Source: AGRICULTURAL RESEARCH SERVICE submitted to
IMPACTS OF GLOBAL CHANGES AND BIOLOGICAL CONTROL OF INVASIVE WEEDS ON WESTERN RANGELANDS
 
PROJECT DIRECTOR: POLLEY H W FAY P A DELOACH JR C J ARNOLD J G
 
PERFORMING ORGANIZATION
(N/A)
AGRICULTURAL RESEARCH SERVICE
TEMPLE,TX 76502
 
NON TECHNICAL SUMMARY:
 
OBJECTIVES: Determine how two manifestations of global change, atmospheric carbon dioxide (CO2) enrichment and reduced precipitation during summer, interact with regionally important differences in soil type to affect plant production and other components of the carbon (C) cycle on tallgrass prairie. Determine how history of cultivation and density and biomass of invasive woody plants affects the vertical distribution and sizes of pools of organic C in mesic grasslands. Determine whether climate change (temperature, precipitation) effects on net ecosystem exchange of C (NEE) from western rangelands may creditably be predicted from the response of NEE to seasonal and inter-annual variation in temperature and precipitation. Develop classical biological control agents for non-native weeds that have invaded western rangelands as directed by NPS. Continue research on saltcedar (Tamarix spp.) to develop the leaf beetle, Diorhabda elongata from the Mediterranean area, to control effectively saltcedars in the U.S. south of the 37th parallel, to include release methodologies, reducing mortality from biotic and abiotic factors, determining rate of spread and degree of control obtained in different ecosystems, and the need for and testing of additional agents from the Old World, and the improvement of native plant and wildlife communities and water supplies. Begin discovery, testing and release of natural enemies from the Old World for control of Russian olive (Elaeagnus angustifolia), giant reed (Arundo donax), African rue (Peganum harmala), camelthorn (Alhagi), and other invasive weeds as directed by NPS.
 
APPROACH: Expose vegetated monoliths of three soil types to a continuous gradient in atmospheric carbon dioxide ranging from low levels of the pre-industrial period to elevated concentrations predicted within the century. Measure plant carbon and changes in soil organic carbon content on never-plowed tallgrass prairie and on four previously cultivated grassland sites following 15 years with different densities of the shrub honey mesquite. Use continuous measurements of carbon dioxide fluxes at each of eight rangeland sites in the western U.S. to quantify relationships between net ecosystem exchange of carbon and precipitation and temperature at seasonal and inter-annual scales. Identify and evaluate candidate biological control agents in Europe and Asia through exploration in collaboration with ARS foreign labs in Montpellier and Beijing and cooperators in Israel, Turkmenistan, Kazakhstan, Turkey, and China; conduct host-range and biological testing at foreign locations and in quarantine at Temple, TX. Develop methodologies for efficient releases and establishment in the field, and for determining and avoiding or mediating the factors that limit control; monitor effectiveness of approved foreign insects in cooperation with colleagues in western states; assess long-term impacts of declining weed densities on population dynamics of native riparian and rangeland communities.
 
CRIS NUMBER: 0409024 SUBFILE: CRIS
PROJECT NUMBER: 6206-11220-004-00D SPONSOR AGENCY: ARS
PROJECT TYPE: USDA INHOUSE PROJECT STATUS: TERMINATED MULTI-STATE PROJECT NUMBER: (N/A)
START DATE: Oct 14, 2004 TERMINATION DATE: Sep 30, 2009

GRANT PROGRAM: (N/A)
GRANT PROGRAM AREA: (N/A)

CLASSIFICATION
Knowledge Area (KA)Subject (S)Science (F)Objective (G)Percent
111043011306.110%
121071011406.310%
132078011306.110%
135079911406.440%
216033011304.210%
111085011406.120%

