The Vegetation: Hierarchical Species-Environment Relationships

2001 ◽  
Author(s):  
Marilyn D. Walker ◽  
Donald A. Walker
Keyword(s):  
Spatial Patterns ◽  
Environmental Gradients ◽  
Spatial Scales ◽  
Elevation Gradient ◽  
Community Research ◽  
Physical Factors ◽  
Community Patterns ◽  
Niwot Ridge ◽  
Critical Boundary ◽  
The Individual

The vegetation of Niwot Ridge has a rich history of study, beginning with phytosociological studies directly on the Ridge and in the surrounding mountains and incorporating more experimental and dynamic approaches in later years. This chapter provides an overview of the spatial patterns of Niwot Ridge plants and plant communities relative to the primary controlling environmental gradients at scales from the individual to the landscape. The spatial patterns of vegetation at all scales are dominated by physical forces, particularly the interaction of wind, snow, and topography. The controls of biotic factors on the distribution and abundance of plant species on Niwot Ridge have received considerably less attention than have physical factors, but recent studies have revealed the importance of competition and certain mutualisms in structuring community composition. Community research on Niwot Ridge has been organized around a hierarchy of spatial scales, from the plot to the region. Plot-based studies have focused on physiological and ecological dynamics of specific species and communities, and more spatially extensive studies have provided a hierarchical framework for the plot studies. In this chapter, we first present an overview of the broader patterns in the vegetation, followed by descriptions of the communities, and then the specifics of physical and biotic controls on species and plant growth that drive the community patterns. The landscape-scale patterns in the Niwot vegetation are driven by a complex elevation gradient, which is a combination of temperature and snow regime, with wind modifying and interacting with temperature and snow at all points along the gradient (chapter 2). Certainly the most critical boundary in the system is the upper tree limit, which defines the alpine system and which lies roughly between 3400 and 3600 m elevation on Niwot Ridge. Billings (1988) provided a climatic-floristic-physiographic review of major North American alpine systems that helps to place Niwot Ridge into a larger perspective. Climatically, Niwot is intermediate between the dry Sierras, which have greater precipitation but almost none of it falling during the summer, and the wetter northern Appalachians (Mt. Washington), which have fairly even annual precipitation and no drought.

scholarly journals Changes in the acoustic structure and composition along a tropical elevational gradient

2017 ◽  
Vol 1 (1) ◽  
pp. 1-1 ◽  
Author(s):  
Marconi Campos-Cerqueira ◽  
T. Mitchell Aide
Keyword(s):  
Environmental Gradients ◽  
Spatial Scales ◽  
Elevation Gradient ◽  
Elevational Gradient ◽  
Conservation Strategies ◽  
Elevational Gradients ◽  
Acoustic Structure ◽  
Lack Of Information ◽  
Luquillo Mountains ◽  
Acoustic Community

Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales.

Relative importance of available energy, environmental heterogeneity, and seed availability for seedling emergence on a limestone pavement

Botany ◽  
2010 ◽  
Vol 88 (12) ◽  
pp. 1045-1056 ◽  
Author(s):  
J. T. Lundholm
Keyword(s):  
Species Richness ◽  
Environmental Heterogeneity ◽  
Environmental Control ◽  
Environmental Gradients ◽  
Spatial Scales ◽  
Elevation Gradient ◽  
Experimental Studies ◽  
Relative Increase ◽  
Available Energy ◽  
Richness Patterns

