efltux from riparian tundra in the northern foothills of the Brooks Range, Alaska, USA
نویسنده
چکیده
Carbon dioxide efflux and soil microenvironmental factors were measured diurnally in Carex aquatilusand Eriophorum angustifolium-dominated riparian tundra communities to determine the relative importance of soil environmental factors controlling ecosystem carbon dioxide exchange with the atmosphere. Measurements were made weekly between 18 June and 24 July 1990. Diurnal patterns in carbon dioxide etttux were best explained by changes in soil temperature, while seasonal changes in efflux were correlated with changes in depth to water table, depth to frozen soil and soil moisture. Carbon dioxide efflux rates were lowest early in the growing season when high water tables and low soil temperatures limited microbial and root activity. Individual rainfall events that raised the water table were found to strongly reduce carbon dioxide efltux. As the growing season progressed, rainfall was low and depth to water table and soil temperatures increased. In response, carbon dioxide efflux increased strongly, attaining rates late in the season of approximately 10 g CO2 m -2 day -1. These rates are as high as maxima recorded for other arctic sites. A mathematical model is developed which derr/onstrates that soil temperature and depth to water table may be used as efficient predictors of ecosystem CO 2 efflux in this habitat. In parallel with the field measurements of CO2 eltlux, microbial respiration was studied in the laboratory as a function of temperature and water content. Estimates of microbial respiration per square meter under field conditions were made by adjusting for potential respiring soil volume as water table changed and using measured soil temperatures. The results indicate that the effect of these factors on microbial respiration may explain a large part of the diurnal and seasonal variation observed in CO2 efflux. As in coastal tundra sites, environmental changes that alter water table depth in riparian tundra communities will have large effects on ecosystem CO2 efflux and carbon balance.
منابع مشابه
Height and growth rings of Salix lanata ssp. richardsonii along the coastal temperature gradient of northern Alaska
WALKER, D. A. 1987. Height and growth rings of Salix lanata ssp. richardsonii along the coastal temperature gradient of northern Alaska. Can. J. Bot. 65: 988-993. Salix lanata ssp. richardsonii from open-tundra and streamside populations were studied at seven sites along a 100-km north-south transect following the Sagavanirktok River from the Alaskan arctic coast to the foothills of the Brooks ...
متن کاملPollen-vegetation calibration for tundra communities in the Arctic Foothills, northern Alaska
1 Palynology has been portrayed as a ‘blunt’ tool for reconstructing variations in arctic tundra vegetation. We tested this characterization in the Arctic Foothills of northern Alaska by analysing 56 modern pollen assemblages from lakes on contrasting glaciated surfaces. The two surfaces, which date to the Sagavanirktok (> 125 000 years BP) and Itkillik II ( c. 11 500 years BP) ice advances fro...
متن کاملRepresentation of tundra vegetation by pollen in lake sediments of northern Alaska
Aim To understand better the representation of arctic tundra vegetation by pollen data, we analysed pollen assemblages and pollen accumulation rates (PARs) in the surface sediments of lakes. Location Modern sediment samples were collected from seventy-eight lakes located in the Arctic Foothills and Arctic Coastal Plain regions of northern Alaska. Methods For seventy of the lakes, we analysed po...
متن کاملAlaska ecosystem carbon fluxes estimated from MODIS satellite data inputs from 2000 to 2010
BACKGROUND Trends in Alaska ecosystem carbon fluxes were predicted from inputs of monthly MODerate resolution Imaging Spectroradiometer (MODIS) vegetation index time-series combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model over the past decade. CASA simulates monthly net ecosystem production (NEP) as the difference in carbon fluxes between net primary p...
متن کاملStatus and Trends of the Nation's Biological Resources - Alaska
A laska is the largest state (1,477,270 square kilometers), more than twice as large as Texas and one-fifth the size of the lower 48 contiguous states. Alaska extends more than 20° in latitude, from Point Barrow at 71°23' to Amatignak Island in the Aleutians at 51°20'. It spans 42° in longitude, from 130° at the Portland Canal in the southeast to 172° at Attu Island in the western Aleutians (Fi...
متن کامل