Ecological Archives A021-144-A2

Philip E. Higuera, Melissa L. Chipman, Jennifer L. Barnes, Michael A. Urban, and Feng Sheng Hu. 2011. Variability of tundra fire regimes in Arctic Alaska: millennial-scale patterns and ecological implications. Ecological Applications 21:3211–3226.

Appendix B. Supplementary results: radiometric dates (14C and 210Pb) and age-depth models, and supplementary pollen and charcoal records for Raven, Uchugrak, Poktovik, and Little Isac lakes.

TABLE B1. Radiometric dates for Raven, Uchugrak, Poktovik, and Little Isac lakes.

Sample
depth (cm)
Material Laboratory
ID1
210Pb Activity (dpm g-1)
OR 14C Date (yr BP)2
Modeled OR Calibrated date
(cal. yr BP)3, 95% CI
Raven Lake
0.00 – 0.39 bulk sediment UIUC M3-1 21.41 ± 1.78 -56 -57 – -55
0.39 – 1.16 bulk sediment UIUC M3-2 22.63 ± 1.86 -51 -52 – -50
1.16 – 1.54 bulk sediment UIUC M3-3 23.68 ± 2.09 -49 -50 – -48
1.54 – 2.31 bulk sediment UIUC M3-4 24.49 ± 1.82 -43 -44 – -42
2.31 – 3.08 bulk sediment UIUC M3-5 21.62 ± 1.59 -37 -38 – -36
3.08 – 3.85 bulk sediment UIUC M3-6 16.92 ± 1.20 -31 -32 – -30
3.85 – 4.62 bulk sediment UIUC M3-7 15.08 ± 1.39 -25 -26 – -24
4.62 – 5.39 bulk sediment UIUC M3-8 14.82 ± 1.11 -18 -19 – -17
5.39 – 6.16 bulk sediment UIUC M3-9 12.30 ± 1.01 -10 -11 – -8
6.16 – 6.93 bulk sediment UIUC M3-11 11.08 ± 0.90 1 0 – 3
6.93 – 8.47 bulk sediment UIUC M3-12 8.12 ± 0.69 30 25 – 35
8.47 – 9.24 bulk sediment UIUC M3-14 4.81 ± 0.38 47 44 – 50
9.24 – 10.01 bulk sediment UIUC M3-15 3.15 ± 0.27 61 58 – 64
10.01 – 10.78 bulk sediment UIUC M3-16 2.16 ± 0.19 71 68 – 75
10.78 – 11.55 bulk sediment UIUC M3-17 1.92 ± 0.19 81 7686
11.55 – 12.32 bulk sediment UIUC M3-18 1.50 ± 0.16 n/a  
12.32 – 13.09 bulk sediment UIUC M3-19 1.42 ± 0.15 n/a  
13.09 – 13.86 bulk sediment UIUC M3-21 1.38 ± 0.19 n/a  
13.86 – 14.63 bulk sediment UIUC M3-22 1.44 ± 0.14 n/a  
14.63 – 15.40 bulk sediment UIUC M3-23 1.17 ± 0.13 n/a  
33.70 – 33.47 wood fragments CAMS 149208 1140 ± 35 1038 969 – 1164
45.75 – 46.00 grass CAMS 149209 1800 ± 35 1734 1623 – 1819
62.00 – 62.50 twig CAMS 137911 2300 ± 35 2325 2176 – 2353
72.50 – 73.00 charred wood CAMS 137909 2600 ± 90 2680 2389 – 2881
89.00 – 89.50 wood CAMS 137908 3180 ± 35 3403 3349 – 3463
137.75 – 138.00 twig CAMS 137910 3715 ± 35 4049 3946 – 4154
222.00 – 222.25 wood and leaf frags. CAMS 138165 6150 ± 30 7062 6954 – 7155
281.50 – 281.75 wood CAMS 137907 7985 ± 35 8867 8678 – 8990
Uchugrak Lake
0.00 – 1.00 bulk sediment UIUC O3-1 21.18 ± 1.66 -53 -54 – -51
1.00 – 2.00 bulk sediment UIUC O3-2 23.29 ± 1.79 -45 -47 – -42
2.00 – 3.00 bulk sediment UIUC O3-3 18.24 ± 1.45 -36 -37 – -33
3.00 – 4.00 bulk sediment UIUC O3-4 15.55 ± 1.12 -22 -24 – -19
