Estructura, composición y diversidad del matorral de duna costera en el litoral yucateco

In order to provide elements to make decisions in future management programs, the scrub vegetation of coastal sand dune was characterized in Yucatan, Mexico. This ecosystem has been deteriorated and fragmented due to anthropogenic activities. We recorded the height, coverage and taxonomic identity of individuals ≥ 50 cm in height, in ten locations. A total of 71 species of vascular plants in 36 families were recorded. Two types of communities, one with a shrub dominance and individuals lees than 3 m and other one with larger individuals ≥ 3 m. Values of alpha diversity (26.6), gamma (71) and beta (2.66) were determined. Classification and ordenation analyzes distinguished three groups of vegetation: G1) in the western part of the coast was characterized by species such as <em>Pithecellobium keyense/<em> and <em>Sideroxylon americanum</em>, G2) in the central part by <em>Coccothrinax readii, Bravaisia berlandieriana</em> and <em>Metopium brownei</em>, G3) in the east, was characterized by <em>Coccothrinax readii, Thrinax radiata</em> and <em>Pseudophoenix sargentii</em>. This study provides ecological elements to take decisions on future programs of restoration and management of the coastal dune in Yucatan, Mexico.</em></em>

Influencia de los mezquites en la composición y cobertura de la vegetación herbácea de un agostadero semiárido del norte de Guanajuato

It has been said for a long time that mesquite reduces significantly cover and productivity of herbaceous vegetation in the range lands. Likewise there are evidences showing the opposite. This controversy make us think that this interaction is not fully understood. This work evaluated the effect of mesquite on the herbaceous vegetation along a gradient which range from open to a heavy dense stands. It was found that isolated arboreal mesquites reduced up to 50% the photosyntetic photon flux density which are not limiting for C4, species, whereas clustered shrubby mesquites reduces 75 % which can limit the growth of these species. Such conditions creates three plant groupings: the first made up of short and caespitose grasses which grow in the open. The second with a better and more diverse group growing under the tree canopy, dominated by bunchgrasses, cacti and shrubs. The third under the close canopy of the clustered shrubby mesquites with shrub dominance.

Meter scale variation in shrub dominance and soil moisture structure Arctic arthropod communities

The Arctic is warming at twice the rate of the rest of the world. This impacts Arctic species both directly, through increased temperatures, and indirectly, through structural changes in their habitats. Species are expected to exhibit idiosyncratic responses to structural change, which calls for detailed investigations at the species and community level. Here, we investigate how arthropod assemblages of spiders and beetles respond to variation in habitat structure at small spatial scales. We sampled transitions in shrub dominance and soil moisture between three different habitats (fen, dwarf shrub heath, and tall shrub tundra) at three different sites along a fjord gradient in southwest Greenland, using yellow pitfall cups. We identified 2,547 individuals belonging to 47 species. We used species richness estimation, indicator species analysis and latent variable modeling to examine differences in arthropod community structure in response to habitat variation at local (within site) and regional scales (between sites). We estimated species responses to the environment by fitting species-specific generalized linear models with environmental covariates. Species assemblages were segregated at the habitat and site level. Each habitat hosted significant indicator species, and species richness and diversity were significantly lower in fen habitats. Assemblage patterns were significantly linked to changes in soil moisture and vegetation height, as well as geographic location. We show that meter-scale variation among habitats affects arthropod community structure, supporting the notion that the Arctic tundra is a heterogeneous environment. To gain sufficient insight into temporal biodiversity change, we require studies of species distributions detailing species habitat preferences.

Meter scale variation in shrub dominance and soil moisture structure Arctic arthropod communities

The Arctic is warming at twice the rate of the rest of the world. This impacts Arctic species both directly, through increased temperatures, and indirectly, through structural changes in their habitats. Species are expected to exhibit idiosyncratic responses to structural change, which calls for detailed investigations at the species and community level. Here, we investigate how arthropod assemblages of spiders and beetles respond to variation in habitat structure at small spatial scales. We sampled transitions in shrub dominance and soil moisture between three different habitats (fen, dwarf shrub heath, and tall shrub tundra) at three different sites along a fjord gradient in southwest Greenland, using yellow pitfall cups. We identified 2547 individuals belonging to 47 species. We used species richness estimation, indicator species analysis and latent variable modeling to examine differences in arthropod community structure in response to habitat variation at local (within site) and regional scales (between sites). We estimated species responses to the environment by fitting species-specific generalized linear models with environmental covariates. Species assemblages were segregated at the habitat and site level. Each habitat hosted significant indicator species, and species richness and diversity were significantly lower in fen habitats. Assemblage patterns were significantly linked to changes in soil moisture and vegetation height, as well as geographic location. We show that meter-scale variation among habitats affects arthropod community structure, supporting the notion that the Arctic tundra is a heterogenous environment. To gain sufficient insight into temporal biodiversity change, we require studies of species distributions detailing species habitat preferences.

Meter scale variation in shrub dominance and soil moisture structure Arctic arthropod communities

The Arctic is warming at twice the rate of the rest of the world. This impacts Arctic species both directly, through increased temperatures, and indirectly, through structural changes in their habitats. Species are expected to exhibit idiosyncratic responses to structural change, which calls for detailed investigations at the species and community level. Here, we investigate how arthropod assemblages of spiders and beetles respond to variation in habitat structure at small spatial scales. We sampled transitions in shrub dominance and soil moisture between three different habitats (fen, dwarf shrub heath, and tall shrub tundra) at three different sites along a fjord gradient in southwest Greenland, using yellow pitfall cups. We identified 2547 individuals belonging to 47 species. We used species richness estimation, indicator species analysis and latent variable modeling to examine differences in arthropod community structure in response to habitat variation at local (within site) and regional scales (between sites). We estimated species responses to the environment by fitting species-specific generalized linear models with environmental covariates. Species assemblages were segregated at the habitat and site level. Each habitat hosted significant indicator species, and species richness and diversity were significantly lower in fen habitats. Assemblage patterns were significantly linked to changes in soil moisture and vegetation height, as well as geographic location. We show that meter-scale variation among habitats affects arthropod community structure, supporting the notion that the Arctic tundra is a heterogenous environment. To gain sufficient insight into temporal biodiversity change, we require studies of species distributions detailing species habitat preferences.