Spatial patterns

2018 ◽  
Author(s):  
Philip James
Keyword(s):  
Spatial Distribution ◽  
Urban Environment ◽  
Distribution Patterns ◽  
Intermediate Disturbance Hypothesis ◽  
Urban Environments ◽  
Individual Species ◽  
Urban Forms ◽  
Intermediate Disturbance ◽  
Urban Rural ◽  
Disturbance Hypothesis

In this chapter, the discussion focuses on the spatial variation of species within urban environment. Studies on urban–rural gradients are discussed. These are studies along gradients of disturbance and environmental stress. The extreme heterogeneity of urban environments, where contrasting urban forms are juxtaposed, is recognized as an issue in drawing generalities. Despite this, some limited generalities in the patterns of species richness and density can be detected. The intermediate disturbance hypothesis is discussed and its limitations identified. Examples are presented from a number of taxa where different spatial distribution patterns are observed. There is also a brief consideration of r- and K-selected species and of urban avoiders and adaptors and how their distributions are affected by urban environments. While it is possible to make general statements regarding the distribution of biodiversity across an urban environment, considerable variations exist in terms of individual species.

scholarly journals Activity density of carabid beetles along an urbanisation gradient

2020 ◽  
Vol 66 (Suppl.) ◽  
pp. 21-36
Author(s):  
Simone Fattorini ◽  
Cristina Mantoni ◽  
Davide Bergamaschi ◽  
Lorenzo Fortini ◽  
Francisco J. Sánchez ◽  
...  
Keyword(s):  
Intermediate Disturbance Hypothesis ◽  
Urban Environments ◽  
Carabid Beetles ◽  
City Centre ◽  
Intermediate Disturbance ◽  
Rural Environments ◽  
Activity Density ◽  
Urban Rural ◽  
The Impact ◽  
The City

Several works have investigated the impact of urbanisation on carabid activity density using urban-rural gradients. Such works compared activity density recorded from green spaces located in different parts of a city and assigned to categories of increasing urban intensity, which poses two problems: (1) since the gradient is divided into categories, it is impossible to model continuous variations in biotic responses, and (2) sites representative of different urbanisation levels are not true segments of the same ecological continuum. To surpass these problems, we modelled variations in carabid activity density along an urban-rural transect within a single green space extending from the city centre of Rome to rural environments. Carabids were sampled by pitfall traps from sites distributed along the entire gradient. We used breakpoint regressions to model how (1) carabid activity density, (2) carabids/beetles ratio, (3) carabids/insects ratio and (3) carabids/arthropods ratio varied along the gradient. As already observed for various organisms in urban environments, we found that activity density of carabids and their contribution to the abundance of beetles, insects and arthropods, peaked in the middle of the gradient. This supports the intermediate disturbance hypothesis, according to which moderate urbanisation may favour diversity by increasing habitat heterogeneity.

scholarly journals Diversity–disturbance relationships: frequency and intensity interact

2012 ◽  
Vol 8 (5) ◽  
pp. 768-771 ◽  
Author(s):  
Alex R. Hall ◽  
Adam D. Miller ◽  
Helen C. Leggett ◽  
Stephen H. Roxburgh ◽  
Angus Buckling ◽  
...  
Keyword(s):  
Species Diversity ◽  
Empirical Evidence ◽  
Empirical Studies ◽  
Ecological Theory ◽  
Intermediate Disturbance Hypothesis ◽  
Intermediate Disturbance ◽  
Disturbance Frequency ◽  
Theoretical Predictions ◽  
Experimental Populations ◽  
Disturbance Hypothesis

An influential ecological theory, the intermediate disturbance hypothesis (IDH), predicts that intermediate levels of disturbance will maximize species diversity. Empirical studies, however, have described a wide variety of diversity–disturbance relationships (DDRs). Using experimental populations of microbes, we show that the form of the DDR depends on an interaction between disturbance frequency and intensity. We find that diversity shows a monotonically increasing, unimodal or flat relationship with disturbance, depending on the values of the disturbance aspects considered. These results confirm recent theoretical predictions, and potentially reconcile the conflicting body of empirical evidence on DDRs.

A phytoplankton community in a temperate reservoir in New South Wales, Australia: relationships between similarity and diversity indices and measures of hydrological disturbance

2005 ◽  
Vol 56 (2) ◽  
pp. 203 ◽  
Author(s):  
Tsuyoshi Kobayashi ◽  
Brian G. Sanderson ◽  
Geoff N. G. Gordon
Keyword(s):  
Phytoplankton Community ◽  
New South ◽  
Diversity Indices ◽  
Intermediate Disturbance Hypothesis ◽  
Species Number ◽  
Intermediate Disturbance ◽  
Consecutive Sampling ◽  
South Wales ◽  
Cell Densities ◽  
Disturbance Hypothesis

Temporal changes in diversity and similarity of a phytoplankton community were investigated in relation to external hydrological disturbance in the Ben Chifley reservoir from September 1998 to January 2002. Species richness varied by a factor of 4–5 at each of three sites studied during the period (n = 53 at each site). Species diversity (measured using Simpson’s D and Shannon–Wiener’s H, based on primarily genus or species number and cell densities) varied by a factor of 8–10, whereas similarity between two consecutive sampling dates (measured using Hurlbert’s index and Pinkham and Pearson’s B) varied by a factor of 10–46. When diversity was measured with H, it had an approximate quadratic (convex) relationship with similarity, as measured with Hurlbert’s index. However, diversity was seldom related to external hydrological disturbance (measured as intensity and variability of daily inflow rates between two consecutive sampling dates). Similarity was significantly and negatively related to disturbance variability. These results suggest that the mechanisms that regulate diversity and similarity may differ from each other, and question the usefulness of observed approximate quadratic relationships between similarity and diversity indices when assessing the effect of disturbance on diversity. Such relationships may therefore not provide support for Connell’s (1978) intermediate disturbance hypothesis.

scholarly journals Avifaunal Assemblage along Rural-Urban Gradients in Aligarh, Uttar Pradesh, India

2019 ◽  
Vol 11 (4) ◽  
pp. 421-427
Author(s):  
Arif SIDDIQUI ◽  
Tanveer AHMED ◽  
Afifullah KHAN
Keyword(s):  
Uttar Pradesh ◽  
Bird Community ◽  
Developed Countries ◽  
Intermediate Disturbance Hypothesis ◽  
Urban Site ◽  
Bird Diversity ◽  
Point Counts ◽  
Intermediate Disturbance ◽  
Urban Rural ◽  
Impact Of Urbanization

Studies assessing the effect of urbanization on bird community structure largely carried out in developed countries and little is known about the developing region particularly in India. Bird diversity, richness, composition and guild structure was examined at urban, semi-urban, semi-rural and rural-natural sites in Aligarh, Uttar Pradesh. Each site was sampled using 90 fixed radius point counts between January and June 2016. Semi-urban site was more species rich (2.38 ± 0.06), diverse (0.80 ± .01) and even (0.90 ± .00) than other three urban-rural gradient sites. Density of bird peaked at urban site (43.09 ± 4.7). Numerically, urban site was dominated by omnivore species which was replaced by insectivorous species at semi-natural, semi-rural and rural-natural sites. The current information corroborates the earlier studies assessing impact of urbanization of birds and Conell’s intermediate disturbance hypothesis of higher richness and diversity at intermediate disturbance. 

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