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Towards reduced herbicide use in forest vegetation management

March 2010
Southern African Forestry Journal 207(1)

DOI:10.2989/10295920609505254

Authors:

Keith Little

Nelson Mandela University

Robert Gordon Wagner

Purdue University

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Mechanical, manual, thermal, biological and chemical methods of managing forest vegetation have, to a large extent, been developed independently. The effectiveness and relatively low cost of chemical herbicides, however, have led to systems of vegetation management that rely on their continued availability and the near exclusion of non-herbicide methods for controlling forest weeds. Greater public concern, perceptions of risk, and pressures exerted by some forest certification systems, have increased the need to provide a wider array of alternative methods that can reduce dependence on herbicides. In response, forest vegetation management research has widened to include investigations of alternatives to herbicides, along with initiatives aimed at reducing chemical use. An international review of progress indicates that reduced herbicide use may already be possible in many countries. There are however, a number of commercial, economic and social issues associated with the practical application of this knowledge, notwithstanding the fact that a more integrated approach is required to combine relevant methods of vegetation management, rather than attempting to practise alternative techniques in isolation from other silvicultural practices. This paper, together with appropriate examples, reviews pressures to reduce herbicide use as well as past and current research to develop alternatives to herbicides in eleven different countries, as well as identifying instances of the successful or unsuccessful implementation of this technology.

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Southern African Forestry Journal – No. 207, July 2006 63

Review Paper

Towards reduced herbicide use in forest

vegetation management

K.M. Little

*, I. Willoughby

, R.G. Wagner

, P. Adams

, H. Frochot

J. Gava

, S. Gous

, R.A. Lautenschlager

, G. Örlander

, K.V.

Sankaran

and R.P. Wei

Institute for Commercial Forestry Research, PO Box 100281, Scottsville, South Africa, 3209

Forestry Commission Research Agency, Alice Holt Lodge, Farnham, Surrey GU10 4LH, United Kingdom

University of Maine, 5755 Nutting Hall, Orono, Maine, USA, 04469

Forestry Tasmania, 79 Melville Street, Hobart, Tasmania, 7000

Lerfob, UMR INRA-ENGREF, CR INRA de Nancy 54280 Champenoux, France

Cia.Suzano de Paper e Cellulose, Tavares, Km 169, Cx Postal 228, CEP 18.200-000, Itapetininga – SP

Forest Health and Protection, Forest Research, Private Bag 3020, Rotorua, New Zealand

Atlanta Canada Conservation Data Centre, PO Box 6416, Sackville, NB E4L 1G6

Växjö University, SE-351 95 VÄXJÖ, Sweden

Kerala Forest Research Institute, Peechi-680 653, Kerala, India

Sino-Forest Corporation, 3129-40, 31/F., Sun Hung Kai Centre, 30 Harbour Road, Wanchai, Hong Kong

* Corresponding author. E-mail: keith@icfr.unp.ac.za

SYNOPSIS

Mechanical, manual, thermal, biological and chemical methods of managing forest vegetation have, to

a large extent, been developed independently. The effectiveness and relatively low cost of chemical

herbicides, however, have led to systems of vegetation management that rely on their continued

availability and the near exclusion of non-herbicide methods for controlling forest weeds. Greater public

concern, perceptions of risk, and pressures exerted by some forest certification systems, have increased

the need to provide a wider array of alternative methods that can reduce dependence on herbicides. In

response, forest vegetation management research has widened to include investigations of alternatives

to herbicides, along with initiatives aimed at reducing chemical use. An international review of progress

indicates that reduced herbicide use may already be possible in many countries. There are however, a

number of commercial, economic and social issues associated with the practical application of this

knowledge, notwithstanding the fact that a more integrated approach is required to combine relevant

methods of vegetation management, rather than attempting to practise alternative techniques in

isolation from other silvicultural practices. This paper, together with appropriate examples, reviews

pressures to reduce herbicide use as well as past and current research to develop alternatives to herbicides

in eleven different countries, as well as identifying instances of the successful or unsuccessful

implementation of this technology.

Keywords: Weed control, integrated forest vegetation management, herbicide alternatives, certification.

INTRODUCTION

Forest vegetation management involves manipu-

lating vegetation and the associated micro-

environment to favour the survival and growth of

trees or other desirable vegetation (Comeau and

Spittlehouse, 1993). Successful vegetation manage-

ment strategies enhance productivity from an existing

or declining land base by increasing fibre yields,

reducing rotation times, and improving stem and

stand uniformity, whilst also improving wood and/or

pulping properties (Little et al., 2003a; Little et al.,

2003b; Wagner et al., 2006). On certain sites, without

suitable vegetation management, competition from

weed vegetation would reduce or eliminate forest

regeneration. To realise the potential productivity of

many forest sites, various vegetation control methods

have been developed, including manual, mechanical,

cultural, thermal, biological approaches, and the use

of herbicides.

