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Bonnefille et al. 10.1073/pnas.0401709101. |
Table 1. Comparison between meteorological measurements and estimated values of climatic parameters calculated from modern pollen data collected at Hadar in 2001
|
Climatic parameters |
Meteorological data |
Pollen-based estimates |
||
|
|
Measured |
Interpolated |
BA |
PFT |
|
T°C |
|
26.6 |
23.8-27.0 |
25.0-25.9 |
|
MTCO °C |
|
24 |
|
22.1-22.7 |
|
Pmm/yr* |
483 (300-800) |
460 |
505-714 |
510-590 |
*Pmm/yr is mean annual precipitation.
Measured precipitation values from Elowaha Station, close to Hadar, show the range for the 1979-1999 period. Interpolated values are calculated with data from meteorological stations in Ethiopia (1, 2). For pollen-based estimates, using Best Analog (BA) and Plant Functional Types (PFT) methods, the minimum value corresponds to the mean of values from surface soil samples (n = 7) and the maximum value to the mean from Awash river mud samples (n = 6). Meteorological data associated with each modern pollen site, which are used to calculate fossil climatic parameters, can be obtained upon request.
1. Jolly, D., Prentice, I., Bonnefille, R., Ballouche, A, Bengo, M., Brenac, P., Buchet, G., Burney, D., Cazet J., Cheddadi, R., et al. (1998) J. Biogeogr. 25, 1007-1027.
2. Bonnefille, R., Chalié, F., Guiot, J. & Vincens, A. (1992) Clim. Dyn. 6, 251-257.
Table 2. Comparison of pollen-based estimates of climatic values obtained by the BA method on three different preparations and pollen counts of sample 2m (see Fig. 2)
|
Subsamples |
Pollen sum |
No. of taxa |
Temp., ° C |
Precip. (mm/yr) |
|
2m (a) |
518 |
24 |
15.4 |
1,080 |
|
2m (b) |
599 |
29 |
15.7 |
1,138 |
|
2m (c) |
484 |
25 |
15.8 |
1,172 |
|
2m (a+b+c) |
1,610 |
38 |
15.7 |
1,127 |
Pollen subsamples are not identical in their composition because taxa representing <1% can occur in one spectrum but not in the others. This variation is reflected in the taxa numbers. The resulting values for temperature, in particular, and precipitation are consistent and attest to the robustness of the climatic reconstruction. The values plotted in Fig. 3 correspond to the
Table 3. Values of pollen-based estimates of climatic parameters obtained for pollen samples plotted in Fig. 3
|
Pollen data |
BA method |
PFTs method |
|||||
|
Samples |
Pollen sum |
No. of taxa |
T °C |
P mm/yr |
a , % |
MTCO, °C |
P mm/yr |
|
13 |
642 |
31 |
21.0 (0.0, 8.1) |
836 (450, 0) |
93.9 (5.9, 6.1) |
11.1 (0.9, 5.9) |
1145 (245, 355) |
|
12 |
358 |
13 |
24.8 (2.2, 1.8) |
871 (122, 49) |
58.9 (34.9, 21.1) |
21.8 (6.8, 3.0) |
941 (516, 609) |
|
11 |
344 |
6 |
21.1 (4.0, 0.0) |
876 (72, 140) |
58.1 (34.1, 21.9) |
21.9 (6.9, 2.9) |
920 (495, 630) |
|
10 |
440 |
5 |
19.2 (1.9, 0.0) |
857 (53, 16) |
59.7 (35.7, 20.3) |
21.6 (6.6, 3.1) |
973 (548, 577) |
|
9 |
511 |
12 |
