supplement of probing the past 30-year phenology trend of us
TRANSCRIPT
Supplement of Biogeosciences, 12, 4693–4709, 2015http://www.biogeosciences.net/12/4693/2015/doi:10.5194/bg-12-4693-2015-supplement© Author(s) 2015. CC Attribution 3.0 License.
Supplement of
Probing the past 30-year phenology trend of US deciduous forests
X. Yue et al.
Correspondence to:X. Yue ([email protected])
The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence.
1
Supporting Information
Derivation of phenological observations
One difficulty in analyzing trend of forest phenology is the missing of long-term records.
In this study, we derive phenological observations in combination of date records, leaf
area index (LAI), and photos. Date records are complete and last for >20 years at Harvard
Forest and Hubbard Brook. However, the data are incomplete at US-UMB and US-MMS.
Budburst dates are documented for 10 years at US-UMB (Fig. S2a). We use the LAI
measurements from 1999 to gap fill the missing dates. In this procedure, the budburst
dates are defined as the days when the interpolated or extrapolated LAI is equal to a
selected threshold (LAIt), which may vary from 0.5 to 2.0. As shown in Fig. S2a, a
different LAIt can determine an independent time series. The most reasonable LAIt is
determined if the derived time series has the lowest root-mean-square error (RMSE)
against the available date records. For example, the RMSE for derived phenology is 5.6
days with LAIt=1.3 m2 m-2, 3.2 days with LAIt=1.5 m2 m-2, and 4.1 days with LAIt=1.7
m2 m-2. As a result, we select LAIt = 1.5 m2 m-2 as the standard threshold to derive the
missing budburst dates. The same spring LAIt is applied to derive dormancy onset dates,
which also show low RMSE against other sources of autumn phenology (Fig. S2b). A
similar procedure is performed for US-MMS and a lower LAIt of 1.4 m2 m-2 is selected
for this site (Figs. S2c-S2d). As a check, we also derive phenological dates for US-Ha1
with A higher LAIt of 1.75 m2 m-2 (Figs. S2e-S2f). However, for US-Ha1, date records
are comprehensive while LAI measurements are incomplete and as a result we do not use
the LAI-derived dates in the model validations at this site (e.g. Fig. 1).
In case that the LAI measurements are also incomplete, we derive those missing dates
using photos from PhenoCam (http://phenocam.sr.unh.edu/webcam/). Different from the
quantitative estimate with LAI, the derivation with photo is qualitative. We define the
budburst date as the middle of the few days when tree colors change rapidly from gray to
light green. On the contrary, a dormancy start date is defined as the middle of days with
rapid color changes from brown to gray. An example of autumn dormancy at US-UMB is
shown in Fig. S3. The comparison shows that the photo-derived dates are not largely
2
different from the LAI-derived ones (Fig. S2b). We aggregate all the available dates to
develop the most complete dataset for validation (Fig. 1). In case of data overlap from
different sources, we select date records as the primary choice and that derived from LAI
as the secondary.
We also derive phenological dates for the USA National Phenology Network (USA-
NPN). The network has limited records before 2009 but is significantly enriched
thereafter. Currently, there are >600000 records for >20000 individual plants at >6500
sites. Due to the large data amount, we select observations during 2011-2012 for 52
deciduous tree species that are the most common in the U.S. (Table S1). In total, we have
records at 588 sites (Table 1); however, not all of these sites provide continuous year-
round observations. We apply the following stringent screening filter to derive the
phenological dates with high confidence. Each USA-NPN record reports 2-10
phenological statuses, including breaking leaf buds, >=75% of full leaf size, >=50% of
leaves colored, >=50% of leaves fallen, all leaves fallen, and so on. We determine
budburst date as the first day with ‘breaking leaf buds’ and dormancy onset as the first
day with ‘all leaves fallen’. To ensure that the selected date is the real ‘first day’ for the
phenological shift, we require that there is at least one record beforehand showing no
onset of the phenological events. For example, a record with true status of ‘breaking leaf
buds’ is not used if no records in the earlier days of this year report a false status for the
same event. The derived dates for individual trees are averaged among species for every
site to achieve the spatial distribution of phenology.
