Population and Global change Flashcards
What is population ecology?
The subfield of ecology that identifies the ecological factors, in the species community or in the ecosystem that regulates a population size
What is a population?
A discrete group of individuals of a single species that are relatively self-contained in space, with little immigration and emigration relative to internal rates of recruitment and mortality. Generally has the same gene pool.
What is a Hutchinsonian niche?
The n-dimensional hyper-volume of the variables that limit a species distribution.
What is the fundamental niche?
Given by the combination of environmental conditions where a species can survive and reproduce.
What is the realised niche?
The range of environmental conditions where species actually occur after interacting with other species and being outcompeted from some regions. the realised niche corresponds to the range of conditions where a species is best adapted.
What determines the limit of geographic ranges?
- abiotic and or biotic factors that prevent further spread.
- human transformation of the landscape
- local population dynamics at the edge of the range
- genetic mechanisms
Where has ‘the human footprint’ been felt most strongly?
Europe, India, China, eastern USA
What are the global effects of deforestation?
-tropical forests have very high projected loss. Deforestation reduces forest area and frequently isolates forest patches . Island biogeography theory and metapopulation theories predict the effects of reduced area and increased isolation on species extinction rates and colonization rates. Local extinctions are more probable in small, isolated patches.
How has fragmentation affected UK woodland birds?
- larger woods contain more breeding species
- The larger the woodland area the higher the probability of breeding
How do area and edge effects affect ecological processes?
- pollinator abundance e.g. visitation rates of bees to chemical baits higher in undisturbed forest
- seed production - no ovules and seeds of Dianthus deltoids in fragmented habitats in Sweden
- Seed predation - higher with distance from forest edge
- dung decomposition - higher percentage of dung decomposed after 9 days in continuous forest.
Explain fragmentation
Forest fragmentation is the replacement of large areas of native forest by other ecosystems, leaving isolated forest patches, with deleterious consequences for native biota, - reduces total area covered by forest which may result in extinction of some species. Fragmentation exposes the organisms that remain to the conditions of the surrounding ecosystem and ‘edge effects’.
What are edge effects?
The result of the interaction between two adjacent ecosystems when the two are separated by an abrupt transition.
Name some abiotic edge effects
1) different microclimate in matrix - e.g. cropland
2) compared to a forest, crops and pastures allow more solar radiation to reach the ground during the day and higher radiation from the ground at night - fluctuating diurnal temperature. As the forest interior is often cooler, moister and more uniform there is a gradient of temperature.
3) movement of chemical compounds across the edge e.g. fertilisers
Name some direct biotic edge effects
1) increases in incident light promotes plant growth
2) As a result of wind throw and/or fire tree mortality can increase
3) edge effects on the physical and chemical environment can affect the distribution of species near the edge because of differences among species in their physiological tolerances - localised shift in species composition.
Name some indirect biotic edge effects
edge driven changes in the forest environment and structure may affect the dynamics of species interactions e.g. brood parasitism - higher nest predation near edge.
