need help on a problem for my problem set, thanks in advance! You are studying t
ID: 70159 • Letter: N
Question
need help on a problem for my problem set, thanks in advance!
You are studying the decomposition and mineralization from leaf litter in a forest. The litter has the following characteristics:
Material
% of litter mass
C/N ratio
Physiological material
20
5
Cellulose
60
No N
Lignin
20
No N
Three groups of organisms decompose this material
Organism
C/N Ratio
Substrate Use Efficiency
They eat:
Bacteria
5
0.50
Only physiological material
Cellulytic fungi
20
0.40
Everything except lignin
Lignolytic fungi
20
0.25
Everything
Assume:
Growth rates:
A- Bacteria grow faster than fungi and have first crack at any material that they can metabolize (physiological material and dead microbes).
B- Cellulytic fungi grow next fastest and will use resources that bacteria don’t.
C- Lignolytic fungi grow the slowest of all three groups (i.e. they have last crack at material).
D- Microbes will only process a material if they have the nitrogen they need to do so.
1. Given those assumptions, run calculations for the first cycle of decomposition. Calculate:
A-How much of each plant carbon pool is decomposed?
B-How much biomass of each group of microorganisms is produced?
C-.Is any nitrogen mineralized? If so, how much?
Material
% of litter mass
C/N ratio
Physiological material
20
5
Cellulose
60
No N
Lignin
20
No N
Explanation / Answer
** Note:- The question is very lengthy. I am answering the first part of the question.
20% of litter mass is physiological material. It is being used by bacteria, cellulytic fungi and lignolytic fungi.
C/N ratio of physiological material is 5, means for every 5 parts of Carbon 1 part of nitrogen is present. So, Carbon present in physiological material is 5/6 * 20 = 16.67%
% of physiological material decomposed by bacteria = 0.50 of 16.67 = 8.33% (in first cycle).
% of physiological material decomposed by cellulytic fungi = 0.40* 16.67 = 6.68%
% of physiological material decomposed by lignolytic fungi = 0.25 of 16.67 = 4.16%
So, total percentage of physiological material decomposed = 8.33 + 6.68+ 4.16 = 19.17% (of carbon pool of physiological material is decomposed in the first cycle of decomposition).
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