| What is diversity and evenness?
What are some diversity indexes that can be used that also take evenness into account? | Species evenness: how evenly are different species distributed: 50/50 or 90/10 etc.
Species richness: number of different species present
Shannon-wiener: both abundance and evenness
Simpsons index: how likely is it that two individuals are the same. |
| Whats the difference between alpha and beta diversity? | Alfa: species richness in one area
Beta: difference between alfa diversity in different areas. For instance high beta diversity - different streams have different communities. Beta is often on the regional scale. |
| How is biodiversity looking in streams atm? | Biodiversity in streams
1/3 of all small vertebrates are declining in streams.
Even the Lc species are declining.
Also 1/3 of plant species are declining. |
| Is ecological status an indicator of biodiversity? | Ecological status is not the same as biodiversity.
They tested the hypothesis that where there is good ecological status there should be many rare species. In 175 out of 187they did not find rare species
Only 6% of sites with high ecological status (DVPI) had rare species and 21% with DVFI
A lot of species could be lost without loosing ecological status.
Species can still be lost in places with high ecological satus. |
| What is a space for time study and why do we use it? | BACI - Before after control impact
Before you add measure you characterize everything. Then introduce measure look at the same reach and see the effects over time. The meassure is only introduces in part of the stream. Then the reach part without meassure is control. This is the strongest statistical meassure
But it takes such a long time. So its maybe not the best strategy because it takes to long.
Instead we use space for time.
Instead of waiting, we look at similar streams. We select are group of streams that are for instance chanelized and a group with neanders that in all other aspects are similar and then we compare them. Then we assume that if we restore the chanalized streams they will turn into the same as neanders.
When modifying remember what the reference stream looks like. Don't just drop giant rocks etc if they would not naturally be there.
The reference site is basicly where do we want to be - how would they have looked naturally. Bottom right - to see if they are more or less equal. The letters indicate where they are different. We want them to mostly the same but of course if we change substrate then substarte will not be the same. |
| Sig kloge ting om ham her | A and b indicates if there is a significant difference. So bb no significant difference. So there is not really a signigficant differnece.
There is not a significant difference in alpha diversity.
Altså det jeg prøver at skrive er f.eks. hvis med insatser har a og referance har a er der ingen forskel. |
| Sig kloge ting om den her | beta diversity is actually decreasing. beta diversity is higher in streams without meassures… wack ****. |
| How come managing seems to lead to a decrease or at least not an increase in biodiversity? | Its a filtering of species when we genopretter.
Many species are associated with the border of the stream. And many in fast current areas with stone and gravel.
The only habitat we are really creating is the one with corse substrates.
We lack back water habitats, strong currents, and the ones that are linking riparian area with the channel itself.
The ones that are underpriotised:
1) Strong current habitats
2) Land water ecotone
3) Backwater habitats - still water habitats.
Another problem is that we don't prioritize which sections to start with. |
