Food sources in Lotic Systems L. 11

Question 1

Autumn shed leaves is…

Answer 1

A major OM input for small broadleaved Forest streams

Question 2

What’s step 1 in leaf processing sequence

Answer 2

Leaves are wetted.

Leaching of 25% dry weight occurs in 24hrs.

Question 3

What’s step 2 of leaf processing sequence

Answer 3

Followed by a period of microbial colonisation & growth.

Converts 75% of leaf mass to FPOM.

Question 4

What’s step 3 in leaf processing sequence.

Answer 4

Fragmentation by mechanical means - river flow.

Question 5

What’s step 4 of leaf processing sequence.

Answer 5

Macroinvertebrate activity enhances fragmentation & mineralization.
Shredders eat softer part, leaving behind skeleton.
This feeding speeds up breakdown of CPOM to FPOM.

Question 6

What’s the 1st factor that can influence the rate of CPOM breakdown.

Answer 6

Variation in time of leaf fall.

Things are changing - climate.

Question 7

What’s the 2nd factor that can influence rate of CPOM.

Answer 7

Chemical & structural differences in leaves.
Non-woody plant leaves decompose quicker (65 days)
Leaves with high lignin breakdown slowly (beech)

Question 8

What’s the 3rd factor that influences the rate of CPOM breakdown.

Answer 8

Feeding activity of detritovores.

Species-specific rates of leaf conditioning by aquatic fungi.

Question 9

What’s the 4th factor to influence the rate of CPOM breakdown.

Answer 9

Environmental variables.
Breakdown rate faster- higher temps.
Metal pollution decrease decomposition rates - negatively affect shredders & microorganisms.