Carbon Balance Arctic Tundra Ecosystem Chaparral Ecosystem Semiarid
Carbon Balance Arctic Tundra Ecosystem Chaparral Ecosystem Semi-arid Coastal Ecosystem Walter C. Oechel Steve J. Hastings Hyojung Kwon Rommel C. Zulueta George Vourlitis Pablo Bryant Global Change Research Group San Diego State University
Flux Tower Sites
INTER- AND INTRA- ANNUAL PATTERNS IN CO 2 EXCHANGE OVER ACRTIC TUNDRA ECOSYSTEMS
Sites Atqasuk
Sites n Barrow n Atqasuk 71 19’N, 156 36’W 70 29’N, 157 25’W Wet-Coastal Tundra Moist Tussock Tundra Coastal Climate Continental Climate Year-Round Measurement
Eddy Covariance Tower Barrow Atqasuk
Objectives • Quantification of intra- and inter annual cycle • Determination temporal and spatial variability • Establishment of long-term data base
Temporal Variability in CO 2 Exchange
Seasonal change in daily variation in net CO 2 Flux Barrow, Alaska (1999 – 2001)
Seasonal change in daily variation in net CO 2 Flux Atqasuk, Alaska (1999 – 2001)
Inter- and Intra Annual Variation in CO 2 Exchange Barrow, Alaska (1998 – 2001)
Inter- and Intra Annual Variation in CO 2 Exchange Atqasuk, Alaska (1999 – 2000)
Spatial Variability of CO 2 Exchange
Climate Condition
Comparison of seasonal change in net CO 2 Flux 1999
Comparison of seasonal change in net CO 2 Flux 2000
Comparison of seasonal change in net CO 2 Flux 2001
Summary • Temporal and spatial variability in net CO 2 flux • The role of soil respiration in carbon balance
Flux Tower Sites
CO 2 and H 2 O Fluxes of Chaparral Ecosystem Following Fire
Disturbance in Chaparral • Fire is an important agent of disturbance in chaparral. • The average return interval for fire is ca. 55 -60 years (Davis and Michaelsen (1995). • Chaparral vegetation displays a variety of adaptations to fire.
1 year following fire 5 years following fire 85 years following fire
Chaparral Senescence • Standing dead biomass accumulates with stand age (Hanes, 1971). • Recruitment declines with stand age (Mooney and Dunn, 1970) • Nutrient availability declines with stand age (Christensen, 1973).
Caveats to the Senescence Paradigm • Chaparral productivity (measured as net photosynthesis) does not decline with age (Reid and Oechel, 1984). • Recruitment does not decline with stand age (Zedler and Zamut, 1989). • N availability does not decline with stand age (Marion and Black, 1988).
Objectives of This Study • To test the hypothesis that ecosystem production declines with stand age. • To determine how seasonal and interannual variations in meteorology alter the net ecosystem production of mature and regenerating chaparral. • To provide regional estimates of net CO 2 and H 2 O vapor flux for Southern California chaparral.
Location and Description of Study Sites • Elevation: 1421 m • Annual rainfall: 530 mm. • Mean annual temperature: 12 °C • Soils: loamy, mixed mesic, shallow Haploxerolls of the Sheephead and the Tollhouse series. • Vegetation: Red shank (Adenostoma sparsifolium) -Chamise (A. fasciculatum) series chaparral.
Physical and chemical characteristics † ¢ Vegetation area index is for leaves + stems. Data are mean + 1 SE values, n = 5 shrubs in the burned stand n = 4 in the intermediate and mature stands.
Daily Pattern of Net CO 2 Flux at Sky Oaks Field Station
Time of Day
Year
Annual summary data for 1997 -1999
Why are older stands larger net CO 2 sinks? • Higher rates of leaf and/or leaf photosynthesis • Improved water relations
Conclusions • Net ecosystem productivity does not decline with stand age. • The relative differences in seasonal and annual net CO 2 flux between the mature and burned stands is modified by interannual variations in precipitation. • Old stands are at least if not more productive than regenerating chaparral stands because leaf are increases with stand age.
Flux Tower Sites
Land-Atmospheric Interactions of CO 2 and H 2 O Fluxes in a Semi-arid Coastal Ecosystem in Baja California San Diego State University Centro de Investigaciones Biológicas del Noroeste
Surface area, mean and total soil organic matter pools, and mean and global net primary production (NPP) for the dominant global biome types Adapted from Whittaker (1975) and Schlesinger (1991).
Objectives n n n Expand the diversity of ecosystem types measured by eddy covariance flux system Determine the seasonal carbon, water and energy flux of a semi-arid coastal ecosystem Form a link between SDSU and CINOR
Site Location La Paz (24'16 N, 110'31 W), The capital of Baja California Sur, Mexico
Climate and Vegetation n Annual Precipitation: 182 mm Annual Mean Temperature: 24. 0 o. C Desert type plants (cactuses: giant cardon cactus (Pachycereus pringlei)) and leafy arid tropical plants
-0. 3 g. C m-2 d-1 -0. 6 g. C m-2 d-1 -0. 8 g. C m-2 d-1
Real Time Data Stream Barrow, Alaska Sky Oaks, California
- Slides: 47