This is a public-interest archive. Personal data is pseudonymized and retained under GDPR Article 89.

Re: Goldenrod


> How did the mixture develop? Has anybody read some good papers or studies
> on the subject, which we all might read and discuss? Steve, send your
> citations to the list, please.

> It would seem unlikely that all the species arrived at the same time,
> doesn't it? So there must have been some mechanism for continued
> colonization that created the present mixes. The question is: does that
> mechanism work within a human lifetime? Maybe the mechanism is irratic
> burning plus irratic herbivory. Throw out the schedules. Bring in the
> buffalo. And use BIG spaces.
> 
> Debby

The citations dealing with interseeding in established stands are:
Packard, S. 1994. Successional restoration: thinking like a prairie.
	Restoration and Management Notes 12(1):32-39.
Packard, S. 1997. Interseeding. pages 163-191 in S. Packard and C.
	Mutel (eds.) The Tallgrass Restoration Handbook: for Prairies,
	Savannas, and Woodlands. Island Press, Washington, D.C.
I think Bill Whitney may have discussed interseeding in Platte Valley
restorations in Nebraska in one of the following articles:
Whitney, B. 1997. A Platte River country restoration: Part I. Getting
	started. Restoration and Management Notes 15(1):6-13.
Whitney, B. 1997. Platte River country restoration: Part II. At work on
	the plains. Restoration and Management Notes 15(2):126-137.

The following citations provide information on the origins of prairies
(tallgrass and otherwise):  
Kucera, C. 1992. Tallgrass prairie. pages 227-268 in R. Coupland (ed)
	Ecosystems of the World, Vol. 8A, Natural Grasslands: Introduction 
	and Western Hemisphere. Elsevier Science Publishers, Amsterdam. -
	There are also chapters about mixed grass and shortgrass prairies,
	all of them very good overviews. This is somewhat hard to find but 
	any competent library should be able to locate it via interlibrary
	loan.
Steinaur, E. and S. Collins. 1996. Prairie ecology - the tallgrass
	prairie. pages 39-52 in F. Samson and F. Knopf (eds) Prairie
	Conservation: Preserving North America's Most Endangered
	Ecosystem. Island Press, Washington, D.C.
Axelrod, D. 1985. Rise of the grassland biome, central North America.
	Botanical Review 51:163-201.

Regarding an explanation for the mixtures of forbs and grasses that are
present in prairies, I can offer my understanding (hopefully it's correct)
of information from lectures by Dr. D. Hartnett here at K-State that deal
with species diversity and coexistence.
Two historic models on the organization of plant communities are
the Clementsian "association unit hypothesis" and the "individualistic
hypothesis" put forth (independently) by Gleason and Ramensky.  In the
Clementsian model plant communities occur as discrete units and consist
of interdependent species. Community boundaries are distinct and
communities can be classified.  Predictions of this model are that
distribution limits of each species will coincide with the distribution of
of the community, sharp distinct ecotones will define the limits of the
communty boundaries, and groups of species will be statistically
positively associated with each other.  
In the individualistic hypothesis species are distributed individually and
independently along environmental gradients and communties are not
distinct and discrete units.  The gist of this model is that a species
will exist wherever the conditions are suitable for its existence,
regardless of what type of community that may be.  I believe current
thought among ecologists leans heavily towards the individualistic
hypothesis.  Indeed, one of the citations I provided above states that
there are few species that are limited solely to tallgrass prairies, and
that a great number of tallgrass species have their origins in different
parts of the continent.
Here's a way of visualizing the individualistic hypothesis in action.
Species A is found in the southwest, species B is found in the southeast,
while species C and D occur in the Great Plains.  Climatic warming after a
glacial period and widespread use of fire by newly arrived aboriginals in
the Great Plains results in species A and B shifting their ranges so that
they now occur in the Great Plains.  The range of species C changes very
little and it remains in the Great Plains, while species D shifts it's
range to the north. Each species responded to a set of environmental
conditions that dictate where it could survive.  Perhaps species D needed 
a low light environment.  It mattered not what other species provided
a conopy that filtered light, only that it could not exist in the Great
Plains any longer because the conditions were no longer suitable.  Species
A may have been shifting it's range wherever it could in response to soil
moisture conditions, while species B may have been responding to the 
presence/absence of an influential herbivore.
Two models that explain how species co-exist within any given community
(it's still a usefull term even if the Clementsian model is incorrect)
that I find usefull are the "niche diversification hypothesis" and the
"intermediate disturbance hypothesis".  With niche diversification each
species is competing with each other for specific resources. Species that
can differentiate the way they exploit these resources (resource
partitioning) will coexist. Examples would be growing at different times
of the year and sending roots to differnt depths in the soil column.
Species that do not partition resources will not coexist, one will
eliminate the other.  An intersting paradox of niche diversification is
that species must be similar enough to occupy the same habitat, but
different enough to coexist. 
In the intermediate disturbance hypothesis, biotic
and abiotic disturbances may prevent a species from competitively
excluding other species, and the disturbances create a hetergenous
environment (greater heterogeneity = more niches).  Extremely frequent
disturbances results in a low number of species because few can cope with
such extreme conditions (plowing a field every day), while lack of
disturbance (never  disturb the soil in any way) results in few species
because stable conditions allow one species to competitively exclude
others.  Intermediate levels of disturbance may result in maximal number
of species.

How does all of this apply to tallgrass prairie?  Species definately
partition resources.  Grasses generally utilize moisture in the upper
layers of the soil column, and may be influenced by slight
variations in seasonal precipitation.  Forbs with very deep taproots may
utilize soil moisture that is depleted only during the most severe
droughts.  Cool season and warm season grasses have partitioned the time
of year when they grow, thus they both exist in the same location.
Disturbances such as small mammal diggings and large herbivore wallowing
or trampling allow annuals and short lived perennials to exist within a
prairie that is dominated by highly competitive long lived perennials.
Repeated grazing of patches of dominant grasses allows subdominant grasses
and forbs to increase their vigor in the immediate vicinity of the patch.
Fire prevents woody vegetation from overtopping and replacing herbaceous
vegetation.

Hope this helps.  Again, I could find some specific citations dealing with
niche diversification and disturbance theory that apply to tallgrass if
anybody is interested.  Just give the word.

Something I'd be really intersted in discussing is the role of grazing by
domestic herbivores in praire management.  I envision this being a lively
exchange of ideas that I would like to participate in.

Steve

---------------------------------------------------------------------
To sign-off this list, send email to majordomo@mallorn.com with the
message text UNSUBSCRIBE PRAIRIE
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index