CLASSIFICATION HEADINGS
KA121 - Management of Range Resources
KA132 - Weather and Climate
KA216 - Integrated Pest Management Systems
KA135 - Aquatic and Terrestrial Wildlife
KA111 - Conservation and Efficient Use of Water
S0850 - Wildlife habitats
S0710 - Desert and semidesert shrub land and shinnery
S0780 - Grasslands, other
S0799 - Rangelands and grasslands, general
S0430 - Climate
S0330 - Wetland and riparian systems
F1130 - Entomology and acarology
F1140 - Weed science
G6.4 - Protect and Enhance Wildlife Habitat
G4.2 - Reduce Number and Severity of Pest and Disease Outbreaks
G6.1 - Ensure Clean Water and Air
G6.3 - Protect and Manage Forests and Rangelands


RESEARCH EFFORT CATEGORIES
BASIC 60%
APPLIED 30%
DEVELOPMENTAL 10%

KEYWORDS: CO2 GLOBAL CHANGE NET ECOSYSTEM CO2 EXCHANGE NITROGEN PLANT PRODUCTIVITY PRECIPITATION RANGELANDS ROOT GROWTH SOIL SOIL CARBON TALLGRASS PRAIRIE TEMPERATURE VEGETATION DYNAMICS WATER WOODY INVASION SALTCEDAR TAMARIX RUSSIAN OLIVE ELAEAGNUS ANGUSTIFOLIA AFRICAN RUE PEGANUM CAMELTHORN ALHAGI CAMELORUM RANGELAND WEEDS WETLAND WEEDS PHREATOPHYTE RIPARIAN WEEDS BIOLOGICAL CONTROL INVASIVE WEEDS INVASIVE SPECIES RISK ANALYSIS

PROGRESS: Oct 1, 2006 TO Sep 30, 2007
Progress Report Objectives (from AD-416) Determine how two manifestations of global change, atmospheric carbon dioxide (CO2) enrichment and reduced precipitation during summer, interact with regionally important differences in soil type to affect plant production and other components of the carbon (C) cycle on tallgrass prairie. Determine how history of cultivation and density and biomass of invasive woody plants affects the vertical distribution and sizes of pools of organic C in mesic grasslands. Determine whether climate change (temperature, precipitation) effects on net ecosystem exchange of C (NEE) from western rangelands may creditably be predicted from the response of NEE to seasonal and inter-annual variation in temperature and precipitation. Develop classical biological control agents for non-native weeds that have invaded western rangelands as directed by NPS. Continue research on saltcedar (Tamarix spp.) to develop the leaf beetle, Diorhabda elongata from the Mediterranean area, to control effectively saltcedars in the U.S. south of the 37th parallel, to include release methodologies, reducing mortality from biotic and abiotic factors, determining rate of spread and degree of control obtained in different ecosystems, and the need for and testing of additional agents from the Old World, and the improvement of native plant and wildlife communities and water supplies. Begin discovery, testing and release of natural enemies from the Old World for control of Russian olive (Elaeagnus angustifolia), giant reed (Arundo donax), African rue (Peganum harmala), camelthorn (Alhagi), and other invasive weeds as directed by NPS. Approach (from AD-416) Expose vegetated monoliths of three soil types to a continuous gradient in atmospheric carbon dioxide ranging from low levels of the pre- industrial period to elevated concentrations predicted within the century. Measure plant carbon and changes in soil organic carbon content on never-plowed tallgrass prairie and on four previously cultivated grassland sites following 15 years with different densities of the shrub honey mesquite. Use continuous measurements of carbon dioxide fluxes at each of eight rangeland sites in the western U.S. to quantify relationships between net ecosystem exchange of carbon and precipitation and temperature at seasonal and inter-annual scales. Accomplishments Plant species composition regulates grassland response to carbon dioxide enrichment: The concentration of carbon dioxide (CO2) gas in air is increasing as the result of land use change and fossil fuel combustion. Plants usually respond to higher CO2 by increasing the rate at which leaves convert CO2 to plant carbon mass (carbon uptake) and by reducing the rate at which leaves expend water (water loss), but these initial responses may not be sustained if plants adjust their physiology or acclimate to higher CO2 levels. Scientists at the Grassland, Soil & Water Research Laboratory in Temple, Texas, measured effects of prior CO2 exposure on the response of grassland carbon uptake and water loss to CO2 change. Following CO2 change, CO2 uptake was 11% greater and water loss was 12% smaller, on average, at high than low CO2. Effects of short-term change in CO2 did not depend on prior CO2 exposure, but the amount by which C uptake was increased by higher CO2 increased as the proportion of broadleaf herbaceous plants (forbs) in the plant canopy (forb plus grass) increased. Our results imply that sensitivity of grasslands to the continuing rise in atmospheric CO2 concentration will depend more on how management and other factors influence plant composition than on the duration of exposure to elevated CO2 levels alone. (NP 204; Component III, Agricultural Ecosystem Impacts; Objective 3, Grazinglands (Range and Pastures)) Implications of extreme precipitation events for grassland carbon balance: Climate change driven by increasing atmospheric CO2 concentrations is causing measurable changes in precipitation patterns. Most climate change scenarios forecast continuing increases in extreme precipitation patterns for North American terrestrial ecosystems, manifest as larger precipitation events separated by longer dry periods. Changes in the size of precipitation events may differentially affect the processes controlling uptake and release of carbon (C) from terrestrial ecosystems, and therefore could alter carbon sequestration on grasslands and other ecosystems. Scientists at the Grassland, Soil & Water Research Laboratory in Temple, Texas, together with university collaborators found that more extreme precipitation patterns (longer intervals between events combined with larger events) shifted experimental grasslands toward greater net uptake of C and made C fluxes less responsive to variation in event size. More extreme precipitation regimes thus may reinforce increases in grassland C-sequestration expected to result from increasing atmospheric CO2, but may also lower plant water status and productivity. Benefits of greater carbon storage on grasslands likely will be offset by reductions in forage quantity and quality. (NP 204; Component IV, Changes in Weather and the Water Cycle at Farm, Ranch and Regional Scales; Objective 5, Climate and Weather Variability and Extremes) Photosynthetic traits of C3 and C4 grassland species: Scientists at the Grassland, Soil & Water Research Laboratory in Temple, Texas, together with university collaborators collected data to test a basic hypothesis in grassland ecology, that grasses with the C4 photosynthetic metabolism dominate in the tallgrass prairie because physiological resource use efficiency is greater than in co-occurring plant species with C3 photosynthesis. Leaf level physiological processes related to carbon gain and water loss were measured for seven C3 and C4 species, both in quasi-natural microcosms with high resource availability and in intact grasslands where plants have been shown to experience multiple resource limitations. C3 and C4 species failed to show expected differences in resource use efficiency in field compared to microcosm conditions. Our findings suggest instead that C4 species shift their resource use strategies as conditions change through the growing season. Results provide a partial mechanistic explanation for the seasonal variation in forage quality observed on tallgrass prairie. (NP 204; Component III, Agricultural Ecosystem Impacts; Objective 3, Grazinglands (Range and Pastures)) Species abundances affect grassland productivity: Humans are changing the relative abundances of plant species on much of the landscape so that some species are becoming very abundant and others are becoming rare. Whether the increasing disparity in species abundances is affecting the capacity of grasslands and other ecosystems to meet human needs is not known. To determine effects of changing species abundances on grasslands, scientists at the Grassland, Soil & Water Research Laboratory in Temple, Texas, experimentally varied the proportional contributions of species to the total number of plants in small plots. Aboveground biomass produced by species mixtures varied with changes in species ratios in only one of the six species combinations studied. For three of six species mixtures, however, species abundances determined whether the biomass of mixtures exceeded the biomass expected based on the yield of each species when grown alone. Our results indicate that the productivity of grasslands may be sensitive in the short-term to changes in species ratios caused by grazing, fire, or herbicide application. (NP 204; Component III, Agricultural Ecosystem Impacts; Objective 3, Grazinglands (Range and Pastures)) Technology Transfer Number of Non-Peer Reviewed Presentations and Proceedings: 10 Number of Newspaper Articles,Presentations for NonScience Audiences: 1

IMPACT: 2006-10-01 TO 2007-09-30

PUBLICATION INFORMATION: 2006-10-01 TO 2007-09-30
Polley, H.W., Wilsey, B.J., Tischler, C.R. 2007. Species abundances influence the net biodiversity effect in mixtures of two plant species. Basic and Applied Ecology. 8:209-218.

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