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Title: The Distribution and Composition of Woody Species in Riparian Forests along the Middle Sacramento River, California |
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Abstract/Description: Riparian forest is a dynamic vegetation type that is shaped by river processes. Channel movement and
sediment deposition initiate a succession sequence that is comprised of several different types of plant
communities (Thompson 1961, Holstein 1984, Katibah 1984, Strahan 1984, Cepello 1991, Chapin et al.
2002). Specifically, plant ecologists recognize four major forest-types of woody riparian vegetation in
upland (as opposed to permanent wetland) habitats in the Central Valley of California such as along the
Sacramento River (Holland 1986, Sawyer and Keeler-Wolf 1995): willow scrub, on newly created sand
and gravel bars; willow-cottonwood forest; mixed riparian forest, and valley oak-elderberry forest.
These four community types are generally thought to occur along a succession sequence, with the main
driving variable of change being continued floodplain accretion and consequent elevation increase
(Nanson and Beach 1977, Cepello 1991, Peterson 2002). Increased elevation above the river level
results in greater drought stress for plants, and thus the community type changes as species better
adapted to summer-dry conditions gain a competitive advantage. However, it has not been well
documented that Sacramento River riparian vegetation always changes according to the succession
sequence outlined above. It is possible that other pathways exist along the Sacramento River (McCune
and Allen 1985, Peterson 2002). Even if the hypothesized succession sequence is correct, the rate of
community change is not known. In order to effectively plan, conservation managers need to know how
much of a given community is being created under the current management regime and determine
whether this differs from what would take place in an unregulated setting. For example, if natural
succession processes are constrained due to river regulation such that little new valley oak forest is
being created from existing mixed riparian forest, managers might seek to find ways to accelerate the
transition to valley oak from mixed riparian or other earlier succession stages.
Few studies of riparian forest chronosequences along the Sacramento River have used field-based
quantitative sampling (exceptions are Strahan 1984, Cepello 1991, A. Fremier, unpublished, and M.
Vaghti, unpublished). Most recent work on riparian vegetation along the Sacramento River used remote
sensing techniques such as air photo interpretation (Greco 1999, Nelson 2002). Whereas remote sensing
techniques excel in their geographic extent, they generally are poor in obtaining detailed data on such
ecological parameters as understory species composition and tree size, density and age. This latter type
of data comes best from field studies. For example, an overstory of Fremont cottonwood forest with an
understory of fig, black walnut and tree-of-heaven saplings is not a healthy forest condition by many
standards due its high potential for becoming a forest dominated by non-native species, but this
unhealthy condition would not be recognized as such by existing remote sensing. Thus, a combination
of extensive remote-sensed geographic data with intensive field data will be the most productive course
of study for obtaining information on actual riparian forest community composition.
The goals of this study are to: (1) quantify the distribution of previously mapped plant communities as a
function of river subreach and to determine if there is a difference in plant community distribution
among reaches. Such a difference among subreaches, if it exists, might arise from such factors as land
use history, hydro-geomorphic attributes of the river (Singer and Dunne 2001) or the effect of
tributaries. Tributaries tend to add species more typical of upland or foothill habitats to bottomland
forests at the confluence with the mainstem from downstream dispersal of propagules. Thus the
community composition around a confluence can be slightly different than at sites away from
confluences (examples of species here are California buckeye (Aesculus californica), hop tree (Ptelea
trifoliata), white alder (Alnus rhombifolia), and additional willows (Salix spp.; T Griggs, pers. comm.; D
Wood, pers. obs); (2) inventory remnant riparian forests of different community types (as mapped by the
GIC) along the middle Sacramento River to document species composition and age; (3) formulate
hypotheses as to the timing of invasion of undesirable species; and (4) establish a well-documented,
baseline set of forest conditions against which to measure future changes and trends in succession.
Associated Projects:
Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Non-Aeration Feasibility Studies Criteria Evaluation for the San Joaquin River Dissolved Oxygen TMDL, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Non-Aeration Feasibility Studies Criteria Evaluation for the San Joaquin River Dissolved Oxygen TMDL, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Non-Aeration Feasibility Studies Criteria Evaluation for the San Joaquin River Dissolved Oxygen TMDL, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Peer Review of San Joaquin River Dissolved Oxygen TMDL Studies, Non-Aeration Feasibility Studies Criteria Evaluation for the San Joaquin River Dissolved Oxygen TMDL
Main Subjects:
Habitat / Species
Specific Subjects:
plants
Species Keywords:
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| Publication & Citation |
Author(s):
David Wood
Contributor(s):
Mike Roberts
Citation:
Wood, D.M. 2003. The distribution and composition of woody species in riparian forests along the middle Sacramento River, California. Report to The Nature Conservancy. Available at http://www.sacramentoriverportal.org
Publisher:
The Nature Conservancy
Publication Date:
December
31,
2002
Currentness:
Funder(s):
The Nature Conservancy,
CALFED
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| Format & Access |
Information Resource Type:
(Documents)
Media Type / Format:
Computer File
Access Limitations:
Public
Use Limitations:
No Limitations
To Obtain:
Open/Download (off-site link)
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| Location Information |
Cities / Urban Areas:
Counties:
Specific Location Names:
Undefined:
Water / Special Districts:
Watershed / Streams:
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First Entered by:
Greg Golet on 2003/10/08
Last Edited by:
Greg Golet on 2003/10/08
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