Using Rushes and Sedges in Revegetation of Wetland Areas in the South West of Wa
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Using rushes and sedges in revegetation of wetland areas in the south west of WA February 2001 WATER AND RIVERS Report No. RR 8 river restoration COMMISSION WATER & RIVERS COMMISSION Hyatt Centre 3 Plain Street East Perth Western Australia 6004 Telephone (08) 9278 0300 Facsimile (08) 9278 0301 We welcome your feedback A publication feedback form can be found at the back of this publication, or online at http://www.wrc.wa.gov.au/public/feedback USING RUSHES AND SEDGES IN REVEGETATION OF WETLAND AREAS IN THE SOUTH WEST OF WA Prepared by Linda Taman Jointly funded by WATER AND RIVERS COMMISSION WATER & RIVERS COMMISSION REPORT NO. RR 8 FEBRUARY 2001 Water and Rivers Commission Waterways WA Program. Managing and enhancing our waterways for the future Acknowledgments This document was prepared by Linda Taman. This document has been jointly funded by the Natural Heritage Trust and the Water and Rivers Commission. Illustrations by Ian Dickinson. Reviewed by Dr Jenny Davis, Murdoch University, Dr River Restoration series co-ordinated by Heidi Bucktin Peter Davies, University of Western Australia and Dr and Virginia Shotter, Water and Rivers Commission. Luke Pen, Water and Rivers Commission. Reference Details The recommended reference for this publication is: Water and Rivers Commission 2000, Using rushes and sedges in revegtation of wetland areas in the south west of WA, Water and Rivers Commission, River Restoration Report No. RR 8 ISBN 1-9-209-4708-6 [PDF] ISSN 1449-5147 [PDF] Text printed on recycled stock, February 2001 i Water and Rivers Commission Waterways WA Program. Managing and enhancing our waterways for the future Foreword Many Western Australian rivers are becoming degraded The Water and Rivers Commission is the lead agency for as a result of human activity within and along waterways the Waterways WA Program, which is aimed at the and through the off-site effects of catchment land uses. protection and enhancement of Western Australia’s The erosion of foreshores and invasion of weeds and waterways through support for on-ground action. One of feral animals are some of the more pressing problems. these support functions is the development of river Water quality in our rivers is declining with many restoration literature that will assist Local Government, carrying excessive loads of nutrients and sediment and community groups and landholders to restore, protect in some cases contaminated with synthetic chemicals and manage waterways. and other pollutants. Many rivers in the south-west This document is part of an ongoing series of river region are also becoming increasingly saline. restoration literature aimed at providing a guide to the The Water and Rivers Commission is responsible for nature, rehabilitation and long-term management of coordinating the management of the State’s waterways. waterways in Western Australia. It is intended that the Given that Western Australia has some 208 major rivers series will undergo continuous development and review. with a combined length of over 25 000 km, management As part of this process any feedback on the series is can only be achieved through the development of welcomed and may be directed to the Catchment and partnerships between business, landowners, community Waterways Management Branch of the Water and Rivers groups, local governments and the Western Australian Commission. and Commonwealth Governments. ii Water and Rivers Commission Waterways WA Program. Managing and enhancing our waterways for the future Using rushes and sedges in revegetation of wetland areas of the south west of WA Introducing rushes and sedges Botanically, rushes are members of the Juncaceae family, while sedges are members of the Cyperaceae While many people are familiar with the trees, shrubs family. Unfortunately the common names are very and herbaceous plants of their area, few are familiar with confusing, with many members of the Cyperaceae the rushes and sedges. Many of the species look similar commonly called rushes. The Typhaceae family is a to the untrained eye, and are easily confused with weed small family but extremely common, and these plants species. are often called Bulrushes. This manual section will deal with the common rushes, sedges and bulrushes of the Rushes and sedges form an extremely important south west of Western Australia, and their use in component of wetlands, rivers and estuaries of the wetland, river and estuary restoration. There are few coastal areas of the south west. They provide food and reference books available to assist with identification of habitat for a wide range of aquatic species, assist with these species. However there are two publications by the aeration of the sediments and filter and bind pollutants, Water and Rivers Commission and Department of particularly nutrients, that enter the ecosystem. In Conservation and Land Management in Perth, Native addition they are often found at the land-water