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A Summary of Biological and Physical Science Presentations
at the First North American Conference on Riparian Ecosystems
and Their Management1
David W. Crumpacker
Among the previous symposia and conferences
held on riparian topics, three are especially
noteworthy for their comprehensive approach and
emphasis on the relationship of ecology to
management: the pioneering regional symposium in
Tucson, Arizona on "Importance, Preservation and
Management of Riparian Habitat" (Johnson and Jones
1977), the first national symposium, "Str:ategies
for Protection and Management of Floodplain
\~etlands and other Riparian Ecosystems" (Johnson
and McCormick 1978), and the massive regional
symposium on "California Riparian Systems:
Ecology, Conservation, and Productive Management"
(Warner and Hendrix 1984) which was held in
Davis, California in 1981. The present conference
continues this tradition in a North American
context with some additional consideration of
riparian ecosystems on other continents. Many
topics were discussed this past week. Some will
be mentioned here to illustrate current trends in
riparian thought, using in most cases the
previously mentioned symposia as a basis for
comparison.
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arid and semiarid west. Both U.S. regional and
national perceptions are lacking on the unique
values of riparian ecosystems. Many of these
systems are not legally wetlands but are equally
valuable. The scientific basis for defining
riparian ecosystems and describing their resources
is reasonably well developed. A challenge to
natural scientists now is to aid in transferring
this knowledge to federal, state, and local
governments, and to private organizations and
citizens.
The scientific hasis for understanding the
processes that take place in riparian ecosystems
is less well documented and must continue to be
developed. This type of information is essential
to predicting and mitigating changes in the
structure and function of riparian systems that are
expected to occur with or without increased human
intervention. An important part of the natural
science papers presented during the past week dealt
with this topic.
One dramatic example of successful riparian
technology transfer concerns the public attitude
towards phreatophytes in the southwestern U.S.
Emphasis has shifted markedly from the negative
opinion of water-loving plants held by numerous
public and private development groups prior to
the 1970's, and still in evidence at the time of
the 1977 Tucson symposium,to an interest in
preserving the integrity of western U.S. riparian
ecosystems through enlightened multiple-use
management. Thus papers were presented in Tucson,
1985 on studies of methods by which, and the degree
to which, ground water can be exported from
riparian ecosystems without endangering them, and
on the need for more accurate determinations of
evapotranspiration from riparian systems (e.g.,
some previous estimates were too high). Taylor
and Barclay's paper on stream renovation rather
than channeliz3tion as a flood control alternative
illustrates another positive attitude change with
regard to riparian ecosystems, ~ince this approach
attempts simultaneously to achieve cost savings
conserve wildlife, and maintain an aesthetic
natural environment.
The trend toward increased emphasis on the
socioeconomic aspects of riparian issues, begun
at the Davis symposium in 1981, was strengthened.
The degree to which riparian ecosystems will
eventually be conserved depends ultimately on the
importance of their natural qualities to humans
rather than to vegetation, wildlife, and livestoc~
This crucial point was clearly understood and
emphasized in a series of papers that have been
summarized by Heyer in these proceedings.
Continuing emergence of the riparian concept
is an issue of great importance that was highlighted by Kusler in his call for increased
emphasis on protection of riparian habitat in the
1
-Paper presented at the First North American
Riparian Conference, "Riparian Ecosystems and
their Management: Reconciling Conflicting Uses,"
Tucson, Ariz., April 16-18, 1985.
2David W. Crumpacker is a Professor of
Environmental, Population and Organismic
Biology, University of Colorado, Boulder, Colo.
3
While the earlier symposia gave considerable
attention to the documentation of riparian
ecosystem impacts and losses, emphasis shifted in
the present conference to consideration of methods
by which impacts can be mitigated or avoided.
This was especially evident in several reports on
effects of livestock grazing. The more anectodal
studies reported at some previous conferences
and symposia, often supported only by general
observations and photographs, are now being
replaced by more carefully designed experiments
that are beginning to produce some interesting
results.
