shifting trends in phenology of the temperate in the …...shifting trends in phenology of the...
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Shifting Trends in Phenology of the Temperate Deciduous Forest in the Midwest and Northeast of US
D. Dragoni1, A.F. Rahman1, and H.P. Schmid2
1Department of Geography, Indiana University ‐USA2Atmospheric Environmental Research, KIT/IMK‐ Germany AmeriFlux/NACP Meeting ‐ 2011
Mer Bleue, O N T
Boreal Cu tover, QU E
Grou nd h og River, ON T
Ozark s, M O
Sylvan ia, M I
Cu b H ill, M D
D u ke, N C
Bo nd ville , IL
UM BS- flu x, M I
MM SF-flu x, IN
Lo st Creek , WI
Mead , N E
Borden , ON TWillow Creek, W I
H ow lan d , M E
H ar vard , MA
G ain s ville, FL
Can aan Valley, W V
W alk er Bran ch, TN
Go od win Creek, M S
Kenn ed y SF C, F L
Kon za P rair ie, KS
Great M ou n tain , CTTu rk ey Pt, ONT
Park Falls/ W L EF, W I
Ottawa
Québecna
Toronto
Winnipeg
Bosto
Aust in
D allas
Detroit
C hicago
Mem phis
H ouston
N ew York
C olumbusBalt imore
Cha rlotte
Milwau kee
Nashville
Washington
Fo rt W orth
San Antonio
Phi lad elp hia
Indianapolis
Jacksonville
Oklahom a C ity
•Mixed deciduous forest•80 year old forest•27 m average canopy height•Continuous measurements since 1989
Morgan‐Monroe State Forest (MMSF)AmeriFlux Site
Local observations of NEP and phenology
Phenology at MMSF
Start of the season
End of the season
Length of the season
Dragoni et al. (2011), Global Change Biology
NEP at MMSF
Late‐summer NEPDOY 260‐299
Mid‐September – End of October
Dragoni et al. (2011), Global Change Biology
Annual NEP vs. Length of vegetative season
Normalized Difference Vegetation Index (NDVI) data from Advanced Very High Resolution Radiometer (AVHRR) satellite from the United States Geological Survey (USGS) at a 1‐km resolution (http://phenology.cr.usgs.gov/ndvi_avhrr.php).
From local to continental scale
SOS EOS
From 1989 to 2008
Start of the season – 1989‐2008 trends
Negative trends = earlier green‐up
SOS shows widespread negative trends north of 36‐40°N
SOS shows no‐trend or positive trends South of 36‐40°N
End of the season – 1989‐2008 trends
positive trends = later senescence
EOS shows widespread positive trends across the entire US Eastern deciduous forests
SOS and EOS time‐series
Areas with negative SOS trends
Areas with positive SOS trends
Areas with positive EOS trends
Areas with either positive SOS (empty squares) or negative SOS (solid dots) and positive EOS trends
Change in annual NEP (gC m2)
Estimates obtained by
• Using the SOS and EOS linear trends from all the pixels in the map
• Assuming a change in annual NEP of 4 gC m2 and 3 gC m2 for each day of change in the SOS and EOS, respectively(Richardson et al., 2009Dragoni et al., 2011)
• Assuming no indirect effects of phenology variability on annual NEP
Conclusions
• Spring phenology seems to show a slow‐down in the green‐up advancing in the ‘northern’ regions of US Eastern deciduous forests, and even a delay in the ‘southern’ regions
• Fall phenology shows a spatially and temporally consistent trend in senescence delay
• The contribution of fall phenology is becoming important in determining the short‐ and long‐term variability of the length of vegetative season and potentially of (net) carbon uptake
• Questions on the drivers, mechanisms, and feedbacks for the observed trends