ISSN:
1573-5036
Schlagwort(e):
acclimation
;
ecosystem carbon balance
;
elevated CO2
;
global change
;
photosynthesis
;
respiration
;
soil carbon
;
soil organic matter
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
Notizen:
Abstract Acclimation of photosynthesis and respiration in shoots and ecosystem carbon dioxide fluxes to rising atmospheric carbon dioxide concentration (C a ) was studied in a brackish wetland. Open top chambers were used to create test atmospheres of normal ambient and elevated C a (=normal ambient + 34 Pa CO2) over mono-specific stands of the C3 sedge Scirpus olneyi, the dominant C3 species in the wetland ecosystem, throughout each growing season since April of 1987. Acclimation of photosynthesis and respiration were evaluated by measurements of gas exchange in excised shoots. The impact of elevated C a on the accumulation of carbon in the ecosystem was determined by ecosystem gas exchange measurements made using the open top chamber as a cuvette. Elevated C a increased carbohydrate and reduced Rubisco and soluble protein concentrations as well as photosynthetic capacity(A) and dark respiration (R d ; dry weight basis) in excised shoots and canopies (leaf area area basis) of Scirpus olneyi. Nevertheless, the rate of photosynthesis was stimulated 53% in shoots and 30% in canopies growing in elevated C a compared to normal ambient concentration. Elevated C a inhibited R d measured in excised shoots (−19 to −40%) and in seasonally integrated ecosystem respiration (R e ; −36 to −57%). Growth of shoots in elevated C a was stimulated 14–21%, but this effect was not statistically significant at peak standing biomass in midseason. Although the effect of elevated C a on growth of shoots was relatively small, the combined effect of increased number of shoots and stimulation of photosynthesis produced a 30% stimulation in seasonally integrated gross primary production (GPP). The stimulation of photosynthesis and inhibition of respiration by elevated C a increased net ecosystem production (NEP=GPP−R e ) 59% in 1993 and 50% in 1994. While this study consistently showed that elevated C a produced a significant increase in NEP, we have not identified a correspondingly large pool of carbon below ground.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00017084
Permalink