Environmental heterogeneity at fine spatial scales is expected to be especially important in determining community patterns at seed germination and establishment stages. I compared seedling and adult species richness patterns in relation to environmental gradients by adding seeds from 39 species across an elevation gradient, unimodally related to species richness on a limestone pavement. Environmental variables linked to habitat fertility (“available energy”), within-plot spatial or temporal variability (“environmental heterogeneity”), and spatial coordinates were evaluated as contributors to richness patterns using variance partitioning. Variables related to available energy explained most of the variance in species richness for adults and seedlings in sown plots; pure spatial variation, shared variation between energy and heterogeneity variables, and other shared fractions explained more of the variance in seedling richness in unsown plots. Seedling density and richness increased with sowing, but the relative increase differed along the elevation gradient; relative increase in richness was greatest at the lowest and highest elevations. Limited seed dispersal from parent plants may result in seedlings colonizing less favorable microsites in unsown plots, whereas sowing resulted in greater explained variance owing to environmental factors, and lower variance attributable to space alone, indicating that appropriate species are more able to reach suitable microsites. While many experimental studies have revealed associations between microsite characteristics and species-specific recruitment responses, seed limitations in natural communities can contribute to the spatial structure of seedling communities and mask environmental control of seedling species richness.

Computerized Image Enhancement for Visually Impaired Persons: New Technology, New Possibilities

1986 ◽  
Vol 80 (7) ◽  
pp. 849-854
Author(s):  
E. Pell ◽  
L. E. Arend ◽  
G. T. Timberlake
Keyword(s):  
Image Enhancement ◽  
Visually Impaired ◽  
Transfer Functions ◽  
Spatial Scales ◽  
New Technology ◽  
Age Related ◽  
Visual Degradation ◽  
The Individual ◽  
Visually Impaired Persons ◽  
Made In

Patients with age-related visual loss suffer reduced ability to recognize faces and other scenes in photographs and on television. Recently, progress has been made in image enhancement, using controlled distortion of digitally stored images that increases their usefulness in particular applications. Described are two approaches to image enhancement for the visually impaired. In one approach, the visual losses that characterize individual patients and disease classes are described using detailed measurements of visual degradation transfer functions, which are profiles of loss of image information at various spatial scales. The particular distortion used for image enhancement is then adjusted to the impairment of the individual patient or disease class. A second approach takes advantage of the resemblance between the visual losses of many patients and the degradation of picture information in other applications due to external limitations (e.g., fog and haze) on photography. Several enhancement algorithms have been found useful with such images and may also improve picture recognition by the visually impaired.

scholarly journals Sensitivity of Evapotranspiration Components in Remote Sensing-Based Models

2018 ◽  
Vol 10 (10) ◽  
pp. 1601 ◽  
Author(s):  
Carl Talsma ◽  
Stephen Good ◽  
Diego Miralles ◽  
Joshua Fisher ◽  
Brecht Martens ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Spatial Scales ◽  
Laboratory Model ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Input Variables ◽  
Added Uncertainty ◽  
Model Components ◽  
The Individual

Accurately estimating evapotranspiration (ET) at large spatial scales is essential to our understanding of land-atmosphere coupling and the surface balance of water and energy. Comparisons between remote sensing-based ET models are difficult due to diversity in model formulation, parametrization and data requirements. The constituent components of ET have been shown to deviate substantially among models as well as between models and field estimates. This study analyses the sensitivity of three global ET remote sensing models in an attempt to isolate the error associated with forcing uncertainty and reveal the underlying variables driving the model components. We examine the transpiration, soil evaporation, interception and total ET estimates of the Penman-Monteith model from the Moderate Resolution Imaging Spectroradiometer (PM-MOD), the Priestley-Taylor Jet Propulsion Laboratory model (PT-JPL) and the Global Land Evaporation Amsterdam Model (GLEAM) at 42 sites where ET components have been measured using field techniques. We analyse the sensitivity of the models based on the uncertainty of the input variables and as a function of the raw value of the variables themselves. We find that, at 10% added uncertainty levels, the total ET estimates from PT-JPL, PM-MOD and GLEAM are most sensitive to Normalized Difference Vegetation Index (NDVI) (%RMSD = 100.0), relative humidity (%RMSD = 122.3) and net radiation (%RMSD = 7.49), respectively. Consistently, systemic bias introduced by forcing uncertainty in the component estimates is mitigated when components are aggregated to a total ET estimate. These results suggest that slight changes to forcing may result in outsized variation in ET partitioning and relatively smaller changes to the total ET estimates. Our results help to explain why model estimates of total ET perform relatively well despite large inter-model divergence in the individual ET component estimates.

