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Introduction to Diffusive Processes
Published in Ranjit Kumar Upadhyay, Satteluri R. K. Iyengar, Spatial Dynamics and Pattern Formation in Biological Populations, 2021
Ranjit Kumar Upadhyay, Satteluri R. K. Iyengar
Dispersion/dispersal: Biological dispersal refers to those processes by which a species maintains or expands the distribution of its population. Dispersal is necessary in populations because members of the species compete for the same limited resources within an ecosystem. Dispersal relieves pressure on resources in an ecosystem. Dispersal mechanisms depend on the competition for these resources. Dispersal may involve replacement of a parent generation by a new generation with only minor changes in the geographic area occupied. Dispersal enables the species population to occupy much of the available habitat and maximize its resources in its favor. Some organisms (plants and especially sedentary animals) have evolved adaptations for dispersal by taking advantage of various forms of kinetic energy occurring naturally in the environment like water flow and wind. Often, dispersal may be purely random, density-dependent, or random plus density-dependent. Dispersal over long distances can be approximated mathematically by deterministic partial differential equations or integro-differential equations. Dispersal over very short distances often results in large spatial correlations. In case of interacting particle systems, local dispersal can result in spatial correlations. The global dispersal results in a Poisson distribution which allows one to study spatially homogeneous models that are at the onset of exhibiting spatial correlation, such as when offspring are dispersed over intermediate distances [79].
Population ecology of agroecosystems
Published in Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz, Agroecology, 2023
Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz
How plants and animals get from one place to another during the dispersal stages of their life cycles depends on the mechanisms they each have for dispersing themselves. These horizontal dispersal mechanisms are quite variable, but most often involve wind, animals, water, or gravity.
Eco-evolutionary priority and the assembly of the New Zealand flora
Published in Journal of the Royal Society of New Zealand, 2022
Matt S. McGlone, Peter B. Heenan, George L. W. Perry
We have compiled a database of the entire New Zealand spermatophyte flora, assigning species to four major plant types: dicot herbs, monocot herbs, shrubs (woody plants ≤5 m) and trees, and including plant dispersal type for all species after Thorsen et al. (2009). For analysis we have simplified dispersal type into biotic (bearing fleshy, bird-attracting, or barbed fruit) and abiotic (wind dispersal structures or no dispersal adaptations). Height of woody species and their latitudinal distribution in one degree segments is recorded following the methodology in McGlone et al. (2010). Disjunct distributions are treated as continuous as the metric is range extent, not area occupied. A separate compilation of over 800 alpine species follows the methodology in McGlone et al. (2001) and includes altitudinal range and distribution across 19 mountain regions (Supplementary 1, figure 1) encompassing the entire alpine distribution. These mountain regions contain alpine habitats of variable extent and represent discrete geographic areas used to record distributions of alpine plants (Mark 2021). Data used in these analyses is available in Supplementary 2.
Dispersed pollen and calyx remains of Diospyros (Ebenaceae) from the middle Miocene “Plant beds” of Søby, Denmark
Published in GFF, 2021
Thomas Denk, Johannes M. Bouchal
Christensen (1975) suggested that the Søby flora represented a local pond in a delta setting and Koch (1989) that the coals and associated sediments were deposited in freshwater lakes, lagoonal swamps and mires (characteristic of the Fasterholt Member). Modern species of Diospyros are insect-pollinated, small to medium-sized trees in the forest understorey and usually have a very low population density (Wallnöfer 2004). They have markedly different ecologies being riparian trees or rheophytes, growing in swamps and on beaches, while others occur in tropical savannah or temperate deciduous forests (Wallnöfer 2001). Fruits and seeds are dispersed by mammals and birds, or may be water-dispersed in species, which grow in periodically flooded habitats. Since calyx remains of Diospyros are very rare in the fossil record (Kvaček & Walther 2004) and flowers are insect-pollinated, we propose that the Diospyros plant from Søby grew close to the depositional area and hence might have been an element of the lowland wetlands or the riparian vegetation along streams of the delta as suggested by Christensen (1975) and Koch (1989). This interpretation would fit with the habitats of the eastern North American D. virginiana and the western Eurasian D. lotus, which include seasonally flooded bottomlands (Denk et al. 2001; Eckenwalder 2009).
Importance of buffer lands to determining risk to ecological resources at legacy contaminated sites: A case study for the Department of Energy’s Hanford Site, Washington, USA
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Joanna Burger, Michael Gochfeld, Christian Jeitner
There are a number of methods to reduce risk to ecological resources on adjacent buffer lands. One of the most important one is to remediate adjacent legacy EUs whenever possible, so that the noise, disturbance, and disruptions are limited in time. Further, laydown areas need to be located on the EU, rather than on buffers, and these need to be placed as far from high-level resources (especially those with state or federally listed species), and as far as possible from large continuous patches of shrub-steppe. Most of the other methods of risk reduction mainly center around reducing disturbance and disruptions on any of the buffer area, and where possible, reducing these on the sections of the EU adjacent to the buffer areas with the highest resource levels. Disruption might occur because of dispersal of invasive species. For example, on some of the EUs on Hanford where cheatgrass and other invasive species were used to stabilize soil during previous cleanup actions, these may be spread both on the EU and into adjacent buffers that may not currently have cheatgrass. Particular attention needs to be given to cheatgrass removal, especially during the stage when seeds are ripe and easily spread.