahuales pobres en especies arbóreas, pueden ser enriquecidos mediante la siembra directa de árboles de fases sucesionales tardías con baja capacidad de dispersión, siempre y cuando se elija cuidadosamente el hábitat (o etapa sucesional) óptimo para la siembra de semillas, con base en la ecología del establecimiento de plántulas de las especies involucradas. En el centro de Veracruz se puede acelerar la recuperación de la selva, sembrando semillas de Enterolobium desde el momento del abandono del pastizal, siempre y cuando se controle el crecimiento de los pastos durante los primeros dos a tres años de crecimiento de las plántulas. A su vez las semillas de Brosimum deberán sembrarse hasta que los arbustos o árboles pioneros hayan colonizado el sitio y sombreado a los pastos.

Vegetación de la Sierra Madre Occidental, México: una síntesis

La Sierra Madre Occidental (SMO) es el complejo montañoso más grande de México, extendiéndose por casi 1200 km desde el noreste de Sonora (30°35' N) hasta el norte de Jalisco (21°00' N). A pesar de su gran importancia ambiental y económica, es todavía deficientemente conocida. Se presenta una sinopsis de los tipos de vegetación, con datos sobre la superficie que ocupan las comunidades reconocidas, intervalos de elevación y climas donde se localizan, así como un mapa. En la zona confluyen tres regiones, albergando ecosistemas templados y semifríos (región Madrense), semiáridos (Madrense-Xerófila) y cálido-secos (Tropical), respectivamente. La región Madrense, en el macizo de la sierra, incluye bosque de pino, bosque mixto de coníferas, bosque de pino-encino, bosque de encino y manchones de bosque mesófilo de montaña, además de comunidades como chaparral (primario y secundario) y vegetación de claros de bosque. La región Madrense-Xerófila, en el piedemonte norte y oriental y estribaciones al oriente de la sierra, presenta bosque bajo abierto (de encino o de pino-encino), matorral perennifolio y zonas de ecotonía hacia pastizal y matorral xerófilo, además de ecotonías con matorral subtropical hacia el sur del Archipiélago Madrense. En la región Tropical, a lo largo de la base occidental de la sierra e ingresando a esta a través de las barrancas y quebradas, predomina bosque tropical caducifolio y matorral subtropical, con pequeñas áreas de bosque tropical subcaducifolio. La alta diversidad de la SMO se ejemplifica con los tres géneros dominantes fisonómicamente en la vegetación: 24 especies de Pinus (46% del total nacional), 54 de Quercus (34%) y 7 de Arbutus (100%).

Modelling Species Richness and Functional Diversity in Tropical Dry Forests Using Multispectral Remotely Sensed and Topographic Data

Efforts to assess and understand changes in plant diversity and ecosystem functioning focus on the analysis of taxonomic diversity. However, the resilience of ecosystems depends not only on species richness but also on the functions (responses and effects) of species within communities and ecosystems. Therefore, a functional approach is required to estimate functional diversity through functional traits and to model its changes in space and time. This study aims to: (i) assess the accuracy of estimates of species richness and tree functional richness obtained from field data and Sentinel-2 imagery in tropical dry forests of the Yucatan Peninsula; (ii) map and analyze the relationships between these two variables. We calculated species richness and functional richness (from six functional traits) of trees from 87 plots of the National Forest Inventory in a semi-deciduous tropical forest and 107 in a semi-evergreen tropical forest. Species richness and functional richness were mapped using reflectance values, vegetation indices, and texture measurements from Sentinel-2 imagery as explanatory variables. Validation of the models to map these two variables yielded a coefficient of determination (R2) of 0.43 and 0.50, and a mean squared relative error of 25.4% and 48.8%, for tree species richness and functional richness, respectively. For both response variables, the most important explanatory variables were Sentinel-2 texture measurements and spectral bands. Tree species richness and functional richness were positively correlated in both forest types. Bivariate maps showed that 44.9% and 26.5% of the forests studied had high species richness and functional richness values. Our findings highlight the importance of integrating field data and remotely sensed variables for estimating tree species richness and functional richness. In addition, the combination of species richness and functional richness maps presented here is potentially valuable for planning, conservation, and restoration strategies by identifying areas that maximize ecosystem service provisioning, carbon storage, and biodiversity conservation.