scholarly journals Phylogeography of two Andean frogs: Test of vicariance versus elevational gradient models of diversification

2019 ◽  
Author(s):  
Daria Koscinski ◽  
Paul Handford ◽  
Pablo L. Tubaro ◽  
Peiwen Li ◽  
Stephen C. Lougheed
Keyword(s):  
Sequence Data ◽  
Environmental Gradients ◽  
Spatial Scales ◽  
Elevational Gradient ◽  
Northwestern Argentina ◽  
Dna Sequence Data ◽  
The Andes ◽  
Common Causes ◽  
History Of ◽  
Historical Range

ABSTRACTThe tropical and subtropical Andes have among the highest levels of biodiversity in the world. Understanding the forces that underlie speciation and diversification in the Andes is a major focus of research. Here we tested two hypotheses of species origins in the Andes: 1. Vicariance mediated by orogenesis or shifting habitat distribution. 2. Parapatric diversification along elevational environmental gradients. We also sought insights on the factors that impacted the phylogeography of co-distributed taxa, and the influences of divergent species ecology on population genetic structure. We used phylogeographic and coalescent analyses of nuclear and mitochondrial DNA sequence data to compare genetic diversity and evolutionary history of two frog species: Pleurodema borellii (Family: Leiuperidae, 130 individuals; 20 sites), and Hypsiboas riojanus (Family: Hyllidae, 258 individuals; 23 sites) across their shared range in northwestern Argentina. The two showed concordant phylogeographic structuring, and our analyses support the vicariance model over the elevational gradient model. However, Pleurodema borellii exhibited markedly deeper temporal divergence (≥4 Ma) than H. riojanus (1-2 Ma). The three main mtDNA lineages of P. borellii were nearly allopatric and diverged between 4-10 Ma. At similar spatial scales, differentiation was less in the putatively more habitat-specialized H. riojanus than in the more generalist P. borellii. Similar allopatric distributions of major lineages for both species implies common causes of historical range fragmentation and vicariance. However, different divergence times among clades presumably reflect different demographic histories, permeability of different historical barriers at different times, and/or difference in life history attributes and sensitivities to historical environmental change. Our research enriches our understanding of the phylogeography of the Andes in northwestern Argentina.

scholarly journals Are Distribution Patterns Correlated with Plant Traits?

2021 ◽  
Author(s):  
◽  
Benjamin Magana-Rodriguez
Keyword(s):  
Life History ◽  
Leaf Area ◽  
Spatial Patterns ◽  
Life History Traits ◽  
Multiple Scales ◽  
Spatial Scales ◽  
Regional Scale ◽  
Distribution Patterns ◽  
Spatial Arrangement ◽  
Scaling Relationship

