Global Change Research Group

The effects of elevated CO2, climate variability, and fire on the functioning of the chaparral of Southern California

John Kim — Thu, 15 Sep 2011 19:18:28 +0000

The effects of elevated CO2, climate variability, and fire on the functioning of the chaparral of Southern California

Presented at MEDECOS XII Conference, July 6-9, 2011, Los Angeles, CA.

Oechel, Walter^1,2, Alessandra Rossi¹, Patrick Murphy¹, John Kim³, Tom Bell¹, Hongyan Luo⁴, David Lipson⁵

¹Global Change Research Group, San Diego State University, San Diego, CA 92182, USA
²Fondazione Edmund Mach (FEM), Centro Ricerca e Innovazione (CRI), Via Edmund Mach, 138010 – San
Michele all’Adige (TN), Italy
³Field Station Program, College of Sciences, San Diego State University, San Diego, CA 92182, USA
⁴The National Ecological Observatory Network (NEON) Science Office, Boulder, CO 80301, USA
⁵Department of Biology, San Diego State University, San Diego, CA 92182, USA

Three decades of research on fire, climate change, and elevated atmospheric CO2 in the chaparral, a Mediterranean-type climate ecosystem, at San Diego State University’s Sky Oaks Biological Field Station, has provided information and insights that are useful to understanding controls on Mediterranean-type ecosystem functioning of southern California under current, and likely future, conditions.

Results from atmospheric carbon dioxide manipulations show that long-term stimulation of NEE, carbon sequestration, leaf area, fuel accumulation, and VOC production occur and that ecosystem composition, species reproduction, soil microbial composition, and plant-animal interactions, are affected by increased atmospheric carbon dioxide levels. Suggested is the fact that at least these water stressed ecosystems see increased water use efficiency and increased NPP over the long-term from elevated atmospheric carbon dioxide. More than a decade of measurement of net ecosystem exchange by eddy covariance demonstrates the long-term pattern of carbon exchange with stand age, and the short term impacts of variation in climate, especially precipitation, on stand water use and NEE. Annual variability in rainfall has profound affects on NEE, the impact of variation in annual rainfall on NEE lasts more than one year. The functioning of this ecosystem adjusts more quickly than does the composition of the ecosystem. Similarly, the sink strength of NEE following fire recovers more quickly than does community composition and percent above ground cover. The combined impacts of anticipated changes in atmospheric carbon dioxide and climate suggests changes in species composition and NPP. Fire intensity and/or frequency are anticipated to increase due to increases in weather conditions conducive to fire and increases in fuel accumulation due to higher atmospheric carbon dioxide levels.

These data show that old chaparral stands can be significant sinks for atmospheric CO2. And that managing for old growth chaparral can increase carbon sequestration while increasing biodiversity and habitat diversity.

Air-sea CO2 exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska

Hiroki Ikawa — Thu, 01 Sep 2011 20:50:51 +0000

Authors: Ikawa, H.; Oechel, WC
Source: CONTINENTAL SHELF RESEARCH Volume: 31 Issue: 13 Pages: 1357-1364 DOI: 10.1016/j.csr.2011.05.012 Published: SEP 1 2011

Abstract: Partial pressure of CO₂ in equilibrium with sample water (pCO₂) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO₂ flux calculated from the pCO₂ and gas transfer coefficients ranged from -0.144 to -0.0701 g C m^-2 day^-1 depending on which gas transfer coefficient was used. The pCO₂ before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO₂ was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO₂ strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO₂ of 35 ppm together with the highest PPFD of 1362 mu mol E m(-2) s(-1) observed in the afternoon on June 28 in the presence of sea ice. The very low pCO₂ observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO_{2 released by melting sea ice early in the season.}

GCRG on LI-COR NewsLine: Measure Methane Where it Matters: Part II, Barrow, Alaska

GCRG — Tue, 23 Nov 2010 20:49:21 +0000

“Although many scientists agree that the current warming trend is likely to continue, it is unknown whether a warmer climate will turn the Arctic Coastal Plain from a sink to a source of greenhouse gases…. Cove Sturtevant and Dr. Walt Oechel from San Diego State University in California are addressing some of these questions in a manipulative experiment near Barrow.”

