Provided for non-commercial research and educational use only. Not for reproduction, distribution or commercial use. This chapter was originally published in the Treatise on Geomorphology, the copy attached is provided by Elsevier for the author’s benefit and for the benefit of the author’s institution, for non-commercial research and educational use. This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier’s permissions site at: http://www.elsevier.com/locate/permissionusematerial Bendix J., and Stella J.C. Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective. In: John F. Shroder (Editor-in-chief), Butler, D.R., and Hupp, C.R. (Volume Editors). Treatise on Geomorphology, Vol 12, Ecogeomorphology, San Diego: Academic Press; 2013. p. 53-74. © 2013 Elsevier Inc. All rights reserved. 12.5 Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective J Bendix, Syracuse University, Syracuse, NY, USA JC Stella, State University of New York College of Environmental Science and Forestry, Syracuse, NY, USA r 2013 Elsevier Inc. All rights reserved. 12.5.1 Introduction 53 12.5.2 Early History: Pattern and Process in Riparian Zones 54 12.5.3 Influence of Hydrogeomorphology on Vegetation: Evolution from Descriptive to Quantitative Studies 55 12.5.4 Specific Mechanisms of Hydrogeomorphic Impact 56 12.5.4.1 Flood Energy 56 12.5.4.2 Sedimentation 56 12.5.4.3 Prolonged Inundation 57 12.5.4.4 Water-Table Depth and Dynamics 57 12.5.4.5 Soil Chemistry 58 12.5.4.6 Propagule Dispersal 58 12.5.5 Influence of Vegetation on Geomorphology 59 12.5.6 Feedbacks between Vegetation and Hydrogeomorphology 60 12.5.7 Patterns in Published Literature 62 12.5.7.1 The Sample and Coding 63 12.5.7.2 General Characteristics of the Sampled Literature 64 12.5.7.3 Differences among Biomes 65 12.5.7.4 Scale-Related Differences 66 12.5.7.5 Hydrogeomorphic Mechanisms in the Context of Scale and Biogeography 67 12.5.8 Patterns and Perceptions Revealed in the Literature 68 References 69 Abbreviations LWD Large woody debris CHILD Channel–hillslope integrated landscape TN Total nitrogen development TOC Total organic carbon Abstract In this chapter, we review the historical arc of research on biogeomorphic interactions between fuvial geomorphology and riparian vegetation. We then report on an examination of the past 20 years of published research on this topic. Having classifed studies according to the key relationships they have identifed, we map those relationships to seek spatial patterns that emerge in terms of either physiographic environment or actual geographic location. We also consider the varied patterns of causal interactions that emerge at different spatial scales. 12.5.1 Introduction understanding of the linked physical and biotic processes that sustain them (Osterkamp and Hupp, 1984; Gregory et al., The recognition of riparian zones as biogeomorphic units in 1991; Naiman and Decamps, 1997; Naiman et al., 2005). For the landscape is critical both for theoretical understanding and much of this time, emphasis was placed on the importance of for conservation of these high-value habitats. Since the middle understanding hydrogeomorphic infuences on riparian vege- of the twentieth century, study of the systematic patterns of tation, because fuvial forces set the physical template for vegetation communities in riparian zones has led to a greater ecological communities. Recently, there has been greater study of the reciprocal infuence of biological organisms and pro- cesses on geomorphic processes, leading to a biogeomorphic Bendix, J., Stella, J.C., 2013. Riparian vegetation and the fuvial understanding of fuvial/riparian ecosystems (Corenblit et al., environment: a biogeographic perspective. In: Shroder, J. (Editor in Chief), Butler, D.R., Hupp, C.R. (Eds.), Treatise on Geomorphology. Academic 2007). This view recognizes the substantial infuence Press, San Diego, CA, vol. 12, Ecogeomorphology, pp. 53–74. that vegetation pattern and structure can have in altering the Treatise on Geomorphology, Volume 12 http://dx.doi.org/10.1016/B978-0-12-374739-6.00322-5 53 Author's personal copy 54 Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective distribution of physical forces of fow and sediment regimes, conclusions about drivers, responses, and landscape patterns which ultimately create feedbacks to biological communities in riparian vegetation communities? In which biomes and at and ecosystems (Bendix and Hupp, 2000). what scales is the direction of infuence primarily from the Early work relating riparian ecology to