Ecology Lesson

I had an ecology lesson today from Freddie and these are my typed up notes from it:

Tropical rainforest ecology:

Subsiding basins or sinking areas can cause a difference in environmental conditions. There will be more water and so can be peat land. Peat lands can also form near rivers. There will be little magnesium and potassium in these areas so low biodiversity. Harsh environment.

In peat areas lots of different communities - dwarf forests etc.

Why diff from each other?

-seed dispersal, close together, similar.

- flooding regimes.

-nutrient status

So different gradients in flooding, nutrients, acidity.

Peatland forests are not seen to be diverse so not protected/ conserved. But there could be endemic species and lots of carbon stored in peat so very important.

The majority of tropical forests are terrifermia forests. Green on Landsat image. Solid/ dry ground. This has a high biodiversity as rivers sediments supply the area with nutrients.

Other areas - White sand forests - remnant patches- very old areas. In the Miocene geological events caused clay to be laid down. White sand was exposed over a long time. So specialist species evolved. Sometimes these specialist species may be found in other areas not White sand forests - great interest to researchers.

Rivers move a lot/ change their course. So where they go they may remove peat that was there.

There are similarities between peat land and White forest areas.

Hydrology of amazonia is changing. Droughts and floods more common. Peatlands more responsive to hydrological change than terrifermia forest. Droughts trees die - carbon lost. But replaced by species that can survive. There will be compositional shifts in forests. They could change the way carbon is stored. Peatlands reliant on being flooded. If peat dries it decomposes as oxygen available so aerobic respiration can occur. Normally aerobic respiration. Methantrophic bacteria breaks down things. Methanogenesis - uses methane instead of air to break things down much slower process so peat remains. Peat will decompose very quickly if it is dried out. Human impacts palm oil farming they dry the peat out. Increase decomposition. That's what has happened in s.e Asia. Also then peat is dry forest fires increase. Dissolved carbon doc in drained peat easily leaves the soil in flooding events in solution. So if floods increase peatland could either sequester more carbon or doc could be washed out of it. Carbon is labile in peat (not locked up/ mobile) 

1970s how the forests change long term looked into. Forest plots set up where 1 hectare 100 x 100 biomass measured repeatedly. Found to increase over 30 years. Trees grow bigger. 2 hypothesises:

Co2 fertilisation - increase emissions. In p.s co2 limiting factor. lots of h2o and sun in forests. So c02 increase hence increase growth rate. Increase turnover increase dying and re-growing.

Disturbance hypothesis - winds, trees fall, gap in forest where trees killed. Pioneer species takes over rapidly growing, mid stage species takes a long time to get back. Disturbance more grows. Residual effect of disturbance never reaches equilibrium. Forest always responding to past disturbance.

Or - remote sensing - generated ho often blow down occurs in given area. Said to be every 4,000 yrs in 1 hectare so not constantly responding to disturbance so can be equilibrium.

Temperate forest in north USA - pumped co2 into forest to see effect. Strong effect for 2 yes but then other factors became limiting e.g. potassium.

Flux towers - measures co2 in and out of forest. Sonic anometer - measures co2 sequested that goes in and out how much co2 stays. Look at how much they match. Amount taken in by plants. Co2 fertilization won't go on for ever. Changes in temp may cause loses. Drought 2010 aided trees to die