3
Figure S1. Observed (markers) and regressed (black lines) phenology at four DBF sites (top row). At each site, sensitivity tests of regressions for the dth day of the year are performed with different budburst dates (D1), growing length (L1), offset start dates (D2), and falling length (L2) as follows (marked in the top left subplot):
P(d) =max 0, min (d !D1) L1, 1[ ]{ }, d " 213
max 0, min (L2+D2! d) L2, 1[ ]{ }, d > 213
#$%
&%
The 213th day of year is correspondent to August 1st. Contour maps of the root-mean-square error (RMSE) for these regressions against observations are shown for spring (middle row) and autumn (bottom row). The optimized regressions with specific dates (D1, L1, D2, and L2), which result in a minimum regression RMSE, are shown as the bold lines in the top figures.
0 100 200 3000
0.5
1199819992005200620072008
LAI at US!Ha1
Day of year
Phen
olog
y
40 60 80 100 120 140 160
20
40
60
80
0.10.150.15
0.20.2
0.250.25
0.3
0.3
0.35
0 35
0.4
0 4
0.4
Spring RMSE for US!Ha1
Budburst D1 (day of year)
Gro
wth
L1
(day
s)
220 240 260 280 300 320
20
40
60
80
0.120.160.16
0.20.2
0.3
0.3
0.4
0.4
Autumn RMSE for US!Ha1
Offset start D2 (day of year)
Fallin
g L2
(day
s)
0 100 200 3000
0.5
1199920002001200220032004200520062007
LAI at US!UMB
Day of year
Phen
olog
y
40 60 80 100 120 140 160
20
40
60
80
0.20.2
0.250.25
0.30.3
0.35
0.35
0.4
0 4
Spring RMSE for US!UMB
Budburst D1 (day of year)
Gro
wth
L1
(day
s)
220 240 260 280 300 320
20
40
60
80
0.20.30.3
0.4
0.4
Autumn RMSE for US!UMB
Offset start D2 (day of year)
Fallin
g L2
(day
s)
0 100 200 3000
0.5
11999200020012002200320042005200620092010
LAI at US!MMS
Day of year
Phen
olog
y
40 60 80 100 120 140 160
20
40
60
80
0.10.150.15
0.20.2
0.25
0.25
0.3
0 3
0.35
0 35
0.4
0 4
0.4
Spring RMSE for US!MMS
Budburst D1 (day of year)
Gro
wth
L1
(day
s)
220 240 260 280 300 320
20
40
60
80
0.20.2
0.3
0.3
0.4
0.4
Autumn RMSE for US!MMS
Offset start D2 (day of year)
Fallin
g L2
(day
s)
0 100 200 3000
0.5
12006200720082009201020112012
LAI at US!MOz
Day of year
Phen
olog
y
40 60 80 100 120 140 160
20
40
60
80
0.150.2
0.20.25
0.250.3
0.3
0.35
0.35
0.4
0 4
0.4
Spring RMSE for US!MOz
Budburst D1 (day of year)
Gro
wth
L1
(day
s)
220 240 260 280 300 320
20
40
60
80
0.120.160.16
0.20.2
0.3
0.3
0.4
0.4
Autumn RMSE for US!MOz
Offset start D2 (day of year)
Fallin
g L2
(day
s)
D1
D2
L1L2
4
Figure S2. Derived (a, c, e) budburst and (b, d, f) dormancy onset date with different LAI thresholds at sites (a, b) US-UMB, (c, d) US-MMS, and (e, f) US-Ha1. Observations from date records are indicated as blue points. Dates derived from photos (e.g., see Fig. S3 for US-UMB) are shown as magenta pentagrams.
