In the mood for wood-habitat specific colonization patterns of benthic invertebrate communities along the longitudinal gradient of an Austrian river

Florian Dossi,Patrick Leitner,Steffen Pauls,Wolfram Graf

doi:10.1007/s10750-017-3307-z

Abstract

Instream large wood (LW) constitutes an indispensable element of natural river ecosystems. It affects local hydraulics, morphology, nutrient budget, overall habitat complexity, and dynamics. Despite numerous studies about LW as a habitat for benthic communities, information on the varying importance along the longitudinal gradient of a river is lacking. The focus of this study is therefore to investigate general differences between lithal and xylal colonizers and to further investigate trends along the river course. We analyzed lithal and xylal communities at ten sites along the medium-sized Lafnitz River in Southeast Austria. Our results significantly show (1) a general differentiation between lithal and xylal communities, (2) an increasing distinction of the lithal and xylal fauna along the longitudinal gradient of the river, and (3) a distinct correlation between the distance from source and the number of exclusive xylal and nowadays predominantly rare taxa. The presence of LW is therefore directly linked to higher aquatic biodiversity compared to rocky substrates and presents a unique element for river restoration, especially in lower river sections.

Highlights

Structural complexity, a key aspect in the maintenance of biodiversity and stability in ecosystems, is significantly affected by instream obstacles such as boulders and logs
The importance of large wood (LW) has mainly been studied in North America (e.g., Anderson et al, 1978; Harmon et al, 1986; Maser & Sedell, 1994; Abbe & Montgomery, 1996; Bilby & Bisson, 1998) as only few pristine river stretches with intact riparian vegetation and LW dynamics remain in Central Europe (Hering & Reich, 1997; Hering et al, 2000; Tockner et al, 2009)
189 benthic invertebrate taxa were identified at ten investigation sites along the river course

Summary

Introduction

Structural complexity, a key aspect in the maintenance of biodiversity and stability in ecosystems, is significantly affected by instream obstacles such as boulders and logs. LW affects the nutrient budget of a river (e.g., Bilby, 1981; Hering & Reich, 1997; Gurnell et al, 2005; Flores et al, 2011) and presents an important habitat structure that increases the density and diversity of fish and benthic invertebrate species in rivers and streams (e.g., Dudley & Anderson, 1982; Copp, 1992; Hoffmann & Hering, 2000; Pilotto et al, 2014, 2016). Submerged logs serve as important land–water interfaces and oviposition sites for merolimnic insects, thereby significantly affecting their reproductive success (Dudley & Anderson, 1982; Sweeney, 1993; Hoffmann & Hering, 2000). Information on the importance of LW for benthic invertebrate communities along the longitudinal gradient of a river is still lacking

Objectives

Methods

Results

Discussion

Conclusion