For example, eight years of research
on several grazing systems in northeastern Oreson
showed a generally rapid enhancement of herbaceous
riparian productivity when not more than 70
percent of the herbaceous forage was removed
annually. A three-year study in southwestern
Montana indicated that time of grazing (in
relation to soil moisture) caused much more
trampling damage in the riparian zone than did
the amount of livestock use. The potential
for purposeful use of livestock to create
improved riparian conditions (positive impacts)
was suggested in two papers, one involving
changes in bank morphology of an ephemeral
stream in Wyoming and the other dealing with
changes in the vegetative structure of shrubwillow habitat in Colorado caused by livestock
tunneling. Other livestock use reports included
an unusual documentation of the interactive
effects between grazing and major storm events on
small stream corridors in Utah and Nevada and a
description of the use of large scale color
infrared photography combined with ground truth
to spot problem riparian sites over large
rangeland areas.
cases it was noted that riparian ecosystems
(natural or artificial) can undergo drastic changes
in wildlife diversity over a relatively short time
due to economic factors associated with cropping
systems.
Several papers discussed ideas or
presented data related to xeroriparian ecosystems,
thereby elaborating on a concept developed by
Lowe (1961) and Johnson et al. (1984). The
extreme importance of these desert riparian
habitats to wildlife and the obligate riparian
nature of some of their othenvise facultative
riparian plant species are interesting features
of xeroriparian ecosystems.
There continue to be important gaps in our
knowledge of the basic biology of riparian plant
species and communities. No trend toward
rectification of this problem was detected during
the past week, as only a few presentations were
given in this area.
Interaction of flooding
regimes with successional processes of riparian
forests in New Mexico and Arizona and with
patterns of reproduction in Wright's sycamore
(~12~2E~~ wrlEhtlj) in southeastern Arizona were
discussed in separate papers. The major factors
affecting regeneration of a southeastern U.S.
hardwood forest riparian ecosystem (mature
cypress-tupelo) were described and the need to
consider these factors in management of floodplain
water levels was stressed. A preliminary study of
the annual phenological profiles of several plant
species growing in two riparian habitats of
southeastern Arizona was also reported.
Inclusion of an entire conference section on
riparian herpetofauna marked an important
departure from the three previous symposia
mentioned earlier which contained only one paper
that featured this topic (Brode and Bury 1984).
Lowe's suggestion that Arizona's obligate
riparian species of amphibians and reptiles be
accorded special status (e.g., "threatened") as
soon as possible dramatized the fact that little
time remains to save these populations before
most of their habitats are seriously modified or
lost.
Recent theoretical discussions of island
biogeography (e.g., Soule and Wilcox 1980,
Harris 1984) and the importance of riparian zones
to forest wildlife (e.g., Thomas 1979) have
created new interest in the potential benefits
to terrestrial wildlife of riparian buffer strips
left after timber harvest. This was reflected
in the discussion of ongoing experiments to
evaluate the effects of streamside riparian zones
of mixed conifer forests in Oregon and streamside
management zones ("stringers") in the pine
forests of eastern Texas. The benefits to
aquatic systems of riparian buffer strips have
been thoroughly described in the past. However,
an interesting paper by Heede discussed the
positive potential of tree fall from buffer zones
on the natural dam building tendencies of mountain
streams.
Several reports involving ecological surveys
were based on carefully controlled designs and
large data sets, thereby indicating the
continuing maturation of riparian ecology as a
science. Examples of these were the detailed
study by Knopf of relationships between riparian
and upland bird populations along an extensive
altitudinal transect in northeastern Colorado and
an investigation by Hunter et al. of avian
responses to salt cedar (Tamarix chinensis) in
three major southwestern IT:S-:---riverine--systems.
Both studies have important managerial
implications, the former with regard to altitude
as a factor in determining the value of riparian
zones to birds and the latter with respect to the
somewhat unpredictable interactions between major
riverine ecosystems and specific plant community
types in determining use of the latter by avian
species.
Two types of riparian ecosystems not
given much previous attention were emphasized at
Tucson in 1985:
those adjacent to or otherwise
dominated by cropland agriculture and those
subject to extreme aridity.
The effects of croplands on avian diversity in the riparian areas
of the lower Colorado River bordering Arizona
and California were discussed by Ohmart et al.
with respect to waterbirds, waders, and
shorebirds, and an interesting description was
given of a large Arizona pecan orchard as a
special type of riparian ecosystem.
