Survival and development of Brosimum alicastrum (Moraceae) and Psidium sartorianum (Myrtaceae) seedlings differ under flooding conditions

Antecedentes y Objetivos: En los bosques tropicales la inundación estacional puede actuar como filtro ambiental afectando la supervivencia, el establecimiento y el crecimiento de las plántulas de especies arbóreas e influir en la estructura de las comunidades. Se simularon condiciones de inundación y sequía con el objetivo de evaluar su efecto como filtro ambiental sobre la supervivencia, crecimiento (longitud del tallo y número de hojas) y biomasa acumulada en plántulas de Brosimum alicastrum y Psidium sartorianum de la selva de Campeche, México. Métodos: Se estableció un experimento en condiciones de vivero con un diseño completamente al azar, con tres tratamientos (sequía, riego regular e inundación). Para cada tratamiento se utilizaron 45 plántulas de cada especie. Se evaluaron la supervivencia, altura y número de hojas de las plántulas al inicio del experimento y a intervalos de 30 días hasta su conclusión a los 120 días. Al finalizar, se cosecharon las plántulas y se midió la longitud de las raíces y la biomasa acumulada. Resultados clave: La inundación disminuyó la supervivencia de plántulas de B. alicastrum y no la de P. sartorianum, limitó la longitud del tallo, el número de hojas y la biomasa acumulada de ambas especies, pero no la biomasa de raíces de P. sartorianum. La supervivencia de las plántulas expuestas a sequía y riego regular no cambió y aumentó el crecimiento y biomasa acumulada. Conclusiones: Las respuestas de las especies contribuyeron a entender el papel del filtro ambiental en el establecimiento de las plántulas de especies arbóreas en los bajos de Calakmul, Campeche. La inundación estacional actúa como un filtro ambiental, elimina las plántulas de B. alicastrum en los bajos, mientras que esta especie predomina en áreas con suelos bien drenados como los lomeríos adyacentes a la zona inundada. Psidium sartorianum se adaptó a las condiciones de sequía e inundación, como se observa en su hábitat natural.Background and Aims: Seasonal flooding in tropical forests may function as an environmental filter that affects the survival, establishment and growth of tree seedlings, with consequences for the assembly of communities. Seasonal flood and drought conditions were simulated with the objective to evaluate their effect on the survival, growth (stem length and number of leaves), as well as biomass accumulation in Brosimum alicastrum and Psidium sartorianum seedlings from the tropical forest of Campeche, Mexico. Methods: A nursery experiment was established with a completely random design with three treatments (flooding, regular irrigation and drought). For each treatment 45 seedlings were used for each species. The survival, height and number of leaves of the seedlings were measured at the beginning of the experiment and at 30 days intervals until the experiment ended at 120 days. The seedlings were then harvested and the length of the roots and the biomass accumulation were measured. Key results: The flood decreased the survival of B. alicastrum and did not change the survival of P. sartorianum. Likewise, it limited the length of the stem, the number of leaves and the biomass accumulated in both species, except for the biomass in roots of P. sartorianum. The survival of the seedlings exposed to drought and regular irrigation were not altered and showed increases in growth and accumulated biomass. Conclusions: The responses of the species contributed to understand the role of the environmental filter in the establishment of arboreal species seedlings in the lowlands of Calakmul, Campeche. Seasonal flooding in the lowlands acts as an environmental filter because it eliminates B. alicastrum seedlings, while it predominates in areas with well-drained soils, such as the hills adjacent to the low floodplains. Psidium sartorianum was well adapted to the conditions of drought and flood, as observed in its natural habitat

Regeneración natural de especies arbóreas en una selva mediana subperennifolia perturbada por extracción forestal

