The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome

2004 ◽  
Vol 207 (3-4) ◽  
pp. 371-398 ◽  
Author(s):  
C JANIS
Keyword(s):  
Species Richness ◽  
Primary Productivity ◽  
North American ◽  
Habitat Type ◽  
The North ◽  
Grassland Biome

Towards a Biogeography of North American Charophytes

1999 ◽  
Vol 47 (3) ◽  
pp. 445 ◽  
Author(s):  
Henry Mann ◽  
Vernon W. Proctor ◽  
Alberto S. Taylor
Keyword(s):  
Species Richness ◽  
North American ◽  
Ecological Niches ◽  
Physical Parameters ◽  
South American ◽  
Lake Titicaca ◽  
The Past ◽  
The North ◽  
The Stability

The great bulk of the world’s charophyte literature of the past 100 years or more suffers from several major limitations. Much is entirely descriptive with but few attempts to ascribe any functionality to the features under consideration, or how they adapt such species to their respective ecological niches. Charophyte distributions have been attributed almost entirely to physical parameters with virtually no consideration given to the role of aquatic herbivores or other biotic environmental factors. Furthermore, most workers have focused on relatively restricted areas with little or no reference to others either near or far removed. That there is much to be gained from a wider focus (both spatially and conceptually) that incorporates greater conjecture as well as enhanced collaboration is here suggested. How are the charophyte floras of one region similar to, or different from, those of another, and, of particular significance, ‘Why?’ The authors, being North American, focus on that continent but with the firm conviction that most generalities applicable there hold equally true for other landmasses, and have done so for the previous 10, if not 100, million years. This account focuses first, if somewhat superficially, on 14 widely distinct North American charophyte communities (plus South American Lake Titicaca) and then in greater detail on four of those. Among other issues considered are how species richness relates to latitude; why some geographical entities support more charophyte species than do others; the extent to which charophyte floras reflect the availability of different habitats; the contributions of herbivory to the preceding; the stability of the North American charophyte flora; the ecological considerations most often reflected by charophyte zonation and how–or to what extent–range extensions reflect niche preferences or requirements. While the authors well appreciate just how minimal their efforts may appear a century hence, at least they hope to have placed on the table some considerations with which colleagues from other landmasses may agree, disagree or suggest modifications.

scholarly journals Using a large-scale biodiversity monitoring dataset to test the effectiveness of protected areas at conserving North-American breeding birds

2018 ◽  
Author(s):  
Victor Cazalis ◽  
Soumaya Belghali ◽  
Ana S.L. Rodrigues
Keyword(s):  
Species Richness ◽  
Protected Areas ◽  
North American ◽  
Large Scale ◽  
Individual Species ◽  
Biodiversity Monitoring ◽  
Breeding Bird ◽  
The North ◽  
Forest Sites ◽  
Declining Species

AbstractProtected areas currently cover about 15% of the global land area, and constitute one of the main tools in biodiversity conservation. Quantifying their effectiveness at protecting species from local decline or extinction involves comparing protected with counterfactual unprotected sites representing “what would have happened to protected sites had they not been protected”. Most studies are based on pairwise comparisons, using neighbour sites to protected areas as counterfactuals, but this choice is often subjective and may be prone to biases. An alternative is to use large-scale biodiversity monitoring datasets, whereby the effect of protected areas is analysed statistically by controlling for landscape differences between protected and unprotected sites, allowing a more targeted and clearly defined measure of the protected areas effect. Here we use the North American Breeding Bird Survey dataset as a case study to investigate the effectiveness of protected areas at conserving bird assemblages. We analysed the effect of protected areas on species richness, on assemblage-level abundance, and on the abundance of individual species by modelling how these metrics relate to the proportion of each site that is protected, while controlling for local habitat, altitude, productivity and for spatial autocorrelation. At the assemblage level, we found almost no relationship between protection and species richness or overall abundance. At the species level, we found that forest species are present in significantly higher abundances within protected forest sites, compared with unprotected forests, with the opposite effect for species that favour open habitats. Hence, even though protected forest assemblages are not richer than those of unprotected forests, they are more typical of this habitat. We also found some evidence that species that avoid human activities tend to be favoured by protection, but found no such effect for regionally declining species. Our results highlight the complexity of assessing protected areas effectiveness, and the necessity of clearly defining the metrics of effectiveness and the controls used in such assessments.

scholarly journals A model-data comparison of gross primary productivity: Results from the North American Carbon Program site synthesis

2012 ◽  
Vol 117 (G3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Kevin Schaefer ◽  
Christopher R. Schwalm ◽  
Chris Williams ◽  
M. Altaf Arain ◽  
Alan Barr ◽  
...  
Keyword(s):  
Primary Productivity ◽  
North American ◽  
Gross Primary Productivity ◽  
Model Data ◽  
Data Comparison ◽  
The North

Abundance, species richness and energy availability in the North American avifauna

2006 ◽  
Vol 15 (4) ◽  
pp. 372-385 ◽  
Author(s):  
Karl L. Evans ◽  
Neil A. James ◽  
Kevin J. Gaston
Keyword(s):  
Species Richness ◽  
North American ◽  
Energy Availability ◽  
The North

