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Re: Question, grass on Jordan mudflats
- To: "Travis, Ginger" <Ginger@athena.dev.unc.edu>, "carolinabirds@duke.edu"<carolinabirds@duke.edu>
- Subject: Re: Question, grass on Jordan mudflats
- From: Clyde Sorenson <clyde_sorenson@ncsu.edu>
- Date: Thu, 01 Aug 2002 15:50:47 -0400
- References: <B9A72DA758B8D111B82E00A024FC704D04528172@athena.dev.unc.edu>
- Sender: carolinabirds-owner@acpub.duke.edu
- User-agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-US; rv:1.0rc2) Gecko/20020512 Netscape/7.0b1
Travis and all,
The grass you are seeing is typically several species of annual grasses
and sedges (like grass but not grass- most have a triangular
cross-section in the stem). Some kinds like represented would include
some panic grasses, sprangletop, and many others.
How the seed get there:
The seed for many of these species can indeed lie dormant under standing
water for a very long time (rice seed also does this); the seed bank can
accumulate from the product of previous drought years, deposition by
wind and waves, and even deposition by geese (not everything gets ground
in a gizzard). These seed will wait patiently for the cool breath of
life- atmospheric oxygen- to germinate, and they're off and running.
Their main mission is to hurry though their life cycle so that they may,
yes, leave another seed bank to wait for the next bout of low water.
Once these grasses and sedges germinate, they can tolerate moderate
flooding (such that the entire plant is not submerged) and will continue
to grow as the water rises until they enter the reproductive phase of
their lifecycles. Some can, under these conditions, grow many feet tall.
(I once saw domestic rice in backwater flooding of Mississippi
bottomland ricefields reach stem lengths near 8 feet under slowly
rising, clear water conditions. These fields collapsed and died when the
flood came off the fields) If the grasses are overtopped, they will
drown, however.
This new seed bank is potentially very important to the waterfowl coming
down this fall- most dabblers make their living off this very kind of
food source. Wildlife managers in most of our refuges try their best to
emulate this exact chain of events in marsh impoundments to provide
abundant food to migrating waterfowl. The flooded grass plants
themselves, however, are not utilized much by waterfowl, although geese
and swans will graze them extensively when they are young and growing.
Take care,
Clyde Sorenson
Clayton and Raleigh, NC
clyde_sorenson@ncsu.edu
Travis, Ginger wrote:
>C-birders, a colleague of mine at work just asked a brilliant question
>(after I told her about all the great shorebirds being seen on the Jordan
>Lake mudflats). She drives up Hwy. 751 over Jordan every day and wants to
>know how the luxuriant stand of grass in the Northeast Creek cove comes to
>be there. In her words, "It looks like someone seeded that place with a
>broadcaster." I see the same thing on the Morgan Creek flats as University
>Lake recedes. It's a meadow (and geese love it). So here's the question:
>is this stuff perennial grass with roots already in the mud, even though the
>flats are covered with water most of the year? Is this annual grass? Does
>the seed float in on the water every year in some uniform distribution and
>then get deposited on the mud when waters recede? Is the seed already in the
>mud from previous years and able to survive inundation for months or even
>years before the waters go down and the seeds sprout? Does anyone even know
>what species of grass it is? And is this grass of any use to dabbling ducks
>after the waters come back up in winter? It's not aquatic, but it's
>underwater after the lake refills. Inquiring minds want to know!
>Ginger Travis
>Chapel Hill, N.C.
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