climate change and rangeland carbon

Climate Change

and

Rangeland Carbon

James Bartolome

ESPM Dept. U.C. Berkeley

Outline

• Introduction -- The role of atmospheric carbon in global change

• Are rangelands important carbon sources and sinks?

• How much do rangelands vary and why?

• Can rangelands contribute significantly to mitigation of global change?

• What kinds of management interventions are likely to be effective?

Vostok – Antarctica:

Analysis of ice and gas bubbles trapped in

ice yields past climate history of last

460,000 years

100

150

200

250

300

0 50 100 150 200 250 300 350 400 450

Thousand Years Before Present

CO

2 (

pp

mv)

-10

-5

0

5

10

Global Carbon Cycle Reservoir Inventory

(PgC=1012kgC)

Compounds Turnover time

Atm 560 + Mainly gases:

CO2, CO, CH4

Land plants 610 Organic 1-100 yr

Soils 1,580 Organic/inorg 5-500 yr

Ocean 39,000 Mainly dissolved

(inorg & org)

Particulates

(inorg & org)

1 yr for upper 100

m;

102-103 yr depth

Marine

sediments and

sedimentary

rocks

100,000,000 Inorganic Marine: >105yr

Rocks: >106 yr

(fossil fuel) 5,000? organic

Mo

bile

Ca

rbo

n C

yc

le

Except for atm, global inventories and fluxes are approximate

Anthony Peak, Sierra Nevada:

more carbon tied up in trees

1966 1982

Outline

• Introduction -- The role of atmospheric carbon in global change

• Are rangelands important carbon sources and sinks?

• How much do rangelands vary and why?

• Can rangelands contribute significantly to mitigation of global change?

• What kinds of management interventions are likely to be effective?

Global patterns of NPP vary with climate

But …high variability due to soils, etc.

Precipitation maximum at 2 m/yr Increases exponentially with T

Some Definitions

• Rangelands – grasslands, savannas, and shrublands, about 50% of the world’s land area

• Grassland – a biome type characterized by non-woody vegetation, usually from the grass family

• Savanna – a grassland with scattered trees

• Shrubland -- a biome type dominated by small woody plants

• Grass – a large (10,000 species) monophyletic family of flowering plants

East African savanna

Mojave desert shrubland

Mojave River

.

Biome

Area (106 km2) Total C pool (Pg C)

Total NPP (Pg C yr-1)

Tropical forests 17.5 340 21.9

Temperate forests 10.4 139 8.1

Boreal forests 13.7 57 2.6

Mediterranean shrublands 2.8 17 1.4 Tropical savannas and grasslands

27.6 79 14.9

Temperate grasslands 15.0 6 5.6

Deserts 27.7 10 3.5

Arctic tundra 5.6 2 0.5

Crops 13.5 4 4.1

Ice 15.5

Total 149.3 652 62.6 Data from Roy, 2001.

Global distribution of terrestrial biomes

and the total carbon in plant biomass

Outline

• Introduction -- The role of atmospheric carbon in global change

• Are rangelands important carbon sources and sinks?

• How much do rangelands vary and why?

• Can rangelands contribute significantly to mitigation of global change?

• What kinds of management interventions are likely to be effective?

Figure 1. As moisture availability increases on rangelands, vegetation growth is greater,

biotic interactions are more important, and carbon sequestration potential increases.

Vegetation growth and characteristics, and hence carbon flows to soil and plant matter,

can be more directly shaped by management interventions.

Mesic Valley Grassland in

northeastern San Joaquin Valley

Nassella pulchra dominated

Grassland at Vasco Caves

Outline

• Introduction -- The role of atmospheric carbon in global change

• Are rangelands important carbon sources and sinks?

• How much do rangelands vary and why?

• Can rangelands contribute significantly to mitigation of global change?

• What kinds of management interventions are likely to be effective?

Productivity and diversity

relationships among biomes Biome g Biomass/m2/yr g C/m2/yr Biodiversity

Tropical Forest 1900 850 very high

Temperate Forest 1250 550 medium

Savanna 900 400 medium

Boreal Forest 800 350 low

Mediterranean Shrubland 700 300 medium

Temperate Grassland 600 250 medium

Tundra 150 70 low

Desert 90 40 low

Cultivated 650 300 very low

Wetlands 2000 900 low

Lakes 250 110 low

Biomass distribution of the major terrestrial biomesa.

Biome Roots (% of total)

Total (g m-2)

Tropical forests 22 38,800

Temperate forests 21 26,700

Boreal forests 27 8,300

Mediterranean shrublands 50 12,000

Tropical savannas and grasslands 30 5,700

Temperate grasslands 67 750

Deserts 50 700

Arctic tundra 62 650

Crops 13 610 a Data from [Roy, 2001 #3858]. Biomass is expressed in units of dry mass.

Much of the Plant Biomass is Belowground

Outline

• Introduction -- The role of atmospheric carbon in global change

• Are rangelands important carbon sources and sinks?

• How much do rangelands vary and why?

• Can rangelands contribute significantly to mitigation of global change?

• What kinds of management interventions are likely to be effective?

Livestock grazing: minor effects confined

to more productive ecological sites

Cultivated grain replaced native

grasses: soil carbon loss

Prescribed fire for barbed goat grass

control and native grass enhancement:

short term carbon losses

Californian blue oak savanna: burn

with no net change in carbon

Elephants in Acacia savanna

Elephants in former Acacia

savanna