Long-term stability of large-scale hydroclimate processes in the North American Great Plains revealed by a Neogene stable isotope study

2020 ◽  
Author(s):  
Livia Manser ◽  
Tyler Kukla ◽  
Jeremy K. Caves Rugenstein
Keyword(s):  
Great Plains ◽  
Primary Productivity ◽  
North American ◽  
Global Climate ◽  
The West ◽  
Air Masses ◽  
Aridity Gradient ◽  
The North ◽  
Late Neogene

<p>The North American Great Plains are characterized by a sharp aridity gradient at around the 100<sup>th</sup> meridian with a more humid climate to the east and a more arid climate to the west. This aridity gradient shapes the region's agriculture and economy, and recent work suggests that arid conditions on the Great Plains may expand eastward with global warming. The abundant Neogene sediments of the Ogallala Formation in the Great Plains present an opportunity to reconstruct regional hydroclimate conditions at a time when <em>p</em>CO<sub>2</sub> and global temperatures were much higher than today, providing insight into the aridity and ecosystem response to warming. We present new paleosol carbonate δ<sup>13</sup>C and δ<sup>18</sup>O data (n=366) across 37 sites spanning the Great Plains and compile previously published measurements (n=381) to evaluate the long-term hydroclimatic and ecosystem changes in the region during the late Neogene. This study combines a spatial and temporal analysis of carbon and oxygen isotope data with reactive-transport modeling of oxygen isotopes constrained by climate model output, providing critical constraints on the paleoenvironmental and paleoclimatological evolution of the Neogene Great Plains. Carbonate δ<sup>18</sup>O demonstrate remarkable similarity between the spatial pattern of paleo-precipitation δ<sup>18</sup>O and modern precipitation δ<sup>18</sup>O. Today, modern precipitation δ<sup>18</sup>O over the Great Plains is set by the mixing between moist, high-δ<sup>18</sup>O moisture delivered by the Great Plains Low-Level Jet and drier, low-δ<sup>18</sup>O westerly air masses. Thus, in the absence of countervailing processes, we interpret this similarity between paleo and modern δ<sup>18</sup>O to indicate that the proportional mixing between these two air masses has been minimally influenced by changes in global climate and that any changes in the position of the 100<sup>th</sup> meridian aridity gradient has not been forced by dynamical changes in these two synoptic systems. In contrast, prior to the widespread appearance of C<sub>4</sub> plants in the landscape of the Great Plains, paleosol carbonate δ<sup>13</sup>C show a robust east-to-west gradient, with higher values to the west. We interpret this gradient as reflective of lower primary productivity and hence soil respiration to the west. Close comparison with modern primary productivity data indicates that primary productivity has declined and shifted eastward since the late Neogene, likely reflecting declining precipitation and/or a reduction in CO<sub>2</sub> fertilization during the late Neogene. Finally, δ<sup>13</sup>C increases across the Miocene-Pliocene boundary, which, consistent with previous studies, we interpret as a shift from a C<sub>3</sub> to a C<sub>4</sub> dominated landscape. We conclude that, to first order, the modern aridity gradient and the hydrologic processes that drive it are not strongly sensitive to changes in global climate and any shifts in this aridity gradient in response to rising CO<sub>2</sub> will be towards the west, rather than towards the east.</p>

scholarly journals SNAKE ASSEMBLAGE STRUCTURES AND SEASONAL ACTIVITY PATTERNS ON A MILITARY BASE IN SOUTH-CENTRAL PENNSYLVANIA:

2014 ◽  
pp. 7-20
Author(s):  
Walter E. Meshaka ◽  
Pablo R. Delis
Keyword(s):  
North American ◽  
Habitat Type ◽  
Thamnophis Sirtalis ◽  
Seasonal Activity ◽  
Potential Predator ◽  
The North ◽  
South Central ◽  
Central Pennsylvania ◽  
The Common ◽  
Disturbed Habitats

We ascertained the assemblage structures of snakes occurring in a mixed habitat matrix of natural and disturbed habitats during 2008–2011 at Letterkenny Army Depot (LEAD), a 7200 ha U.S. Army base in south-central Pennsylvania, to understand the patterns of species abundance as they related to habitat type of managed lands. We detected eight species in 12 sites comprising natural and disturbed habitats of wetlands, forest, and thicket and open fields. The Common Gartersnake (Thamnophis sirtalis) occurred in the most sites, the Red-bellied Snake (Storeria occipitomaculata) was the rarest species in the study. Two to six species occupied each site and were distributed unevenly. Dynamics of assemblages could be explained in part by habitat and also by the presence of the North American Racer (Coluber constrictor). All species for which data were available exhibited a unimodal pattern to their seasonal activity (mostly May and June); however, seasonal activity peaks differed between sexes. Sex ratios varied among species but were consistently female–biased in the Common Gartersnake and Ring-necked Snake (Diadophis punctatus) in Pennsylvania and surrounding areas. As elsewhere in Pennsylvania and the Northeast, body sizes of adults were larger for species syntopic with the North American Racer than for species not syntopic with this potential predator. We found a degree of predictability with respect to snake assemblage dynamics among habitats at LEAD, which in turn can prove useful in resource management of this large and protected human-impacted system.

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