Genetic composition, genetic diversity, and small-scale environmental variation matter for the experimental reintroduction of a rare plant

Aims Reintroduction has become an important tool for the management of endangered plant species. We tested the little-explored effects of small-scale environmental variation, genotypic composition (i.e. identity of genotypes), and genotypic diversity on the population survival of the regionally rare clonal plant Ranunculus reptans. For this species of periodically inundated lakeshores genetic differentiation had been reported between populations and between short-flooded and long-flooded microsites within populations.Methods We established 306 experimental test populations at a previously unoccupied lake shore, comprising either monocultures of 32 genotypes, mixtures of genotypes within populations or mixtures of genotypes between populations. In 2000, three years after planting out at the experimental site, a long-lasting flood caused the death of half of the experimental populations. In 2003, an extreme drought resulted in the lowest summer water levels ever measured.Important findings Despite these climatic extremes, 27 of the established populations survived until the end of the experiment in December 2003. The success of experimental populations largely differed between microsites. Moreover, the success of genotype monocultures depended on genotype and source population. Genetic differentiation between microsites played a minor role for the success of reintroduction. After the flood, populations planted with genotypes from different source populations increased in abundance, whereas populations with genotypes from single source populations and genotype monocultures decreased. We conclude that sources for reintroductions need to be selected carefully. Moreover, mixtures of plants from different populations appear to be the best choice for successful reintroduction, at least in unpredictably varying environments.

Neighbourhood abundance and small-tree survival in a lowland Bornean rainforest

Conspecific effects of neighbours on small-tree survival may have a role in tree population dynamics and community composition of tropical forests. This notion was tested with data from two 4-ha plots in lowland forest at Danum, Sabah (Borneo), for a 21-year interval (censuses at 1986, 1996, 2001, 2007). Species with ≥45 focal trees 10 to <100 cm stem girth per plot in 1986 were selected. Logistic regressions fitted mean focal tree size and mean inverse-distance-weighted basal area abundance of neighbours (within 20 m), for the periods over which each focus tree was alive. Coefficients of variation of neighbourhood basal area abundance, both spatially and temporally, quantified the changing environment of each focus tree. Fits were critically and individually evaluated, with corrections for spatial autocorrelation. Conspecific effects at Danum was generally very weak or non-existent: species’ mortality rates varied also across plots. The main reasons appear to be that (1) species were not dense enough to interact despite frequent although weak spatial aggregation, and their neighbourhoods were highly differing in species composition; and (2) these neighbourhoods were highly variable temporally, meaning that focus trees experienced stochastically fluctuating neighbourhood environments. Only one species, Dimorphocalyx muricatus, showed strong conspecific effects (varying between plots) which can be explained by its distinct ecology. This understorey species is highly aggregated on ridges and is drought-tolerant. That this functionally and habitat-specialized species, has implied intraspecific density-dependent feedback in its dynamics is a remarkable indication of the overall processes maintaining stability of the Danum forest.

Temporal and small-scale spatial variation in grassland productivity, biomass quality, and nutrient limitation

Characterization of spatial and temporal variation in grassland productivity and nutrition is crucial for a comprehensive understanding of ecosystem function. Although within-site heterogeneity in soil and plant properties has been shown to be relevant for plant community stability, spatiotemporal variability in these factors is still understudied in temperate grasslands. Our study aimed to detect if soil characteristics and plant diversity could explain observed small-scale spatial and temporal variability in grassland productivity, biomass nutrient concentrations, and nutrient limitation. Therefore, we sampled 360 plots of 20 cm × 20 cm each at six consecutive dates in an unfertilized grassland in Southern Germany. Nutrient limitation was estimated using nutrient ratios in plant biomass. Absolute values of, and spatial variability in, productivity, biomass nutrient concentrations, and nutrient limitation were strongly associated with sampling date. In April, spatial heterogeneity was high and most plots showed phosphorous deficiency, while later in the season nitrogen was the major limiting nutrient. Additionally, a small significant positive association between plant diversity and biomass phosphorus concentrations was observed, but should be tested in more detail. We discuss how low biological activity e.g., of soil microbial organisms might have influenced observed heterogeneity of plant nutrition in early spring in combination with reduced active acquisition of soil resources by plants. These early-season conditions are particularly relevant for future studies as they differ substantially from more thoroughly studied later season conditions. Our study underlines the importance of considering small spatial scales and temporal variability to better elucidate mechanisms of ecosystem functioning and plant community assembly.

Associations between ambient levels of combustion pollutants and small for gestational age infants in Texas

There is scant evidence regarding the associations between ambient levels of combustion pollutants and small for gestational age (SGA) infants. No studies of this type have been completed in the Southern United States. The main objective of the project presented was to determine associations between combustion pollutants and SGA infants in Texas using three different exposure assessments. ^ Birth certificate data that contained information on maternal and infant characteristics were obtained from the Texas Department of State Health Services (TX DSHS). Exposure assessment data for the three aims came from: (1) U.S. Environmental Protection Agency (EPA) National Air Toxics Assessment (NATA), (2) U.S. EPA Air Quality System (AQS), and (3) TX Department of Transportation (DOT), respectively. Multiple logistic regression models were used to determine the associations between combustion pollutants and SGA. ^ For the first study looked at annual estimates of four air toxics at the census tract level in the Greater Houston Area. After controlling for maternal race, maternal education, tobacco use, maternal age, number of prenatal visits, marital status, maternal weight gain, and median census tract income level, adjusted ORs and 95% confidence intervals (CI) for exposure to PAHs (per 10 ng/m3), naphthalene (per 10 ng/m3), benzene (per 1 µg/m3), and diesel engine emissions (per 10 µg/m3) were 1.01 (0.97–1.05), 1.00 (0.99–1.01), 1.01 (0.97–1.05), and 1.08 (0.95–1.23) respectively. For the second study looking at Hispanics in El Paso County, AORs and 95% confidence intervals (CI) for increases of 5 ng/m3 for the sum of carcinogenic PAHs (Σ c-PAHs), 1 ng/m3 of benzo[a]pyrene, and 100 ng/m3 in naphthalene during the third trimester of pregnancy were 1.02 (0.97–1.07), 1.03 (0.96–1.11), and 1.01 (0.97–1.06), respectively. For the third study using maternal proximity to major roadways as the exposure metric, there was a negative association with increasing distance from a maternal residence to the nearest major roadway (Odds Ratio (OR) = 0.96; 95% CI = 0.94–0.97) per 1000 m); however, once adjusted for covariates this effect was no longer significant (AOR = 0.98; 95% CI = 0.96–1.00). There was no association with distance weighted traffic density (DWTD). ^ This project is the first to look at SGA and combustion pollutants in the Southern United States with three different exposure metrics. Although there was no evidence of associations found between SGA and the air pollutants mentioned in these studies, the results contribute to the body of literature assessing maternal exposure to ambient air pollution and adverse birth outcomes. ^

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.