<p>The current crisis in loss of biodiversity requires rapid action. Knowledge of species' distribution patterns across scales is of high importance in determining their current status. However, species display many different distribution patterns on multiple scales. A positive relationship between regional (broad-scale) distribution and local abundance (fine-scale) of species is almost a constant pattern in macroecology. Nevertheless interspecific relationships typically contain much scatter. For example, species that possess high local abundance and narrow ranges, or species that are widespread, but locally rare. One way to describe these spatial features of distribution patterns is by analysing the scaling properties of occupancy (e.g., aggregation) in combination with knowledge of the processes that are generating the specific spatial pattern (e.g., reproduction, dispersal, and colonisation). The main goal of my research was to investigate if distribution patterns correlate with plant life-history traits across multiple scales. First, I compared the performance of five empirical models for their ability to describe the scaling relationship of occupancy in two datasets from Molesworth Station, New Zealand. Secondly, I analysed the association between spatial patterns and life history traits at two spatial scales in an assemblage of 46 grassland species in Molesworth Station. The spatial arrangement was quantified using the parameter k from the Negative Binomial Distribution (NBD). Finally, I investigated the same association between spatial patterns and life-history traits across local, regional and national scales, focusing in one of the most diverse families of plant species in New Zealand, the Veronica sect. Hebe (Plantaginaceae). The spatial arrangement was investigated using the mass fractal dimension. Cross-species correlations and phylogenetically independent contrasts were used to investigate the relationships between plant life-history traits and spatial patterns on both data bases. There was no superior occupancy-area model overall for describing the scaling relationship, however the results showed that a variety of occupancy-area models can be fit to different data sets at diverse spatial scales using nonlinear regression. Additionally, here I showed that it is possible to deduce and extrapolate information on occupancy at fine scales from coarse-scale data. For the 46 plantassemblage in Molesworth Station, Specific leaf area (SLA) exhibits a positive association with aggregation in cross-species analysis, while leaf area showed a negative association, and dispersule mass a positive correlation with degree of aggregation in phylogenetic contrast analysis at a local-scale (20 × 20 m resolution). Plant height was the only life-history trait that was associated with degree of aggregation at a regional-scale (100 × 60 mresolution). For the Veronica sect. Hebe dataset, leaf area showed a positive correlation with aggregation while specific leaf area showed a negative correlation with aggregation at a fine local-scale (2.5-60 m resolution). Inflorescence length, breeding system and leaf area showed a negative correlation with degree of aggregation at a regional-scale (2.5-20 km resolution). Height was positively associated with aggregation at national-scale (20-100 km resolution). Although life-history traits showed low predictive ability in explaining aggregation throughout this thesis, there was a general pattern about which processes and traits were important at different scales. At local scales traits related to dispersal and completion such as SLA , leaf area, dispersule mass and the presence of structures in seeds for dispersal, were important; while at regional scales traits related to reproduction such as breeding system, inflorescence length and traits related to dispersal (seed mass) were significant. At national scales only plant height was important in predicting aggregation. Here, it was illustrated how the parameters of these scaling models capture an important aspect of spatial pattern that can be related to other macroecological relationships and the life-history traits of species. This study shows that when several scales of analysis are considered, we can improve our understanding about the factors that are related to species' distribution patterns.</p>

scholarly journals EXPRESS: Sources of Variation In Search and Foraging A Theoretical Perspective

2021 ◽  
pp. 174702182110503
Author(s):  
Alastair David Smith ◽  
Carlo De Lillo
Keyword(s):  
Spatial Scales ◽  
Theoretical Perspective ◽  
Search Space ◽  
Visual Exploration ◽  
Two Dimensional ◽  
Search Behaviour ◽  
Wide Range ◽  
Search Processes ◽  
Sources Of Variation ◽  
The Individual

Search – the problem of exploring a space of alternatives in order to identify target goals – is a fundamental behaviour for many species. Although its foundation lies in foraging, most studies of human search behaviour have been directed towards understanding the attentional mechanisms that underlie the efficient visual exploration of two-dimensional scenes. With this review, we aim to characterise how search behaviour can be explained across a wide range of contexts, environments, spatial scales, and populations, both typical and atypical. We first consider the generality of search processes across psychological domains. We then review studies of interspecies differences in search. Finally, we explore in detail the individual and contextual variables that affect visual search and related behaviours in established experimental psychology paradigms. Despite the heterogeneity of the findings discussed, we identify that variations in control processes, along with the ability to regulate behaviour as a function of the structure of search space and the sampling processes adopted, to be central to explanations of variations in search behaviour. We propose a tentative theoretical model aimed at integrating these notions and close by exploring questions that remain unaddressed.