In both
A trend toward increased efforts to model the
structure and function of riparian ecosystems was
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evident at the 1985 Tucson conference. This may
be partly a result of the development of riparian
data bases that make some modeling efforts
possible and partly due to the greatly increased
access to, and familiarity with, computerized
techniques that has occurred in the past five
years. However, the orientation of some of these
models towards planning and decision making also
suggests that riparian scientists are becoming
more cognizant of the need to integrate the
natural and social aspects of riparian ecosystem
management. Examples include the "second
generation" of simpler models devised by Ohmart
and colleagues that relate wildlife species to
vegetative parameters for use in mitigating
wildlife impacts through revegetation, Short's
description of habitat structure in terms. of
habitat layers to provide simple riparian
habitat impact prediction models, and the
watershed modeling of nutrient levels and effects
of riparian vegetation on water quality in the
southeastern United States. Additional modeling
efforts stressing aquatic components of natural
systems included an attempt to conceptualize the
effects of beavers on lower order streams and a
more detailed treatment of instream and riparian
cover in the prediction of trout biomass, both
in the context of Wyoming streams.
LITERATURE
CIT~D
Brode, J.M., and R.B. Bury. 1984. The
importance of riparian systems to amphibians
and reptiles. p. 30-36.
In R.E. Warner
and K.M. Hendrix (Ed.), Cali-fornia riparian
systems:
ecology, conservation, and
productive management.
[Based on proc. of
conf. at Davis, Calif., Sept. 17-19, 1981.J
1035 p. Univ. Calif. Press, Berkeley, Calif.
Harris, L.D. 1984. The fragmented forest island biogeography theory and the
preservation of biotic diversity.
211 p.
Univ. Chicago Press, Chicago, Ill.
Johnson, R.R., S.W. Carothers, and J.M. Simpson.
1984. A riparian classification system.
p. 375-382.
In R.E. Warner and K.M. Hendrix
(Ed.), Califor~ia riparian systems: ecology,
conservation, and productive management.
[Based on proc. of conf. at Davis, Calif.,
Sept. 17-19, 1981.J 1035 p. Univ. Calif.
Press, Berkeley, Calif.
Johnson, R.R., and D.A. Jones (Tech. Coord.).
1977. Importance, preservation and
management of riparian habitat: a symposium.
[Tucson, Ariz., July 9, 1977.J USDA For.
Servo Tech. Rep. RM-43, 217 p. Rocky Mt.
For. and Range Exper. Sta., Fort Collins,
Colo.
Johnson, R.R., and J.F. McCormick (Tech. Coord.).
1978. Strategies for protection and
management of floodplain wetlands and other
riparian ecosystems. [Proc. symp.,
Callaway Gardens, Ga., Dec. 11-13, 1978.J
USDA For. Servo Gen. Tech. Rep. WO-12,
410 p. USDA For. Serv., Wash., D.C.
The attempt of the conference to address
riparian issues throughout all of North America
was modestly successful and it was especially
good to have some descriptions of riparian
ecosystems in Mexico and Alaska. Discussions of
Canadian riparian ecosystems and issues were
conspicuously lacking. Perhaps a Second North
American Riparian Conference can be held that
will include more information on Canadian,
Mexican,and Central American riparian topics.
Lowe, C.H., Jr. 1961. Biotic communities in the
sub-Mogollon region of the inland southwest.
J. Ariz. Acad. Sci. 2(1): 40-49.
Soul~, M.E., and B.A. Wilcox (Ed.).
1980.
Conservation biology: an evolutionary ecological perspective.
395 p. Sinauer
Associates, Sunderland, Mass.
Thomas, J.W. (Tech. Ed.). 1979. Wildlife habitats
in managed forests - the Blue Mountains of
Oregon and Washington. USDA For. Servo
Agric. Handb. No. 553. USDA For. Servo in
coop. with Wildl. Manage. Inst. and USDI Bur.
Land Manage., Wash., D.C.
Warner, R.E., and K.M. Hendrix (Ed.). 1984.
California riparian systems:
ecology,
conservation, and productive management.
[Based on proc. of conf. at Davis, Calif.,
Sept. 17-19, 1981.J 1035 p. Univ. Calif.
Press, Berkeley, Calif.
Those of us who attended the First North
American Riparian Conference are greatly indebted
to its technical coordination committee and
especially to Roy Johnson who guided it from
inception to successful completion. Besides the
accomplishments of the formal program, this
conference provided an opportunity for Roy to
direct the formation of a "North American Riparian
Council. " Goals of the council are now being
formulated, a charter is being developed, and
alliances with other public and private
organizations that have riparian interests will
be sought. "Extracurricular" activities of this
sort, together with the establishment and reestablishment of personal contacts, are always
part of a successful conference and may in some
instances have more lasting impact than anyone
of the professional presentations.
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