Although fire is occurring at greater frequencies and spatial scales in the moist tropics, few studies have examined the ecological impacts of fire in tropical montane cloud forest (TMCF). This study, conducted in the Chimalapas region of Oaxaca, Mexico, documents changes in live tree biomass, live fine-root biomass, and fallen and standing dead wood 4 y following deep ground fires occurring in TMCF during the 1997–98 El Niño Southern Oscillation event. Forests growing on two different substrates (metamorphic and sedimentary) and having three different statures (mean canopy heights: 20–30 m, 15–20 m and 4–6 m) were assessed within six paired plots established on adjacent burned and unburned forest sites. Total live tree biomass was 82% and 88% lower for burned TMCF growing on metamorphic and sedimentary substrates, respectively, compared with unburned TMCF. Nearly 100% of the living biomass was killed in elfin TMCF located on exposed sedimentary limestone at the highest elevations. Live fine-root biomass in the upper organic soil horizon of burned TMCF sites was 49% lower on metamorphic substrates and 77% lower on sedimentary substrates compared with unburned sites. The amount of total dead wood was 3- to 14-fold greater in burned forests compared with unburned forests. These results suggest that first-time fires in relatively undisturbed TMCF can cause dramatic changes in live above- and below-ground biomass at levels greatly exceeding values reported for most lowland tropical rain forests. These patterns may be attributed to the slower decomposition rates and thick organic soils typical of TMCF, combined with the relatively fast drainage associated with steep topography and, in some locations, sedimentary limestone-derived substrates.
Phenotypic variation of traits can reflect the ability of plants to adjust to particular environments, but how much of this variation is heritable is not frequently analyzed in natural populations. In the present paper, we investigated the patterns of phenotypic expression in light-related leaf traits of Olea europaea subsp. guanchica, a woody sclerophyllous species endemic to the Canary Islands. We explored phenotypic differentiation and heritable variation across several island populations differing in light environment. A suite of morpho-functional (leaf size, SLA and leaf angle) and physiological (pigment pools: Chl a/b ratio, xantophyll cycle and β-carotene) traits was measured in six populations on three islands. In addition, we estimated heritabilities for these traits following Ritland's method. Variation in morpho-functional, but not in physiological, traits was observed across the islands and was significantly related to the amount of diffuse light experienced by each population. In addition, significant heritabilities were found for morpho-functional traits, whereas expression of similar phenotypes among populations was accompanied by a lack of heritable variation in physiological traits. Most recently established populations did not exhibit lower heritabilities in quantitative traits than older populations, and apparently displayed congruent phenotypes under the local conditions. Our results strongly support the idea that different types of traits show contrasted levels of genetic and phenotypic variation in populations experiencing marked environmental differences.
Zuelania guidonia is a tree species of cultural importance in Totonac society. This tree is a central element of the Los Voladores (the "flying men") pre-Hispanic ritual ceremony. However, the populations of Z. guidonia have decreased due to anthropogenic activity. This study aimed to codesign an agroforestry model for the recovery of Z. guidonia populations by combining scientific and traditional agroforestry knowledge at the El Tajín archaeological site in Veracruz, Mexico. We assessed the abundance of Z. guidonia and analyzed plant species richness and diversity in forest fragments. Species were classified according to plant regeneration modes (light-demanding and shade-tolerant) and to the local uses of secondary forests and conserved forest fragments. In addition, we worked collaboratively in a project that consisted of workshops, focus groups, open interviews, drawings, and field walks with community members. We studied a small population of Z. guidonia and recorded 116 woody species. Our findings showed that conserved forests were more diverse than secondary forests. Seventy-four percent of the species are useful to people. The Totonac people chose traditional vanilla plantations as a guiding model to shape their agroforestry system for restoring native vegetation. The results of our collaborative work revealed the Totonac extensive Traditional Ecological Knowledge and the need for the Voladores' group to strengthen alliances with other government and nongovernment organizations. They designed a model of a diversified traditional agroforestry vanilla system enriched with multipurpose plants as the outset of local well-being and regional agrobiodiversity restoration. This study reveals a distinct heterogenous land management scheme that provides the necessary conditions for preserving plant diversity, which will be used by local people for different purposes. We argue for studies that build on the relationship between scientific knowledge and Traditional Ecological Knowledge in transformed landscapes as a step forward for the long-term conservation of biocultural diversity.