4.00 – 5.00 bulk sediment UIUC O3-5 13.61 ± 0.91 -6 -8 – -3
5.00 – 6.00 bulk sediment UIUC O3-6 8.72 ± 0.65 14 11 – 17
6.00 – 7.00 bulk sediment UIUC O3-7 5.28 ± 0.44 35 3040
7.00 – 8.00 bulk sediment UIUC O3-8 1.76 ± 0.17 n/a  
8.00 – 9.00 bulk sediment UIUC O3-9 2.47 ± 0.23 n/a  
9.00 – 10.00 bulk sediment UIUC O3-11 1.85 ± 0.19 n/a  
10.00 – 10.50 bulk sediment UIUC O3-12 2.04 ± 0.22 n/a  
10.50 – 11.00 bulk sediment UIUC O3-13 2.18 ± 0.22 n/a  
11.00 – 11.50 bulk sediment UIUC O3-14 1.60 ± 0.16 n/a  
11.50 – 12.00 bulk sediment UIUC O3-15 1.51 ± 0.15 n/a  
12.00 – 12.50 bulk sediment UIUC O3-16 2.09 ± 0.20 n/a  
12.50 – 13.00 bulk sediment UIUC O3-17 1.69 ± 0.13 n/a  
13.00 – 13.50 bulk sediment UIUC O3-18 2.02 ± 0.18 n/a  
13.50 – 14.00 bulk sediment UIUC O3-19 1.48 ± 0.15 n/a  
35.75 – 36.75 wood fragments CAMS 136545 720 ± 35 671 571 – 720
41.75 – 42.75 wood fragments CAMS 136546 1120 ± 35 1019 955 – 1139
69.00 – 70.00 wood fragment CAMS 136547 1925 ± 35 1871 1765 – 1951
97.00 – 98.00 wood fragments CAMS 136548 2490 ± 35 2576 2385 – 2716
118.00 – 119.00 wood and bark CAMS 137916 3570 ± 45 3868 3725 – 3981
132.25 – 133.25 wood and bark CAMS 137915 3685 ± 40 4024 3905 – 4139
169.00 – 170.00 wood fragments CAMS 136549 4805 ± 35 5517 5470 – 5598
182.25 – 183.25 wood CAMS 137917 5975 ± 35 6812 6714 – 6905
Poktovik Lake
0.00 – 1.46 bulk sediment UIUC K3-1 22.80 ± 1.58 -50 -48 – -51
1.46 – 2.92 bulk sediment UIUC K3-2 22.52 ± 1.71 -40 -38 – -41
2.92 – 4.38 bulk sediment UIUC K3-3 20.70 ± 1.32 -25 -23 – -26
4.38 – 5.85 bulk sediment UIUC K3-4 16.52 ± 1.17 3 7 – -1
5.85 – 7.31 bulk sediment UIUC K3-5 7.89 ± 0.61 36 42 – 30
7.31 – 8.77 bulk sediment UIUC K3-6 3.43 ± 0.26 63 70 – 55
8.77 – 10.23 bulk sediment UIUC K3-7 2.59 ± 0.25 94 77112
10.23 – 11.69 bulk sediment UIUC K3-8 1.82 ± 0.15 n/a  
11.69 – 13.15 bulk sediment UIUC K3-9 1.85 ± 0.20 n/a  
13.15 – 14.62 bulk sediment UIUC K3-11 1.70 ± 0.14 n/a  
14.62 – 16.08 bulk sediment UIUC K3-12 1.46 ± 0.14 n/a  
16.08 – 17.54 bulk sediment UIUC K3-13 1.48 ± 0.12 n/a  
17.54 – 19.00 bulk sediment UIUC K3-14 1.75 ± 0.16 n/a  
19.00 – 20.46 bulk sediment UIUC K3-15 1.79 ± 0.18 n/a  
20.46 – 21.92 bulk sediment UIUC K3-16 1.44 ± 0.13 n/a  
21.92 – 23.38 bulk sediment UIUC K3-17 1.81 ± 0.21 n/a  
23.38 – 24.84 bulk sediment UIUC K3-18 1.63 ± 0.15 n/a  
26.00 – 27.00 twig w/bark CAMS 149210 835 ± 30 740 690 – 859
32.50 – 33.50 wood CAMS 138741 3015 ± 35 3225* 3085 – 3331
37.50 – 38.50 wood CAMS 138738 2235 ± 40 2231 2150 – 2334
62.00 – 63.00 wood frag w/bark CAMS 136539 2675 ± 35 2779 2748 – 2850
79.50 – 80.50 wood fragments CAMS 136540 3165 ± 35 3391 3321 – 3451
97.25 – 98.25 wood CAMS 138739 3170 ± 35 3395* 3336 – 3455
