climate change and rangeland carbon
TRANSCRIPT
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