1,320 research outputs found
High dissimilarity within a multiyear annual record of pollen assemblages from a North American tallgrass prairie
Citation: Commerford, J. L., McLauchlan, K. K., & Minckley, T. A. (2016). High dissimilarity within a multiyear annual record of pollen assemblages from a North American tallgrass prairie. Ecology and Evolution, 6(15), 5273-5289. doi:10.1002/ece3.2259Grassland vegetation varies in composition across North America and has been historically influenced by multiple biotic and abiotic drivers, including fire, herbivory, and topography. Yet, the amount of temporal and spatial variability exhibited among grassland pollen assemblages, and the influence of these biotic and abiotic drivers on pollen assemblage composition and diversity has been relatively understudied. Here, we examine 4 years of modern pollen assemblages collected from a series of 28 traps at the Konza Prairie Long-Term Ecological Research Area in the Flint Hills of Kansas, with the aim of evaluating the influence of these drivers, as well as quantifying the amount of spatial and temporal variability in the pollen signatures of the tallgrass prairie biome. We include all terrestrial pollen taxa in our analyses while calculating four summative metrics of pollen diversity and composition -beta-diversity, Shannon index, nonarboreal pollen percentage, and Ambrosia: Artemisia -and find different roles of fire, herbivory, and topography variables in relation to these pollen metrics. In addition, we find significant annual differences in the means of three of these metrics, particularly the year 2013 which experienced high precipitation relative to the other 3 years of data. To quantify spatial and temporal dissimilarity among the samples over the 4-year study, we calculate pairwise squared-chord distances (SCD). The SCD values indicate higher compositional dissimilarity across the traps (0.38 mean) among all years than within a single trap from year to year (0.31 mean), suggesting that grassland vegetation can have different pollen signatures across finely sampled space and time, and emphasizing the need for additional long-term annual monitoring of grassland pollen
Weighted averaging partial least squares regression (WA-PLS): an improved method for reconstructing environmental variables from species assemblages
Weighted averaging partial least squares regression (WA-PLS): an improved method for reconstructing environmental variables from species assemblages
Relationships between quality of life and family function in caregiver
<p>Abstract</p> <p>Background</p> <p>There are caregivers who see their quality of life (QoL) impaired due to the demands of their caregiving tasks, while others manage to adapt and overcome the crises successfully. The influence of the family function in the main caregiver's situation has not been the subject of much evaluation. The aim of this study is to analyse the relationship between the functionality of the family and the QoL of caregivers of dependent relatives.</p> <p>Methods</p> <p>We conducted a cross-sectional study including 153 caregivers. Setting: Two health centers in the city of Salamanca(Spain). Caregiver variables analysed: demographic characteristics, care recipient features; family functionality (Family APGAR-Q) and QoL (Ruiz-Baca-Q) perceived by the caregiver. Five multiple regressions are performed considering global QoL and each of the four QoL dimensions as dependent variables. The Canonical Correspondence Analysis (CCA) was used to study the influence of the family function questionnaire on QoL.</p> <p>Results</p> <p>Family function is the only one of the variables evaluated that presented an association both with global QoL and with each of the four individual dimensions (p < 0.05). Using the CCA, we found that the physical and mental well-being dimensions are the ones which present a closer relationship with family functionality, while social support is the quality dimension that is least influenced by the Family APGAR-Q.</p> <p>Conclusion</p> <p>We find an association between family functionality and the caregiver's QoL. This relation holds for both the global measure of QoL and each of its four individual dimensions.</p
Photosynthetic traits of Sphagnum and feather moss species in undrained, drained and rewetted boreal spruce swamp forests
Peer reviewe
Globally sparse PLS regression
Volume 56 ; Print ISBN : 978-1-4614-8282-6Partial least squares (PLS) regression combines dimensionality reduction and prediction using a latent variable model. It provides better predictive ability than principle component analysis by taking into account both the independent and re- sponse variables in the dimension reduction procedure. However, PLS suffers from over-fitting problems for few samples but many variables. We formulate a new criterion for sparse PLS by adding a structured sparsity constraint to the global SIMPLS optimization. The constraint is a sparsity-inducing norm, which is useful for selecting the important variables shared among all the components. The optimization is solved by an augmented Lagrangian method to obtain the PLS components and to perform variable selection simultaneously. We propose a novel greedy algorithm to overcome the computation difficulties. Experiments demonstrate that our approach to PLS regression attains better performance with fewer selected predictor
Microhabitat use by the white-clawed crayfish in a Tuscan stream.