2000 2005 2010100
120
140
160
Day
of y
ear
(a) Budburst date at US UMB
LAIt = 1.3LAIt = 1.5LAIt = 1.7
2000 2005 2010280
290
300
310
320
330(b) Dormancy onset date at US UMB
Day
of y
ear
2000 2005 201080
100
120
140
160
Day
of y
ear
(c) Budburst date at US MMS
LAIt = 1.2LAIt = 1.4LAIt = 1.6
2000 2005 2010290
300
310
320
330(d) Dormancy onset date at US MMS
Day
of y
ear
1998 2000 2002 2004 2006 2008
100
120
140
160
Year
Day
of y
ear
(e) Budburst date at US Ha1
LAIt = 1.65LAIt = 1.75LAIt = 1.85
1998 2000 2002 2004 2006 2008290
300
310
320
330(f) Dormancy onset date at US Ha1
Day
of y
ear
Year
5
Figure S3. Photos of autumn phenology at US-UMB sites. A dormancy start date is defined as the middle of a few days with rapid color changes from brown to gray The photos after 2008 have better quality relative to earlier years due to an update of equipment.
2005.11.09 2006.10.29 2007.11.10
2011.11.03 2012.10.23
2009.10.29 2010.10.19 2008.11.02
6
Figure S4. Comparison of predicted (blue) budburst dates at Harvard Forest with observations (red) for 1992-2012. Each panel represents results using a spring phenology model (Table 5).
1995 2000 2005 2010
110
120
130
140
Day
of y
ear
Sequential CF1
ObsModel
1995 2000 2005 2010
110
120
130
140
Sequential CF2
1995 2000 2005 2010
110
120
130
140
Parallel1 CF1
1995 2000 2005 2010
110
120
130
140
Parallel1 CF2
Day
of y
ear
1995 2000 2005 2010
110
120
130
140
Parallel2 CF1
1995 2000 2005 2010
110
120
130
140
Parallel2 CF2
1995 2000 2005 2010
110
120
130
140
Alternating CF1
Day
of y
ear
Years1995 2000 2005 2010
110
120
130
140
Alternating CF1 t1 fixed
Years1995 2000 2005 2010
110
120
130
140
Alternating CF1 Modified
Years
7
Figure S5. The same as Fig. S4 but for the site at Hubbard Brook.
1995 2000 2005 2010120
130
140
150
160
Day
of y
ear
Sequential CF1
ObsModel
1995 2000 2005 2010120
130
140
150
160Sequential CF2
1995 2000 2005 2010120
130
140
150
160Parallel1 CF1
1995 2000 2005 2010120
130
140
150
160Parallel1 CF2
Day
of y
ear
1995 2000 2005 2010120
130
140
150
160Parallel2 CF1
1995 2000 2005 2010120
130
140
150
160Parallel2 CF2
1995 2000 2005 2010120
130
140
150
160Alternating CF1
Day
of y
ear
Years1995 2000 2005 2010
120
130
140
150
160Alternating CF1 t1 fixed
Years1995 2000 2005 2010
120
130
140
150
160Alternating CF1 Modified
Years
8
Figure S6. The same as Fig. S4 but for the site at US-UMB for 1999-2012.
2000 2005 2010100
110
120
130
140
150
Day
of y
ear
Sequential CF1
ObsModel
2000 2005 2010100
110
120
130
140
150Sequential CF2
2000 2005 2010100
110
120
130
140
150Parallel1 CF1
2000 2005 2010100
110
120
130
140
150Parallel1 CF2
Day
of y
ear
2000 2005 2010100
110
120
130
140
150Parallel2 CF1
2000 2005 2010100
110
120
130
140
150Parallel2 CF2
2000 2005 2010100
110
120
130
140
150Alternating CF1
Day
of y
ear
Years2000 2005 2010
100
110
120
130
140
150Alternating CF1 t1 fixed
Years2000 2005 2010
100
110
120
130
140
150Alternating CF1 Modified
Years
9
Figure S7. The same as Fig. S4 but for the site at US-MMS for 1999-2012.
