Proportion of roots
Soil
depth
(cm)
Table 5. Estimates of survival for roots by treatment and sampling location using LIFETEST
procedure in SAS.
Sampling location
Ambrosia dumosa
Larrea tridentata
Community
CO2 Treatment
Ambient
Number
roots
3163
% censored
48.7
Elevated
3196
45.8
Ambient
4055
44.0
Elevated
4353
43.0
Ambient
5148
44.0
Elevated
6017
42.4
75% survival 50% survival
(95% CI)
(95% CI)
803
440
(761, 869)
(420, 457)
791
427
(756, 819)
(406, 446)
410
(385, 426)
412
(398, 433)
723
(659, 754)
750
(734, 771)
440
(414, 446)
377
(356, 390)
759
(735, 787)
723
(711, 737)
Percentage censored indicates percent of individual roots that were right censored (i.e. roots that
were either present at the beginning of the study or present at the end of the study) of the total
number of roots for each sampling location – treatment combination. Percent survival is the
number estimated days until the percentage of roots surviving is 75% or 50% of the original
population; numbers in parentheses are lower and upper 95% confidence intervals for the
estimate.