Burrow builders as ecosystem engineers for pit-building antlions (Neuroptera: Myrmeleontidae).

Burrow builders are often classified as ecosystem engineers because their digging activities regulate the availability of resources for other organisms. As antlion larvae prefer to construct their traps in bare sandy or loose soil, they could benefit from burrowing activities. We investigated the role of burrow builders as ecosystem engineers for antlions (Myrmeleontidae) in a tropical semideciduous forest in Mexico. The number of traps of antlion larvae was recorded on 30 sampling quadrats (45cm) at the entrance of burrows (of unidentified builders) and on 30 paired off-burrow quadrats. Additionally, the percentage of bare soil was estimated for the 60 quadrats sampled. Of the 30 quadrats at the entrance of burrows, a total of 336 traps were recorded, with 21 (70%) of them having at least one trap, while for the 30 off-burrows quadrats, only two (6.6%) of them had traps, just three in total. The percentage of bare soil and the abundance of traps were significantly greater in quadrats at the entrance of burrows compared to quadrats without burrows. The abundance of traps at the entrance of burrows was positively affected by the percentage of bare soil. The few traps in the off-burrows quadrats suggested that, in addition to the limited bare soil, ground compactness probably limits the establishment of antlion larvae. Otherwise, when digging, burrow builders create small patches of bare sandy soils that are used by these insects. We concluded that the ecosystem engineering effect of burrow builders is an important structuring element for antlion populations in the tropical semideciduous forest studied.

Population trends and viability of the critically endangered Cozumel Curassow: a 25-year perspective

ABSTRACT The Cozumel Curassow (Crax rubra griscomi) is a critically endangered endemic bird from Cozumel Island, Mexico. After it was believed to be extinct, it was rediscovered in 1994. Its population status was assessed in 1994–1995, and later in 2005, predicting a population decline over the next four decades. A new evaluation of its population size was carried out in 2017 and 2019. Some of the main factors that affect the population size of this cracid were identified with a generalized linear model. With a line transect sampling effort over 360 km, a population size of 499 ± 172 individuals was estimated in the tropical semi-deciduous forest occurring in the island, which was slightly higher compared to previous population evaluations. The distance to water bodies was significantly associated with the population size of the Cozumel Curassow, as well as the abundance of some species of fauna and flora. By modeling various scenarios, population viability was assessed over a period of 100 years, predicting a relatively stable population size with great variability depending on scenarios. However, as estimated in previous studies, given its small population size and continued threats, the Cozumel Curassow continues to be endangered.

Diversity and Vertical Distribution of Epiphytic Angiosperms, in Natural and Disturbed Forest on the Northern Coast of Jalisco, Mexico

