Soil Water Supply

Question 0

Available water capacity (AWC) is the

Answer 0

Soils ability to retain water.

Question 1

Water use efficiency (WUE) is the

Answer 1

Ratio used to describe the amount of CO2 absorbed per unit of water lost.

Question 2

Soils with a low AWC are

Answer 2

At risk of water shortage.

Question 3

Soil water potential - ψ soil - describes

Answer 3

How tightly water is held in pores of soil matrix.

Question 4

Ψ soil =

Answer 4

-m (matrix pressure)

Question 5

If soil is greater (more positive) than

Answer 5

-5 kPa then water is lose enough to be drawn by gravity.

Question 6

If water is less (more negative) than

Answer 6

-1500 kPa then water is held too tightly to be extracted by most plants.

Question 7

CAM plants: (5)

Answer 7

Crassulacean acid method.
Succulent.
Stomata is opened at night instead of the day when atmosphere has a lower demand for water and the relative humidity is higher.
CO2 is also taken up at night whilst stomata are open.
Can be 10x more efficient in their use of water than normal plants.

Question 8

Responses to water shortage: ruderal (3)

Answer 8

Rapid growth whilst soil is moist.
Remain dormant in seed bank during late summer when most soils are likely to dry out.
Life cycle allows them to specifically avoid drought.

Question 9

Responses to water shortage: stress tolerant (3)

Answer 9

May compromise growth rate.
Minimise water loss.
Leaves reflect radiation to keep plant cool; traps a layer of moisture around the leaf.

Question 10

Responses to water shortage: competitive (2)

Answer 10

Maximise the amount of water absorbed.

Sends roots into deeper profile; more roots = greater area coverage.