2000 2005 201080
90
100
110
120
Day
of y
ear
Sequential CF1
ObsModel
2000 2005 201080
90
100
110
120Sequential CF2
2000 2005 201080
90
100
110
120Parallel1 CF1
2000 2005 201080
90
100
110
120Parallel1 CF2
Day
of y
ear
2000 2005 201080
90
100
110
120Parallel2 CF1
2000 2005 201080
90
100
110
120Parallel2 CF2
2000 2005 201080
90
100
110
120Alternating CF1
Day
of y
ear
Years2000 2005 2010
80
90
100
110
120Alternating CF1 t1 fixed
Years2000 2005 2010
80
90
100
110
120Alternating CF1 Modified
Years
10
Figure S8. Comparison of predicted (blue) dormancy onset dates at Harvard Forest with observations (red) for 1992-2012. Each panel represents results using an autumn phenology model (Table 5).
1995 2000 2005 2010280
290
300
310
320
Day
of y
ear
Jolly 2005 Origin
ObsModel
1995 2000 2005 2010280
290
300
310
320Jolly 2005 Adjusted
1995 2000 2005 2010280
290
300
310
320Delpierre 2009
Years1995 2000 2005 2010
280
290
300
310
320CDD photoperiod
Day
of y
ear
Years
11
Figure S9. The same as Fig. S8 but for the site at Hubbard Brook.
1995 2000 2005 2010270
280
290
300
310
Day
of y
ear
Jolly 2005 Origin
ObsModel
1995 2000 2005 2010270
280
290
300
310Jolly 2005 Adjusted
1995 2000 2005 2010270
280
290
300
310Delpierre 2009
Years1995 2000 2005 2010
270
280
290
300
310CDD photoperiod
Day
of y
ear
Years
12
Figure S10. The same as Fig. S8 but for the site at US-UMB for 1999-2012.
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320
Day
of y
ear
Jolly 2005 Origin
ObsModel
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320Jolly 2005 Adjusted
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320Delpierre 2009
Years2000 2002 2004 2006 2008 2010 2012
280
290
300
310
320CDD photoperiod
Day
of y
ear
Years
13
Figure S11. The same as Fig. S8 but for the site at US-MMS for 1999-2012.
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320
330
Day
of y
ear
Jolly 2005 Origin
ObsModel
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320
330Jolly 2005 Adjusted
2000 2002 2004 2006 2008 2010 2012280
290
300
310
320
330Delpierre 2009
Years2000 2002 2004 2006 2008 2010 2012
280
290
300
310
320
330CDD photoperiod
Day
of y
ear
Years
14
Figure S12. Comparison of the simulated (a, b) budburst and (c, d) dormancy dates with in situ observations (colored circles) from the USA National Phenology Network for 2011. Simulations are performed with the spring model S9 and autumn model A4. The number of the sites and the correlation coefficients are shown in the scatter plots.
(a) Start of budburst date in 2011
80 90 100 110 120 130 140 150 160 (DOY)
(c) Start of dormancy date in 2011
270 280 290 300 310 320 330 340 350 (DOY)
70 100 130 160Simulation (DOY)
70
100
130
160
Obs
erva
tions
(DO
Y)
(b) Budburst dates
r = 0.70n = 88
270 290 310 330 350Simulation (DOY)
270
290
310
330
350
Obs
erva
tions
(DO
Y)
(d) Dormancy dates
r = 0.48n = 45
15
Figure S13. The same as Fig. S12 but for the year 2012.
(a) Start of budburst date in 2012
80 90 100 110 120 130 140 150 160 (DOY)
(c) Start of dormancy date in 2012
270 280 290 300 310 320 330 340 350 (DOY)
70 100 130 160Simulation (DOY)
70
100
130
160
Obs
erva
tions
(DO
Y)
(b) Budburst dates
r = 0.62n = 136
270 290 310 330 350Simulation (DOY)
270
290
310
330
350
Obs
erva
tions
(DO
Y)
(d) Dormancy dates
r = 0.69n = 72
16
Fig. S14 Trend of surface air temperature for (a, b) January, (c, d) April, and (e, f) September over deciduous forest during 1982-2012. The temperature data are from (a, c, e) MERRA reanalyses and (b, d, f) USHCN Network. Significant trends (p<0.05) are denoted with dots (a, c, e) or filled circles (b, d, f).