Background and AimsEpiphytes are an important component of tropical forests, also they are sensitive to disturbance and deforestation caused by humans, since they depend on their host trees and the micro environmental conditions that these provide. The aim of this study was to analyze the differences in species richness, composition, and vertical distribution of epiphytic angiosperms between areas with natural and disturbed forest at the Northern Coast of Jalisco state, Mexico.MethodsThe presence/absence of epiphytic angiosperms was evaluated in each vertical zone of a selected tree, as well as those present in the understory, both in natural and disturbed sites in three types of vegetation (gallery forest, oak forest, tropical semideciduous forest) with a total of 30 plots of 20 m × 20 m in six sites. Alpha diversity was calculated for each site, as well as species turnover (beta diversity) between habitats. An analysis of variance was performed to determine if there was a significant difference in species richness between sites and, also to compare the height and diameter at breast height (DBH) of the host trees. Multivariate analyzes were used to group the sites according to their floristic composition. Furthermore, a linear regression was performed to detect any relationship between the number of species and the phorophyte structure.ResultsWe recorded 45 species, 29 genera and nine families of epiphytic angiosperms. The most diverse families were Bromeliaceae and Orchidaceae and the richest genus was Tillandsia. Although the disturbed sites had more species, a significant difference in richness was not found, except for the disturbed gallery forest. Epiphytic angiosperms presented a high beta diversity, since the sites shared only between 2 and 18% of the recorded species. The inner portion of the canopy (Z3 and Z4) hosted most of the species in all sites and the understory had a high representation of epiphytes except for the disturbed oak forest, where these were absent. A relationship between the DBH and the number of species was found only at the disturbed sites, however, it was highly influenced by the high number of taxa registered in disturbed gallery forest. Therefore, the size of the trees could not be considered a factor in determining the diversity of epiphyte species.ConclusionThe diversity of epiphytic angiosperm species from the North Coast of Jalisco has not been severely affected by the human disturbance. Most of the species have morphological and physiological adaptations that allow their establishment and survival in adverse climatic conditions. Our results suggest that epiphytic angiosperms cannot be considered as a good indicator for natural or disturbed environments in this region but should be considered in environmental conservation, as they present a high beta diversity.

Carbon accumulation in soil layers under degraded, intact and planted forest cover types in tropical semi-deciduous and moist evergreen forests

Carbon accumulation in soil layers under degraded, intact and planted forest cover types in tropical semi-deciduous and moist evergreen forests

Soil CO2 efflux fluctuates in three different annual seasons in a semideciduous tropical forest in Yucatan, Mexico

Tropical forest soils store a third of the global terrestrial carbon and control carbon dioxide (CO2) terrestrial effluxes to the atmosphere produced by root and microbial respiration. Soil CO2 efflux varies in time and space and is known to be strongly influenced by soil temperature and water content. However, little is known about the influence of seasonality on soil CO2 efflux, especially in tropical dry forests. This study evaluated soil CO2 efflux, soil temperature, and soil volumetric water content in a semideciduous tropical forest of the Yucatan Peninsula under two sites (flat areas close to and far from hills), and three seasons: dry, wet, and early dry (a transition between the rainy and dry seasons) throughout a year. Additionally, six 24-h periods of soil CO2 efflux were measured within these three seasons. The mean annual soil CO2 efflux was 4±2.2 μmol CO2 m-2 s-1, like the mean soil CO2 efflux during the early dry season. In all seasons, soil CO2 efflux increased linearly with soil moisture, which explained 45% of the spatial-temporal variation of soil CO2 efflux. Soil CO2 efflux was higher close to than far from hills in some months. The daily variation of soil CO2 efflux was less important than its spatial and seasonal variation likely due to small diel variations in temperature. Transition seasons are common in many tropical dry forests, and they should be taken into consideration to have a better understanding of the annual soil CO2 efflux, especially under future climate-change scenarios.

Ecological Study of the Active Ciliate Community from Bromeliads during the Humid Season in Different Types of Forests of the Mexican Neotropics

Bromeliads are a Neotropical family of monocots, colonized by several families of ciliates, with some species that inhabit only this type of microecosystems. Ecological factors such as the presence of water, plant volume, seasonality and predators, have been recognized as important factors, which play a role in the ciliate community structure in tank bromeliads. The objective of this study is to describe different communities of active ciliates from epiphytic and terrestrial bromeliads that inhabit the dry tropical forest, montane cloud forest, oak forest and semideciduous tropical forest in the Mexican Neotropics during the humid season of the year 2016. We found 22 species of active ciliates. A higher richness of ciliate species was found in the bromeliads of the montane cloud forest. Based on statistical tests, we determine that the pH and water temperature, plant diameter, its distance above the ground and altitude above sea level in relation to ciliate abundance explain <50% of the variation; however, the combination of plant diameter and its distance above the ground shows a positive effect in relation to ciliate abundance. We provide new evidence that bromeliads that inhabit mountains and lowland forests in a larger geographic area host ciliate communities with different species composition.