Preface: Multiscale Feedbacks in Ecogeomorphology

Abstract

1. IntroductionGeomorphic systems are known to exhibit nonlinear responses tophysical–biological feedbacks (Thornes, 1985; Baas, 2002; Reinhardtet al., 2010). These responses make understanding and/or predictingsystem response to change highly challenging. With growingconcerns over ecosystem health, a pressing need exists for researchthat tries to elucidate these feedbacks (Jerolmack, 2008; Darby, 2010;National Research Council, 2010). A session was convened at the Fall2008 meeting of the American Geophysical Union (AGU) to providean outlet for some of this truly interdisciplinary and original research,which is central to understanding geomorphic and ecologicaldynamics. The session attracted over 39 contributions, which weredivided into two well-attended oral sessions and a very busy postersession.This special issue presents new research from the AGU session,which highlights clear physical–biological feedbacks. The aim is tobring together contrasting perspectives on biological and geomorphicfeedbacks in a diversity of physiographic settings, ranging fromwetlands and estuaries, through rivers, to uplands. These papershighlight biological and physical feedbacks which involve themodulation or amplification of geomorphic processes. These paperswill be of interest to a core geomorphology audience, and should alsodraw attention from the fields of ecohydraulics, hydroecology,ecohydrology, ecomorphology, biogeochemistry and biogeography,and biogeomorphology as well as the more traditional fields ofhydrology, ecology and biology.In this preface to the special issue, we a) review past contributionsto the emerging field of ecogeomorphology and related disciplines, b)provide some context for how this topical special issue came tofruition, and c) summarize the contributions to this special issue.2. What is ecogeomorphology?Examples of studies explicitly integrating ecology and geomor-phology date back to at least the late 1800s (e.g. Cowles, 1899), withmore examples appearing in the 1950s (e.g. Olson, 1958) and 1960s(e.g. Hack and Goodlet, 1960). Terms such as ecogeomorphology andbiogeomorphologyonlybecamepopularinthe1990s(OsterkampandHupp, 2010). The 1990 British Geomorphology Research GroupAnnual Meeting (Thornes, 1990) and the 1995 Binghamton Sympo-sium on Biogeomorphology (Hupp et al., 1995b) were two of the firstsymposiums to emphasize the theme of biogeomorphology. Ecogeo-morphology and biogeomorphology are generally considered syno-nyms (Hupp et al., 1995a), but they do sprout from slightly differentresearch interests. Both are part of a larger family of terms thatresearchers have used somewhat inconsistently to describe researchat the interface between some combination of hydrology, geomor-phologyand/orecology/biology(Fig.1).Unlikesomeoftheothereco-geo-hydro combinations in Fig. 1, the eco- or bio-root is an adjectivemodifying the noun geomorphology. Based on the types of researchpublished under these two banners, the biogeomorphology commu-nity has generally focused more on how chemical and physicalweathering are amplified and modulated with biological feedbacks;ecogeomorphology is commonly used to describe studies that focusmore on the amplification and modulation of erosion and depositionprocesses. Both are fundamentally concerned with the bidirectionalinfluences of biota and landscapes on each other. Biogeomorphologyis concerned with both the influence of landforms on plants, animalsand micro-organisms distribution and development; as well as theinfluence of those plants, animals and micro-organisms on earthsurfaceprocessesandthelandformsshapedbythoseprocesses(Viles,1988). Naylor et al. (2002: p. 4) loosely define biogeomorphology asinvolving ‘the cooperation between ecology and geomorphology’ tostudy two-way linkages between ecological and geomorphologicalprocesses. Murray et al. (2008) argue that biomorphodynamics is amore restrictive term than biogeomorphology or ecogeomorphology,and that it highlights landscape dynamics in which an explicit twoway coupling (i.e. feedback) occurs between biotic and physicalprocesses.Therelatedzoogeomorphology(e.g. Butler,1995)termhasreceived less play, but it is worth mentioning that research under thisbanner focuses on examples of animals influencing geomorphicprocesses and landforms (e.g. beaver, salmon, burrowing animals,etc.).The term biogeomorphology has been more widely used sinceViles (1988) first attempted to provide a comprehensive overview ofwhat was, at that time, an emerging discipline. A review of Web of