Effects of climate change and deforestation on potential of carbon sequestration and its implication in forest landscape restoration

Effects of climate change and deforestation on

potential carbon sequestration and its implication in

forest landscape restoration

World Agroforestry Centre (ICRAF)

Nairobi, March 14, 2016

aWorld Agroforestry Centre (ICRAF), United Nations Avenue, P.O. Box 30677-00100, Nairobi, Kenya bInstitute of Geography, Friedrich-Alexander-University Erlangen-Nuremberg, Wetterkreuz 15, 91058

Erlangen, Germany

Mulugeta Mokriaa,b, Dr. Aster Gebrekirstosa , Dr. Ermias Aynekulua, Prof. Dr.

Achim Bräuningb



• Brief introduction (forests, drivers of deforestation and

tree mortality)

• Methodology (site description, field, laboratory and

modeling analysis)

• Results (carbon stock, sequestration, growth rate,

impact, resilience and range of ecotone shift)

• Management and restoration implications

Outline



• Tropical forests and agroforests: an important biome,

to stabilize atmospheric carbon cycle and to minimize

climate change impact

• Continued to be degrade due to livelihood related

issues and climate change

• Become major carbon sources and accelerating global

climate change

• There is a need to understand the drivers, processes

and impacts to suggest possible policy and

management options

Introduction

Drivers of deforestation

Picture source: https://www.google.de/search?q=forest+clear+cutting+in+africa&biw=1600&bih=1089&tbm=isch&tbo=u&source=univ&sa=X&ei=6lxXVZ2JMoHaUsq_gbgL&sqi=2&ved=0CDcQ7Ak,

https://www.google.de/search?q=drought+induced+tree+mortality+pictures&biw=1600&bih=1089&tbm=isch&tbo=u&source=univ&sa=X&ei=Ll5XVayOOqahyAP2tIDABw&ved=0CE4Q7Ak



anthropogenic

..since deforestation is the permanent destruction of trees and

forests, it is considered to be one of the contributing factors to

global climate change. (Adams et al. 2010).

https://www.google.de/search?q=forest+clear+cutting+in+africa&biw=1600&bih=1089&tbm=isch&tbo=u&source=univ&sa=X&ei=6lxXVZ2JMoHaUsq_gbgL&sqi=2&ved=0CDcQ7Ak








climate (drought /temperature)

https://www.google.com/search?q=drought+induced+tree+mortality+picture

https://www.google.com/search?q=drought+induced+tree+mortality+picture

drought induced tree/forest mortality: Across the globe

Australia Europe

Africa

Asia



America

drought induced forest mortality is projected to increase



Allen et al., 2010,2015



Ethiopia

ALLEN et al., 2015

Since 1970

Before 2010

Between 2010-2015



…forms a climatic buffer

zone between……

Study area



disaggregate anthropogenic and climate related effects

estimate the extent of the impact of tree dieback on

ecosystem services (C-sequestration potential)

assess resilience/adaptation of foundation species in

their natural environment

recommend policy and restoration options



https://www.google.com/search

Dendrochronology: "reading history books of trees"

Methodology

https://www.google.com/search

- Greenhouse effect - Heavy metals - Air pollution - Forest diseases

GLACIO-

LOGY

ENVIRONMENTAL

RESEARCH

CLIMATOLOGY GEOMORPHOLOGY

HYDROLOGY

TEKTONICS/

VOLCANISM

DENDRO-

ECOLOGY

- Ground water- fluctuations - Peat bog growth - Flood reconstruction - River history

- Dating of moraines - glacier- fluctuations

- Climate and wood formation - climate reconstruction - wind-/ fire-/ snow impact

- Erosion rates - Debris flow frequency - Slope movement - Permafrost

dynamics

- Volcanic eruptions - earthquakes

© Bräuning, Insitut für Geographie, Univ. Stuttgart, 24.04.2002



Interview with local people and experts in the area:

Their local knowledge about the forest and their

perception

Drivers of deforestation

Change in climate and its impacts

When the tree dieback started and its trend



Method- field data collection

Biometric data

• Five transects (1km)

• 57 plots

• 50m X 50m size

• Tree height and DBH>

5cm were measured



Sample collection for tree-ring analysis



20 disks (dead and living)

DBH range 20- 48 cm

Wood characteristics and growth ring identification

Bark

J. procera forms distnict growth-rings

DRP DRP



Methods- laboratory analysis

double staining with

Safranin-Astra blue

Radioactive carbon analysis



Methods- laboratory analysis

Year

19

50

19

55

19

60

19

65

19

70

19

75

19

80

19

85

19

90

19

95

20

00

20

05

20

10

F1

4C

_N

H_

zo

ne

3

1.0

1.2

1.4

1.6

1.8

F14C-NH zone 3

Tree ring (14C)