The abundance, species richness, similarity and dominance of braconid parasitoid wasps were estimated for 4 types of land use (secondary forest, rubber plantations, living fences and pastures), and remnants of preserved tropical rain forest in southern Mexico. We also analyzed whether specialist (koinobionts) taxa are more negatively affected by forest disturbance than generalists (idiobionts), and whether braconid abundance is correlated with adult host abundance. Braconids were sampled using 3 Malaise traps for each type of land use during March 2010 and May 2011. We collected 143 individuals belonging to 65 species and 15 subfamilies. Species richness and abundance were higher in preserved and secondary forests, than in other types of land use. Although abundance and richness were low in pastures, these sites potentially contain hosts for braconids. We detected no variation in abundance or species richness by land use, even when comparing idio-and koinobionts. The most dominant species belonged to the genera Apanteles (Microgastrinae) and Hetersopilus (Doryctinae) in all land use types, except pasture, where Bracon (Braconinae) dominated. We detected a positive relationship between braconids and adult host abundance. Altogether, the 4 types of land use and the preserved forest are able to host a diverse braconid community.
1Autor para la correspondencia: novelazquez@uv.mx Resumen: En los bosques mesófi los de montaña, los disturbios antropogénicos afectan la abundancia y diversidad de las comunidades de epífi tas; sin embargo, las causas de estos cambios han sido poco exploradas. En este trabajo se evalúa la variación del área foliar, grosor de la lámina foliar, masa seca por unidad de área, densidad foliar y contenido de humedad en las diez especies de epífi tas vasculares más abundantes de bosque mesófi lo y vegetación derivada (bosque conservado, acahual de 20 años y cafetal bajo sombra), ubicado en la región central de Veracruz, México. El propósito del estudio fue entender de qué manera la variación mircroambiental (temperatura, humedad relativa y radiación fotosintéticamente activa), determinada por la apertura del dosel que provocan las actividades antrópicas, infl uye en las características funcionales de las epífi tas. Las condiciones de mayor estrés hídrico y mayor radiación se registraron en la comunidad más modifi cada y con mayor apertura del dosel (cafetal), y disminuyeron conforme se incrementa el grado de conservación y el dosel es más cerrado (acahual-bosque). Estos cambios microambientales se asociaron con las respuestas funcionales de las especies estudiadas. En el bosque conservado, las epífi tas presentaron signifi cativamente hojas más delgadas, con mayor contenido de humedad, menor masa seca y densidad foliar; mientras que en el cafetal se encontró el patrón opuesto. Las características funcionales de las comunidades de epífi tas fueron útiles para determinar el estado de conservación en el bosque mesófi lo y, permitieron entender que factores microambientales determinan sus respuestas funcionales. Palabras clave: bromelias, gradiente de conservación, helechos, orquídeas, rasgos morfo-ecofi siológicos. Abstract:The abundance and diversity of epiphytic communities in the tropical montane cloud forests are commonly affected by anthropogenic disturbances. However, the exact causes triggering such changes in the communities have poorly been explored. Canopy structure changes is one of the main factors affecting the communities of epiphytes, but plant responses to micro-environmental factors are largely unknown. In a landscape dominated by anthropogenic changes, we aimed to understand the effects of microclimatic factors (temperature, relative humidity and photosynthetically active radiation) on the functional responses (variation in leaf area, leaf blade thickness, dry mass per unit area, leaf density and moisture content) of the ten most abundant species of epiphytes. This study was done in Central Veracruz, Mexico, and included a well-conserved cloud forest, a 20-year-old secondary forest and a shade coffee plantation. Hydric stress and radiation were correlated with canopy openness, being the coffee plantation the most stressful community for the epiphytes and the conserved forest the less stressful site. We detected plant specifi c functional responses to microclimatic factors, but in general, in the natural...
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