The Role of Trees in Sustainable Agriculture: Review papers presented at the Australian Conference, The Role of Trees in Sustainable Agriculture, Albury, Victoria, Australia, October 1991

192 Pages·1993·5.21 MB·English

by  N. J. Schofield (auth.)

THE ROLE OF TREES IN SUSTAINABLE AGRICULTURE
FORESTRY SCIENCES
Volume 43
The titles published in this series are listed at the end of this volume.
The Role of Trees in
Sustainable Agriculture
Review papers presented at the Australian Conference,
The Role of Trees in Sustainable Agriculture,
Albury, Victoria, Australia, October 1991
Edited by
ROSLY N TAMARA PRINS LEY
Manager, Research and Strategy,
Rural Industries Research and Development
Corporation, Canberra, Australia
Compiled by
JAMIE ALLNUTT
Reprinted from Agroforestry Systems, Volume 20, Nos. 1-2 (1992)
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
Library of Congress Cataloging-in-Publication Data
Australian Conference, the Role of Trees in Sustalnable Agrieulture
(1991 Albury, N.S.W.)
The role of trees in sustalnable agrleulture review papers
presentea at the Australian Conferenee, the Role of Trees in
Sustainable Agrieulture, Albury, Vietorla, Australia, Oetober 1991 /
edited by Roslyn Tamara Prinsley ; eompiled by Jamie Allnutt.
p. em. -- (Forestry seiences ; v. 43)
ISBN 978-94-010-4809-5 ISBN 978-94-011-1832-3 (eBook)
DOI 10.1007/978-94-011-1832-3
1. Agroforestry--Australia--Congresses. 2. Tree crops--Australia
-Congres5es. 3. Sustainable agrieulture--Austral ia--Congre5ses.
1. Prinsley, Roslyn Tamara. Ir. Allnutt, Jamle. IIr. Title.
IV. Series.
S494.5.A45A92 1991
634.9·9'0994--dc20 92-36592
ISBN 978-94-010-4809-5
Printed on acid-free paper
All Rights Reserved
© 1993 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 1993
Softcover reprint of the hardcover 1s t edition 1993
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any mcans, elcctronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
Table of Contents
Preface Vll
N. J. Schofield: Tree planting for dryland salinity control in Australia 1
A. Boutland, M. Robinson, J. Field, M. Scheltema, B. Hawkins, P.
Bulman, J. Scarvelis, B. Mason, M. Wallace, M. Castley, P. A.
Ryan, R. T. Henderson, G. B. Applegate, C. Lansdown and R.
Reid: Alternative products from trees and shrubs to 'The Role of
Trees in Sustainable Agriculture' conference, Albury, September
30th - October 3rd 1991 25
P. R. Bird, D. Bicknell, P. A. Bulman, S. J. A. Burke, J. F. Leys, J. N.
Parker, F. J. van der Sommen and P. Voller: The role of shelter in
Australia for protecting soils, plants and livestock 59
R. Prinsley: The role of trees in sustainable agriculture - an overview 87
E. C. Lefroy, P. R. Dann, J. H. Wildin, R. N. Wesley-Smith and A. A.
McGowan: Trees and shrubs as sources of fodder in Australia 117
J.C. Scanlan, R. Prinsley, J. P. Pigott, S. Wakefield, F. van der
Sommen, F. Duncan, T. Stadler, R. McLellan and A. Farago:
Retention of native woody vegetation on farms in Australia:
management considerations, planning guidelines and information
gaps 141
R. Moore: Integrating wood production into Australian farming
systems 167
v
The Conference Organising Committee is grateful to the following
sponsors:
Rural Industries Research and Development Corporation
National Afforestation Program
Australian Newsprint Mills (ANM, Albury)
Greening Australia
Bureau of Rural Resources
Treecrops
Sure Gro (Cheltenham, Victoria)
vi
Agroforestry Systems 20: vii, 1992.
Preface
Agroforestry has the potential to become a widespread from of land use,
changing and improving the sustainability and profitability of agriculture and
forestry. Trees are used on farms for shelter, shade, production of timber,
fodder and other products, and for conservation of biodiversity and soil.
Trees can be used simultaneously for all of these benefits. Uses of trees on
farms will vary depending on the particular farm's physical environment, the
farmer's economic and other aims and relevant Government policies.
Thus, agroforestry, unlike many other rural industries, is a multi-faceted,
multi-purpose land use. In the wet temperate zones of Australia, it is more
likely to refer to commercial timber production from trees which are
integrated with the farm in some way, such as timberbelts. However, in
rangelands, in the semi-arid zone, it may mean the use of saltbush for fodder.
In many cases, agroforestry may have no direct product such as timber
associated with it, but rather the trees may be used, for example, to lower
watertables in order to prevent salinisation or to act as wildlife corridors.
In many parts of Australia the benefits of trees on farms are not well
understood, and agroforestry as a land use is very much in its infancy. For
any land use to expand successfully, appropriatc research and development is
necessary.
Agroforestry research and development in Australia has been largely
fragmented and many of the research results have never been published and
are unknown. The purpose of this volume is to comprehensively review all of
the research that has taken place in the field of agroforestry in Australia
including previously unpublished results, providing readers with the latest
technical and economic information about using trees in agriculture for
controlling salinity and erosion, for shelter and shade, and for production of
timber, fodder and minor forest products. The chapters in the book provide
information concerning planted trees within all of these categories and
include a special review of the management of native vegetation on farms.
These papers also examine research needs where appropriate.
This book stems from the National Australian Conference on 'The Role of
Trees in Sustainable Agriculture' which took place in Albury, Victoria,
Australia in October 1991. Each national review paper is based upon a
summary of six or more state review papers of research and development
prepared specifically for the national conference. The book thus provides
readers with a comprehensive overview of agroforestry research in Australia
which is introduced and summarised in the first chapter.
Roslyn Tamara Prinsley
