BER Research Highlights

Search Date: June 28, 2017

6 Records match the search term(s):


October 25, 2010

AmeriFlux Contributes New Insights into Evapotranspiration

Large scale changes in the Earth's water cycle have been hypothesized to result from global warming. DOE-funded investigators and DOE's AmeriFlux network report in Nature evidence of systematic changes in global land evapotranspiration, although the authors are not able to assign causality to the changes. Using a combination of long-term observational (including data from numerous AmeriFlux sites), meteorological and remote sensing records, combined with model results, the authors identify a systematic increase in global land evapotranspiration from 1982 to 1997. From 1998 to 2008, this trend appears to have declined or leveled off. The authors suggest that soil moisture limitations, particularly in the southern hemisphere are responsible for the change. If this continues over the long-term, it may indicate that climate-driven changes in terrestrial hydrological cycles exist and that there are limits to the ability of these cycles to respond to changing climate.

Reference: Jung, M., M. Reichstein, P. Ciais, S. Seneviratne, J. Sheffield, M. Goulden, G. Bonan, A. Cescatti, J. Chen, R. de Jeu, A. J. Dolman, W. Eugster, D. Gerten, D. Gianelle, N. Gobron, J. Heinke, J. Kimball, B. Law, L. Montagnani, Q. Mu, B. Mueller, K. Oleson, D. Papale, A. Richardson, O. Roupsard, S. Running, E. Tomelleri, N. Viovy, U. Weber, C. Williams, E. Wood, S. Zaehle, and K. Zhang. 2010. "Recent Decline in the Global Land Evapotranspiration Trend Due to Limited Moisture Supply," Nature 467, 951–954. DOI: 10.1038/nature09396.(Reference link)

Contact: Mike Kuperberg, SC-23.1, (301) 903-3281
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


October 18, 2010

Changing Climate Alters Plant Communities

A long-term ecosystem manipulation study was conducted in an old-field ecosystem on the Oak Ridge Reservation. Temperature, precipitation, and atmospheric carbon dioxide were manipulated over several years. The study found that while precipitation was the dominant factor, all manipulated factors impacted plant productivity and community structure. Plant species differed in their responses to each climate change factor, resulting in changes in the composition of the plant community. Such compositional shifts can alter ecosystem biomass production and nutrient inputs, and are an important part of ecosystem response to climatic change. This study highlights the complexity of understanding ecosystems and their responses to change.

Reference: Kardol, P; C. Campany; L. Souza; R. Norby; J. Weltzin and A. Classen; 2010. "Climate change effects on plant biomass alter dominance patterns and community evenness in an experimental old-field ecosystem," Global Change Biology, 16, 2676–2687, doi: 10.1111/j.1365-2486.2010.02162.x

Contact: Mike Kuperberg, SC-23.1, (301) 903-3281
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


March 15, 2010

DOE's AmeriFlux Network Improves Understanding of Global Carbon Cycle

A critical uncertainty in the terrestrial carbon cycle is the relationship between incoming solar radiation and the productivity of plants receiving that radiation. Data was collected from 35 carbon flux measurement sites around the world, including 13 U.S. AmeriFlux sites. By combining carbon flux and supporting biological and meteorological data with NASA satellite data, water availability was shown to have a larger impact on the function of vegetation than other measured physical parameters such as temperature. These results will improve estimates of how plant function is likely to respond to changing climate. The DOE-led multi-agency Ameriflux network provides measurements on the function and carbon cycle of ecosystems that advances understanding of processes regulating carbon assimilation, respiration, and storage, and linkages between carbon, water, energy, and nitrogen through measurements and modeling.

Reference: Martín F. Garbulsky, Josep Peñuelas, Dario Papale, Jonas Ardö, Michael L. Goulden, Gerard Kiely, Andrew D. Richardson, Eyal Rotenberg, Elmar M. Veenendaal and Iolanda Filella; 2010; "Patterns and controls of the variability of radiation use efficiency and primary productivity across terrestrial ecosystems," Global Ecology and Biogeography, 19, 253-267.