116.50 – 117.50 wood and leaf frags. CAMS 138740 4345 ± 45 4919 4846 – 5039
143.00 – 144.00 wood frags w/bark CAMS 136541 4480 ± 35 5165 4982 – 5284
164.50 – 165.50 wood fragments CAMS 136542 4730 ± 35 5476 5331 – 5577
202.25 – 203.25 small twig with bark CAMS 136543 4960 ± 35 5684 5610 – 5842
230.00 – 231.00 twig with bark CAMS 136544 5025 ± 40 5786 5661 – 5891
Little Isac Lake
0.00 – 1.00 bulk sediment UIUC N3-1 5.30 ± 0.54 -31 -41 – -22
1.00 – 2.00 bulk sediment UIUC N3-2 3.09 ± 0.29 -12 -24 – 0
2.00 – 3.00 bulk sediment UIUC N3-3 2.96 ± 0.44 29 -1875
3.00 – 4.00 bulk sediment UIUC N3-4 1.82 ± 0.19 n/a  
4.00 – 5.00 bulk sediment UIUC N3-5 1.48 ± 0.16 n/a  
5.00 – 6.00 bulk sediment UIUC N3-6 1.73 ± 0.16 n/a  
6.00 – 7.00 bulk sediment UIUC N3-7 1.98 ± 0.25 n/a  
7.00 – 8.00 bulk sediment UIUC N3-8 1.56 ± 0.17 n/a  
8.00 – 9.00 bulk sediment UIUC N3-9 1.80 ± 0.20 n/a  
9.00 – 10.00 bulk sediment UIUC N3-11 1.73 ± 0.18 n/a  
10.00 – 11.00 bulk sediment UIUC N3-12 1.84 ± 0.20 n/a  
11.00 – 12.00 bulk sediment UIUC N3-13 1.82 ± 0.19 n/a  
12.00 – 13.00 bulk sediment UIUC N3-14 1.93 ± 0.16 n/a  
13.00 – 14.00 bulk sediment UIUC N3-15 1.71 ± 0.15 n/a  
14.00 – 15.00 bulk sediment UIUC N3-16 1.74 ± 0.13 n/a  
15.00 – 15.50 bulk sediment UIUC N3-17 1.98 ± 0.19 n/a  
15.50 – 16.00 bulk sediment UIUC N3-18 1.68 ± 0.18 n/a  
16.00 – 16.50 bulk sediment UIUC N3-19 2.32 ± 0.27 n/a  
16.50 – 17.00 bulk sediment UIUC N3-21 1.26 ± 0.18 n/a  
17.00 – 17.50 bulk sediment UIUC N3-22 2.91 ± 0.33 n/a  
17.50 – 18.00 bulk sediment UIUC N3-23 2.41 ± 0.30 n/a  
18.00 – 18.50 bulk sediment UIUC N3-24 2.51 ± 0.33 n/a  
18.50 – 19.00 bulk sediment UIUC N3-25 2.43 ± 0.28 n/a  
19.00 – 19.50 bulk sediment UIUC N3-26 1.76 ± 0.16 n/a  
19.50 – 20.00 bulk sediment UIUC N3-27 1.55 ± 0.14 n/a  
22.25 – 22.50 twig with bark CAMS 136532 3570 ± 35 3869* 3734 – 3966
23.25 – 27.00 charcoal CAMS 138745 1330 ± 410 1271 565 – 2172
49.25 – 49.75 twig no bark CAMS 136533 3360 ± 30 3601* 3491 – 3681
52.25 – 52.50 birch bract and small
organic fragments
CAMS 149207 2780 ± 90 2901 2757 – 3161
74.75 – 76.00 charcoal CAMS 137914 1880 ± 100 1813* 1576 – 2059
94.00 – 94.25 twig with bark CAMS 136534 4225 ± 30 4757 4651 – 4847
125.25 – 25.50 charcoal CAMS 137912 5090 ± 50 5818 5708 – 5924
148.25 – 148.50 2 charred twigs, charcoal,
and leaf fragments
CAMS 137913 6430 ± 150 7333 6985 – 7573
223.25 – 223.75 wood fragment CAMS 136535 9975 ± 35 11396 11275 – 11610
304.50 – 305.00 wood fragments w/bark CAMS 136536 10,010 ± 35 11487 11317 – 11695
346.00 – 346.50 twig CAMS 136537 10,075 ± 35 11639 11409 – 11888
407.25 – 407.75 wood fragment CAMS 136538 10,050 ± 35 11557 11371 – 11756

