Effects of increased nutrients and warming on CO{sub 2} exchanges in Alaskan wet sedge tundras: Mechanism of response

Journal Article · Thu Jun 01 04:00:00 EDT 1995 · Bulletin of the Ecological Society of America

OSTI ID:95818

Johnson, L C; Shaver, G R; Cades, D C ^[1]

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1. Ecosystems Center, Woods Hole, MA (United States); and others

We measured ecosystem- and leaf-level CO{sub 2} exchanges in Alaskan wet sedge tundra that had been warmed or fertilized for 6 years. Gross ecosystem photosynthesis (GEP), both diurnally and seasonally, was nearly double in N+P fertilizer additions. With N+P additions, GEP greatly exceeded ecosystem respiration, thereby increasing ecosystem C storage. Warming for 6 years (in a field greenhouse) had little effect on GEP, ecosystem respiration, or ecosystem C storage compared to controls.(Controls stored {approximately}90 gC m{sup -2} season{sup -1}.) In the N+P additions, higher canopy photosynthetic rates (P{sub max}) under saturating light conditions accounted for the higher GEP; under low light, GEP was similar among treatments. The increased canopy P{sub max} with N+P additions was due more to increased leaf mass than to increased photosynthesis per unit leaf area. Ecosystem respiration (plant plus microbial) strongly increased in response to greater nutrient availability. This increase was due to a stimulation of plant respiration (mostly aboveground) because the microbial component of the gaseous CO{sub 2} flux was small and unresponsive to treatments. In summary, ecosystem response to increased nutrients appears to be primarily dominated by aboveground plant response.

• OSTI ID: 95818
• Report Number(s): CONF-9507129--
• Journal Information: Bulletin of the Ecological Society of America, Journal Name: Bulletin of the Ecological Society of America Journal Issue: 2 Vol. 76; ISSN 0012-9623; ISSN BECLAG
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
55 BIOLOGY AND MEDICINE
BASIC STUDIES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
BIOLOGICAL EFFECTS
CARBON CYCLE
CARBON DIOXIDE
CLIMATIC CHANGE
ECOSYSTEMS
GRAMINEAE
GREENHOUSE EFFECT
NITROGEN
NUTRIENTS
PHOSPHORUS
PHOTOSYNTHESIS
RESPIRATION
RESPONSE MODIFYING FACTORS
TUNDRA