Natural regeneration of eight species of trees in three different types of gaps caused by selective logging of mahogany in a rainforest of Quintana Roo, Mexico, was studied. Point centered quarter method was applied randomly in each of the 10 replications per site. Height and density of the seedling and saplings were evaluated. Results indicate that selective logging creates gaps in which there are recruitment and growth of all eight species studied. In general, the type of gap did not show significant effect on plant density, but the growth of Swietenia macrophylla and Metopium brownei was significantly affected by the type of gap. Seedlings and saplings growing in gaps caused by roads and by falling of logs had significant higher heights than the control. After six years of disturbance, the gaps are an important reservoir seedlings and saplings of economically important trees with the possibility of conforming over time a rainforest dominated by these species.Se evaluó la regeneración natural de ocho especies arbóreas en una selva mediana subperennifolia perturbada por la explotación forestal comercial, en Quintana Roo. La densidad y altura de las especies estudiadas en la regeneración natural se registraron en sitios seleccionados al azar, mediante el método de “cuadrantes centrados en un punto”.  Los resultados indican que con la extracción forestal se abren claros que favorecen la incorporación y el crecimiento de cada una de las especies estudiadas. En general, la densidad no muestra diferencias significativas respecto al tipo de perturbación. Sólo Swietenia macrophylla y Metopium brownei presentaron un crecimiento significativo en el “camino” y en el “derribo-fuste”, respectivamente, con relación al testigo. Después de seis años estos claros representan una fuente importante de plántulas de especies con interés forestal, con la posibilidad de que a largo plazo, constituyan rodales dominados por dichas especies

Conservative nutrient use by big-leaf mahogany (Swietenia macrophylla king) planted under contrasting environmental conditions

We analyzed the nutritional composition and isotope ratios (C and N) of big-leaf mahogany (Swietenia macrophylla King) leaves in plantations established on contrasting soils and climates in Central America (State of Quintana Roo, Yucatán, México) and South America (State of Pará, Brazil). The objective was to determine the adaptability of this species to large differences in nutrient availability and rainfall regimes. Nutrient concentrations of leaves and soils were determined spectrophotometrically, and isotope ratios were measured using mass spectrometric techniques.In Pará soils were sandier, and acidic, receiving above 2000 mm of rain, whereas in Quintana Roo soils were predominantly clayey, with neutral to alkaline pH due to the underlying calcareous substrate, with about 1300 mm of rain. Leaf area/weight ratio was similar for both sites, but leaves from Quintana Roo were significantly smaller. Average N and K concentrations of adult leaves were similar, whereas Ca concentration was only slightly lower in Pará in spite of large differences in Ca availability. Leaves from this site had slightly higher P and lower Al concentrations. Differences in water use efficiency as measured by the natural abundance of 13C were negligible, the main effect of lower rainfall in Quintana Roo seemed to be a reduction in leaf area. The N isotope signature (δ15N) was more positive in Pará than in Quintana Roo, suggesting higher denitrification rates in the former. Results reveal a calciotrophic behavior and a remarkable capacity of mahogany to compensate for large differences in soil texture and nutrient availability

EFFECT OF THE PLANTATION DENSITY IN THE GROWTH AND PRODUCTIVITY OF Cnidoscolus chayamansa MCVAUGH (EUPHORBIACEAE)

The plantation density (PD) is a decisive factor in the agronomical resources of cultivation; as such, in this experiment, the effect of the growth and the productivity of the chaya plants were evaluated, as an associated growing in the cedar-lime system, to determine its optimum PD. The chaya plants were positioned at 1.50 x 3.00 m, utilizing cuttings without leaves; associated with young trees (less than 2 years) of Cedrela odorata and Citrus latifolia in a circular plantation design 'Nelder' of 3154 m2. Eight PD from 2602 to 3772 plants·ha-1 were defined with 10 repetitions. The variables were: rhizogenic potential (RP), growth rate (GR), index of vigor (IV), index of leaf area (ILA) and production of dry biomass (PDB). The results indicated that of the 3046 to 3772 plants·ha-1 were found to have the best RP, the ILA (5.44) and PDB (8.48 kg·plant-1); even though the IV (1.16) and GR (0.51 cm·day-1) were the best in 2602 to 2647 plants·ha-1. As the primary objective in this specie is the PDB, the PD optimal was 3046 to 3772 plants·ha-1

