Response of tundra ecosystems to elevated atmospheric carbon dioxide. [Annual report]

摘要: Our past research shows that arctic tussock tundra responds to elevated atmospheric CO{sub 2} with marked increases in net ecosystem carbon flux and photosynthetic rates. However, at ambient temperatures nutrient availabilities, homeostatic adjustments result rates dropping those found a contemporary levels within three years. Evidence for ecosystem-level acclimation the first season of exposure was 1987. Photosynthetic Eriophorum vaginatum, dominant species, adjusts weeks. Past also indicates other changes potentially important structure function. Elevated treatment apparently delays senescence period positive activity. Recent results from 1987 field verify obtained 1983--1986 seasons: resulted increased Regressions fitted seasonal indicate an apparent 10 d extension uptake reflecting delay onset plant dormancy. This could increase frost sensitivity system. Major end points proposed this include effects interaction withmore » soil temperature availability on: (1) Net flux; (2) rates; (3) Patterns resource controls on adjustment above processes 2}; (4) Plant-nutrient status, litter quality, forage quality; (5) Soil-nutrient status; (6) Plant-growth pattern shoot demography.« less