TY - JOUR
T1 - Response of net ecosystem productivity of three boreal forest stands to drought
AU - Kljun, N.
AU - Black, T. A.
AU - Griffis, T. J.
AU - Barr, A. G.
AU - Gaumont-Guay, D.
AU - Morgenstern, K.
AU - McCaughey, J. H.
AU - Nesic, Z.
PY - 2006/11
Y1 - 2006/11
N2 - In 2001-03, continuous eddy covariance measurements of carbon dioxide (CO2) flux were made above mature boreal aspen, black spruce, and jack pine forests in Saskatchewan, Canada, prior to and during a 3-year drought. During the 1st drought year, ecosystem respiration (R) was reduced at the aspen site due to the drying of surface soil layers. Gross ecosystem photosynthesis (GEP) increased as a result of a warm spring and a slow decrease of deep soil moisture. These conditions resulted in the highest annual net ecosystem productivity (NEP) in the 9 years of flux measurements at this site. During 2002 and 2003, a reduction of 6% and 34% in NEP, respectively, compared to 2000 was observed as the result of reductions in both R and GEP, indicating a conservative response to the drought. Although the drought affected most of western Canada, there was considerable spatial variability in summer rainfall over the 100-km extent of the study area; summer rainfalls in 2001 and 2002 at the two conifer sites minimized the impact of the drought. In 2003, however, precipitation was similarly low at all three sites. Due to low topographic position and consequent poor drainage at the black spruce site and the coarse soil with low water-holding capacity at the jack pine site almost no reduction in R, GEP, and NEP was observed at these two sites. This study shows that the impact of drought on carbon sequestration by boreal forest ecosystems strongly depends on rainfall distribution, soil characteristics, topography, and the presence of vegetation that is well adapted to these conditions.
AB - In 2001-03, continuous eddy covariance measurements of carbon dioxide (CO2) flux were made above mature boreal aspen, black spruce, and jack pine forests in Saskatchewan, Canada, prior to and during a 3-year drought. During the 1st drought year, ecosystem respiration (R) was reduced at the aspen site due to the drying of surface soil layers. Gross ecosystem photosynthesis (GEP) increased as a result of a warm spring and a slow decrease of deep soil moisture. These conditions resulted in the highest annual net ecosystem productivity (NEP) in the 9 years of flux measurements at this site. During 2002 and 2003, a reduction of 6% and 34% in NEP, respectively, compared to 2000 was observed as the result of reductions in both R and GEP, indicating a conservative response to the drought. Although the drought affected most of western Canada, there was considerable spatial variability in summer rainfall over the 100-km extent of the study area; summer rainfalls in 2001 and 2002 at the two conifer sites minimized the impact of the drought. In 2003, however, precipitation was similarly low at all three sites. Due to low topographic position and consequent poor drainage at the black spruce site and the coarse soil with low water-holding capacity at the jack pine site almost no reduction in R, GEP, and NEP was observed at these two sites. This study shows that the impact of drought on carbon sequestration by boreal forest ecosystems strongly depends on rainfall distribution, soil characteristics, topography, and the presence of vegetation that is well adapted to these conditions.
KW - Boreal forest
KW - Carbon dioxide
KW - Drought
KW - Eddy correlation
KW - Fluxnet Canada Research Network
KW - International climate variability
KW - Soil moisture content
UR - http://www.scopus.com/inward/record.url?scp=33751506627&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33751506627&partnerID=8YFLogxK
U2 - 10.1007/s10021-005-0082-x
DO - 10.1007/s10021-005-0082-x
M3 - Article
AN - SCOPUS:33751506627
SN - 1432-9840
VL - 9
SP - 1128
EP - 1144
JO - Ecosystems
JF - Ecosystems
IS - 7
ER -