Potential climate-induced vegetation change in Siberia in the 21st century




Дата канвертавання19.04.2016
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Potential climate-induced vegetation change in Siberia in the 21st century
Nadezhda M. Tchebakova1, Elena I. Parfenova1 and Amber J. Soja2


1V.N. Sukachev Institute of Forest, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, Russia,

2 National Institute of Aerospace, Hampton, Virginia, USA

Correspondence author e-mail: ncheby@forest.akadem.ru
Regional studies in Siberia have already registered a change in climate at the end of the 20th century. Additionally, we found that in some regions, warming primarily in winter has already exceeded Atmosphere Ocean General Circulation Model predictions. A mounting body of evidence of the changes in Siberian vegetation and in the forests in particular related to climate warming is available in the literature and summarized in the reviews of Soja et al.(2007) and Tchebakova et al. (2008). At the northern treeline, the forest shifted into tundra and open forests become more stocked. In Evenkia, in the permafrost zone which is dominated by only L. dahurica, undergrowth of Siberian cedar (Pinus sibirica), fir and spruce up to 40 years old was found possibly because of permafrost melting. Upper treeline shifts 40-100 m upslope was registered in the mountains in the south: Altai, Kuznetsky Alatau, West Sayan and even in the north in Putorana Plateau. At the lower treeline, changes in forest structure also occur. In the West Sayan, the Pinus sibirica seed production significantly decreased for 1990-1999, the warmest decade of the last century, presumably because of the cone damage by the moth Dioryctria abietella (Schft.){ that may produce two generations for a longer vegetation period}.

In this study, we examined the potential effect of two climate change scenarios on the spatial vegetation redistribution across Siberia for the 21st century and predicted locations where possible changes in climate would create new habitats for vegetation change. We used our bioclimatic vegetation model for predicting vegetation zones (zonobiomes) across Siberia. Our model is an “envelope-type” model (Box, 1981) that determines a unique vegetation class (unique climatic limits for a vegetation class) from three bioclimatic indices: growing degree-days, base 50C, representing plant requirements for warmth; negative degree-days, base 00C, characterizing plant cold tolerance, and AMI characterizing plant drought resistance. Vegetation predicted only from climatic variables was then corrected for permafrost which is the primary factor controlling the vegetation and tree species distribution over Siberia.

Data from about 1000 Siberian weather stations across the study area (within the Siberian window 60-1400 E and 50-750 N) were used to map current climatic variables and indices using Hutchinson’s (2000) thin plate splines on DEM grids (1 km). Future bioclimatic indices were calculated using climatic anomalies for 2020, 2050, and 2080 derived from two climate change scenarios the HadCM3 A1FI and B1 of the Hadley Centre in the U.K. based on the Special Report on Emission Scenarios, SRES (IPCC, 2000). These scenarios reflect opposite ends of the SRES range, the largest temperature increase from the A1FI scenario and the smallest temperature increase from the B1 scenario. Temperature increases across Siberia in both the A1FI and B1 scenarios do not differ much for 2020 but double for 2080, with the A1FI showing greater warming, 8-9oC versus 4-5oC in the B1 scenario.

Our research showed that Siberian vegetation would already be disturbed by 2020 and severely disturbed by 2080. Disturbances for each time slice differ in different scenarios: moderate changes are predicted from the B1 scenario and dramatic - from the A1FI scenario (fig.1). Habitats for northern vegetation classes (tundra, forest-tundra, and taiga) would shrink, habitats for southern vegetation (forest-steppe, steppe and semidesert) would expand (table, fig.1). Biomes and major tree species may shift northwards as far as 600-1000 km. Despite the large predicted warming, permafrost will not thaw deep enough across Siberia to support darkleaf taiga which requires 1-2 m of the active layer depth (ALD). Over the plain of Siberia, the larch (Larix dahurica) taiga withstanding shallow ALD will remain the dominant zonobiome. Because of a predicted dryer climate, forest-steppes and steppes rather than forests would dominate over half of Siberia. These lands would be suitable and may be used for growing both traditional crops in the north and new crops in the south for additional food, forage and biofuel production. In the very south of Siberia, desertification is predicted to occur due to the precipitation decrease along with the large temperature increase. Our model also showed that new habitats for some temperate vegetation (broadleaf forest and forest-steppe) would occur by 2080. Melting permafrost and fire are the principal mechanisms that facilitate equilibrium between the vegetation and the climate across Siberian landscapes.


