Past and present climate change impacts on rangeland production

Bolortsetseg B., Erdenetuya M., Sanjid S., Manibazar N., Gantsetseg B., Bat-Oyun Ts.

Impact of climate change

• Introduction to rangeland

• Rangeland productivity

• Pasture carrying capacity

• Plant phenology

• Plant population

• Land cover change

• Modeling of rangeland ecosystem

Introduction to rangeland• The total agricultural used land - 130541.3 thousand ha in

Mongolia

– Pasture – 97.5 % (127307.0 thousand ha)

– Hay – 1.5 % (1986.6 thousand ha)

– Agricultural land per person - 53.8 ha (20 times the world average)

– Livestock –23.6 million

• Scientific research of vegetation has started since 1950 by Russian scientists and national specialists.

• Geobotanical field surveys were done in 1950-1955, water resource exploration expedition in 1959-1961, rangeland mapping and expedition in 1991-1992.

Rangeland ecosystems• The high mountain belt

• The mountain taiga belt

• The forest steppe

• The steppe

• The desert steppe

• The desert

Forest steppe

6%

High mountain

5%steppe & desert steppe65%

desert 19%

Other5%

Rangeland biomass

• Data: Rangeland monitoring biomass data of 64 sites for 1966-2001

Ecosystem N of stations

time series

4.Jun

14.Jun

24.Jun

4.Jul

14.Jul

24.Jul

4.Aug

14.Aug

24.Aug

peak

the forest steppe

18 16-31 1.3 1.9 2.5 3.0 3.6 4.3 4.9 5.3 5.3 5.9

the steppe13 19-34 1.2 1.5 1.8 1.8 2.0 2.3 2.7 2.8 2.8 3.0

the Altai mountains5 17-24 0.7 0.7 0.9 1.0 1.1 1.3 1.3 1.4 1.3 1.7

the desert steppe18 17-29 0.7 0.8 1.0 1.0 1.2 1.4 1.5 1.6 1.7 2.2

the desert2 18-21 0.6 0.7 0.8 0.9 1.2 1.2 1.4 1.5 1.4 1.7

the forest steppe 0.01 -0.01 0.01 -0.05 -0.03 -0.03 -0.06 -0.05 -0.07 -0.06

the steppe     -0.04 -0.07 -0.06 -0.07 -0.07 -0.07 -0.05 -0.05

the Altai mountains   0.00 -0.01 -0.02 -0.02 -0.01 -0.02 -0.01 -0.01 -0.02

the desert steppe -0.01 -0.02 -0.04 -0.01 -0.01 -0.01 0.00 -0.02 -0.01 -0.03

the desert       -0.01 -0.03 -0.04 -0.05 -0.06 -0.05 -0.07

Changes in biomass, g/m2/1year

Biomass, 100kg/ha

Rangeland biomass (continued)

Àðâàéõýýð

0

1

2

3

4

5

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9

1965 1970 1975 1980 1985 1990 1995 2000 2005

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4

6

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1965 1970 1975 1980 1985 1990 1995 2000 2005

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1965 1970 1975 1980 1985 1990 1995 2000 2005

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1965 1970 1975 1980 1985 1990 1995 2000 2005

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• Peak biomass trend at Arvaiheer (steppe), Erdenemandal (forest steppe), Mandalgobi (desert steppe), Ulgii (Altai mountains)

Pasture carrying capacity• The total pasture carrying capacity - 44.5 million sheep unit based on

average observed peak biomass. • Based on the decreasing trend of peak biomass by 20-30 %, the total

pasture capacity was calculated as 32.6 million sheep unit. • Past 40 years the total pasture carrying capacity was drop down by 27

% because of biomass decrease.

Ecosystemsbased on average

biomasstaking account of biomass decrease

the forest steppe 15090140 12223013

the steppe 11065023 7413566

the Altai mountains

957624 737370

the Gobi desert 17417462 12192224

total 44530249 32566173

Pasture carrying capacity• The total pasture carrying capacity - 44.5 million sheep unit based on

average observed peak biomass. • Based on the decreasing trend of peak biomass by 20-30 %, the total

pasture capacity was calculated as 32.6 million sheep unit. • Past 40 years the total pasture carrying capacity was drop down by 27

% because of biomass decrease.

Ecosystemsbased on average

biomasstaking account of biomass decrease

the forest steppe 15090140 12223013

the steppe 11065023 7413566

the Altai mountains

957624 737370

the Gobi desert 17417462 12192224

total 44530249 32566173

Plant phenology• Phenological date of 8 dominant plants such as Agropyron sp.,

Cleistogenes sp., Festuca sp., Leymus chinensis, Stipa sp., Carex sp., Allium polyrrhizum and Artemisia frigida was analysed and defined their trends. Time series longer than 15 years were selected for the analysis.

• Plants emergency is tend to start earlier in the forest steppe and the steppe. In the Altai mountains, the desert steppe and the desert some of plants (Artemisia frigida, Stipa sp.) have had delayed onset trend.

• Plant senescence occurred earlier in the forest steppe, the steppe and the Altai mountains, later in the desert steppe and the desert.

•  Plant EcosystemN of

stations

time series, years

emergen-cy

headingFlowe-

ringseeding

Senes-cence

Trend-

emrg

Trend-Sensc.

