La selva inundable de canacoite en Tabasco, México, una comunidad vegetal amenazada

The structure, composition and diversity of the floodplain forest (SMPC) of Bravaisia integerrima were studied in the two largest forest stands in Tabasco, Mexico: the Ecological Reserve Yu-Balcah (YCAH) with 271 ha, and State Park La Chontalpa (PECH) with 191 ha. In each forest stand 10 plots of 1000 m2 were sampled. Tree individuals sampled were identified to species, and evaluated in three age categories, seedlings, saplings, and adults. The relationship between species richness and sampling effort was analyzed using Chao 2, ICE, Jacknife 1, Jacknife 2 and Bootstrap. The structural analysis was based on the importance value index. The diversity of species was evaluated, using the Margalef index (DMg), α de Fisher, Shannon-Wiener (H') and equity of Pielou J. The dominance indices of Berger-Parker (d) and Simpson (D) were also used. The total number of species was 76, belonging to 64 genera and 33 botanical families. The richest family was Leguminosae with 15 species. The basal area of the sites YCAH and PECH was 37.2 and 29.5 m2ha-1, respectively. Bravaisia integerrima was the most important tree species in all stands, with an Importance Index of 277. The value of the Shannon index was 2.0 in both sites. YCAH showed the best ecological condition. Six species present in the stands are considered as threatened in Mexico (NOM-059-SEMARNAT-2010). The current extent of the floodplain forest of Bravaisia in Tabasco State is 490 ha. The results suggest that the structure and composition of this forest has been affected by human activity. As a consequence, to guarantee the conservation of these remnants of SMPC in Tabasco, it is important to verify their legal situation and the application of management plans, designed to improve the productive activities of the rural communities that live around the stands. To succeed in this endeavor, it is necessary that governmental actors, academics, non-governmental organizations, and civil society work together.Se analizó la estructura, composición y diversidad arbórea de los dos rodales más importantes de selva mediana perennifolia de Bravaisia integerrima (SMPC) de Tabasco, México: el de la Reserva Ecológica Yu-Balcah (YCAH) con una superficie de 271 ha y el del Parque Estatal La Chontalpa (PECH) con 191 ha. En cada uno se levantaron 10 parcelas de muestreo de 1000 m2, cubriendo un área total de 2 ha. Se identificó y registró a las plantas arbóreas, diferenciando brinzales, plantas juveniles y adultos. Se aplicaron diversos índices para analizar el esfuerzo de muestreo, la diversidad de especies, la abundancia proporcional, la dominancia y la equidad. El análisis estructural se basó en el valor de importancia. La riqueza total fue 76 especies, pertenecientes a 64 géneros y 31 familias botánicas, de las que la mejor representada fue Leguminosae con 15 especies. El área basal de YCAH y PECH fue de 37.2 y 29.5 m2ha-1, respectivamente. Bravaisia integerrima fue el árbol con mayor valor de importancia en los dos rodales con un Índice correspondiente de 277. Ambos fragmentos tienen un valor del índice de Shannon de 2.0. El sitio con mejor condición ecológica fue YCAH. Se identificaron seis especies catalogadas en la NOM-059-SEMARNAT-2010. La SMPC presenta una cobertura actual en Tabasco de 490 ha. Los resultados sugieren que su estructura y composición se han visto afectados por la actividad antrópica en la región. Para garantizar la conservación de los remanentes de SMPC en el estado, es importante revisar y actualizar su situación legal y sus planes de manejo, así como generar alternativas sociales y productivas en las poblaciones cercanas. Para lograrlo se requiere de la participación de actores gubernamentales, académicos, organizaciones no gubernamentales, particulares y sociedad en conjunto

Model comparisons for estimating carbon emissions from North American wildland fire

Research activities focused on estimating the direct emissions of carbon from wildland fires across North America are reviewed as part of the North American Carbon Program disturbance synthesis. A comparison of methods to estimate the loss of carbon from the terrestrial biosphere to the atmosphere from wildland fires is presented. Published studies on emissions from recent and historic time periods and five specific cases are summarized, and new emissions estimates are made using contemporary methods for a set of specific fire events. Results from as many as six terrestrial models are compared. We find that methods generally produce similar results within each case, but estimates vary based on site location, vegetation (fuel) type, and fire weather. Area normalized emissions range from 0.23 kg C m−2 for shrubland sites in southern California/NW Mexico to as high as 6.0 kg C m−2 in northern conifer forests. Total emissions range from 0.23 to 1.6 Tg C for a set of 2003 fires in chaparral-dominated landscapes of California to 3.9 to 6.2 Tg C in the dense conifer forests of western Oregon. While the results from models do not always agree, variations can be attributed to differences in model assumptions and methods, including the treatment of canopy consumption and methods to account for changes in fuel moisture, one of the main drivers of variability in fire emissions. From our review and synthesis, we identify key uncertainties and areas of improvement for understanding the magnitude and spatial-temporal patterns of pyrogenic carbon emissions across North America

An estimate of the number of tropical tree species

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e. at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa

Fenología reproductiva de las especies arbóreas del bosque tropical de Tenosique, Tabasco, México