Ethiopia

Hua et al., 2013. Atmospheric

radiocarbon for the period

1950–2010. RADIOCARBON ,

Vol 55, Nr 4, 2013, p 2059–

2072 Mokria et al., in preparation



GRB

Wider

rings Narrow ring

Wider

rings

Tree ring width measurement

r1

r2

r3

r4 pith



Density measurement

Water displacement method

- Fresh volume

- Oven dry for 72h under 105 oC

- Density = dry weight/ fresh

volume (g/cm3)

Two biomass estimation allometric equations

improved pan-tropical allometric model by Chave et al., 2014

• where, coefficient a = 0.0673 and b = 0.976 and parameter AGB (kg), ρ = specific wood density (g/cm3),

D (cm) and H (m).

the flexible tropical mixed-species biomass estimation model by

Ketterings et al. (2001):

• where, with coefficients D in centimeter, ρ in gram per cubic centimeter, AGBest, in kilogram, ϒ is a

constant parameter over a range of sites calculated as ϒ = a/ρ(wood specific gravity), where a = 0.066,

is the constant parameter, b is a scaling exponent derived from species-specific height-diameter

allometry (this study).



bHDaAGB )( 2

1

bDAGB 2

2

Biomass estimation

….. Propagation of measurement errors in σD, σH , σρ and σr , to

estimated AGB:

(Chave 2004, Schöngart et al., 2011)

Eq.1

Eq.2

total uncertainty per plot uncertainty in each trees

… then, the mean AGB and new variance form Eq. (1) and (2) to

consider errors due to model selection

Wood Science Underpinning Tropical Forest Ecology and Management,

Tervuren, May 26-29, 2015

Mokria et al.; Tree dieback affects carbon sequestration potential of a dry afromontane forest

2bH)(ρD

σ1b)2(Dba

2b)2D(ρH

σ1bHba2

b)2D(Hp

σ1bρba)AGB(2

σ

1

50

1

21

.

)()( ))(

AGBAGB

2

Dbr2

Dr2

D)AGB(2

σ bD

bbr

12

)(

50

2

2

2

.

)()( ))(AGBAGB

25022

122 .)()()( AGBAGBmeanAGB

Species Status No. of

trees

Mean [SE]

DBH (cm)

Mean [±

SE] H (m)

Range of

DBH

(cm)

Range of

H (m)

Proportion of trees (%) under

diff. diameter class (cm)

5-15 15-30 30-50 >50

Juniperus alive 1069 16.5 [0.96] 6.1 [0.29] 5-88 2-17.5 60.6 33.8 4.8 0.8

snag 607 17.2 [1.17] 5.9 [0.29] 5-90 2-20 48.4 44.2 5.6 1.8

Olea alive 1313 18.5 [0.83] 5.5 [0.16] 5 - 90 2-17 39.2 52.7 7.0 1.1

snag 802 19.6 [1.23] 4.7 [0.16] 5-114 2-13.5 48.3 46.4 3.7 1.6

Co-occurring alive 1747 11.4 [0.43] 4.2 [0.09] 5-85 2-17 78.1 20.8 1.0 0.1

snag 120 10.5 [0.73] 3.6 [0.20] 5-27 2-8.4 74.2 22.5 0.0 3.3

Summary of plot inventory data: DBH, H, and SE, refer to diameter at

breast height, tree height, and standard error, respectively…..

92.2% of snags are from foundation tree species (i.e. juniperus and olea)



Total= 5658

Results

From inventory

25% were dead trees

Total estimated - aboveground C-stock

At landscape level, 34.5% C-stock is going to be a source of carbon…



Mean aboveground C-stock

(Kg C tree-1)

Total aboveground C-stock

(Mg C ha-1)

Species Living trees Snags Eq. 2 Eq. 3 Mean

Proportion of C-stock

estimated from snags

(%)

J. procera 41.0 (±7.7) 57.8 (±10.9) 8.3 (±1.5) 10.6 (±1.8) 9.4 (±1.6) 44.5 %

O. europaea 80.7 (±17.6) 72.9 (±15.9) 11.0 (±2.2) 13.9 (±2.6) 12.4 (±2.4) 35.6 %

Co-occurring 22.1 (±6.6) 12.2 (±3.6) 2.0 (±0.5) 2.4 (±0.7) 2.2 (±0.6) 3.7 %

All species 43.6 (±9.9) 62.0 (±14.1) 17.2 (±3.5) 21.4 (±4.3) 19.3 (±3.9) 34.5 %

Total above ground C-stock/ha -19.3 Mg C/ha ,

Diameter class (cm)

5-1

0

10

-15

15

-20

20

-25

25

-30

30

-35

35

-40

40

-45

45

-50

>5

0

Ca

rbo

n s

tock (

Mg

)

0

2

4

6

8

10

12

Living trees

Snags

(a) J. procera

Diameter class (cm)

5-1

0

10

-15

15

-20

20

-25

25

-30

30

-35

35

-40

40

-45

45

-50

>5

0

Ca

rbo

n s

tock (

Mg

)

0

4

8

12

16

20

24

28

Living trees

Snags

(b) O. europaea

Diameter class (cm)

