Additional Past Accomplishments:
The following are selected highlights of recent research supported by CCSP participating agencies (as reported in the fiscal year 2009 edition of the annual report, Our Changing Planet).
Climate Interactions with Tree Mortality and Regeneration are Complex.1,2 Recent research is improving understanding of the complex interactions that can determine the effect of changing climate on vegetation mortality and regeneration. In the southern Appalachians, factors favoring seedling regeneration of particular tree species include warmer spring temperatures and dryer soil conditions, reduction of pathogen attacks on seeds in dryer soils, and warmer average temperatures. A synthesis of recent research indicates that with current climate trends, only higher elevation forests in this region are in danger of extinction. Changes in snowpack might be an important factor in other regions. Yellow cedar has been mysteriously dying in Alaska for over a century. After 20 years of study, researchers now hypothesize that this trend primarily results from decreasing snowpack, which increases soil freezing, kills vulnerable roots, and leads to foliar mortality and death. Recent tests of seedling survival in artificial snowpacks also support this mechanism as a factor in declining regeneration.
Soil Responses to Environmental Change.3,4,5 Experimental warming of tundra indicated that ecosystem respiration increases most in dry tundra; that saturated soils dampen responses in wetter tundra; and that both carbon gain and respiration respond to warming. A Florida scrub oak ecosystem exposed to elevated carbon dioxide (CO2) showed the largest increase in plant growth reported to date, but a 25% decline in soil carbon offset half of this increase in carbon accumulation, indicating that models may overestimate the potential for ecosystems to slow atmospheric CO2 increase by storing carbon in soils (see Figure 17). Finally, in a constructed old-field ecosystem in eastern Tennessee, soil respiration increased with elevated atmospheric CO2 and decreased with reduced soil moisture, but responses to experimental warming varied. This complexity in responses indicates that models should include mechanistic representations of the effects of multiple global change factors on ecosystem processes.
Competitive Interaction of Trees Altered by Carbon Dioxide and Ozone.6 Changes in atmospheric CO2 and ozone (O3) concentrations may alter competitive interactions between tree species. Results from a long-term (10-year) field study in northern Wisconsin indicate that rising atmospheric CO2 or O3 concentrations would give a competitive advantage to paper birch over trembling aspen. Birch was less sensitive than aspen to damage by O3, and in mixed stands birch was more responsive to the positive effects of rising CO2 than aspen. While earlier, shorter duration experiments found little influence of these two gases on forest succession, these new results indicate that rising concentrations of either CO2 or O3 could alter the species composition of mixed aspen-birch stands that now cover millions of acres in the north central and northeastern United States.
Changes in Habitat Suitability for Tree and Bird Species.7,8 One of the first steps in projecting possible impacts of climate change on plant and animal distributions and developing adaptive approaches to forest management is understanding how the distribution of environmental conditions suitable for individual species is likely to change over time. A new Climate Change Atlas web site presents results of extensive modeling efforts that combine current environmental relationships and species distributions with global climate models to project changes in potential suitable habitat for 134 trees and 150 birds of eastern North America by the end of the century (see Figure 18). Each species was modeled individually to show current distribution and potential distribution of suitable habitat in the future according to regionalized outputs of models for two Intergovernmental Panel on Climate Change (IPCC) emission scenarios and three climate models.
Modeling Impacts of Changing Climate on Intertidal Species Distributions.9 A rich historical data record makes the intertidal zone a model system for examining the effects of climate change. Comparisons of historical and 2006 geographic distributions of the arctic barnacle Semibalanus and the tropical sand-worm Diopatra show parallel northward shifts at rates of 15 to 50 km per decade since 1872. Using modeled climate data from weather reanalyses, which provide the large-scale environmental envelope in which organisms existed over time, and simulation models of animal body temperatures, which allow simulation of organism response to the environment, researchers accurately modeled changes in the distributions of the two species over the past 50 years. Parallel shifts in distribution indicate that similar responses to a warming climate control the geographic limits of both species.
Climate Impacts on Zooplankton Composition and Fish Feeding Preferences.10 A series of studies on the Pribilof Island ecosystem in the eastern Bering Sea investigated why this area is able to support a large biomass of top predators, and whether the mechanisms responsible for production are sensitive to climate variability. One of these studies documented differences in the zooplankton community and the food ingested by juvenile walleye pollock on the Bering Sea shelf and in the Pribilof ecosystem for relatively cold and warm climate conditions. During the warm year, there were significantly fewer large, lipid-rich zooplankton prey for the juvenile fish than during the cool year.
Climate and Marine Fisheries—Spatial and Temporal Variability.11,12 Understanding variation in time and space is critical to evaluating impacts of ocean changes on marine resources. Information from marked hatchery salmon has revealed local covariability in survival between adjacent coho stocks within a region of the Pacific Ocean and coherence in survival in adjacent regions, but no clear evidence of covariability at greater spatial scales. Other research suggests that Labrador Sea seawater from melting of the Greenland Ice Sheet is causing freshening of surface waters in the Gulf of Maine and Georges Bank. This fresher water flows southwest along the coast, keeping plankton near the surface under better growing conditions. Researchers expect higher plankton concentrations to provide more food for fish larvae, with higher survival and recruitment of adult cod and haddock stocks on Georges Bank.
California Current: Disruptions in Seasonal Cycles of Production.13,14,15,16 California Current ecosystems are characterized by strong seasonal variability in productivity driven by the strength and duration of upwelling. Climate change scenarios suggest disruptions in phenology and biological interactions that depend upon seasonally predictable upwelling cycles. Recent observations support these expectations: A 4-year period of strong upwelling, cold ocean conditions, and high productivity from 1999 to 2002 was followed by 4 years of delayed or reduced upwelling, warm ocean conditions, and reduced productivity. In 2005, due to delayed upwelling, plankton biomass declined, seabirds failed to fledge young, and survival of salmon was very low. Should warm ocean conditions continue (as from 2003 to 2006), productivity in the California Current may decline.