ABOVE AND BELOW GROUND INTERACTIONS IN THE AGROFORESTAL ASSOCIATION 'RED CEDAR-PERSIAN LIME-CHAYA'

Above and below ground interactions were analyzed in the agroforestal association 'red cedar-Persian lime-chaya', to know the initial optimum planting density (PD), in Quintana Roo, Mexico. Red cedar and Persian lime were placed in a 'Nelder' circle of 3154 m2 which consisted of 20 concentric circles alternating red cedars and Persian limes to 1.50 m apart and 10 plants per circle; chaya rectangular frame was set at 1.50 x 3.00 m, superimposed on the 'Nelder' circle. Defined eight PD 2602 to 3772 pl·ha-1 with 10 repetitions, to evaluate the length of main root (LMR), radical exploration range (RER), below ground interaction (BGI), plant height (PH), crown diameter (CD), above ground interaction (AGI) and soil fertility (SF). The growth intraspecific he present statistical difference (P≤0.05) when moving from one PD to another PD, while the growth interespecific manifested different growth habit. The agroforestal association propitious in soil decreased phosphorous ±2 %, and increases organic matter ±14 % and nitrogen ±10 % on all PD. The BGI was increased in direct relation with the PD, reaching its highest value (64±5.8 %) to 3772 pl·ha-1; the AGI also increased in direct relation with the PD, its highest value (52±3.1 %) went to 3772 pl·ha-1; therefore, to higher PD increased BGI and AGI, at 20 months after planting

Cambios en la diversidad de aves ante la perturbación de hábitats del sur de Quintana Roo, México

Actualmente, los ecosistemas enfrentan una gran pérdida de biodiversidad debido a perturbaciones antrópicas, lo cual que tiene efectos negativos en los procesos ecológicos. Para conocer el estado de conservación de un ambiente se pueden determinar especies indicadoras, que desempeñan un rol importante en distintos procesos ecológicos y son sensibles a los disturbios. El objetivo de este estudio fue determinar la diversidad y composición de aves en respuesta a diferentes perturbaciones del hábitat en el ejido Laguna Om, Quintana Roo, México, mediante conteo por puntos de agosto a septiembre de 2017. Se seleccionaron hábitats con diferente estado de conservación denominados: Selva, Laguna, Carretera, Potrero y Helechal. La mayor riqueza de especies se registró en los hábitats de Laguna y Carretera. Los patrones de abundancia de especies tolerantes a la perturbación fueron mayores en las áreas perturbadas. Encontramos mayor similitud en la composición de los gremios tróficos de las especies entre Laguna y Selva, y entre Helechal y Carretera, mientras que la composición en Potrero no mostró similitudes respecto a los otros hábitats. La diversidad y la composición de las especies de aves dependen de la complejidad estructural a nivel de hábitat, más que el tipo de perturbación que se asocia localmente.Currently, ecosystems face a great loss of biodiversity due to human disturbances, which has negative effects on ecological processes. To know the state of conservation of an environment, indicator species can be identified, which play an important role in different ecological processes and are sensitive to disturbances. The objective of this study was to determine the diversity of birds in response to different habitat disturbances in the ejido Laguna Om, Quintana Roo, Mexico, by means of counting by points from August to September 2017. We selected sites with different conservation status: Tropical Forest, Lagoon, Road, Pasture, and Invasive Fern habitat. In total 103 species of birds were recorded. We found a greater richness of species in Lagoon and the Road. The abundance patterns of species tolerant to disturbance was greater in disturbed areas. We found greater similarity in the trophic guilds composition shared between the Lagoon and the Tropical Forest, and in those shared between the Invasive Fern habitat and the Road, while the composition in the Pasture did not show similarities with respect to the other habitats. Bird species diversity and composition depend on the structural complexity at the habitat level, rather than the type of disturbance that is associated locally