(a) Trend in JAN MERRA TAS (b) Trend in JAN USHCN TAS
(c) Trend in APR MERRA TAS (d) Trend in APR USHCN TAS
(e) Trend in SEP MERRA TAS (f) Trend in SEP USHCN TAS
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 (oC/decade)
17
Figure S15. Trend in the simulated (a, b, c) budburst and (d, e, f) dormancy dates for deciduous forests in the U.S. during different periods. Significant trends (p<0.05) are denoted with dots.
(a) budburst 2000-2012
(b) budburst 2000-2011
(c) budburst 1982-2011
(d) dormancy 2000-2012
(e) dormancy 2000-2011
(f) dormancy 1982-2011
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 (day/yr)
18
Figure S16. Trend of surface air temperature for (a, b) December, (c, d) April, and (e, f) September during 2000-2012. The temperature data are from (a, c, e) MERRA reanalyses and (b, d, f) USHCN Network. The results are shown only for the grid squares where the fraction of deciduous forest is larger than 3%. Significant trends are denoted with dots (a, c, e) or solid points (b, d, f).
(a) Trend in JAN MERRA TAS (b) Trend in JAN USHCN TAS
(c) Trend in APR MERRA TAS (d) Trend in APR USHCN TAS
(e) Trend in SEP MERRA TAS (f) Trend in SEP USHCN TAS
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 (oC/decade)
19
Figure S17. Trend in the simulated (a) budburst and (b) dormancy dates for deciduous forests in the U.S. during 1982-2012 using models without (a) chilling requirement and (b) photoperiod limit. The results are shown only for the grid squares where the fraction of deciduous forest is larger than 3%. Significant trends (p<0.05) are denoted with dots.
(a) Trend in start of budburst date for 1982-2012
(b) Trend in start of dormancy date for 1982-2012
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 (day/yr)
20
Figure S18. Trend in the simulated (a, c) budburst and (b, d) dormancy dates for deciduous forests in the U.S. during 1982-2012 using parameters derived based on phenological records of (a) Sweet Birch (Betula Lenta) and (c) Striped Maple (Acer Pensylvanicum) for spring, and (b) Paper Birch (Betula Papyrifera) and (d) Black Oak (Quercus Velutina) for autumn. The temperature sensitivity of each species is shown in Fig. 8. The results are shown only for the grid squares where the fraction of deciduous forest is larger than 3%. Significant trends (p<0.05) are denoted with dots.
(a) Trend in budburst with low sens.
(b) Trend in dormancy onset with low sens.
(c) Trend in budburst with high sens.
(d) Trend in dormancy onset with high sens.
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 (day/yr)
21
Table S1. Detailed information of phenological records for 52 species from the National Phenology Network during 2011-2012.