1UIUC: University of Illinois, Urbana-Champaign; CAMS: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA.
2Lead-210 activity, with standard deviation, or conventional radiocarbon years before present (CE 1950), with standard deviation.
3See Methods for details on 210Pb modeling and calibration of 14C dates. Italicized 210Pb ages determined using old-age-correction (see Methods).
*Date not used in chronology.




FIG. B1. Full age-depth models for each site. Radiometric ages (210Pb and 14C) and the cubic spline fit, sedimentation rate, and sample resolution, all with 95% confidence intervals. Confidence intervals were based on Monte-Carlo resampling of 1000 chronologies, with the age of each sample randomly selected from the probability distribution of each calibrated 14C and 210Pb date (Higuera et al. 2009). Compare to Fig. 2 in the main text.




FIG. B2. Pollen percentages of major taxa for Raven, Uchugrak, Poktovik, and Little Isac lakes. The y-axis is scaled individually for each taxon but consistent across sites. Solid black line represents a 2000-yr center-weighted moving average.




FIG. B3. Raw charcoal records and analytical steps for peak identification for Raven, Uchugrak, Poktovik, and Little Isac lakes. (A) Raw charcoal concentrations are multiplied by (B) the sediment accumulation rate (“Sed. acc. rate”) to obtain (C) charcoal accumulation rates (CHAR). Panels D – E are duplicated from Figure 4 in the main text: (D) Interpolated charcoal record (Cint) and 750-yr trends defining background charcoal (Cback). (E) Peak charcoal (Cpeak, defined as Cint – Cback), locally-defined thresholds for peak detection, and peaks identified (ID) from samples exceeding the positive threshold and passing the minimum-count screening (see Methods). Peaks identified by three threshold levels are shown above the record (grey dots), with those used for final interpretation identified by the “+” symbol.


Historical lightning density

Historical lightning ignitions from the Alaska Interagency Coordination Center (see
footnote 3 in main text) record greater lightning strikes at up-valley sites, making
ignition density (strikes per unit area per unit time) an unlikely explanation for the
observed pattern in FRIs among sites. Specifically, from 1986 through 2010, a total
of 15, 11, 16, and 24 lightning strikes were recorded within 5 km of Raven,
Uchugrak, Poktovik, and Little Isac lakes, respectively.

LITERATURE CITED

Higuera, P. E., L. B. Brubaker, P. M. Anderson, F. S. Hu, and T. A. Brown. 2009. Vegetation mediated the impacts of postglacial climate change on fire regimes in the south-central Brooks Range, Alaska. Ecological Monographs 79:201–219.


[Back to A021-144]