Habitat modification, pollution, overfishing, poaching, competition from nonindigenous
species, and diseases have led to the extinction in Europe of many
populations of indigenous crayfish. Under the rationale that any programme of
reintroduction should be preceded by a thorough understanding of habitat
requirements of the species of concern, we studied the microhabitat use of an
Austropotamobius pallipes population in Tuscany, central Italy. Microhabitat use
was assessed for water depth, current velocity, substrate, percentages of boulders,
underwater tree roots, and in-stream vegetation cover. Results show that A.
pallipes’ habitat use is size-partitioned. Smaller individuals mostly occupy stream
edges in shallow waters with submerged roots, whereas larger individuals use
deeper waters, often associated with boulders. Crayfish spatial distribution is
restricted mostly to the microhabitats characterised by extensive cover and slow
current velocity. The study highlights the importance of habitat heterogeneity and
cover elements for the protection of this indigenous species
Inter-specific aggression generates ant mosaics in canopies of primary tropical rainforest
The ant mosaic is a concept of the non-random spatial distribution of individual ant species in trees built upon the assumption of interspecific behavioural associations. However, colony identity and environmental variance may also play a role in species distribution. Here we assess the presence of ant mosaics in a primary forest ecosystem and whether they are structured by species' aggressive behaviours or by habitat filtering.
We sampled arboreal ants from vertically stratified baits exposed in 225 canopy trees in a 9-ha plot of primary lowland forest in Papua New Guinea, the largest forest area surveyed to detect ant mosaics. We performed behavioural tests on conspecific ants from adjacent trees to determine the territories of individual colonies. We explored the environmental effects on the ant communities using information on the plot vegetation structure and topography. Furthermore, we created a novel statistical method to test for the community non-random spatial structure across the plot via spatial randomisation of individual colony territories. Finally, we linked spatial segregation among the four most common species to experimentally assessed rates of interspecies aggression.
The ant communities comprised 57 species of highly variable abundance and vertical stratification. Ant community composition was spatially dependent, but it was not affected by tree species composition or canopy connectivity. Only local elevation had a significant but rather small effect. Individual colony territories ranged from one tree to 0.7 ha. Species were significantly over-dispersed, with their territory overlap significantly reduced. The level of aggression between pairs of the four most common species was positively correlated with their spatial segregation. Our study demonstrates the presence of ant mosaics in tropical pristine forest, which are maintained by interspecific aggression rather than habitat filtering, with vegetation structure having a rather small and indirect effect, probably linked to microclimate variability.publishedVersio
Disturbance and resource availability act differently on the same suite of plant traits: revisiting assembly hypotheses.
Understanding the mechanisms of trait selection at the scale of plant communities is a crucial step toward predicting community assembly. Although it is commonly assumed that disturbance and resource availability constrain separate suites of traits, representing the regenerative and established phases, respectively, a quantification and test of this accepted hypothesis is still lacking due to limitations of traditional statistical techniques. In this paper we quantify, using structural equation modeling (SEM), the relative contributions of disturbance and resource availability to the selection of suites of traits at the community scale. Our model specifies and reflects previously obtained ecological insights, taking disturbance and nutrient availability as central drivers affecting leaf, allometric, seed, and phenology traits in 156 (semi-) natural plant communities throughout The Netherlands. The common hypothesis positing that disturbance and resource availability each affect a set of mutually independent traits was not consistent with the data. Instead, our final model shows that most traits are strongly affected by both drivers. In addition, trait-trait constraints are more important in community assembly than environmental drivers in half of the cases. Both aspects of trait selection are crucial for correctly predicting ecosystem processes and community assembly, and they provide new insights into hitherto underappreciated ecological interactions. © 2012 by the Ecological Society of America
Meat production and maintaining biodiversity: Grazing by traditional breeds and crossbred beef cattle in marshes and grasslands
Questions: Sustainable rangeland utilization considering traditions and economic reasons is compulsory for harmonising the needs of the agricultural and nature conservation sectors. For proper rangeland management it is crucial to compare the grazing
effects of traditional breeds and crossbred animals of the same species that might have
different effects on the rangelands. To fill this knowledge gap, in a grazing experiment,
we investigated the effect of cattle breeds on the vegetation to test the effects on
nature conservation value and agricultural production value. We hypothesized that the
effects of cattle grazing on habitat conservation values and forage quality depend on
the grazing breed, because breeds differ in selectivity, body size and trampling effect.
Location: Marshes and alkaline wet grasslands in Hortobágy National Park, Hungary.
Methods: We recorded the percentage cover of vascular plants in three consecutive
years in a total of 60 plots in 12 areas grazed by traditional (0.61 AU/ha) and largesized crossbred beef cattle (0.68 AU/ha).
Results: We found that the effect of cattle breed on the habitat conservation values
and forage quality is dependent on the habitat type. The traditional breed maintained
a significantly higher species number and Shannon diversity in marshes than the
crossbred beef cattle. Grazing of crossbred cattle led to decreasing moisture indicator values in marsh habitats.
Conclusions: Our findings revealed that traditional breeds should be prioritized in the
management of wet alkaline grasslands and marshes. Crossbred beef cattle might be
a substitute but only in case traditional breeds are not available for the management
of alkaline wet grasslands. In marshes, however, we recommend prioritizing the traditional breeds as they maintain higher diversity compared to crossbred beef cattle
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