ms thesis presentation_ hafez

Title: Decomposer metabolism and litterdecomposition rate as a function of climate andelemental stoichiometry in terrestrial and aquatic

ecosystems

Master’s Thesis Presentation:

ecosystems

Presented by:

Mohammad Hafez Ahmed

Supervisor: Dr. Stefano Manzoni

Examiner: Dr. Steve W. Lyon

Department of Physical Geography, Stockholm University

Date: 12 May, 2016

Organization of Thesis

Chapter 1:- Introduction

• Background information

• Study Aim

Chapter 2:- Materials and methods

• Data collection

• Carbon-use efficiency (CUE) and Decomposition rate • Carbon-use efficiency (CUE) and Decomposition rate constant [k; /yr]

• Climate and litter chemistry effects on CUE and k

• Relationship between CUE and growth rate [r; /yr]

• ANOVA test (Statistical significance test)

Chapter 3:- Results

Chapter 4:- Discussions

Chapter 5:- Conclusions

Background information (continue).

Litter decomposition:Important for carbon-nutrient cycling and plant

productivity (Hobbie et al. 2013).

Decomposition: Physical and chemical changes oflitters.litters.

Decomposer metabolism:• All biochemical reactions (catabolism and anabolism)

involved to maintain cell growth of organisms.• Carbon-use efficiency (CUE) is the ratio of

microbial growth over carbon uptake (Manzoni et al, 2012).

Decomposition rate constant [k; /yr]:• Relative mass loss rate per unit of time

Background information (continue).

CC C

Litter Decomposer

Uptake Release

CO2

C

N P

C C

N P

C stabilization

Nutrients

Figure: Conceptual diagram of litter decomposition.

Study aim

Main objectives:

• To estimate the bacterial CUE and decomposition

k of various litter types across terrestrial andaquatic ecosystems.aquatic ecosystems.

• Climate (e.g. Temperature and precipitation) and litterchemistry impacts on CUE and k.

• Is there any relationship between CUE and microbialgrowth rate?

Materials and methods

Data collection:

Data types:• Litter decomposition data (C/Co, N/No, P/Po, initial C/N and

C/P ratio.

• Climate data (temperature and precipitation)• Climate data (temperature and precipitation)

Sources:• 28 literature sources for terrestrial ecosystems and 20 literature

sources for aquatic ecosystems including CIDET and LIDET datasets.

• Climate research unit (CRU) and global map

Materials and methods (continue)....

Figure: A qualitative diagram from which data are collected and thenapplied to models to estimate k and CUE


Figure: Study locations (small squares) around the world


)1.......(]

)(

)(1[

)(

)()( 1

10,0,e

B

N

B

N

c

N

CN

C

N

CN

C

ccn

Decomposer CUE :

Eq. (1)- Initial fraction of N as a function of initial fraction of CNN

Rate constant k:

)3......()1(

)2.......(

21

0

tktk

ktt

eeC

eC

CC

•Note: Decomposer (C/N)B ratio : 5 to 15 (Manzoni et al. 2008)[ Assumed , (C/N)B = 10]

[Single-pool model (mostly used)]

[Double-pool model]


)5.....(ln)1

)(()ln(

)4.......(

ATR

ECUE

RT

E

AeCUE

Climate effect on CUE:

[Arrhenius function]

TR

Litter chemistry effect on CUE :

)7.......(ln)ln(*)ln(

)6........()(

ACNRbCUE

CNRACUE b

[Power-law]


1

)8.......(

E

RT

E

Aek

Climate effect on k:

[Arrhenius function]

Temperature effect: Precipitation effect:

1. Exponential function2. Power-law function3. Linear fit

)9.....(ln)1

)(()ln( ATR

Ek

Litter chemistry effect on k :

)11.......(ln)ln(*)ln(

)10........()(

ACNRbk

CNRAk b

[Power-law]


)13)....((*)(*

)12......(11

LCCUE

kr

GYr

m

CUE

Relation between CUE and growth rate [r; /yr]:

[Pirt (1965)]

)13)....((*)1

(*

MBC

LC

CUE

CUEkr

•CMB/CL varies 1-3% (van Meeteren et al. 2008), assumed= ~2%

Materials and methods (continue).

