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There is a lack of knowledge on the factors driving epiphytic community assemblage along water-limited environments. Epiphytic bromeliad and host communities were analyzed in a range of vegetation types, following a precipitation gradient from 500 to 1500 mm y−1. Plots were set up in scrub mangrove, coastal sand dune scrub, deciduous, semi-deciduous and sub-perennial forests within the Yucatan Peninsula in Mexico. Identity and abundance of hosts and epiphytes, as well as host height and seasonal microenvironmental variables, were recorded at each vegetation type. The study found epiphytic bromeliads to be mainly located in the lower canopy strata of all but the wettest site (sub-peren nial forest). Total epiphyte richness (estimated using species accumulation curves) increased with annual precipitation. Bromeliad species density decreased with vapor pressure deficit and increased with host species density. Semi-variograms and kriging analysis showed a high spatial correlation in bromeliad and host species density. The species composition, however, was unrelated to space, according to a Mantel test, but related to host species composition. The current study shows that diversity and structural integrity of the canopy may be as important as climate in the conservation of epiphytic composition in water-limited environments, where epiphytes are found in sheltered, lower canopy strata.

Temperature is one of the main environmental factors involved in global warming and has been found to have a direct effect on plants. However, few studies have investigated the effect of higher temperature on tropical crops. We therefore performed an experiment with a tropical crop of Habanero pepper (Capsicum Chinense Jacq.). Three growth chambers were used, each with 30 Habanero pepper plants. Chambers were maintained at a diurnal maximum air temperature (DMT) of 30 (chamber 1), 35 (chamber 2) and 40°C (chamber 3). Each contained plants from seedling to fruiting stage. Physiological response to variation in DMT was evaluated for each stage over the course of five months. The results showed that both leaf area and dry mass of Habanero pepper plants did not exhibit significant differences in juvenile and flowering phenophases. However, in the fruiting stage, the leaf area and dry mass of plants grown at 40°C DMT were 51 and 58% lower than plants at 30°C DMT respectively. Meanwhile, an increase in diurnal air temperature raised both stomatal conductance and transpiration rate, causing an increase in temperature deficit (air temperature – leaf temperature). Thus, leaf temperature decreased by 5°C, allowing a higher CO2 assimilation rate in plants at diurnal maximum air temperature (40°C). However, in CO2 measurements when leaf temperature was set at 40°C, physiological parameters decreased due to an increase in stomatal limitation. We conclude that the thermal optimum range in a tropical crop such as Habanero pepper is between 30 and 35°C (leaf temperature, not air temperature). In this range, gas exchange through stomata is probably optimal. Also, the air temperature–leaf temperature relationship helps to explain how temperature keeps the major physiological processes of Habanero pepper healthy under experimental conditions.

Palms are a resource of great importance in the tropics and are found in a variety of ecosystems, including the wetlands of the tropical coastal plains. In order to recover wetland ecosystems, we studied the traditional uses of wetland palms, by conducting interviews in the communities of four municipalities on the Gulf of Mexico coast. We found that people use five species of palm: Cocos nucifera, Sabal mexicana, Attalea liebmannii, Roystonea dunlapiana and Acrocomia aculeata. Main uses for the five species were for food and construction materials. Although palms are still used, traditional knowledge is declining in the younger generations, likely as a result of various social, cultural and economic factors. It is important to recover and promote the traditional use and value of palm trees, especially for the native species, because of both the economic benefits and the environmental services they provide. More participatory work with the inhabitants is needed to initiate palm breeding programs to assist in the recovery of wetland ecosystems.

Se analizó el patrón de preferencias en el uso de leña combustible en 1153  viviendas de seis localidades de Yucatán, mediante la aplicación de cuestionarios estructurados a informantes clave y muestreos en los sitios de extracción. Las localidades de estudio presentan heterogeneidad en la composición florística  y distancia a la ciudad capital de estado, factores que modifican las preferencias y hábitos de consumo. El promedio de consumo en las localidades de estudio oscilo entre 1,26 y 2 ,89 kg/día/habitante, el promedio general de los sitios estudiados fue de 2,06 kg/día/habitante. La leña se extrae de la vegetación aledaña,  la milpa y el solar. La colecta se hace a una distancia promedio de 3,8 km respecto a la vivienda. Los medios básicos para su transporte son el triciclo, la carga directa en la espalda del usuario y mediante uso de vehículo automotor.  La leña se colecta fundamentalmente como material seco desprendido o seco en pie, debido a su menor peso, facilidad de acarreo y rápida ignición. Los usos fundamentales son la cocción de alimentos y calentamiento de agua de baño. 41 son las especies más usadas como combustible, pero las principales son: Acacia gaumeri, Havardia albicans, Lysiloma latisiliquum, Gymnopodium floribundum, Bursera simaruba, Caesalpinia gaumeri, Conocarpus erectus y Piscidia piscipula, debido a su mayor abundancia, fácil encendido, duración en el fuego y/o baja emisión de humo.

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El metabolismo ácido de las crasuláceas es una adaptación de algunas plantas a condiciones de escasez de agua o bióxido de carbono y está relacionado con mecanismos de respuesta anatómicos, morfológicos y fi siológicos para tolerar períodos prolongados de sequía. La luz puede afectar diferentes procesos metabólicos, fi siológicos y estructurales de las plantas cuando es excesiva, por lo que en ambientes cambiantes, como en las selvas caducifolias, las hojas presentan respuestas de fotoprotección. El objetivo de este trabajo fue determinar esas respuestas, en dos microambientes de luz y dos temporadas del año, en una bromeliácea terrestre (Bromelia karatas) de la selva baja caducifolia en el Parque Nacional Dzibilchaltún, Yucatán. Las características morfológicas y fi siológicas de las hojas refl ejaron la infl uencia del ambiente, lo que les permitió conservar potenciales hídricos diurnos elevados y minimizar la pérdida de agua para mantener la fotosíntesis. Estas características, en conjunto con las espinas foliares y el crecimiento asexual de esta especie, pueden ayudar a explicar su alto valor de importancia ecológica en esta selva baja caducifolia.