Plant-Herbivore Interactions

2001 ◽  
Author(s):  
Denise Dealing
Keyword(s):  
Community Dynamics ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Secondary Compounds ◽  
Nutritional Composition ◽  
Secondary Chemistry ◽  
Niwot Ridge ◽  
Herbivore Interactions ◽  
Ultimate Objective ◽  
Plant Herbivore

The alpine provides a tremendous opportunity for studying plant-herbivore interactions at the population, community, and ecosystem levels. For herbivores, variations in topography and microclimate result in a relatively large amount of spatial variation in plant communities within short distances (chapter 6). A large community of herbivores, from nematodes to grasshoppers to elk, occurs on Niwot Ridge. Furthermore, given the low rates of nutrient availability in alpine soils (Fisk and Schmidt 1995; chapter 12) combined with the slow-growing perennial habit of the vegetation, alpine plants should, in theory, invest heavily in defense against herbivores (Coley et al. 1985). The goal of this chapter is to provide: (1) a summary of the feeding behaviors of the herbivores on Niwot Ridge, (2) information on the nutritional and secondary chemistry of plants on Niwot Ridge as it relates to herbivory, and (3) a review of hypotheses on community dynamics of herbivores and plants relevant to the alpine. The ultimate objective is to provide a synthesis of information that will stimulate interest in alpine tundra as a system for studying the dynamics of plant-herbivore interactions at all levels of ecological organization. The flora of Niwot Ridge has been divided into six communities (May and Webber 1982; chapter 6). Regardless of community association, nearly all of the plant species occurring on the ridge are perennials and several are very long lived (May and Webber 1982). Communities can change across small spatial scales (meters), and community origin and maintenance are believed to be largely determined by abiotic factors (Walker et al. 1994; chapter 6). However, several studies suggest that biotic factors such as herbivory may have a significant impact on plant community dynamics (Huntly et al. 1986; Davies 1994). There is significant variation in the nutritional composition of plants on Niwot Ridge. Generally, and in the absence of plant secondary compounds, species that are high in nitrogen and low in fiber are presumed to be the most desirable as forage. Based solely on these nutritional variables, the clover Trifolium parryi is hypothesized to be one of the more-preferred forages, whereas alpine sandwort, Minuartia obtusiloba, should be one of the less-preferred food items.

Spatially Explicit, Statistical Land-Change Models in Data-Sparse Conditions

2004 ◽  
Author(s):  
Jacqueline Geoghegan ◽  
Laura Schneider
Keyword(s):  
Satellite Imagery ◽  
Geographical Information Systems ◽  
Census Data ◽  
Spatial Scales ◽  
Global Environmental Change ◽  
Geophysical Data ◽  
Land Change ◽  
Change Models ◽  
Fine Grained ◽  
The Individual

A range of research interests beyond global environmental change science increasingly calls for advances in land-change models and, specifically, models that have fine-grained locational outputs. The rationale for such modeling about land change has been articulated elsewhere in this book (Ch. 1; Introduction to Part IV) and need not be reiterated here. It is important to note, however, that advances in question are assisted by the advances in the analytical sophistication of geographical information systems, hardware (GPS) that permits geographical coordinates to be established easily in the field, and for land-change studies, increasing temporal and spatial resolution of satellite imagery. Much of the first phase of land-change models that incorporate these systems and data has been empirical-based, time series assessments, such as Markov-chain models (e.g. Turner 1988), that let the record of land change determine future projections, or the spatial level of assessment has been large-grain (e.g. counties, states, regions). The SYPR project seeks a different approach demonstrated here: to test theories of land change in regard to their ability to explain fine-grained land change in the region at different spatial scales of assessment. Two complementary econometric modeling approaches are used here to investigate the factors that affect deforestation at the regional and household scales of analysis. Both approaches use the individual satellite pixels as the data on land-use change, from the classification of TM imagery described in Ch. 6. A regional model spans the entire study area of agricultural ejidos, and links the satellite imagery with publicly available geophysical data and socio-demographic government census data. The second model focuses exclusively on the parcels associated with the household survey data collected specifically for this project, discussed in Part III, especially Ch. 8. This latter approach uses the same geophysical data of the aggregate approach, but uses the much richer socio-demographic data derived from the linkage of individual farm plots and the satellite imagery via the sketch mapping exercise described in Chs. 8 and 9. While both models take a theoretical approach of individual maximization, they differ in a number of ways, the most important of which is the role of time in the decision-making process.

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