Impacts of Conversion and Drainage of Tropical Peat Forests on Carbon Fluxes to Atmosphere and Water

Hiroki Ikawa — Tue, 05 Oct 2010 22:46:56 +0000

Indonesia has the largest tropical peats, ranging from 18 to 27 million hectares. It is
estimated that about 12 million hectares of these peats have been disturbed and
substantially drained in order to lower water table depths which are required for
agricultural uses (i.e. rice paddy, industrial pulp, and recently oil palm plantation).
Drained and converted peatland forests lead to accelerated peat subsidence and
potentially act as an important Carbon source. Contemporarily, impacts of peatland
drainage and land cover change of peat forests into mono-crop plantations of oil palms
are barely investigated. This research aims to generate models of carbon flux
at open peats, oil palm plantations on peats, and forested peats. We are investigating
factors that control the accumulation and decomposition of peat carbon stocks at
various peatland uses. We are also calculating Long Term Carbon Accumulation
(LORCA) based on the age of peat formation, and the rate of peat decomposition in
relation to subsidence and drainage depth. We are measuring carbon fluxes in the forms
of CO? gas and lateral Dissolved Organic Carbon (DOC) and Particulate Organic
Carbon (POC), and pCO?. We use Eddy Covariance Technique to measure CO?
gas, and combustion-infrared method, using Total Organic Carbon (TOC) analyzer, to
measure DOC and POC, and a non-dispersive infrared gas sensor (LI-840, LI-COR
Biosciences, USA) to measure pCO?.

Project Personnel:
Dr. Gusti Z Anshari, Universitas Tanjungpura
Dr. Evie Gusmayanti, Universitas Tanjungpura
Lucy Arianie, Msi, Universitas Tanjungpura
Dr. Walter Oechel, SDSU-GCRG
Hiroki Ikawa, SDSU-GCRG
Oscar Abelleira, SDSU-GCRG

Seasonal and Inter-Annual Controls on CO2 Flux in Arctic Alaska

John Kim — Fri, 01 Oct 2010 22:03:42 +0000

The Arctic landscape holds massive potential to affect the global carbon balance. Soils of the northern permafrost region account for approximately 50 percent of the estimated global below-ground organic carbon pool. The total soil organic carbon in the first 3 m in northern circumpolar permafrost, excluding yedoma, is ca.1024 PgC. Under a projected warmer and drier climate, the decomposition and release of even a fraction of these massive quantities of soil carbon in Arctic soils could create an additional positive feedback and further warming of the planet.

It is critical to continually assess the rate of carbon flux from the Arctic landscape, and study how the thawing and rising ground temperature over the region affect the atmospheric concentrations of CO2 and CH4. Long-term measurements are especially critical as Arctic terrestrial ecosystems are changing dramatically in response to persistent and accelerating regional warming trends. Dramatic changes in Arctic hydrology have become evident in recent years. Changes in hydrology including soil water content, lake formation, and lake loss have profound effects on CO2 and CH4 fluxes.

Global Change Research Group (GCRG) at San Diego State University (SDSU) has maintained eddy covariance flux towers at three sites in Arctic Alaska: Barrow, Atqasuk, and Ivotuk. The three sites form a 300 km N-S transect on the North Slope of Alaska, each site representing distinct vegetation communities common to the Arctic. Prior flux measurements at the three SDSU-GCRG flux tower sites have generated important discoveries about the role of the Arctic regions to global climate change. Data from SDSU-GCRG flux towers in the Arctic support high-impact research by scientists at SDSU and a wide array of research institution, as evidenced by journal publications.

The importance of these tower measurements cannot be understated: these towers create a long-term record of one of the largest, most volatile carbon stocks on the planet. These towers measure net fluxes of CO2, CH4, H2O vapor, sensible heat, latent heat, and momentum in addition to standard meteorological and environmental variables (MET data), and all data are made available in the public domain through direct access via selected online databases, including the Carbon Dioxide Information Analysis Center website, the AmeriFlux website, the GCRG website, and others.

Data collected by the project are being used to determine the seasonal and inter-annual patterns of CO2 and methane flux, and their relationship to changes in environmental factors. The data are also being used to identify important differences in carbon flux at different Arctic landscape types. Project results have the potential to contribute to the refinement global carbon flux models. The information on spatial, annual, and inter-annual variation in sensible and latent heat flux and CO2 and CH4 fluxes is critical to better inform ecosystem and land surface models and to improve and make more realistic their operation under current and likely future conditions.