Species Latin Name Common Name Sites Trees Records ACMA Acer Macrophyllum Bigleaf Maple 26 41 129 ACNE Acer Negundo Boxelder Maple 27 32 685 ACPE Acer Pensylvanicum Striped Maple 6 11 42 ACPL Acer Plantanoides Norway Maple 6 12 160 ACRU Acer Rubrum Red Maple 177 306 4239 ACSA1 Acer Saccharinum Silver Maple 11 14 154 ACSA2 Acer Saccharum Sugar Maple 75 123 1652 AEFL Aesculus Flava Yellow Buckeye 3 17 327 ALRU Alnus Rubra Red Alder 13 14 163 AMLA Amerlanchier Laevis Serviceberry 2 3 58 BEAL Betula Alleghaniensis Yellow Birch 16 39 301 BELE Betula Lenta Sweet Birch 9 13 86 BEPA Betula Papyrifera Paper Birch 38 63 1226 CACA Carpinus Caroliniana American Hornbeam 11 40 142 CAGL Carya Glabra Pignut Hickory 13 28 492 CAIL Carya Illinoinensis Pecan 14 36 217 CAOV Carya Ovata Shagbark Hickory 5 7 45 CECA Cercis Canadensis Redbud 60 94 1574 CEOC Celtis Occidentalis Hackberry 11 40 243 COFL Cornus Florida Flowering Dogwood 85 115 1193 DIVI Diospyros Virginiana Persimmon 12 17 262 FAGR Fagus Grandifolia American Beech 37 59 1458 FRAM Fraxinus Americana White Ash 12 16 135 FRPE Fraxinus Pennsylvanica Green Ash 20 38 489 GIBI Ginkgo Biloba Ginkgo 5 10 81 GLTR Gleditsia Triacanthos Honey Locust 8 15 101 HAVI Hamamelis Virginia Witch Hazel 17 26 280 ILVE Ilex Verticillata Winterberry 2 3 57 JUNI Juglans Nigra Black Walnut 27 48 579 LIST Liquidambar Styraciflua Sweetgum 33 55 511 LITU Liriodendron Tulipifera Tuliptree 44 89 716 NYSY Nyssa Sylvatica Black Gum 9 16 156 OXAR Oxydendrum Arboreum Sourwood 3 5 26 PLOC Platanus Occidentalis Sycamore 4 5 24 PODE Populus Deltoides Eastern Cottonwood 7 7 54 POTR Populus Tremuloides Trembling Aspen 75 135 3410 PRAM Prunus Americana American Plum 16 16 136 PRSE Prunus Serotina Black Cherry 43 73 1582 QUAL Quercus Alba White Oak 40 59 1158
22
QUMA Quercus Macrocarpa Bur Oak 23 38 549 QUPA Quercus Palustris Pin Oak 7 9 33 QURU Quercus Rubra Red Oak 45 57 1191 QUVE Quercus Velutina Black Oak 5 6 65 RHCA Rhamnus Cathartica Common Buckthorn 5 5 121 RHGL Rhus Glabra Smooth Sumac 2 2 111 ROPS Robinia Pseudoacacia Black Locust 14 19 362 SAAL Sassafras Albidum Sassafras 5 5 69 SAPU Sambucus Pubens Red Elderberry 8 16 781 TIAM Tilia Americana American Basswood 17 21 553 ULAM Ulmus Americana American Elm 13 34 236 VACO Vaccinium Corymbosum Highbush Blueberry 12 25 737 VIAL Viburnum Alnifolium Hobblebush 2 4 129
23
Table S2. Detailed information of phenological records for 7 species from the National Phenology Network during 2004-2012.
Species Latin Name Common Name Trees Records Start End SYCH Syringa Chinensis Red Rothomagensis lilac 68 1770 2004 2012 SYVU Syringa Vulgaris Common Lilac 108 1581 2004 2012 LOTA Lonicera Tatarica-arnoldred Arnold Red honeysuckle 13 725 2004 2012 FOSP Forsythia Spp Forsythia 2 38 2005 2010 COCA Cornus Canadensis Bunchberry Dogwood 1 34 2006 2012 ACRU Acer Rubrum Red Maple 1 56 2006 2012 COFL Cornus Florida Flowering Dogwood 2 27 2007 2012
24
Table S3. Parameters for the phenology models (S9+A4) selected for the regional simulations.