5-1

0

10

-15

15

-20

20

-25

25

-30

30

-35

35

-40

40

-45

45

-50

>50

Carb

on s

tock (

Mg)

0

2

4

6

8

Living trees

Snags

(C) Other species

Total aboveground carbon-stock - under different

diameter classes

Note: C-stock in snags increase with increasing diameter class



Total aboveground carbon-stock - along an elevation

gradient

Elevation (m.a.s.l)

14

00

15

00

16

00

17

00

18

00

19

00

20

00

21

00

22

00

23

00

24

00

25

00

26

00

27

00

28

00

Ca

rbo

n s

tock (

Mg

)

0

5

10

15

20

Living trees

Snags

(b) O. europaea

Elevation (m.a.s.l)

14

00

15

00

16

00

17

00

18

00

19

00

20

00

21

00

22

00

23

00

24

00

25

00

26

00

27

00

28

00

Ca

rbo

n s

tock (

Mg

)

0

2

4

6

8

10

12

14

16

Living trees

Snags

(a) J. procera

Elevation (m.a.s.l)

14

00

15

00

16

00

17

00

18

00

19

00

20

00

21

00

22

00

23

00

24

00

25

00

26

00

27

00

28

00

Ca

rbo

n s

tock (

Mg

)

0

2

4

6

Living trees

Snags

(C) Other species



the trees at lower elevation are vulnerable due to increase in temperature

and heat wave from Dallol

shifting ecotone by 500m

what is the implication of this change when we consider restoration of

degraded landscapes?

Tree age and diameter increment

tree age ranges from 106 to 248 years

the radial increment range: 0.25 to 2.1 mm year-1

the overall mean of 0.91 (± 0.02) mm year-1



C-sequestration determination

Year (Age)

50 100 150 200 250

Cu

mu

lati

ve d

iam

ete

r (

cm

)

0

10

20

30

40

50

Age and C-stock in AGB relationship

• From the above model we drive the annual carbon sequestration (kg

year-1 tree-1): C-sequestration = CC-stock (t + 1) – CC-stock (t), where

CC–stock is cumulative carbon stock over the entire life span of tree

growth



Year(Age)

100 125 150 175 200 225 250

C-s

tock

in

AG

B (

Kg

C)

0

100

200

300

400

500

Eq. 2

Eq. 3

Sigmoidal (Eq.2)

Sigmoidal (Eq. 3)

Eq.2 a = 577.8

b = 40.3

c =207.4

r2

= 0.81, p < 0.001

n = 20 Eq.3

a = 479.4

b = 36.4

c = 186.9

r2 = 0.8, P < 0.001

n = 20

Mean annual C-sequestration rate per tree

The mean annual C-sequestration rate: 1.12 (± 0.05) kg C tree-1 yr-1.



Years(age)

0 25 50 75 100 125 150 175 200 225 250

C-s

eq

ues

tra

tio

n i

n

AG

B (

Kg

C y

r-1

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0C-sequestration[M2]

C-sequestration[M3]

Mean C-sequestration

Carbon-sequestration potential- at landscape level

Mean annual C-sequestration potential (Mg C ha-1 year-1)

Species Pre-tree-dieback Post-tree dieback Lost CS-potential

(%)

J. procera 0.22 (± 0.03) 0.14 (± 0.03) 36.4

O. europaea 0.18 (± 0.02) 0.11 (± 0.02) 39.0

Co-occurring species 0.15 (± 0.01) 0.14 (± 0.01) 6.7

All species 0.45 (± 0.03) 0.33 (± 0.03) 27.0

• Pre and Post-tree dieback carbon-sequestration • Lost carbon-sequestration potential due to dieback



Note: Annual C-sequestration per hectare

= 1.12 (± 0.05) kg C tree-1 year-1 X stem density per ha

It is an indication of required period of time to reach

optimum harvestable size under natural condition



Other ecological implications

Years (Age)

0 50 100 150 200 250

CG

W (

cm

)

0

10

20

30

40

50

MA

I (c

m)

0.06

0.12

0.18

0.24

CGW

MAI

J. procera require more than 100 years to

reach… the impact is long lasting impact



What is the implication if we consider to restore this degraded landscapes?

trees at lower elevation are more vulnerable due to increase

in temperature and heat wave from Dallol

dieback caused upward ecotone shift by about 500m,

ecotone shift Indicates changing environmental conditions

the impact of tree dieback on the ecosystem is long-lasting

It is costly to curb the situation after major vegetation loss

conservation is cheaper than restoration

restoration should consider a micros site conditions and

climate resilient species

Dendrochronology is very useful tool to determine annual

carbon sequestration (temporal and spatial), to asses

resilience of species , understand landscape history and

population dynamics



Conclusion and recommendation



Thank you!

Acknowledgement

CRP 6.4 for co-funding

Mekele University for support during field work

Edith Anyango for assisting laboratory work

Environment

Effects of climate change and deforestation on potential of carbon sequestration and its implication in forest landscape restoration