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Objective 9 |
Objective 9. Determining the
physiological and ecological traits of the NLR's, and learning if the NLR's
have characteristics appropriate to the place-niches determined in the field. Table 1 shows the taxa present in the
Buchanan Lake Formation. Nearest living relatives have been determined for a
number of taxa, with most showing affinity to living representatives growing
in the mixed mesophytic forests of southeast Asia. Although all of the taxa
studied to date have been gymnosperms, most of the angiosperms from the Axel
Heiberg forests appear to be most similar to their relatives growing in
China. Some physiological characteristics have been measured for a few of the
NLR's, and the ecological characteristics are known in a general way for
some. To achieve Objective 9 we propose to use existing literature and
selected field measurements to update and extend the list of NLR's for the
key Eocene taxa and determine the following for as many NLR's as is
practical: 1) Shade tolerance/ light response curves
for photosynthesis 2) Limits of warm and cold season mean
monthly temperatures in the natural range of each NLR. 3) soil moisture and drainage requirements 4) reproductive strategies including
flowering, fertilization and seed set requirements, seed dispersal
mechanisms, germination and seedling establishment requirements 5) symbionts 6) deciduous/evergreen The fit between NLR physiological and
ecological characteristics and the Eocene forest niches is difficult to
predict for some of the species. For Metasequoia, the data we have
suggests that the characteristics of the extant species are very appropriate
for its Eocene niche. We have preliminary data on the photosynthesis light
response curve for modern Metasequoia growing in Maine and in
Washington, DC. Figure
10 shows that this species saturates at very low light levels. Modern Metasequoia
could effectively fix appreciable carbon at the low light levels of Arctic
latitude summers, and it is shade tolerant and capable of reproducing under a
dense canopy (Chu and Cooper 1950). Compared to Picea and Pinus,
modern Metasequoia would be a better competitor in low-light
environments. It even surpasses red spruce (Picea rubens) which
is one of the most shade tolerant species in the forests of the northeastern
U.S. The fact that Metasequoia is deciduous gives it an even a greater
advantage over the evergreen conifers that would have had to use more of
their reserve carbon during the dark season for foliar maintenance. Thus the
first evidence from NLR's is consistent with Metasequoia dominating
mature forests at high latitudes. |