Variables Description Units Value Reference
Spring model S9
t1 Starting day for spring accumulation DOY 356 Fixed
Tc Base temperature for budburst forcing °C 5 Murray et al. (1989)
a Parameters for budburst threshold Gb Degree day -110 Calibrated
b Parameters for budburst threshold Gb Degree day 550 Calibrated
r Parameters for budburst threshold Gb Dimensionless -0.01 Murray et al. (1989)
Lg Growing length constraint Degree day 380 Calibrated
Autumn model A4
t3 Starting day for autumn accumulation DOY 173 Fixed
Tb Base temperature for senescence forcing °C 20 Dufrene et al. (2005)
Fs Threshold for leaf fall Degree day 140 Calibrated
Lf Falling length constraint Degree day 410 Calibrated
Px Daylength threshold for leaf fall Minutes 695 Calibrated
Pi Daylength threshold for full dormancy Minutes 585 Calibrated
25
Table S4. Summary of calibrated parameters for all phenology models except for S9 and
A4. A variable is dimensionless if no units are indicated.
ID Parameters
Spring models
S1 t1 = Dec 23rd, Tf = 15 °C, Tc = 0 °C, C* = 85 days, F* = 230 degree days
S2 t1 = Jan 10th, Tc = -2 °C, C* = 17, F* = 137
S3 t1 = Jan 8th, Tf = 9 °C, Tc = 20 °C, C* = 85 days, a = 42 degree days, b=-0.01
S4 t1 = Jan 10th, Tc = -3 °C, C* = 16, a = 202, b=-0.01
S5 t1 = t2 = Dec 16th, Tf = 8 °C, Tc = 4 °C, C* = 105 days, a = 77 degree days, b=-0.01
S6 t1 = t2 = Jan 10th, Tc = -3 °C, C* = 21, a = 205, b=-0.01
S7 t1 = t2 = Jan 3rd, Tf = Tc = 8 °C, a = 590 degree days, b=-0.03
S8 t1 = t2 = Dec 22nd, Tf = Tc = 7 °C, a = 430 degree days, b=-0.02
Autumn models
A1 Ti = -2 °C, Tx = 5 °C, Pi = 600 minutes, Px = 660 minutes
A2 Ti = -1 °C, Tx = 1 °C, Pi = 600 minutes, Px = 690 minutes
A3 Pstart = 700 minutes, Tb = 25 °C, x = 1, y = 2, Ycrit = 20, Lf =402
26
Table S5. Summary of correlation coefficients, RMSE, the Akaike Information Criterion
(AIC) for the evaluation of different spring models and autumn models.
Models Correlation Coefficient RMSE AIC
Spring Models
S1 0.74 ± 0.13 a 6.14 ± 1.60 75.45 ± 13.67
S2 0.64 ± 0.20 8.71 ± 3.64 76.87 ± 6.91
S3 0.65 ± 0.16 8.41 ± 3.67 90.71 ± 10.05
S4 0.63 ± 0.15 9.46 ± 4.22 85.32 ± 8.29
S5 0.66 ± 0.14 8.85 ± 4.45 90.67 ± 10.20
S6 0.53 ± 0.31 10.39 ± 5.75 89.36 ± 10.93
S7 0.71 ± 0.11 7.33 ± 2.66 72.38 ± 16.24
S8 0.72 ± 0.09 6.90 ± 2.57 73.37 ± 11.43
S9 0.68 ± 0.09 6.64 ± 1.77 66.74 ± 20.20
Autumn models
A1 -0.23 ± 0.25 9.03 ± 4.79 71.40 ± 34.23
A2 -0.24 ± 0.21 8.88 ± 5.22 82.15 ± 33.96
A3 0.43 ± 0.12 7.46 ± 3.06 87.98 ± 23.15
A4 0.27 ± 0.13 7.60 ± 3.13 76.04 ± 15.55 a The numbers are denoted as A ± σ, where A is the mean value at four calibrated sites and σ is half of the (maximum – minimum).
27
References Dufrene, E., Davi, H., Francois, C., le Maire, G., Le Dantec, V., and Granier, A.: Modelling carbon and water cycles in a beech forest Part I: Model description and uncertainty analysis on modelled NEE, Ecol Model, 185, 407-436, 2005. Murray, M. B., Cannell, M. G. R., and Smith, R. I.: Date of Budburst of fifteen Tree Species in Britain Following Climatic Warming, J Appl Ecol, 26, 693-700, 1989.