Stand Characteristics and Leaf Litter Composition of a Dry Forest Hectare in Santa Rosa National Park, Costa Rica

One hectare of tropical dry forest in Guanacaste Conservation Area, Costa Rica was mapped and all trees larger than 10 cm diameter at breast height (DBH) identified. The same hectare was sampled for leaf litter and the two data sets, forest and litter, were compared. Dominant and subdominant species of the forest are represented in the leaf litter, whereas rare tree species are highly variable in their representation in the leaf litter. Relative abundance of dominant and subdominant tree species is represented well by the litter although absolute rank-order is nor identical between source forest basal area and leaf litter mass. The litter adds a significant component to the source forest data owing to the presence of vines and lianas, and more rarely small trees or shrubs. This indicates that litter studies may be able to add depth to forest diversity surveys. The source forest also was used to test foliar physiognomic reconstructions of climate that have been proposed recently by paleobotanists as an alternative to taxonomic affinities methods. The observed climate of the area does not conform to the climatic values that were predicted by application of these new methods. RESUMEN Una hectÁrea de bosque seco tropical en el Area de ConservaciÓn de Guanacaste, Costa Rica fue mapeada, y todos los Árboles mayores de 10 cm de dap fueron identificados. En la misma hectÁrea, se tomaron muestras de hojarasca y los dos colecciones de datos. bosque y hojarasca, fueron comparadas. Se encontrÓ que las especies dominantes y subdominantes del bosque estaban representadas en las muestras de hojarasca, mientras que la presencia de especias arbÓreas raras en las muestras de mojarasca fue muy variable. La abundancia relativa de especies arbÓreas dominantesestÁ bien representada en la hojarasca aunque el Área basal del bosque de origen y la masa de hojarasca no heron idÉnticos en rangos absolutos. La hojarasca aÑade un componente significativo a los datos del bosque de origen debido a la presencia de bejucos y lianas en la hojarasca, y mÁs raramente Árboles pequeÑos y arbustos. Estos datos indican que los estudios de hojarasca pueden incrementar la precisiÓn de las estimaciones de la diversidad de los bosques. El bosque de origen fue usado tarnbien para examinar reconstrucciones del clima basados en la fisiognomia foliar recientemenre propuesras por paleobotÁnicas como una alternativa a mÉtodos de afinidad raxonÓmicas. El clima observado en el Área no corresponde con los valores climÁticos que fueron predecidos por la aplicaciÓn de estos nuevos mÉtodos.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73234/1/j.1744-7429.1997.tb00034.x.pd

Data S1: Raw data on the plants from the Nacozari tailings

Phytostabilization is a remediation technology that uses plants for in-situ stabilization of contamination in soils and mine tailings. The objective of this study was to identify native plant species with potential for phytostabilization of the abandoned mine tailings in Nacozari, Sonora in northern Mexico. A flora of 42 species in 16 families of angiosperms was recorded on the tailings site and the abundance of the most common perennial species was estimated. Four of the five abundant perennial species showed evidence of regeneration: the ability to reproduce and establish new seedlings. A comparison of selected physicochemical properties of the tailings in vegetated patches with adjacent barren areas suggests that pH, electrical conductivity, texture, and concentration of potentially toxic elements do not limit plant distribution. For the most abundant species, the accumulation factor for most metals was <1, with the exception of Zn in two species. A short-term experiment on adaptation revealed limited evidence for the formation of local ecotypes in Prosopis velutina and Amaranthus watsonii. Overall, the results of this study indicate that five native plant species might have potential for phytostabilization of the Nacozari tailings and that seed could be collected locally to revegetate the site. More broadly, this study provides a methodology that can be used to identify native plants and evaluate their phytostabilization potential for similar mine tailings

Above-ground productivity, nutrient dynamics and leaf characteristics in a chalk grassland

SIGLEAvailable from British Library Document Supply Centre- DSC:D60178 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Hurricane impact on biogeochemical processes in a tropical dry forest in western Mexico

