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Spring in the boreal environment: observations on pre- and post-melt energy and CO2 fluxes in two central Siberian ecosystems

Arneth, Almut LU ; Lloyd, Jon ; Shibistova, Olga ; Sogachev, Andrej and Kolle, Olaf (2006) In Boreal Environment Research: An International Interdisciplinary Journal 11(4). p.311-328
Abstract
A range of observations points towards earlier onset of spring in northern high latitudes. However, despite the profound effects this may have on vegetation-atmosphere exchange of carbon (NEE), vegetation-atmosphere physical coupling, or the location of the tundra-taiga interface, the number of studies that investigate winter-spring transition fluxes in contrasting northern vegetation types is limited. Here, we examine spring ecosystem-atmosphere energy and carbon exchange in a Siberian pine forest and mire. Divergent surface albedo before and during snow-melt resulted in daytime net radiation (R-n) above the forest exceeding R. above the mire by up to 10 MJ m(-2). Until stomata could open, absorbed radiation by the green pine canopy... (More)
A range of observations points towards earlier onset of spring in northern high latitudes. However, despite the profound effects this may have on vegetation-atmosphere exchange of carbon (NEE), vegetation-atmosphere physical coupling, or the location of the tundra-taiga interface, the number of studies that investigate winter-spring transition fluxes in contrasting northern vegetation types is limited. Here, we examine spring ecosystem-atmosphere energy and carbon exchange in a Siberian pine forest and mire. Divergent surface albedo before and during snow-melt resulted in daytime net radiation (R-n) above the forest exceeding R. above the mire by up to 10 MJ m(-2). Until stomata could open, absorbed radiation by the green pine canopy caused substantial daytime sensible heat fluxes (H > 10 MJ m(-2)). H above the mire was very low, even negative (<-2 MJ M-2), during that same period. Physiological activity in both ecosystems responded rapidly to warming temperatures and snow-melt, which is essential for survival in Siberia with its very short summers. On days with above-zero temperatures, before melt. was complete, low rates of forest photosynthesis (1-2 mu mol m(-2) s(-1)) were discernible. Forest and mire NEE became negative the same day, or shortly after, photosynthesis commenced. The mire lagged by about two weeks behind the forest and regained its full carbon uptake capacity at a slower rate. Our data provide empirical evidence for the importance the timing of spring and the relative proportion of forest vs. mire has for late winter/spring boundary-layer growth, and production and surface-atmosphere mixing of trace gases. Models that seek to investigate effects of increasingly earlier spring in high latitudes must correctly account for contrasting physical and biogeochemical ecosystem-atmosphere exchange in heterogeneous landscapes. (Less)
Please use this url to cite or link to this publication:
author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Boreal Environment Research: An International Interdisciplinary Journal
volume
11
issue
4
pages
311 - 328
publisher
Finnish Zoological and Botanical Publishing Board
external identifiers
  • wos:000240423000006
  • scopus:33749179189
ISSN
1239-6095
language
English
LU publication?
yes
id
c44baa74-740e-4654-b447-f5257f186203 (old id 394260)
alternative location
http://www.borenv.net/BER/pdfs/ber11/ber11-311.pdf
date added to LUP
2016-04-01 16:37:47
date last changed
2021-09-15 05:16:01
@article{c44baa74-740e-4654-b447-f5257f186203,
  abstract     = {A range of observations points towards earlier onset of spring in northern high latitudes. However, despite the profound effects this may have on vegetation-atmosphere exchange of carbon (NEE), vegetation-atmosphere physical coupling, or the location of the tundra-taiga interface, the number of studies that investigate winter-spring transition fluxes in contrasting northern vegetation types is limited. Here, we examine spring ecosystem-atmosphere energy and carbon exchange in a Siberian pine forest and mire. Divergent surface albedo before and during snow-melt resulted in daytime net radiation (R-n) above the forest exceeding R. above the mire by up to 10 MJ m(-2). Until stomata could open, absorbed radiation by the green pine canopy caused substantial daytime sensible heat fluxes (H &gt; 10 MJ m(-2)). H above the mire was very low, even negative (&lt;-2 MJ M-2), during that same period. Physiological activity in both ecosystems responded rapidly to warming temperatures and snow-melt, which is essential for survival in Siberia with its very short summers. On days with above-zero temperatures, before melt. was complete, low rates of forest photosynthesis (1-2 mu mol m(-2) s(-1)) were discernible. Forest and mire NEE became negative the same day, or shortly after, photosynthesis commenced. The mire lagged by about two weeks behind the forest and regained its full carbon uptake capacity at a slower rate. Our data provide empirical evidence for the importance the timing of spring and the relative proportion of forest vs. mire has for late winter/spring boundary-layer growth, and production and surface-atmosphere mixing of trace gases. Models that seek to investigate effects of increasingly earlier spring in high latitudes must correctly account for contrasting physical and biogeochemical ecosystem-atmosphere exchange in heterogeneous landscapes.},
  author       = {Arneth, Almut and Lloyd, Jon and Shibistova, Olga and Sogachev, Andrej and Kolle, Olaf},
  issn         = {1239-6095},
  language     = {eng},
  number       = {4},
  pages        = {311--328},
  publisher    = {Finnish Zoological and Botanical Publishing Board},
  series       = {Boreal Environment Research: An International Interdisciplinary Journal},
  title        = {Spring in the boreal environment: observations on pre- and post-melt energy and CO2 fluxes in two central Siberian ecosystems},
  url          = {http://www.borenv.net/BER/pdfs/ber11/ber11-311.pdf},
  volume       = {11},
  year         = {2006},
}