Your discussion on habitat is way too good not to share it with
folks on the
list. I hope it will trigger broad discussion.
---------------------- Forwarded Message: ---------------------
From: "Colby Rucker"
Date: Mon, 8 Sep 2003 21:20:17 -0400
When you began your cottonwood quest, I sort of yawned because
I've only seen
cottonwoods that were kidnapped and stuck in some inhospitable
piece of soil
where they retaliated by growing rapidly just so they could
become a stag-headed
menace as soon as possible.
Of course, I wasn't being fair, because cottonwoods are rather
to luxuriate in soils built or replenished by the seasonal
floods. And I, being
a child of the coastal plain, think of rivers as being languid
the often exhausted sands of a flat landscape inhabited by scrub
oak, post oak, blackjack oak and beetle-infested locusts.
No wonder I retreat to the cool green haunts of Chase Creek
Woods, in the
Highlands of the Severn, Maryland's "Hudson in
Miniature." Chase Creek, once
called Timberneck Creek, lies at the narrowest, and therefore,
part of the Severn watershed. It coincides with the great Aquia
its glauconite-laden greensands rich in potassium. Belt Woods is
also on the
greensands, but lacks the dramatic topography.
The east-running ravines are sheltered from the prevailing
westerly winds, and
the deepest escape the summer droughts that kill the oaks and
their time, and turn the tops of the tuliptrees once eager to
reach new heights.
In the deepest ravines, unweathered greensands still yield
from ancient deposits where Late Cretaceous shells are but
impressions. And so, starting with the entire Chesapeake
environment, we come
down to a few small low slopes where the the afternoon suns
never turn the
corner, and we find ideal habitat.
Well, I don't know if it's ideal habitat, so I just say it
habitat. The indicator species speak to that. There's glade
fern, silvery spleenwort, broad beech fern, pawpaw, spicebush,
mayapple, richweed, wild hydrangea and hercules club. Here is
largest white oak, spicebush, northern red oak and perhaps seven
species. Many of the indicator species also occur at Belt Woods,
and both sites
have tuliptrees, white oaks, black oaks, northern red oaks and
other trees of
exceptional height in close proximity to the indicator species.
So, what do indicator species indicate? Obviously, there's the
fertile soils, especially those that are circumneutral.
Tuliptree, pawpaw and
bitternut are associates of the rare glade fern, but those trees
aren't rare, so
what's special about these tall-tree sites? In large measure,
comparative freedom from drought stress. Of course, in the
rainfall is greater, temperatures lower, and sheltering
extensive, trees do grow taller.
That said, are the mentioned indicator species a relevant guide
tree sites off the coastal plain? Are there others in those
habitats? If so,
do they indicate factors beyond freedom from drought stress? It
are still relevant; after all, glade fern isn't common anywhere.
So, how do we break down habitat in an entire county or state,
by the best of
the best, until we come down to a few acres of exemplary
habitat? If a pawpaw
is an uncommon find at Baxter Creek, does that suggest it's not
habitat, but only mimicks such? If so, are there sites with
What indicators would lead us in that direction? Do we need to
attention to shell marl as at Carters Grove, or Chapman's
Landing, or limestone,
as at the Brevard Fault line?
Yes, your cottonwoods are a picky lot, but impressive with the
We've measured a lot of tall trees all over, and it's probably
time to associate
numbers with habitat. Good habitat isn't self-evident; many
sites just mimick
exceptional conditions, sort of like actors masquerading as the
Still, the numbers are there, are we need to ask what roles
these sites play on
the larger stage.