Friday, December 12, 2008

It's the substrate, silly.

I learned this week that plant ecologists haven't really investigated the odd ecology of possumhaw. The little tree whose seeds are spread by birds grows just as well in wet bottomland forests as on Missouri's limestone glades. Rigorous online searches and lunch hour investigations in the Natural History Program's herbarium came up empty of answers to my question.

My trusty colleague muddled the topic even more today when he volunteered "oh, yeah, and supple jack (Berchemia scandens) grows in swamps of southeast Missouri and dry limestone glade openings of the southwest. Huh. I guess that doesn't answer your question, does it...." No, dear colleague, it doesn't.

So I collaborated all of the information I could gather about possumhaw and supple jack to determine that, indeed, these plants depend on limestone and limestone-based soils to thrive. Flipping back to the occurrence map in Julian Steyermark's benchmark Flora of Missouri, I notice that possumhaw is known from counties in the lower and upper Ozarks, west to the Osage Plains, but it doesn't appear in the Ste. Genevieve area (dominated as it is by sandstone), the granite-based St. Francois Mountains, or those counties with chert-based natural communities around Springfield.

Oh, as usual, I'm open to suggestions about the growth patterns of deciduous holly. At this point, I merely surmise they're all based on the high pH of limestone and the associated soils. Sounds like a good project for a graduate student.

1 comment:

Pam Croom said...

I read your post, "Bright Red Berries" the other day. I thought hmmm, I'd just done a bullet post on supplejack and had too wondered: a. how does it get up there (for I don't think they are common on rocky out crops and glades) and b. how can it possibly grow on dry, rocky glades? Supplejack and possumhaw seem to be in same boat.

Then your next post, "It's the Substate Silly", I see your colleague had the same thought, perhaps muddled thought!

Possum haw will grow in pH ranges from neutral to very acidic. It likes slightly acidic.

Supplejack will grow on slightly acidic to neutral. It prefers neutral.

Those are growing pH's I don't know about germination.

Well, it has been rolling around in my head and finally something turned up. Germination restrictions! Some plants will grow almost anywhere, but only germinate in specific location or conditions. Possibly seed germinated other places and were transported to the glades. (Though washing down to the more moist lowland areas makes more sense.) Perhaps they germinate and then gets stuck on feather or fur (still a long way to travel), but that might explain their scarcity in glades, but common in moist spots where germination conditions are optimum.

It is a thought anyway!

The related winterberry (Ilex verticillata) grows in the St. Francis mountains and along the shut-ins. Kurz's "Shrubs and Woody Vines of Missouri," does show some over-lap with possumhaw in Iron, Madison, and St. Genevieve.