Longitudinal- and transverse-scale environmental influences on riparian vegetation across multiple levels of ecological organization
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Riparian vegetation is distinct from adjacent upland terrestrial vegetation and its distribution is affected by various environmental controls operating at the longitudinal scale (along the river) or transverse scale (perpendicular to the river). Although several studies have shown how the relative importance of transverse or longitudinal influences varies with the scale of observation, few have examined how the influences of the two scales vary with the level of ecological organization. We modeled vegetation-environment relationships at three hierarchically nested levels of ecological organization: species, plant community, and vegetation type. Our hierarchically structured analyses differentiated the spatial extent of riparian zones from adjacent upland vegetation, the distribution of plant community types within the riparian zone, and the distribution of plant species within community types. Longitudinal gradients associated with climate and elevation exerted stronger effects at the species level than at the community level. Transverse gradients related to lateral surface water flux and groundwater availability distinguished riparian and upland vegetation types, although longitudinal gradients of variation better predicted species composition within either riparian or upland communities. We concur with other studies of riparian landscape ecology that the relative predictive power of environmental controls for modeling patterns of biodiversity is confounded with the spatial extent of the study area and sampling scheme. A hierarchical approach to spatial modeling of vegetation-environment relationships will yield substantial insights on riparian landscape patterns.
KeywordsGradient analysis Scale Hierarchy Great Basin Riparian vegetation Ordination Random Forests
Funding for Jian Yang, Thomas Dilts, and Peter Weisberg was provided by the U.S. Bureau of Reclamation (Cooperative Agreement 06FC204044). Funding for Otis Bay Ecological Consultants was provided through the USFWS—Lahontan National Fish Hatchery Complex using Desert Terminal Lakes Funds (Public Law 109-103, Sect. 208(c) administered through the BOR). LiDAR was provided by the USFWS—Lahontan National Fish Hatchery Complex using Desert Terminal Lakes Funds (Public Law 109-103, Sect. 208(c) administered through the BOR). Stephanie Kilburn, Gina Jones, Shwetha Bayya, Randy Goetz, Serena Rogers and Kurt Sable at Otis Bay Ecological Consultants provided assistance in the field or in the office. Blake Engelhardt, Joy Giffin, Dr. Jianguo (Jingle) Wu, and two anonymous reviewers provided comments on earlier drafts.
- Chambers JC, Tausch RJ, Korfmacher JL, Germanoski D, Miller JR, Jewett D (2004) Effects of geomorphic processes and hydrologic regimes on riparian vegetation. In: Chambers JC, Miller JR (eds) Great Basin riparian ecosystems: ecology, management and restoration. Island Press, Covelo, CA, pp 196–231Google Scholar
- Dufrène M, Legendre P (1997) Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecol Monogr 67:345–366Google Scholar
- Franklin J, McCullough P, Gray C (2000) Terrain variables used for predictive mapping of vegetation communities in Southern California. In: Wilson J, Gallant J (eds) Terrain analysis: principles and applications. Wiley & Sons, New York, US, pp 331–353Google Scholar
- Friedman JM, Auble GT, Andrews ED, Kittel G, Madole RF, Griffin ER, Allred TM (2006) Transverse and longitudinal variation in woody riparian vegetation along a montane river. West North Am Nat 66:79–91Google Scholar
- Hill MO (1979) TWINSPAN: a FORTRAN program for arranging multivariate data in an ordered two-way table by classification of the individuals and attributes. Cornell University, Section of Ecology and Systematics, Ithaca, NY, USGoogle Scholar
- Junk JW, Bayley PB, Sparks RE (1989) The flood pulse concept in river floodplain systems. Canad Spec Publ Fish Aquat Sci 106:110–127Google Scholar
- McCune B, Mefford MJ (1999) PC-ORD: multivariate analysis of ecological data; Version 4 for Windows; User’s Guide. MjM Software DesignGoogle Scholar
- Reed PB (1988) National list of vascular plant species that occur in wetlands. US Fish and Wildlife Service, Washington, DC, USA. Biological report 88:24Google Scholar
- Turner MG, Gergel SE, Dixon MD, Miller JR, Woods K (2004) Distribution and abundance of trees in floodplain forests of the Wisconsin River: environmental influences at different scales. J Veg Sci 15:729–738Google Scholar
- United States Fish Wildlife Service, prepared by Otis Bay Ecological Consultants (2009) Walker river biophysical assessment. Lahontan NHF Complex, Reno, NVGoogle Scholar
- Urban D, Goslee S, Pierce K, Lookingbill T (2002) Extending community ecology to landscapes. Ecoscience 9:200–212Google Scholar