Cleistogenes the steppe 5 18-25 5/13 7/29 8/17 9/6 9/18 -0.14 -0.34

Cleistogenes the Altai mountains 1 27 5/16 6/26 7/30 8/25 9/13 0.65 -0.31

Cleistogenes the desert steppe 11 16-30 5/24 7/14 8/17 9/8 9/16 -0.01 0.14

Stipa the forest steppe 17 15-32 5/9 7/4 7/28 8/21 9/11 -0.49 -0.12

Stipa the steppe 14 14-34 5/8 7/7 8/3 8/26 9/15 -0.46 -0.04

Stipa the Altai mountains 5 18-29 5/15 6/18 7/12 8/10 8/31 0.00 -0.75

Stipa the desert steppe 14 19-32 5/11 6/19 7/13 8/5 9/6 0.07 -0.11

Stipa the desert 2 22-24 5/3 6/11 6/21 7/17 9/9 -0.03 0.30

Plant phenology (continued)• Because of extended drought, some plants such as Allium polirrhizum,

Rheum nanum, Limonium tenellum, Ferula bungeana and etc. have not flowered and develop just after rain.

• As a result, summer flowering plants have been become to flower early spring or late autumn and flowering occurred indefinite time.

• Some plants such as Pulsatilla, Caragana sp. have flowered in autumn which is considered as plant special responces to environmental negative effects.

• Flowering rhythm changes in the desert steppe •  

flowering season in 1970 years in 2000 years

No of species % No of species %

spring 9 16,6 15 27,0

the whole summer 15 27,8 18 31,6

summer 23 42,6 2 3,5

autumn 7 13,0 14 24,5

not stable     8 14,0

Source: Sanjid, 2002

Plant population

0

20

40

60

80

100

120

1970 1975 1980 1985 1990 1995 2000 2005

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Plant composition and species number changes of communities with Leymus - Potentilla bifurca, Leymus chinensis – Stipa krylovii, Agrostis mongolica – Carex orthostachys, Carex orthostacys – Potentilla anserine in Orkhon meadow.

Due to field survey of communities with Leymus - Potentilla bifurca, Leymus chinensis – Stipa krylovii, Agrostis mongolica – Carex orthostachys, Carex orthostacys – Potentilla anserine, plant composition and species numbers in autumn of 2002 are more than in the beginning of 1980 years that those years were very dry, but less than in the middle of 1980 years. In some sources, biomass of low nutrient plants increased and production of high quality plants decreased because of intensified grazing.

Source: Manibazar N

Land cover change

1992

1997

2002

Modeling of rangeland ecosystem

• Century 4.0 is used for the study.

• 37 sites in different ecosystems were selected.

• 0.5x0.5 0 grids were prepared.

• Monthly climate data were input.

• Soil data () for sites and grids were defined in the model.

• Plant composition C3:C4 was defined

• The average annual nitrogen (N) fixation rate was defined as 0.2 to 0.8 g/m-2 year-1.

Modeling of soil organic matter

• Soil organic C

• Soil organic N

SOC g/m2

y = 0.587x + 1023.6

R2 = 0.91130

2000

4000

6000

8000

10000

12000

0 2000 4000 6000 8000 10000 12000

actual

SON g/m2

y = 0.619x + 1.6857R2 = 0.6657

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

actual

Comparison of simulated and actual steady state soil carbon and nitrogen

Soil organic matter changes for past 40 years

• Soil organic N

• Soil organic C

According to soil organic matter changes distribution, soil organic matter raised in the north part of the forest steppe and the eastern steppe. Generally in the southern part of the country had decreased trend of soil organic matter.

Simulation of rangeland biomass

• Comparison of simulated and actual biomass

• Simulated aboveground live peak biomass, g/m2 Aboveground live biomass g/m2

y = 2.0897x + 9.3946R2 = 0.6377

0

50

100

150

200

250

300

0 50 100 150 200 250 300

actual

sim

ula

ted

Rangeland peak biomass changes

N EcosystemNPP, g/m2

simulated biomass,

g/m2

measured biomass,

g/m2

change in simulated

biomass, %/40 years

change in rain, %/40

years

1 The forest steppe 584.5 179.5 71.7 -11.84 -1.58

2 The steppe 418.4 119.7 47.1 -12.31 -3.07

3The Altai mountains

198.8 36.8 16.3 19.76 16.26

4 The Gobi desert 142.1 24.0 21.3 21.30 12.38

Annual NPP, biomass and biomass and rainfall changes for 1961-2000 years

Rangeland spring biomass and its changes

Spring biomass and biomass and precipitation changes

ecosystem

April May

biomass, g/m2

biomass change,

g/m2/1 year

precipitation

change, cm/1 year

biomass, g/m2

biomass change, g/m2/1

year

precipitation change, cm/1 year

the forest steppe 26.75 -0.20 -0.01 50.27 -0.34 -0.12

the steppe 14.97 -0.04 -0.01 32.60 -0.18 -0.01

the Altai mountains 4.53 0.04 0.00 13.13 0.05 0.01

the desert steppe 2.54 0.01 0.00 5.74 0.01 0.00

Thank you for your attention