Contact: Mike Kuperberg, SC-23.1, (301) 903-3281
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


March 15, 2010

Elevated CO2 Changes Plant Dynamics in a Forest Ecosystem

DOE has developed and supported a number of long-term Free-Air CO2 Enrichment (FACE) studies to evaluate the response of entire ecosystems to increased CO2 associated with a changing climate. Oak Ridge National Laboratory has managed one of those sites for over 11 years and reports a set of findings in a recent issue of the Journal of Plant Ecology. Over the course of the experiment, the understory plant community changed dramatically. Above ground biomass was ~25% greater in plots exposed to elevated concentrations of carbon dioxide. Early in the study (2001-2003), herbaceous species made up 94% of the total understory biomass. After multiple years of treatments (2008), woody shrubs and saplings comprised 39% of total understory biomass in plots not receiving additional CO2 treatments and 67% in plots receiving elevated CO2 treatments. Understory communities in plots receiving elevated CO2 treatments also showed more rapid transition from herbaceous to woody-dominated communities, indicating faster succession. These results suggest that rising atmospheric CO2 concentration could accelerate ecosystem succession and have long-term impacts on forest dynamics.

References: Souza L, Belote RT, Kardol P, Weltzin JF, Norby RJ (2010) "CO2 enrichment accelerates successional development of an understory plant community," Journal of Plant Ecology 3(1): 33-39.

Contact: Mike Kuperberg, SC-23.1, (301) 903-3281
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


February 01, 2010

Limitations to Modeling Heterogeneous Landscapes in Climate Research

Characterizing the carbon balance and heat fluxes in heterogeneous landscapes is difficult, yet critical to understand present and future climate-land surface interactions, including ecosystem feedbacks to climatic change. A recent DOE study investigated modeling approaches, using three years of high quality measurements, to characterize land-atmosphere interactions in the very heterogeneous U.S. southern Great Plains. The modeling approach used in current land-surface models led to discrepancies in the regional carbon balance of up to 50% (weekly total) and 20% (annual total). Discrepancies in predicted weekly average regional latent heat fluxes were smaller but also existed for spatial and diurnal predictions. In this heterogeneous system, more rigorous characterization of spatial variation of land surface properties than that used in present models is needed to make accurate regional simulations.

Citation: Riley WJ, Biraud SC, Torn MS, Fischer ML, Billesbach DP, Berry JA (2009) Regional CO2 and latent heat surface fluxes in the Southern Great Plains: Measurements, modeling, and scaling. J. Geophys. Res. - Biogeosciences 114 Article Number: G04009

Contact: Jeffrey S. Amthor, SC-23.1, (301) 903-2507
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


January 11, 2010

New Insights Into Climate Change and Mortality in Western Forests

Drought causes significant tree mortality at the regional and global scales, but it is difficult to predict likely effects of ongoing and future climatic changes on tree mortality because the relationships between climate and mortality remain unclear. Recently published DOE-sponsored research examined relationships between tree-climate interactions and mortality of ponderosa pine in northern New Mexico. Ponderosa pine is widely distributed in North America, ranging from central Mexico to southern Canada, and may be representative of a large group of tree species. The study results indicate that trees from drier areas (i.e., growing under long-term water-limited conditions) were predisposed to mortality caused by an acute drought event, which is an unexpected result. Because increased drought severity and frequency are projected for many mid-latitude regions, it appears possible that forest mortality events will increase in the drier regions of the western United States in the coming decades.

Reference: McDowell NG, Allen CD, Marshall L (2010) Growth, carbon-isotope discrimination, and drought-associated mortality across a Pinus ponderosa elevational transect. Global Change Biology 16:399-415.

Contact: Jeffrey S. Amthor, SC-23.1, (301) 903-2507
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER