How do elevated [CO2], warming, and reduced precipitation interact to affect soil moisture and LAI in an old field ecosystem?

Soil moisture content and leaf area index (LAI) are properties that will be particularly important in mediating whole system responses to the combined effects of elevated atmospheric [CO2], warming and altered precipitation. Warming and drying will likely reduce soil moisture, and this effect may be exacerbated when these factors are combined. However, elevated [CO2] may increase soil moisture contents and when combined with warming and drying may partially compensate for their effects. The response of LAI to elevated [CO2] and warming will be closely tied to soil moisture status and may mitigate or exacerbate the effects of global change on soil moisture. Using open-top chambers (4-m diameter), the interactive effects of elevated [CO2], warming, and differential irrigation on soil moisture availability were examined in the OCCAM (Old-Field Community Climate and Atmospheric Manipulation) experiment at Oak Ridge National Laboratory in eastern Tennessee. Warming consistently reduced soil moisture contents and this effect was exacerbated by reduced irrigation. However, elevated [CO2] mitigated the effects of warming and drying on soil moisture. LAI was determined using an AccuPAR ceptometer and both the leaf area duration (LAD) and canopy size were increased by irrigation and elevated [CO2]. Changes in LAI were closely linked to soil moisture status. The climate of the southeastern United States is predicted to be warmer and drier in the future, and this research suggests that although elevated [CO2] will ameliorate the effects of warming and drying, losses of soil moisture will cause declines in the LAI of old field ecosystems in the futur

Direct and Indirect Effects of Elevated Carbon Dioxide and Ozone on the Canopy of a Soybean Agroecosystem

126 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.It is unknown how rising atmospheric CO2 and O3 will directly and indirectly alter canopy structure and scale to affect ecosystems. I determined how leaf area index (LAI) was directly affected by elevated [CO 2] and [O3]. By increasing photosynthetic efficiency, elevated [CO2] may increase maximum LAI. However, [O3] accelerates senescence and may reduce LAI. My second objective was to determine how changes in canopy size altered the radiation use efficiency of the canopy in elevated [CO2] and [O3]. Radiation use efficiency (&egr;) is a measure of the conversion efficiency of absorbed radiation (APAR) into biomass. I expected elevated [CO2] to increase &egr; however, elevated [O3] may have the opposite effect. Folivorous insects indirectly reduce canopy size through the removal of leaf area, and the changes in leaf chemistry in elevated [CO2] and [O3] may lead to increased herbivory. These predictions were tested using Soy bean F&barbelow;ree-A&barbelow;ir C&barbelow;oncentration E&barbelow;nrichment technology (SoyFACE) with plots exposed to ambient air (∼370ppm), elevated CO2 (∼550ppm) and elevated O3 (1.2*ambient). Elevated [CO2] increased maximum LAI and delayed LAI loss to senescence, although the effects varied among years. Elevated [O3] consistently reduced LAI by accelerating senescence. These effects combined with corresponding changes in biomass, to increase &egr; in elevated [CO2] and reduce &egr; in elevated [O3]. Increased &egr; in elevated [CO2] was driven primarily by increased biomass however, in elevated [O3] increased LAI loss to senescence droves decrease in biomass. Growth in elevated [CO2] increased the susceptibility of soybeans to herbivory, particularly by non-native insects. Chronic exposure to elevated [O3] produced few significant effects on herbivory. The impacts of altered tropospheric chemistry on soybeans will be complicated by the complex behavior of insect pests and their indirect effects on plant canopies and productivity.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Anthropogenic changes in tropospheric composition increase susceptibility of soybean to insect herbivory

Increased concentrations of CO and ozone are predicted to lower nutritional quality of leaves for insect herbivores, which may increase herbivory as insects eat more to meet their nutritional demands. To test this prediction, we measured levels of herbivory in soybean grown in ambient air and air enriched with CO or O using free air gas concentration enrichment (FACE). Under open-air conditions and exposure to the full insect community, elevated [CO ] increased the susceptibility of soybeans to herbivory early in the season, whereas exposure to elevated [O ] seemed to have no effect. In the region of the canopy exposed to high levels of herbivory, the percentage of leaf area removed increased from 5 to \u3e11% at elevated [CO ]. We found no evidence for compensatory feeding at elevated [CO ] where leaf nitrogen content and C:N ratio were unaltered in plants experiencing increased herbivory. However, levels of leaf sugars were increased by 31% at elevated [CO ] and coincided with a significant increase in the density of the invasive species Popillia japonica Newman (Japanese beetle). In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO ] to foliage grown at ambient [CO ]. These data support the hypothesis that the increased level of sugar in leaves grown at elevated [CO ] may act as a phagostimulant for the Japanese beetle. If these results apply more widely to soybean production, the expectation of agricultural yield increases as a result of increasing elevated [CO ] may need to be reevaluated. © 2005 Entomological Society of America. 2 2 3 2 3 2 2 2 2 2 2

Impact of elevated levels of Atmospheric CO 2 and herbivory on Flavonoids of soybean (Glycine max Linnaeus)

Atmospheric levels of carbon dioxide (CO 2) have been increasing steadily over the last century. Plants grown under elevated CO 2 conditions experience physiological changes, particularly in phytochemical content, that can influence their suitability as food for insects. Flavonoids are important plant defense compounds and antioxidants that can have a large effect on leaf palatability and herbivore longevity. In this study, flavonoid content was examined in foliage of soybean (Glycine max Linnaeus) grown under ambient and elevated levels of CO 2 and subjected to damage by herbivores in three feeding guilds: leaf skeletonizer (Popillia japonica Newman), leaf chewer (Vanessa cardui Linnaeus), and phloem feeder (Aphis glycines Matsumura). Flavonoid content also was examined in foliage of soybean grown under ambient and elevated levels of O 3 and subjected to damage by the leaf skeletonizer P. japonica. The presence of the isoflavones genistein and daidzein and the flavonols quercetin and kaempferol was confirmed in all plants examined, as were their glycosides. All compounds significantly increased in concentration as the growing season progressed. Concentrations of quercetin glycosides were higher in plants grown under elevated levels of CO 2. The majority of compounds in foliage were induced in response to leaf skeletonization damage but remained unchanged in response to non-skeletonizing feeding or phloem-feeding. Most compounds increased in concentration in plants grown under elevated levels of O 3. Insects feeding on G. max foliage growing under elevated levels of CO 2 may derive additional antioxidant benefits from their host plants as a consequence of the change in ratios of flavonoid classes. This nutritional benefit could lead to increased herbivore longevity and increased damage to soybean (and perhaps other crop plants) in the future. © Springer Science+Business Media, LLC 2010.Fil: O'Neill, Bridget F.. University of Illinois; Estados UnidosFil: Zangerl, Arthur R.. University of Illinois; Estados UnidosFil: Dermody, Orla. Pioneer Hi-bred Switzerland S.A.; SuizaFil: Bilgin, Damla D.. University of Illinois; Estados UnidosFil: Casteel, Clare L.. University of Illinois; Estados UnidosFil: Zavala, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; ArgentinaFil: DeLucia, Evan H.. University of Illinois; Estados UnidosFil: Berenbaum, May R.. University of Illinois; Estados Unido