In Site Soil Seed-Banks: Size, Composition and Persistence across Tropical Successional Stages.

I investigated the size, composition and persistence of the seed-bank in primary forests, secondary forests and old-fields in southern Mexico. I also assessed the contribution of the seed-bank to regeneration relative to other propagule sources. In all habitats, I removed by hand all plants and litter and excluded the seed-rain. For one year, I counted the number of plant species (5-50 cm tall) emerged and grouped them into different growth-forms: trees, shrubs, palms, herbs, woody lianas, epiphytes and hemi-epiphytes. A total of 95 species emerged. The seed-bank size, composition and persistence showed strong variation among successional stages. Emergence was low for primary and secondary forests, but high for old-fields (19, 26, and 68 plants per m-2, respectively). Herbs were the most abundant in the seed-bank and palms the less. Time had a negative effect on seed-bank size in primary forests and old-fields; whereas for secondary forests size remained constant throughout the year. The number of emerged plants in different growth-forms changed significantly across time for all successional stages. Overall, the seed-bank provided a greater number of plants in old-fields relative to other propagule sources combined. The results showed that forest modification alters the input of propagules throughout the seed-bank for different plant growth-forms.

Wood density relates negatively to maximum plant height across major angiosperm and gymnosperm orders.

PREMISE: Wood density is a crucial plant functional trait related to plant life history strategies. Its ecological importance in small-stature growth forms (e.g., shrubs) has not been extensively examined. Given that hydraulic conduit dimensions vary positively with plant height and that there is a negative relationship between conduits' diameter and wood density, I hypothesized an also negative relationship between wood density and plant height. Knowing that bark and pith proportions are significant in small-diameter stems, I additionally disentangled the contribution of wood, bark, and pith to stem density. METHODS: I determined density in small-diameter stems across 153 species spanning all major angiosperm and gymnosperm orders by considering a diversity of growth forms (trees, treelets, shrubs, vines, and hemiparasites). Stem cross sections were dissected to consider the densities of wood with bark and pith; wood with pith and without bark; wood with bark and no pith; and wood without bark and pith. Secondary growth was also measured. RESULTS: Trees showed similar wood densities as non-self-supporting vines, and both showed significantly less dense wood than treelets, shrubs, and hemiparasites. General comparisons showed that wood was significantly denser than all other tissues, and these differences did not depend on growth form. Wood density was significantly and negatively related to growth rate and pith area proportions but not to bark thickness proportion. CONCLUSIONS: An implicit negative relationship between maximum plant height and stem density emerges as a property of plants likely linked to hydraulic conductive size.

Riqueza y distribución de musgos en un bosque subandino en Bolívar-Santander, Colombia / Richness and distribution of mosses in a sub-Andean forest in Bolívar- Santander, Colombia

Resumen La brioflora colombiana es considerada una de las más diversas y de amplia distribución en zonas de vida andina y paramuna, debido a la variedad de ambientes, cumple una función como amortiguadora de erosión, regulación de la humedad que incide en el ambiente y en la conservación del hábitat. Este trabajo se realizó en un bosque subadino de 100 ha, del municipio de Bolívar (Santander, Colombia), mediante nueve transectos lineales de 100 x 4 m y se realizaron levantamientos de plantas no vasculares en todos los sustratos encontrados (suelo, rocas, raíces aflorantes, troncos de árboles, materia orgánica en descomposición y tubo de agua -drenajes-). Se registraron 129 ejemplares, pertenecientes a 72 especies en 48 géneros y 21 familias, que corresponden al 7.78 % de especies en el país y representan el 11.16 % de los registros actuales para el departamento de Santander. Las familias con mayor número de especies fueron: Pilotricaceae (15), Neckera ceae y Fissidentaceae con siete cada una, y Brachythe ciaceae, Leucobryaceae y Thuidiaceae con cinco especies cada una. Los géneros más ricos son: Lepidopilum (7), Fissidens (7) y Syrrhopodon (4). Treinta y cuatro géneros tienen solo una especie. La mayoría de especies de musgos se encontraron sobre corteza de árboles (20), seguido de las rocas (17) y en suelo (9). Con respecto a las formas de vida, las más abundantes fueron: los cojines (24 especies), ces pitosas (23), dendroides (8), reptantes (4) y péndulas (3). A partir de un análisis DCA se observó una mayor riqueza de especies en los transectos ubicados al interior del bosque. Adicionalmente, se encontraron 36 nuevos registros para Santander y uno para Colombia (Homaliodendron pini forme (Brid.) Enroth). Estos resultados muestran que los bosques subandinos colombianos pueden ser el hábitat de una riqueza considerable de especies de musgos, y que es necesario ampliar los inventarios de briófitos en regiones puntuales colombianas como es el caso de estos pequeños remanentes de bosque.

Abstract The Colombian bryoflora is considered one of the most diverse and widely distributed in the Andean mountains and the paramo areas, due to the variety of environments; it works like an erosion buffer zone and a humidity regulation that supports the environment and habitat conservation. This work was developed in a 100 ha Andean forest area, using nine linear transects of 100 x 4 m in the municipality of Bolívar (Santander, Colombia), and non-vascular plants were sampled in all substrates (soil, rocks, outcrops, organic matter and water tube-drainage). We recorded a total of 129 samples that belong to 72 species, 48 genera and 21 families, which represent the 7.78 % of the species in the country, and the 11.16 % of the current records in the department of Santander. Families with the highest number of species were Pilotricaceae (15), Neckeraceae and Fissidentaceae with seven species each one, and Brachytheciaceae, Leucobryaceae and Thuidiaceae with five species each one. The richness genera are Lepidopilum (7), Fissidens (7) and Syrrhopodon (4); a total of 34 genera with just one species. Most of the moss species were found on the bark trees (20), followed by rocks (17) and soil (9) substrates. Concerning to life forms, the most abundant were, cushions (24 especies), turfs (23), dendroid (8), creeping (4) and pendulous (3). Using a DCA analysis we observed a greater richness in transects located inside the forest. Moreover, we found 36 new records for Santander and one for the country (Homaliodendron piniforme (Brid.) Enroth). These results showed that the Colombian sub-Andean forest may be the habitat of a considerable richness of mosses species, and that is necessary to expand inventories of bryophytes in some Colombian regions.