La fenología de 341 árboles que corresponden a 75 especies fue estudiada en las montañas de Tenosique, Tabasco, entre agosto del 2003 hasta agosto del 2005. Para ello, se establecieron cinco transectos de 500 m de largo por cinco metros de ancho, los cuales se evaluaron mensualmente. Si alguno de los individuos de las especies tenía flores o frutos, la especie como un todo fue considerada en floración o fructificación en ese mes. Se aplicaron pruebas de homogeneidad de ji-cuadrada para evaluar la homogeneidad de la floración y fructificación a lo largo del año y por periodos bimensuales. La floración fue bimodal, con un pico de mayor floración de marzo a abril que corresponde a menor precipitación. En julio se presentó un segundo pico de floración con 21 especies, correspondiendo igualmente a un decrecimiento de la precipitación. El mayor número de especies con fruto se presentó entre mayo y junio, el cual no fue significativo estadísticamente. También se analizan los patrones fenológicos de las familias con mayor número de especies, los cuales difirieron entre sí. No se encontró relación entre el número de especies floreciendo o fructificando y la precipitación promedio mensual. Se encontraron picos fenológicos poco marcados debido a que en la zona de estudio la estacionalidad es poco marcada. Los patrones fenológicos varían dentro de una especie, entre años y entre localidades. Los datos que se aportan en el presente trabajo son relevantes para definir los periodos apropiados de recolecta de semillas para la realización de prácticas de manejo y conservación

Database of 478 allometric equations to estimate biomass for Mexican trees and forests

International audienceKey messageWe present a comprehensive database of 478 allometric equations to estimate biomass of trees and other life forms in Mexican forest and scrubland ecosystems.ContextAccurate estimation of standing biomass in forests is a prerequisite for any approach to carbon storage and a number of additional applications.AimsTo provide a comprehensive database with allometric equations applicable to a large number of tree and shrub species of Mexico.MethodsAn intensive literature search was carried out to pull together all publications related to allometric equations in the libraries of the most important forest research institutes across Mexico and the neighboring countries.ResultsA total of 478 equations were compiled. Four hundred fourteen equations included a detailed analysis of all compartments of the trees; 7 equations applied to shrubs, 15 to bamboos, and 2 to palms. The collected equations are applicable to a wide variety of forest ecosystems in Mexico ranging from desert scrublands in the North to lowland evergreen rainforests in the South. The attached database of allometric equations is possibly the most extensive compilation of equations currently available for Mexico.ConclusionThe database covers almost 100 % of the individuals recorded in the National Forest Inventory

Hábitat y distribución de cinco especies de Quercus (Fagaceae) en la Meseta Central de Chiapas, México

We describe the habitat ofspecies within .the Fagaceae subgenus Lepidobalanus (genus Quercus) and identify environmental variables relatedto their distribution in the Meseta Central of Chiapas, Southern Mexico. In 258 plots adortúnance index was used, combining tree density arid crown cover, for Quercus peduncularis, Q. polymorpha,Q. rugosa, Q. sebifera and Q.segoviensis. The following variables were measmed:. altitude, pre' cipitatioh from November through April (PPNA), exposure, slope, fuelcwoódharvesting and grazing. Detrended Carmonical correspondence Analysis was used for the statistical evaluation of data. Negative relationships among the donimance index of Q. peducularís and Q .. segoviensis, and altitude and PPNAvalues were found. The' dominance index oiQ. rugusa and Q. segoviensis was correlated with exposure .and intusity of fuel-wood harvesting. Altitude, and to a les ser extent PPNA;. determinedthe distribution of the evaluáted specíes. The results sUggest thatQuercus peduncularis, Q. polymorpha, Q. rugosa, Q. segovíensis and Q.sibijefa display different ecological patterusWe describe the habitat ofspecies within .the Fagaceae subgenus Lepidobalanus (genus Quercus) and identify environmental variables relatedto their distribution in the Meseta Central of Chiapas, Southern Mexico. In 258 plots adortúnance index was used, combining tree density arid crown cover, for Quercus peduncularis, Q. polymorpha,Q. rugosa, Q. sebifera and Q.segoviensis. The following variables were measmed:. altitude, pre' cipitatioh from November through April (PPNA), exposure, slope, fuelcwoódharvesting and grazing. Detrended Carmonical correspondence Analysis was used for the statistical evaluation of data. Negative relationships among the donimance index of Q. peducularís and Q .. segoviensis, and altitude and PPNAvalues were found. The' dominance index oiQ. rugusa and Q. segoviensis was correlated with exposure .and intusity of fuel-wood harvesting. Altitude, and to a les ser extent PPNA;. determinedthe distribution of the evaluáted specíes. The results sUggest thatQuercus peduncularis, Q. polymorpha, Q. rugosa, Q. segovíensis and Q.sibijefa display different ecological patteru

Assessment of Hammocks (Petenes) Resilience to Sea Level Rise Due to Climate Change in Mexico.

There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at "Los Petenes Biosphere Reserve", in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide

Germinación de semillas y clave para la identificación de plántulas de seis especies arbóreas nativas de humedales del sureste de México

Especies arbóreas de humedales son de importancia económica y para fines de restauración. Nosotros describimos el proceso de germinación y morfología de plántulas de seis especies arbóreas nativas típicas del sureste de México: Annona glabra, Ceiba pentandra, Pachira aquatica, Haematoxylum campechianum, Coccoloba barbadensis y Crataeva tapia. Un total de 300 semillas por especie fueron sembradas en una mezcla de arena, cascarilla de cacao y tierra negra (1: 1: 1), y mantenidas en invernadero a 30% de sombra artificial, de febrero a noviembre de 2007. Se realizó la caracterización morfológica, y elaboró una clave de plántulas con base en: 1) tipo de germinación 2) eje de la plántula y 3) elementos foliares. P. aquatica presenta germinación criptocotilar hipogea, las otras tienen germinación fanerocotilar epigea. Las tasas de germinación fueron altas ( > 86%), a excepción de C. barbadensis (69%)

Weighting values applied to the scores of all the indicators of each criterion to assess hammocks persistence.

<p>Weighting values applied to the scores of all the indicators of each criterion to assess hammocks persistence.</p