fuvial processes was physical to the biotic, the reverse, or one of strongly linked primarily descriptive in nature, with a common thread being feedbacks? How does the biome or geographic setting infu- the classifcation of riparian vegetation communities and their ence the relative strength of ecosystem drivers, including dis- association with particular fuvial landforms, or even simply turbance regimes (fooding, scour, and sediment deposition), particular vertical locations relative to stream channels. These abiotic stress (e.g., seasonal drought), soil chemistry, and/or studies were generally place- and taxa-specifc. The develop- limitations on life-history processes such as propagule ment of geomorphology as a more quantitative science since dispersal? the middle of the last century (e.g., Leopold and Maddock, We believe that a biogeomorphic approach is necessary for 1953; Leopold et al., 1964) laid the basis for more generality a legitimate understanding of either fuvial processes or the and a common biogeomorphic process approach to the study ecology of the riparian zone. The large volume of relevant of rivers and riparian zones (Osterkamp and Hupp, 2010). empirical research since several landmark papers in the 1980s Examples of this work include the hydraulic geometry ap- and early 1990s (e.g., Osterkamp and Hupp, 1984; Hupp and proach (Leopold and Maddock, 1953), process-based classi- Osterkamp, 1985; Gregory et al., 1991) suggests the need to go fcation of river environments (Montgomery and Buffngton, beyond a catalog-style review to a more analytical approach to 1997), and quantifcations of interactions between sediment understanding the complex relationships between the eco- transport capacity and supply across a wide range of spatial logical and geomorphic elements of the riparian environment. and temporal scales (e.g., Howard et al., 1994). We therefore seek to examine the literature on the interactions However, much of the early work was conducted on North between riparian plant communities and fuvial landforms/ American streams, with particular ecological communities and processes, within a bipartite, spatially oriented framework that physical regimes infuencing a great deal of the development emphasizes how biogeomorphic interactions between riparian in early theories and empirical examples. The histories of both vegetation and fuvial geomorphology vary with both geog- geomorphology and ecology include reminders of the danger raphy and the scale of observation. of generalizing theories across dissimilar environments. Cri- In this chapter, we begin with a condensed review of the tiques of the roles of William Morris Davis in the former historical arc of research on the varied fuvial impacts on discipline and of Frederick C Clements in the latter have noted vegetation, the means whereby vegetation infuences fuvial that theoretical models developed in distinctive geographic geomorphology, and the feedbacks between the two. The bulk settings did not translate appropriately when imposed else- of that research has been on the specifc mechanisms of where. In a recent example, studies by Walter and Merritts hydrogeomorphic infuence on riparian plant communities; (2008) in eastern North America suggest that the geomorphic therefore, these mechanisms receive particular emphasis in context in the region where much of the early hydraulic our review. We then report on an examination of the past 20 geometry research (e.g., Leopold and Maddock, 1953)was years of published research on this topic. Having classifed conducted may have been in disequilibrium due to historical studies according to the key relationships they have identifed, human infuences (i.e., mill dams). These well-known ex- we map both the causal directions and the mechanisms to amples serve as reminders that processes and relationships seek spatial patterns that emerge in terms of either physio- vary spatially. In particular, the very different environmental graphic environment or actual geographic location. We also conditions and vegetation structure occurring in different consider the varied patterns of causal interactions that may biomes suggest that plant adaptations to hydrogeomorphic emerge at different spatial scales. constraints, and the subsequent infuence of vegetation on fuvial processes, may vary widely from one setting to another. Another spatial complication arises when we consider the 12.5.2 Early History: Pattern and Process in scale at which biogeomorphic relationships are observed. A Riparian Zones