AgroforestrySystems 20: 1-23, 1992.
© 1992 Kluwer Academic Publishers.
Tree planting for dryland salinity control in Australia
N. J. SCHOFIELD
Western Australian Water Resources Council, PO Box 100, Leederville, Western Australia 6007
Key words: salinity, salinisation, dryland salinity, irrigation salinity, tree, reforestation, planta
tion, agroforestry, water, water table, groundwater, social, political, economic, financial
Abstract. Dryland salinity is emerging as a major form of land and water degradation in
southern Australia, particularly in Western Australia, South Australia and Victoria, and to a
lesser extent in New South Wales, Tasmania and Queensland.
Tree planting, in combination with other vegetation treatments, is regarded as a leading
solution to dryland salinity. Research has now shown that planting trees can significantly lower
groundwater tables, and thereby reverse the causal process of salinisation. Substantial progress
has been made towards answering the basic questions of which species to grow, how to plant,
where to plant, at what density and configuration to plant, and how much area to plant. The
economic potential for commercial tree planting has given impetus to partial reforestation in
higher rainfall (> 600 mm yc1) areas. Even so, serious constraints are apparent, relating
primarily to cost, uncertainty and attitude. The future should bring increasing community
input and control, technical refinement and gradual adoption, provided all aspects of the issue
are well researched, relevant information is well communicated and programmes are well
administered. Some specific requirements for future research are identified in this review.
1. Introduction
Secondary or man-induced salinisation is of growing concern in southern
Australia and in limited areas of northern Australia. This concern arises
because salinity usually decreases the productive potential of the land,
decreases the water resources available for consumption, and degrades the
ecological values of wetlands, rivers and their associated habitats.
Secondary salinisation is a by-product of replacing native vegetation with
dryland agriculture or irrigated agriculture. Observations of salinisation
following clearing of native vegetation go back to the turn of the century and
earlier [65]. However, it is only in relatively recent times that the community
has begun to respond seriously to this slowly emerging problem. Even now
there is a good deal of scepticism about whether salinisation can and need be
controlled.
Considerable progress has been made toward understanding the mecha
nisms of salinisation and determining solutions [e.g. 28, 35, 54, 55]. This
research has led to the increasing acceptance of tree planting (in combination
with other vegetation measures) as a preferred option for control of dryland
salinity and as having a potential role in controlling irrigation salinity [26].
2
However there still remains a lack of information, uncertainty and difference
of opinions on basic questions such as: which species to plant, where to
locate plantings, at what densities to plant, and how much area to plant. This
situation has contributed to the reticence of some governments and commu
nities to act.
Perhaps over-riding all the technical uncertainties has been the question of
cost and benefit. Sustainable rehabilitation can be expensive, and the benefits
are not always substantial or immediate in financial terms. A commonly
expressed difficulty is the concept of replanting prime agricultural land to
trees to restore downslope salinised areas, or at least to control the spread of
salinisation. Unless the planted trees have high value and can be harvested,
or it can be demonstrated that the land to be reforested will ultimately go
saline, there is little incentive for landholders to reallocate precious, produc
tive land.
If sound technical and economic arguments for tree planting can be made,
there remains the question of how best to implement such programmes. How
can government bureaucracies and local communities become motivated,
who makes decisions on what, where, when and how much planting; and how
can financial and human resources be increased? Once programmes are
formulated, what will be the social impacts in their implementation, and how
would this compare to their absence?
The foregoing raises some of the leading questions in this important issue.
This paper attempts some generalised statements relating to the technical,
economic, social and administrative aspects of tree planting programmes. As
such, it is a subset of the broader question of how whole farm systems can be
developed for sustainable land use. The States have progressed to greater
and lesser degrees in these areas as can be seen from the State and general
papers [8, 9, 19, 39, 56, 62] whieh have contributed to this review. The task
here is not to identify the strengths and weaknesses of eaeh State's pro
grammes, but rather to draw together common experiences and views whilst
utilising differing views as a means of self-criticsm.
2. Extent of secondary salinisation in Australia
2.1. Current situation
Areas of Australia that have been identified as hosting or being susceptible
to dryland salinity are shown in Table 1 and Fig. 1. In terms of area, south
ern Western Australia is most affected, followed by South Australia, Victoria,
New South Wales, Tasmania and Queensland. The ranking in terms of cost
impact is not available.
Some degree of correlation between native vegetation clearing in Australia
(Fig. 2) and dryland salinity (Fig. 1) is evident. Although such a correlation
3
Table 1. Areas of dryland secondary salinity in Australia.
State Area Source
(ha)
New South Wales 12,000 [58]
Queensland 8,000 [64]
South Australia 250,000 [18]
Tasmania 11,000 [16]
Victoria 55,000* [20]
Western Australia 440,000 [19]
* [64] quotes 100,000 ha, which includes incipient salinity.
Fig. 1 Areas susceptible or containing dryland salinity in Australia (figure should be consid
ered schematic as definitions of dryland salinity areas vary from State to State) [Sources: 8, 19,
39,66].