Interception Flashcards
what is canopy interception and where does the water go
precipitation that is temporarily stored on plant surfaces. water never reaches the soil surface, directly evaporates off leaves
what is stemflow
water that reaches ground by flowing down tree trunks and stems
what is throughfall
water reaching ground directly through openings in canopy
what does interception depend on (2)
nature and density of vegetation
how to calculate net rainfall
stemflow add throughflow
what impact does interception have on raindrops in terms of chemistry
alters size and chemical composition of drops as it changes the kinetic energy of rain drops
spatial variability of net rainfall is __ than gross rainfall
greater
where is throughfall concentrated on vegetation
concentrated stemflow near trunks
what are the two major hyptheses in relation to interception
- Interception losses have no effect on catchment water balance
- Interception losses reduces net inputs, diminishing soil water recharge and streamflow
what does interception represent in terms of the catchment hydrological balance
a net loss
when does precipitation evaporate at a greater rate
when it is intercepted as opposed to transpired
how much more evaporation occurs than transpiration
2-3 times more
what is the formula for calculating interception
precipitation above the vegetation layer MINUS throughfall MINUS stemflow
I = P - T - S
how to measure throughfall
gauges
how to measure stemflow
gutters around plants
what does throughfall depend on (5 factors)
Canopy cover Leaf area index (LAI) – (surface area/crown area) Evergreen or deciduous Leaf surface smoothness Leaf shapes and orientation
what are 2 factors that stemflow depends on
branch orientation
roughness of bark
when is interception storage capacity greatest
when canopy is dry (at start of rainfall event)
what is altered when the leaves become wet and how does this impact the way the rain moves
once leaves are wet, surface tension is overcome and most rainfall is lost as leaf drip or throughfall
what vegetation characteristics mean that interception loss will be greater
denser vegetation
taller vegetation
what type of ecosystem are intercepetion losses greater at
coniferous forests
coniferous forests on peat bogs intercept __% of annual precipitation
25-35% (A LOT) - average is 15-25%
how to calculate interception ratio
interception loss / gross precipitation
as rainfall increases what happens to the interception ratio
it reduces
is interception loss greater from forests or grasslands
forests