21.7 (2.5, 0.0) |
879 (16, 118) |
61.2 (19.2, 18.8) |
21.2 (6.2, 3.6) |
991 (566, 559) |
|
8 |
630 |
7 |
20.5 (3.2, 0.0) |
894 (90, 30) |
59.7 (35.7, 20.3) |
21.6 (6.6, 3.1) |
972 (547, 578) |
|
7 |
1543 |
35 |
22.7 (5.4, 0.7) |
778 (71, 50) |
50.9 (26.9, 19.1) |
22.6 (7.6, 2.1) |
797 (472, 303) |
|
6 |
626 |
4 |
19.2 (1.9, 0.0) |
859 (55, 15) |
59.8 (35.8, 20.2) |
21.6 (6.6, 3.1) |
974 (549, 576) |
|
5 |
302 |
9 |
21.0 (3.7, 0.1) |
911 (107, 50) |
47.6 (23.6, 42.4) |
22.9 (7.9, 1.9) |
731 (406, 369) |
|
4 |
274 |
11 |
21.3 (4.0, 0.3) |
901 (206, 0) |
61.2 (19.2, 18.8) |
21.1 (6.1, 3.7) |
968 (543, 582) |
|
3 |
312 |
19 |
20.4 (0.5, 3.2) |
949 (24,197) |
56.2 (32.2, 23.9) |
21.1 (6.1, 3.7) |
826 (501, 324) |
|
2m |
1654 |
61 |
15.7 (0.9, 0.9) |
1127 (115,103) |
76.1 (24.1, 23.9) |
15.0 (2.5, 3.8) |
1192 (292, 308) |
|
2 l-2 |
684 |
35 |
15.5 (0.1, 1.2) |
1046 (134, 167) |
69.1 (17.1, 18.9) |
17.7 (3.2, 5.3) |
1063 (713, 337) |
|
2 l-1 |
846 |
33 |
15.5 (0.9, 1.1) |
1143 (231, 88) |
70.5 (18.5, 29.5) |
17.6 (3.1, 5.4) |
1101 (201, 399) |
|
2 k |
435 |
20 |
18.1 (4.0, 0.0) |
1035 (37, 594) |
89.7 (17.7, 10.3) |
12.3 (2.0, 4.7) |
1222 (322, 428) |
|
2 j |
627 |
23 |
20.1 (0.0, 5.8) |
845 (429, 45) |
62.8 (20.8, 17.2) |
20.3 (5.3, 4.5) |
976 (551, 574) |
|
2i |
683 |
18 |
20.2 (2.1, 0.0) |
997 (130, 7) |
58.3 (34.3, 21.7) |
21.8 (6.8, 2.9) |
930 (505, 620) |
|
2h |
431 |
20 |
21.0 (1.6, 1.5) |
981 (98, 165) |
60.8 (18.8, 19.2) |
21.2 (6.2, 3.6) |
972 (547, 578) |
|
2g |
343 |
21 |
19.4 (7.7, 0.0) |
904 (27, 120) |
52.7 (28.7, 17.3) |
21.9 (6.9, 2.9) |
781 (456, 319) |
|
2f |
211 |
11 |
21.5 (2.2, 0.3) |
738 (0, 240) |
60.6 (18.6, 19.4) |
21.2 (6.2, 3.5) |
958 (533, 592) |
|
2e |
552 |
13 |
21.2 (2.0, 0.3) |
907 (46, 92) |
57.2 (33.2, 22.8) |
21.9 (6.9, 2.8) |
923 (498, 627) |
|
2d-b |
303 |
15 |
20.7 (0.2, 1.8) |
878 (0, 268) |
62.4 (20.4, 17.6) |
20.7 (5.7, 4.0) |
990 (565, 560) |
|
2d-a |
256 |
12 |
22.2 (0.5, 4.4) |
756 (298, 0) |
50.9 (26.9, 19.1) |
22.8 (7.8, 2.0) |
780 (455, 320) |
|
2c |
936 |
17 |
21.3 (2.1, 0.0) |
915 (40, 98) |
52.4 (28.4, 17.6) |
22.3 (7.3, 2.5 ) |
806 (481, 344) |
|
2b |
94 |
8 |
19.5 (2.2, 0.0) |
866 (62, 12) |
51.4 (27.4, 18.6) |
22.6 (7.6, 2.2) |
804 (479, 346) |
|
2a |
261 |
10 |
21.0 (3.7, 0.0) |
908 (104, 22) |
60.6 (18.6, 19.4) |
21.4 (6.4, 3.4) |
979 (554, 571) |
|
1 |
930 |
57 |
20.6 (2.9, 0.0) |
743 (148, 255) |
69.1 (17.1, 18.9) |
17.7 (3.2, 5.3) |
927 (502, 623) |
|
Total pollen |
15,228 |
|
|
|
|
|
|
T° C is mean annual temperature, Pmm/yr is mean annual precipitation, a , % is the humidity coefficient, and MTCO, °C is mean temperature of the coldest month, as estimated by the Best Analog (BA) and Plant Functional Types (PFTs) methods. See text for the definition of error (in parentheses). Pollen sums used for climatic reconstruction of each sample exclude swamp taxa.