Forests, Water and Climate
25 important questions on Forests, Water and Climate
Are forests hydrologically beneficial?
What did they find in a Wagon Wheel research in Colorado 1928:
Give the formula for a model for the Budyko curve to calculate E/P or water balance partitioning? What did they find?
- Land cover matters: grass vs. Forest (increased w with more vegetation)
- Streamflow increases with deforestation, as evaporation increases. (min 21)
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Another model of Zhang: estimating annual ET from annual P, depending on land cover. What is their main finding?
- ET increases in increasingly forested catchments
Give the formulas from Zhang et al. (2001) for ET in a catchment, both the general relation (simplified version of fitted model) and the fitted model.
Play around with this formulas yourself!
Paste formulas.
f = fraction of forest cover
ETh = for short vegetation?
Partitioning of terrestrial evapotranspiration. What are main partitioners for global and forest scales?
E = evaporation
Global:
Transpiration via stomata 80%
Bare soil E 11%
Interception E 7%
Snow sublimation 2%
Forest (Germany)
Interception E 44%
Transpiration via stomata 37%
Bare soil evaporation 19%
Interception capacity is higher in forest, especially in needle forests, that have high interception capacity in winter (copmared to bare fields).
Forests aerodynamiccaly stronger coupled than lower vegetation.
Turbulence/rough surface from forests, that enables higher ET.
Annually, this apparantly becomes larger than T.
Lower streamflow, .. (min 30)
What is a negative effect of FLUXNET, that measures turbulence?
Measure turbulence
Quite a bit of uncertainty higher sthigher streamflow after deforestationream (min 31) .
Streamflow is a slow process, that can be measured properly by eddy covar(?)
Turbulence processes produce sampling uncertainty (one aspect).
Only global network for measuring ET.
higher streamflow after deforestation
Forest ET paradox: two contradicting concluding papers. Why can the sign of ET be either +/- in these papers?
Explain the Castricum lysimeter experiment: why lysimeters and why was this location chosen?
North-Holland is main drinking water source for Amsterdam. Water managers wanted to know the land cover that gains most drinking water.
Explain main findings of Castricum lysimeter experiment?
Coniferous: very water limited system, difference between blue and green line is the drainage from base of root zone. This is very little for the coniferous forest, where the coniferous forests grows/matures over time, the difference becomes smaller and water availability reduces further.
Bare soil has the largest difference. For the drinking company, bare soil allows higher water extraction.
More GW recharge and more salt water pushback in the Dutch Dunes on bare soils.
Check min 55: What is the sponge theory and what is the current status of debate?
Already criticism since 100 years. Currently, there is still a large debate. People might like to see that forests only have positive effects.
Min 57-61: What is the effect of forests on peak flow?
Effect on permeability, rooting depth, etc. Might not be well modeled.
Observation based studies show there is no influence -->??
What are the effects of forests in boreal areas?
Min 71
Min 74-77: energy explanation!
Temp is much closer to atmosphere temp. Grass warms up more,
Sensible heat is compressed
Forests:
Sensible heat flux (warming of atmosphere)
ET is compressed
Forests in NL have a warming effect on atmosphere (different than walking in the forest, which is cooling).
Min 80: Relation on forests and clouds: very confusing signals. Give
Australia: clear distinction farmland (no clouds) and scrubland (with clouds). Thus opposite of occurence in Amazon.
Review paper Lawrence & Vandecar (2015): processes min 81
...
Locally: deforestation leads to increase of clouds, but you need the ... From local regions.
As turbulence, clouds are very erratic. Continuous sampling averaging over many days are necessary to measure clouds. How is this done?
15 min, 1 km resolution
When researching clouds, you should exclude topography (so no mountainous areas).
What happens in the EU forests on the front of cloud cover, based on the satellite data?
Tropics: ET or sensible heating? -_> Min 88/89!!
Link with energy cycle that explains cloud formation.
Turbulence and sensible heating of land surface. Some wind direction effects.
What is the forest-breeze in the tropics?
What was the impact of cyclone Klaus?
How do mega-cities impact cloud cover?
Larger scale (Spracklen 2012 & Aragao 2012) : more ET on average means that this ET should go somewhere. (min 92)
P = precip
Spracklen:
Air passing over forest day before: P was higher. Very difficult to quantify this.
Aragao:
Forest: rainfall recycling
Deforest: remove ET, increase runoff
Further deforest: ET gets very low, reduced rainfall, runoff more direct.
Water cycle and downwind precip is changed while deforesting.
Feedbacks might play at larger scale than previously though.
Explain main findings of forests on water on smaller and larger scales?
Larger scale: remote rainfall, .. rainfall, (min 100:50). Moisture recycling.
Lot of debate and uncertainty still going on.
What is the forest effect on a small scale?
On larger scale: adding this up, forests may cause increased P due to increased ET, hence the runoff may be compensated by this increased P.
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