GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • nitrification  (2)
  • arctic  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Epilithic chlorophyll a, photosynthesis, and respiration in control and fertilized reaches of a tundra stream (1992)
    Springer
    Hydrobiologia 240 (1992), S. 121-131 
    Details
    ISSN: 1573-5117
    Keywords: streams ; arctic ; tundra ; epilithon ; photosynthesis ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis and respiration by the epilithic community on cobble in an arctic tundra stream, were estimated from oxygen production and consumption in short-term (4–12 h), light and dark, chamber incubations. Chlorophyll a was estimated at the end of each incubation by quantitatively removing the epilithon from the cobble. Fertilization of the river with phosphate alone moderately increased epilithic chlorophyll a, photosynthesis, and respiration. Fertilization with ammonium sulfate and phosphate, together, greatly increased each of these variables. Generally, under both control and fertilized conditions, epilithic chlorophyll a concentrations (mg m−2), photosynthesis, and respiration (mg O2 m−2, h−1) were higher in pools than in riffles. Under all conditions, the P/R ratio was consistent at ∼ 1.8 to 2.0. The vigor of epilithic algae in riffles, estimated from assimilation coefficients (mg O2 [mg Chl a]−1 h−1) was greater than the vigor of epilithic algae in pools. However, due to the greater accumulation of epilithic chlorophyll a in pools, total production (and respiration) in pools exceeded that in riffles. The epilithic community removed both ammonium and nitrate from water in chambers. Epilithic material, scoured by high discharge in response to storm events and suspended in the water column, removed ammonium and may have increased nitrate concentrations in bulk river water. However, these changes were small compared to the changes exerted by attached epilithon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013457
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Riparian nitrogen dynamics in two geomorphologically distinct tropical rain forest watersheds: nitrous oxide fluxes (1992)
    Springer
    Biogeochemistry 18 (1992), S. 77-99 
    Details
    ISSN: 1573-515X
    Keywords: denitrification ; nitrification ; nitrous oxide ; rain forest ; riparian ; solute transport ; tropical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Fluxes of N2O at the soil surface, dissolved N2O in near-surface groundwater, and potential N2O production rates were measured across riparian catenas in two rain forest watersheds in Puerto Rico. In the Icacos watershed, mean N2O fluxes were highest at topographic breaks in the landscape (≃ 40–300 μg N2O­N m−2 h−1). At other locations in the riparian zone and hillslope, fluxes were lower (⩽ 2 μg N2O­N m−2 h−1). This pattern of surface N2O fluxes was persistent. In the Bisley watershed, mean suface N2O fluxes were lower (〈40 μg N2O­N m−2 h−1) and no identifiable spatial or temporal pattern. Although the spatial patterns and intensities of N2O emissions differed between the two watersheds, surface soils from both sites had a high potential to reduce NO3 to N2O (and perhaps N2). This potential declined sharply with depth as did soil %C, %N, and potential N-mineralization. Simple controls on denitrification (i.e. aeration, nitrate, and carbon) explained characteristics of potential N2O production in surface and deep soils from riparian and upslope locations. In the field, spatial patterns in these controlling variables were defined by geomorphological differences between the two watersheds, which then explained the spatial patterns of observed N2O flux
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002704
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Gaseous nitrogen emmissions from undisturbed terrestrial ecosystems: An assessment of their impacts on local and global nitrogen budgets (1986)
    Springer
    Biogeochemistry 2 (1986), S. 249-279 
    Details
    ISSN: 1573-515X
    Keywords: ammonia volatilization ; nitrification ; denitrification ; chemodenitrification ; nitrogen cycling ; atmospheric chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract There is increasing interest in the importance of nitrogen gas emissions from natural (non-agricultural) ecosystems with respect to local as well as global nitrogen budgets and with respect to the effects of nitrogen oxides on atmospheric ozone levels and global warming. The volatile forms of nitrogen of common interest are ammonia (NH3), nitrous oxide, (N2O), dinitrogen (N2), and NOx (principally NO + NO2). It is often difficult to attribute emissions of these compounds from soils to a single process because they are produced by a variety of common biogeochemical mechanisms. Although environmental conditions in the soil often appear to favor nitrogen gas emissions, the potential nitrogen gas emission rate from undisturbed ecosystems is rarely approached. The best estimates to date suggest that nitrogen gas emission rates from undisturbed ecosystems typically range from 〉 1 to perhaps 10 or 20 kg N ha-1 yr-1. Under certain conditions, however, emission rates may be much higher. For example, excreta from animals in grasslands may elevate ammonia volatilization up to 100 kg N ha-1 yr-1 depending on grazer density; tidal input of nutrients to coastal wetlands may support denitrification rates of several hundred kg N ha-1 yr-1 . Excepting such cases, gaseous nitrogen losses are probably a small component of the local nitrogen budget in most undisturbed ecosystems. However, emissions from undisturbed soils are an important component of the global source strengths for (N2O + N2), N2O and NOx (50%, 21%, and 10% respectively). Emission rates of N2O from natural ecosystems are higher than assumed previously by perhaps 10 times. Large-scale disturbance may have a stimulatory effect on nitrogen emission rates which could have important effects on global nitrogen budgets. There is a need for more sophisticated methods to account for natural temporal and spatial variations of emissions rates, to more accurately and precisely assess their global source strengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02180161
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...