ANOVA test: statistical significance test

Results and discussions

N release pattern and decomposer CUE

Litter

type

Terrestrial

CUE

Aquatic

CUE

Grass 0.21 0.24

Broadleaf 0.26 0.19

Table: Average CUE

Figure : Nitrogen release pattern for a specific value of CUE.

Needle 0.17 0.15

Root 0.12 0.12

Wood 0.09 0.04

Results and discussions (continue)...

Figure: CUE-T relationship Figure: CUE- precipitation relationship

•Terrestrial ecosystems show a positive relationship withtemperature and precipitation, whereas aquatic ecosystemsdemonstrate the opposite patterns.


Figure: One-way ANOVA (across temperature windows)

Figure: One-way ANOVA (across precipitation windows)


)6........()(

b

CNRACUE

Figure: ln(CUE) vs. ln(CN0) relationship

•Relationship is steeper in aquatic systems compared to terrestrial systems.

)7.......(ln)ln(*)ln( ACNRbCUE

Results and discussions (continue)...Decomposition k

Figure: Changes in C mass in litter using decomposition models

)3......()1(

)2.......(

21

0

tktk

ktt

eeC

eC

CC


Table: Decomposition rate constants, k

Terrestrial ecosystems Aquatic ecosystems

Aquatic grass and broadleaf litter types have significantlyhigher k values than terrestrial grass and broadleaf litter types.

Results and discussions (continue)...Figure: ln(k) vs. 1/T graph

Table: Activation energy in ecosystems

)9.....(ln)1

)(()ln(

)8.......(

ATR

Ek

RT

E

Aek

•Have warmer climate andlower value of CN0, but higherE for aquatic grass and rootlitter.•Indicates a shift from theArrhenius-type assessment oftemperature sensitivity.

Table: Apparent E of litter types


Table: k vs. precipitation relationships

• k-value has a little sensitivity with precipitation.•Only important in terrestrial ecosystems forenzyme transportation.

Results and discussions (continue)...Table: ln k vs. ln(CN0) relationship

)11.......(ln)ln(*)ln(

)10........()(

ACNRbk

bCNRAk

•Relationship is more steeper in aquatic ecosystems

Results and discussions (continue)...Table: Summary of significant regression analyses

Terrestrial ecosystems

Aquatic ecosystems


Most influencing parameter in litter decomposition

•Temperature is the mainparameter in terrestrial ecosystemsacross the biomes. •Litter chemistry is the mostacross the biomes.•Within a biome litter chemistry isdominant parameter, except intundra regions

•Litter chemistry is the mostimportant parameter inaquatic ecosystems within abiome and across the biomes

Terrestrial ecosystems Aquatic ecosystems

Results and discussions (continue).

CUE vs. Growth rate:

Figure: Double reciprocal graphs of microbial CUE and growth rate r

• Two parameters are positivelycorrelated in both ecosystems,whereas questions arise in caseof aquatic grass and needle littertypes.

)13)....((*)1

(*

)12......(11

MBC

LC

CUE

CUEkr

GYr

m

CUE

Conclusions

• Temperature and precipitation do not matter for CUEin both ecosystems.

• CUE decreases with increased CN0 of litter in bothecosystems.

• Temperature is the main predicting parameter of• Temperature is the main predicting parameter oflitter decomposition in terrestrial ecosystems at thelarger scale. In contrast, litter chemistry is ofprimary importance in aquatic ecosystems.

• Microbial growth rate is positively correlated withCUE

Thank you for listening !!!

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ms thesis presentation_ hafez

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