Identifying Factors Contributing to Coral Reef Resilience.17,18 Climate variability and change can negatively affect coral reef ecosystems (see Figure 19). Effective management needs to assess reef vulnerabilities, identify adaptive management strategies, and integrate these with existing decisions and mandates. Results from American Samoa show that adaptive management strategies could be implemented to increase reef resilience. A second study demonstrates how marine reserves contribute to resilience. Caribbean reefs became susceptible to changing from one stable state to another after a sea urchin (Diadema antillarum) die-off. Although the establishment of marine reserves increased predation on parrotfishes, the current dominant species, protection from overfishing had a greater impact and ultimately allowed parrotfish densities to further increase. Increased grazing pressure from parrotfishes caused a fourfold reduction in cover of macroalgae, the principal competitors of corals.
Additional Past Accomplishments:
ECOSYSTEMS CHAPTER REFERENCES
2) Hennon, P., D. D’Amore, D. Wittwer., A. Johnson., P. Schaberg, G. Hawley, C. Beier, S. Sink, and G. Juday, 2006: Climate warming, reduced snow, and freezing injury could explain the demise of yellow cedar in southeast Alaska. World Resource Review, 18, 427-445.
3) Oberbauer, S.F., C.E. Tweedie, J.M. Welker, J.T. Fahnestock, G.H.R. Henry, P.J. Webber, R.D. Hollister, M.D. Walker, A. Kuchy, E. Elmore, and G. Starr, 2007: Tundra CO2 fluxes in response to experimental warming across latitudinal and moisture gradients. Ecological Monographs, 77, 221-238.
4) Carney, K.M., B.A. Hungate, B.G. Drake, and J.P. Megonigal, 2007: Altered soil microbial community at elevated CO2 leads to loss of soil carbon. Proceedings of the National Academy of Sciences, 104, 4990-4995.
5) Wan, S.Q., R.J. Norby, J. Ledford, and J.F. Weltzin, 2007: Responses of soil respiration to elevated CO2, air warming, and changing soil water availability in a model old-field grassland. Global Change Biology, 13, 2411-2424, doi:10.1111/j.1365-2486.2007.01433.x.
7) Prasad, A.M., L.R. Iverson, S. Matthews, and M. Peters, 2007-ongoing: A Climate Change Atlas for 134 Forest Tree Species of the Eastern United States [database]. Northern Research Station, USDA Forest Service, Delaware, Ohio. <www.nrs.fs.fed.us/atlas/tree>.
8) Iverson, L.R., A.M. Prasad, S.N. Matthews, and M. Peters, 2008: Estimating potential suitable habitat for 134 eastern US tree species under six climate scenarios. Forest Ecology and Management, 254, 390-406, doi:10.1016/j.foreco.2007.07.023.
10) Coyle, K.O., A.I. Pinchuk, L. Eisner, and J.M. Napp, 2008: Zooplankton species composition, abundance, and biomass on the southeastern Bering Sea shelf during summer: the potential role of water column stability and nutrients in structuring the zooplankton community. Deep-Sea Research II, Topical Studies in Oceanography. in press.
11) Teo, S.L.H., L.W. Botsford, and A. Hastings, 2008. Spatio-temporal covariability in coho salmon (Oncorhynchus kisutch) survival, from California to Southeast Alaska. Deep-Sea Research II, Topical Studies in Oceanography. submitted.
13) Barth, J.A., B.A. Menge, J. Lubchenco, F. Chan, J.M. Bane, A.B. Kirincich, M.A. McManus, K.J. Nielsen, S.D. Pierce, and L. Washburn, 2007: Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California Current. Proceedings of the National Academy of Science, 104, 3719-3724.
14) Mackas, D.L., W.T. Peterson, M.D. Ohman, and B.E. Lavaniegos, 2006: Zooplankton anomalies in the California Current system before and during the warm ocean conditions of 2005. Geophysical Research Letters, 33, L22S07, doi:10.1029/2006GL027930.
15) Pierce, S.D., J.A. Barth, R.E. Thomas, and G.W. Fleischer, 2006: Anomalously warm July 2005 in the northern California Current: historical context and the significance of cumulative wind stress. Geophysical Research Letters, 33, L22S04, doi:10.1029/2006GL027149.
16) Sydeman,W.J., R.W. Bradley, P. Warzybok, C.L. Abraham, J. Jahncke, K.D. Hyrenbach, V. Kousky, J.M. Hipfner, and M.D. Ohman, 2006: Planktivorous auklet Ptychoramphus aleuticus responses to ocean climate, 2005: unusual atmospheric blocking? Geophysical Research Letters, 33, L22S09, doi:10.1029/2006GL026736.
17) USEPA, 2007: Climate Change and Interacting Stressors: Implications for Coral Reef Management in American Samoa. EPA/600/R-07/069. Global Change Research Program, National Center for Environmental Assessment, Washington, DC.
18) Mumby, P.J., C.P. Dahlgren, A.R. Harborne, C.V. Kappel, F. Micheli, D.R. Brumbaugh, K.E. Holmes, J.M. Mendes, K. Broad, J.N. Sanchirico, K. Buch, S. Box, R.W. Stoffle, and A.B. Gill, 2006: Fishing, trophic cascades, and the process of grazing on coral reefs. Science, 311, 98-101.