References
Box E.O.1981. Macroclimate and Plant Forms: An Introduction to Predictive Modeling in Phytogeography. Junk, The Hague, P. 258.

Hutchinson MF (2000) ANUSPLIN Version 4.1 User’s Guide. Australian National University, Centre for Resource and Environmental Studies, Canberra.

IPCC. 2000. Emissions Scenarios. Special Report of the Intergovernmental Panel on Climate Change. N. Nakicenovic and R. Swart (Eds.). Cambridge University Press, UK. P. 570.

Soja A.J., Tchebakova N.M. French N.F. et al. 2007. Climate-induced boreal forest change: Predictions versus current observations. Global and Planeary Change, 56, 274-296.

Tchebakova N.M., Parfenova E.I. and Soja A.J. 2008. Climate change and hot spots in forest shifts in central Siberia by the end the XXth century. Forest snow and landscape research (in press).

Figure and Table legends
Figure 1. Vegetation change from current climate to 2080 in Siberia was mapped by coupling our bioclimatic vegetation model with maps of bioclimatic indices and of the permafrost which drive the model for different time slices and two climate change scenarios.
Table 1. Siberian vegetation change (%) in the 21st century predicted from HadCM3 A1FI and B1 climate change scenarios. Blue is an area decrease, red is an area increase.

C


Vegetation classes: BOREAL: 1 – Tundra; 2 – Forest-Tundra; Northern Taiga: 3 – darkleaf, 4 – lightleaf; Middle taiga: 5 – darkleaf, 6 – lightleaf; Southern Taiga: 7 – darkleaf, 8 – lightleaf; 9 – Subtaiga, Forest-Steppe; 10– Steppe; 11 – Semidesert; TEMPERATE: 12 – Broadleaf; 13 – Forest-Steppe; 14 – Steppe, 15 – Desert, 0- Water
urrent climate


Scenario HadCM3 A1FI 2020 Scenario HadCM3 B1 2020


Scenario HadCM3 A1FI 2050 Scenario HadCM3 B1 2050


Scenario HadCM3 A1FI 2080 Scenario HadCM3 B1 2080


Figure 1. Vegetation change from current climate to 2080 in Siberia was mapped by coupling our bioclimatic vegetation model with maps of bioclimatic indices and of the permafrost which drive the model for different time slices and two climate change scenarios.
Table 1. Siberian vegetation change (%) in the 21st century predicted from HadCM3 A1FI and B1 climate change scenarios. Blue is an area decrease, red is an area increase.


Vegetation zone

BOREAL:


Current

climate


Scenario HadCM3 B1

Scenario HadCM3 A1FI

2020

2050

2080

2020

2050

2080

Tundra

18.3

8.2

4.7

3.6

7.6

1.8

0.1

Forest-tundra

8.5

7.1

6.3

4.9

7.5

3.0

0.5

Northern Dark Taiga

0.2

0.4

0.7

0.9

0.4

0.8

0

Light Taiga

13.6

10.6

9.0

6.4

11.0

7.0

2.4

Middle Dark Taiga

4.7

2.0

1.6

1.7

2.0

1.4

0.6

Light Taiga

17.0

14.2

10.9

9.1

14.4

8.2

6.1

Southern Dark Taiga

7.5

5.8

5.6

8.3

6.9

2.9

2.1

Light Taiga

8.6

11.1

7.9

7.9

10.2

6.5

4.3

Forest-steppe

7.5

17.8

24.4

21.9

19.3

24.8

15.9

Steppe

10.0

12.7

14.2

17.2

13.2

18.7

9.2

Semidesert

1.5

3.9

4.6

4.9

2.2

5.1

6.6

TEMPERATE:




Broadleaf Forest

0.8

1.8

3.9

0.8

2.4

6.5

8.0

Forest-steppe

0.8

1.4

3.3

8.1

1.0

9.3

19.6

Steppe

0

0

0.3

1.3

0

1.1

17.8

Semidesert/Desert

1.0

2.8

2.6

2.8

18

29

6.8


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