Lecture 19 Flashcards
What controls diversity?
. Physical structure
. Nutrition/ resources
Are environments with low or high nutrients more diverse?
Usually the environments with low nutrients have the highest diversity because when there are high nutrients then usually the dominant species that like high nutrient environments take over. (This example is at cockle park where there are 14 strips of hay meadow that have experienced different treatments)
What does adding fertiliser do?
Increases resources, encourages dominant species and reduces diversity
What is the plant dominance index? What is it used in?
Used a lot in conservation, important in the restoration of habitat, it measures the competitive ability of plant species
Aggressive plant competitors need what? What does this restrict them to? Give examples
Need high resources.
Restricted to habitats with plentiful light, water, nutrients.
E.g. Nettle, bracken, rose bay willow herb, they tend to grow in well fertilised areas and completely take over
What do you look at when calculating dominance index in plants/ how do you calculate dominance index?
- Growth rate- higher growth rate plants are more dominant
- Potential height- higher shade and shade out other plants
- Potential for lateral spread (morphology)- moving horizontally outwards
- Litter production
Species is given a score of 1-5 on each character. Score is summed and divided by 2 to give a score /10
If you have grasslands with very low diversity and you want to improve the diversity of these grasslands what do you do? Give an example
You can use some key species to do that.
E.g. Hay rattle- you get an overall less biomass but a more even spread of species, no single dominant species
What is the diversity index? When does maximum diversity occur?
Measure of the number of species/ families/ genera and number of individuals of each (evenness)
Maximum diversity occurs when you have lots of species that occur very evenly in an area
What is the richness of an area?
The number of different species (does not take into account evenness)
What does drawing k-dominance curves do?
Will give ecologists a rough idea of whether the environment they are looking is even or dominated by one or more species
What does the Shannon diversity (H’) and evenness assume?
. Individuals are randomly distributed and sampled
. That all species in a community are sampled
Why do we multiply the Shannon diversity (H’) and evenness equation by a negative?
Because the values tend to come out negative, so you multiply it to give you a positive value
What does the Simpson dominance index measure? What does the score mean?
The degree of dominance by a few species in the sample.
The higher the dominance score= the more dominant a single species is
What are the issues with using scales when studying the amount of species in an area?
. Larger ‘islands= more species
. Not a linear relationship (e.g. flora of Tyne area (a fairly small area) ~400, Northumberland ~800 species, UK ~1500species)
. Larger area- variation in environment- more niches
Soil quality/ composition can influence biodiversity. Give an example
Calcareous grassland- 25 species m^-2 (orchids, thyme)
Vs
Acidic grassland- 12 species m^-2 (heather, bilberry)