interface, Vegetation of Freshwater Rivers and Creeks in South and play an important role in stabilizing the banks. The Western Australia (1997), and Native Vegetation of root mass binds the soil, while the many stems reduce Estuaries and Saline Waterways in South Western the impact of wave action or fast-flows at the water’s Australia (1997), and a book produced in New South edge. Wales by Geoff Sainty et al (1994) (Waterplants in Rushes and sedges reproduce by seed, but many species Australia: A Field Guide) which are quite useful. set little viable seed and extend their range by forming The other similar family of sedge-like plants is the large clonal colonies through underground spread of Restionaceae, or Southern Rushes, many of which are rhizomes. Some species produce a high percentage of dryland plants. This large and diverse group are not viable seed, but the seed has a complicated dormancy described in this section, but a new publication by pattern which may require many years of weathering to Meney and Pate (1999), Australian Rushes, will assist in break. Fortunately many of the species which are identifying these species. difficult to grow from seed are readily propagated from tissue culture or division of rhizomes. Tissue culture Wetland zones involves the extraction of embryos from viable seed and the production of seedlings grown in sterile media Rushes and sedges have specific hydrological within the laboratory. requirements. The areas in which they will grow are determined largely by the minimum and maximum water Many of the rushes and sedges spend much of their life levels. Very few of these plants are adapted to a static with their roots submerged, and in order to survive, have water level, as the wetlands, rivers and estuaries of the developed air-filled cells within their root systems, southwest of Western Australia generally have a large called aerenchyma. This allows the plants to draw fluctuation in water level from winter to summer. oxygen down into their rhizomes, from where it may Although stream and river systems vary considerably, diffuse into the sediments. Many microbial organisms the following hydrological zones for rushes, sedges and which break down organic matter depend on well other aquatic plants can be defined along most oxygenated sediments to survive. Thus many rushes and watercourses. sedges promote removal of nutrients from waterbodies through the creation of habitat for suitable bacteria and fungi, as well as by the nutrients they take up in order to grow. iii Water and Rivers Commission Waterways WA Program. Managing and enhancing our waterways for the future • Submergent zone edges. It is also the most important area for erosion control, as this is the area in which most erosion This zone has surface water for a good proportion of occurs, and also the most important for nutrient and the year. Submergent plants grow beneath the water sediment removal. surface, although their leaves may float on the surface, • Damp zone and the flowering spikes may extend above the water. Many submergent species may live comfortably as The damp zone, as its name suggests, is permanently terrestrial plants as the water drops, or may become damp or damp near the surface for most of the year, dormant until water levels rise again. There are a without having standing water, except for flood range of plant families which live as submergents, but events. Almost all of the rushes and sedges can live they do not include any of the rushes and sedges. The happily in this zone. The damp zone often extends for plants in this zone provide aquatic habitat, stabilise the a large distance across the floodplain. It is very stream bed, slow water flow, assist in nutrient removal important as a filtering zone for surface runoff and help to cool the water surface by shading. entering the system, as sediment and debris settle out while water passes through this zone. In flood events • Emergent zone the dense vegetation prevents erosion, and provides habitat for a wide range of fauna, particularly birdlife. The emergent zone supports plants which have their roots submerged beneath the water for at least some of • Ephemeral zone the year, but extend their leaves and stems above the water surface. This area can range from 1m deep in This zone is quite dry for much of the year, and may winter to damp in the driest part of summer. Many only become wet in flood events. It is the interface species from the Cyperaceae and Typhaceae families between the bushland and the riparian zone. There are live in this zone, as well as one species from the a few hardy species of rush and sedge which will live Juncaeae. in this zone, members of the Cyperaceae and Juncaceae families. This zone is extremely important for many fauna species, providing shelter and food along the shallow Exceptional flood level Typical high water level Ephemeral zone Damp zone Typical low water level Emergent zone-upper Emergent zone- lower Submergent zone Figure 1: Wetland zones and typical distribution of some sedge and rush species.