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  • Air pollution effects  (1)
  • Carbon cycle  (1)
  • Lupinus arboreus  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Elevated CO2 increases belowground respiration in California grasslands (1996)
    Springer
    Oecologia 108 (1996), S. 130-137 
    Details
    ISSN: 1432-1939
    Keywords: Carbon cycle ; Ecosystem ; Global change ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was designed to identify potential effects of elevated CO2 on belowground respiration (the sum of root and heterotrophic respiration) in field and microcosm ecosystems and on the annual carbon budget. We made three sets of respiration measurements in two CO2 treatments, i.e., (1) monthly in the sandstone grassland and in microcosms from November 1993 to June 1994; (2) at the annual peak of live biomass (March and April) in the serpentine and sandstone grasslands in 1993 and 1994; and (3) at peak biomass in the microcosms with monocultures of seven species in 1993. To help understand ecosystem carbon cycling, we also made supplementary measurements of belowground respiration monthly in sandstone and serpentine grasslands located within 500 m of the CO2 experiment site. The seasonal average respiration rate in the sandstone grassland was 2.12 μmol m-2 s-1 in elevated CO2, which was 42% higher than the 1.49 μmol m-2 s-1 measured in ambient CO2 (P=0.007). Studies of seven individual species in the microcosms indicated that respiration was positively correlated with plant biomass and increased, on average, by 70% with CO2. Monthly measurements revealed a strong seasonality in belowground respiration, being low (0–0.5 μmol CO2 m-2 s-1 in the two grasslands adjacent to the CO2 site) in the summer dry season and high (2–4 μmol CO2 m-2 s-1 in the sandstone grassland and 2–7 μmol CO2 m-2 s-1 in the microcosms) during the growing season from the onset of fall rains in November to early spring in April and May. Estimated annual carbon effluxes from the soil were 323 and 440 g C m-2 year-1 for the sandstone grasslands in ambient and elevated CO2. That CO2-stimulated increase in annual soil carbon efflux is more than twice as big as the increase in aboveground net primary productivity (NPPa) and approximately 60% of NPPa in this grassland in the current CO2 environment. The results of this study suggest that below-ground respiration can dissipate most of the increase in photosynthesis stimulated by elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333224
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of multiple stresses on radish growth and resource allocation (1989)
    Springer
    Oecologia 81 (1989), S. 124-131 
    Details
    ISSN: 1432-1939
    Keywords: Plant stress ; Raphanus sativus X raphanistrum ; Air pollution effects ; Plant nutrition ; Physiological responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Acclimation of wild radish plants to a simultaneous combination of SO2 fumigation and decreasing nitrate availability was investigated. Plants were grown for 24 d under continuous daytime (10h) exposure to 0 or 0.4 ppm SO2 and were grown in a nutrient solution with stable nitrate concentrations of 100 μM for the first 15 d, 50 μM from day 15 to day 19, and 25 μM from day 19 to day 24. Analysis of relative growth rates (RGR) showed that radish plants responded rapidly to changes in nitrate availability and that SO2 treatment affected those responses. Shoot RGR of plants from both treatments and root RGR of control plants showed rapid declines and subsequent recoveries in response to decreasing nitrate availability. Root RGR of SO2-treated plants declined rapidly in response to decreased nitrate availability, but did not recover as quickly or completely as root RGR of control plants. Analysis of specific leaf weights and tissue nitrogen concentrations showed that control plants had significantly higher amounts of nitrogen in tissues after nitrate availability was lowered, and had higher rates of nitrate uptake in comparison to SO2-treated plants; especially when nitrate availability was highest. Furthermore, control plants had temporarily higher rates of root respiration in comparison to SO2-treated plants, suggesting that control plants temporarily allocated more resources to physiological processes occurring in roots, such as nutrient uptake. Although SO2-induced changes in growth and resource allocation of plants were relatively small, it was probable that SO2 treatment of radish plants affected plant nitrogen balance, and subsequently affected the ability of plants to respond to decreased nitrate availibility, by affecting resource partitioning to nitrate uptake and root growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377021
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  • 3
    Electronic Resource
    Electronic Resource
    Resource heterogeneity generated by shrubs and topography on coastal sand dunes (1996)
    Springer
    Plant ecology 122 (1996), S. 83-93 
    Details
    ISSN: 1573-5052
    Keywords: Artemisia pycnocephala ; Light availability ; Lupinus arboreus ; Resource patchiness ; Soil moisture ; Soil nitrogen availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In early stages of primary succession, colonizing plants can create resource patches that influence the abundance and distribution of other species. To test whether different colonizing shrubs generate contrasting patches on coastal sand dunes, we compared soil characteristics and light availability under the nitrogen-fixing shrub Lupinus arboreus, under the non-nitrogen-fixing shrub Artemisia pycnocephala, and between shrubs on dunes at a site in northern California. Concentrations of inorganic nitrogen and net nitrogen mineralization rates were generally 1–10 times greater in soil under Lupinus than under Artemisia or between shrubs. Soil water content was mostly lower under shrubs. Mean photon flux density near ground level was reduced by at least 80% at ≥ 35 cm inside shrub canopies. Topography appeared to have more effect on soil moisture but less direct effect on nitrogen availability than did Lupinus. However, Lupinus probably increases nitrogen levels more on higher, drier dunes. Microhabitats under and between nitrogen-fixing shrubs constitute a mosaic of individually poor but complementary patches in which high levels of light and moderate levels of soil nitrogen are present but tend not to occur together.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052818
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