Extreme climatic events (ECEs), such as hurricanes, significantly affect biogeochemical processes and their intensity is predicted to increase. We documented the immediate and short-term consequences of the impact of Hurricane Jova on such processes in primary undisturbed tropical dry forest at the Estación de Biología Chamela. Data from our long-term study in five contiguous small watersheds were used to provide perspective to the hurricane effects. Carbon (C), nitrogen (N) and phosphorus (P) concentrations and fluxes were measured in runoff, litterfall and surface litter prior to and after the impact of the hurricane. Dissolved organic P (DOP) and C (DOC) concentrations in runoff in October 2011 (hurricane landfall), were 96% and 33% greater than the mean concentrations of previous months (July-September 2011). Nutrient fluxes were 10 (DOC), 3 (DON) and 15 (DOP) times greater than the mean fluxes of previous months. N and P concentrations in litterfall collected a few days after the hurricane were not different from pre-disturbance values, but P concentrations were much greater a few months after disturbance. Nutrient fluxes from vegetation to soil due to Jova represented 42% (N) and 30% (P) of the mean annual N and P litterfall fluxes in the period 2010-2012. Surface litter P concentrations, but not N, were very high at the end of the dry season following Jova. In addition, N and P stocks at this time were about 40% higher than the mean stocks in May of the other years of study. Both, litterfall and surface litter P returned to average values about a year after the hurricane. Litterfall P use efficiency, but not N, decreased after hurricane impact. Mean residence time of organic matter and N were similar and did not respond to hurricane disturbance, whereas P residence time was lower and decreased after the hurricane. Overall, our results indicate that hurricane Jova can be identified as an ECE. The return to pre-disturbance values within a year after the event suggests a high degree of short-term biogeochemical resilience in this forest. Variables related to N were resistant (no change) to the impact of Jova and to rainfall variability, but those related to P were highly responsive, quickly recovering to pre-disturbance and long-term dynamics. The P response to the hurricane and its relevance in the ecosystem are discussed in terms of long-term forest productivity and resilience under a scenario of increasing extreme hydrometeorological events

An assessment of natural and human disturbance effects on Mexican ecosystems: Current trends and research gaps

Mexico harbors more than 10% of the planet's endemic species. However, the integrity and biodiversity of many ecosystems is experiencing rapid transformation under the influence of a wide array of human and natural disturbances. In order to disentangle the effects of human and natural disturbance regimes at different spatial and temporal scales, we selected six terrestrial (temperate montane forests, montane cloud forests, tropical rain forests, tropical semi-deciduous forests, tropical dry forests, and deserts) and four aquatic (coral reefs, mangrove forests, kelp forests and saline lakes) ecosystems. We used semi-quantitative statistical methods to assess (1) the most important agents of disturbance affecting the ecosystems, (2) the vulnerability of each ecosystem to anthropogenic and natural disturbance, and (3) the differences in ecosystem disturbance regimes and their resilience. Our analysis indicates a significant variation in ecological responses, recovery capacity, and resilience among ecosystems. The constant and widespread presence of human impacts on both terrestrial and aquatic ecosystems is reflected either in reduced area coverage for most systems, or reduced productivity and biodiversity, particularly in the case of fragile ecosystems (e. g., rain forests, coral reefs). In all cases, the interaction between historical human impacts and episodic high intensity natural disturbance (e. g., hurricanes, fires) has triggered a reduction in species diversity and induced significant changes in habitat distribution or species dominance. The lack of monitoring programs assessing before/after effects of major disturbances in Mexico is one of the major limitations to quantifying the commonalities and differences of disturbance effects on ecosystem properties. © 2011 Springer Science+Business Media B.V

An assessment of natural and human disturbance effects on Mexican ecosystems: current trends and research gaps

Mexico harbors more than 10% of the planet’s endemic species. However, the integrity and biodiversity of many ecosystems is experiencing rapid transformation under the influence of a wide array of human and natural disturbances. In order to disentangle the effects of human and natural disturbance regimes at different spatial and temporal scales, we selected six terrestrial (temperate montane forests, montane cloud forests, tropical rain forests, tropical semi-deciduous forests, tropical dry forests, and deserts) and four aquatic (coral reefs, mangrove forests, kelp forests and saline lakes) ecosystems. We used semiquantitative statistical methods to assess (1) the most important agents of disturbance affecting the ecosystems, (2) the vulnerability of each ecosystem to anthropogenic and natural disturbance, and (3) the differences in ecosystem disturbance regimes and their resilience. Our analysis indicates a significant variation in ecological responses, recovery capacity, and resilience among ecosystems. The constant and widespread presence of human impacts on both terrestrial and aquatic ecosystems is reflected either in reduced area coverage for most systems, or reduced productivity and biodiversity, particularly in the case of fragile ecosystems (e.g., rain forests, coral reefs). In all cases, the interaction between historical human impacts and episodic high intensity natural disturbance (e.g., hurricanes, fires) has triggered a reduction in species diversity and induced significant changes in habitat distribution or species dominance. The lack of monitoring programs assessing before/after effects of major disturbances in Mexico is one of the major limitations to quantifying the commonalities and differences of disturbance effects on ecosystem properties