This project is funded by a generous grant from the US Dept of Energy.

Personnel:
Dr. Walt Oechel
Dr. John Kim
Pablo Bryant
Cove Sturtevant
Gladie Jaffe

GCRG Awarded DOE Grant to Operate Arctic Carbon Flux Towers

John Kim — Tue, 14 Sep 2010 23:50:21 +0000

GCRG was awarded a grant by the US Department of Energy for the proposal, “Seasonal and Inter-Annual Controls on CO2 Flux in Arctic Alaska” (PI: Walt Oechel). The grant will allow GCRG to operate eddy covariance flux towers at Barrow, Atqasuk and Ivotuk for the next 3 years.

Summer 2010 Field Report: Barrow, Alaska

Cove Sturtevant — Wed, 01 Sep 2010 23:30:57 +0000

Our 2010 summer research activities near Barrow were very successful. From July 1 to August 12, 2010 Ph.D. candidate Cove Sturtevant and assistant Tim Hubbard placed portable eddy covariance towers at 21 lake or vegetated drained lake features over a 150 square mile area near Barrow, Alaska. A total of three portable towers were deployed on the tundra continuously during this period, and were moved using two 4-wheelers and a trailer every three to four days.

The data collected will be used to assess the spatial variability of land-atmosphere fluxes of CO2 and CH4 and evaluate the trajectory of these fluxes accompanying the edaphic and vegetation changes along the thaw lake chronosequence on the Arctic Coastal Plain of Alaska. We plan to repeat these portable tower measurements during the summer of 2011 and hope to add aircraft measurements covering a much larger area.

Summer 2010 Field Report: La Paz, Mexico

Thomas Bell — Wed, 01 Sep 2010 20:52:25 +0000

During the summer of 2010 Master’s degree candidate Tom Bell completed his field research in the CIBNOR desert preserve near La Paz, BCS, Mexico. From June to August, Tom monitored lateral litter flux experiments, which had commenced in the summer of 2009. Collection of vertical and lateral litter traps was completed over two time periods and litter and vegetation surveys were also executed. Experiments were terminated in mid-August and samples were dried, weighed and recorded. The data collected will be used to assess the significance of lateral carbon flux in litter to the overall carbon budget of the desert ecosystem.

Tom was assisted by fellow GCRG Master’s student Yareli Sanchez and Southwestern College student Steven Becotte. Steven was the recipient of a paid internship from Southwestern College and was selected by GCRG to assist with data collection. Steven gained experience in many areas such as experimental design and general desert ecology.

GCRG Heads for the Skies with NASA-Funded Research

GCRG — Thu, 27 May 2010 19:25:54 +0000

GCRG will work with the National Aeronautics and Space Administration’s Jet Propulsion Lab to measure the greenhouse gas effect on the Arctic. The research team will collect data that will provide unprecedented experimental insights into Arctic carbon cycling, especially the release of the important greenhouse gases such as carbon dioxide and methane. The study is one of five new airborne science missions announced by NASA last week. Other projects will examine soil-based ecosystems, hurricanes and air quality. The competitively selected proposals are the first investigations in the new Ventureclass series of low-to-moderate cost projects established by the agency last year. The Earth Venture missions are part of NASA’s Earth System Science Pathfinder program. More >>

Seasonal Variations of Trace Gas Flux in Mangrove Ecosystem in Baja California Sur, Mexico

Yareli Sanchez-Ramirez — Mon, 24 Aug 2009 00:03:51 +0000

Anthropogenic activities have disrupted biogeochemical cycles with subsequent increases in the emission of radiatively important trace gases. Wetlands are natural sources of CO2, CH4 and N2O with seasonal variations in anthropogenic inputs, temperature, salinity, and water modulating emissions. Variations in trace gas flux in mangrove ecosystems using eddy covariance, soil coring, leaf litter sampling, and static chambers, will reveal correlations between seasonal variations in fluxes and environmental variables. This information will show the response of mangrove ecosystems to growing anthropogenic pressures, such as elevated CO2 and nutrient inputs, and their seasonal contribution to the emission of trace gases.