Since their development in the 1940’s, synthetic

herbicides have been used extensively, and have

become fully integrated for managing natural

regeneration, plantations and forest ecosystems

world-wide. Their ability to control a wide range of

competitive plant species has meant that herbicides,

Southern African Forestry Journal – No. 207, July 2006

more than any other form of vegetation control, have

helped forestlands achieve their productive potential

(Wagner et al., 2006). Consistent and predictable

vegetation control has meant that the benefits from

other silvicultural practices, such as fertilisation

and genetic improvement could also be realised.

Globally there has been increased emphasis placed

on reducing pesticide residues in food, water and soil

(Navas, 1991; Wyse, 1992; Franklin et al., 1994).

Greater public concern, availability of data and

perceptions related to the use of natural resources,

have also led to increasing pressure to practice more

sustainable forest management.

The principles associated with sustainable forest

production are not new. Chapman (1931) described

sustained yield as the actual net yield of a productive

industry in which there is no permanent depletion of

the capital resource, which in forestry is represented

by the soil and growing stock. Sustainable production

is a fundamental objective in any business striving

for long-term survival, and as such, the continuity of

supply of forest products is central to the practice of

forestry (von Gadow and Bredenkamp, 1992).

However, the principles associated with “sustained

yield” are more far-reaching than conservation of the

productive capacity of the forest only. Interest in

monitoring the condition of natural resources has

grown world-wide and this is reflected in increased

community awareness and concern for the protection

of natural resources. The concept of sustainability

has been expanded to that of meeting the needs of the

current generation without compromising the ability

of the environment to meet the needs of future

generations (Norman, 1997). Many international

and national organisations and sectors within

communities have developed ecosystem or industry-

based indicators of resource condition. The Montreal

Process, International Standards Organisation (ISO-

14001), Forest Stewardship Council (FSC), Pan

European Forest Certification (PEFC) are examples

of systems providing a framework to describe, assess

and evaluate progress towards sustainable forest

management (Norman, 1997; Obser, 1998). Included

within many of the forest certification systems are

guidelines striving to reduce or eliminate herbicide

use. Together with increased social concern and

perceptions of risk, this has led forest managers to

question their dependence on herbicide technology

alone. Public demands for greater protection of forest

ecosystems, while at the same time demanding high-

quality timber products at low prices, present a

formidable dilemma to forest managers.

Over the past five decades, the effectiveness and

relatively low cost of herbicides have, in many

countries, led to management systems that are reliant

upon their continued availability. In these countries,

this trend has resulted in the almost near exclusion

of non-herbicidal methods of vegetation control. The

advent of herbicides provides a good example of how

scientific research, extension, industry and growers

can co-operate to propel new technology into the

mainstream of society (Wyse, 1992). However, since

the early 1990’s, in response to increased pressure

from the public and non-governmental groups, there

has been renewed interest from managers and

researchers into methods of reducing the reliance on

herbicides as the exclusive method for managing

forest vegetation. As a consequence, the scope of

forest vegetation management research in many

countries has been widened in recent years to include

alternatives to herbicides, along with initiatives

aimed at reducing present herbicide use. A few

countries in Europe have since the 1970’s had

restrictions concerning the use of herbicides in

forestry. For example, in Sweden this has led to the

development and use of non-chemical methods for

the successful establishment of conifer stands (Nilsson

and Örlander 1999). Although a number of papers

and conference proceedings highlighting these aspects

have been produced (Canadian Journal of Forest

Research, 23(10) 1993; Harrington and Parendes,

1993; McMcormack, 1994; Wagner, 1994; New

Zealand Journal of Forestry Science, 26(1/2) 1996;

Canadian Journal of Forest Research, 29(7) 1999;

Annals of Forest Science, 60(7) 2003), there has been

no review of the success of these initiatives, nor the

constraints with regard to their application. Progress

on the development of alternatives to herbicides

varies from country to country, and is dependent on

economic viability, regulatory processes, social

acceptance and ecological impact. For this reason,

eleven countries were assessed that exhibited

diversity in terms of: the types, ownership, and value

of their forests; where and when (if at all) pressure

came for a reduction in herbicide use; and any

actions or initiatives proposed and put in place for a

reduction in herbicide use, together with potential

reasons for their success or failure.

IMPORTANCE OF FOREST VEGETATION

MANAGEMENT, HIGHLIGHTING CHANGES

IN HERBICIDES USE

Australia

Australia has a significant forest industry based on

the multiple use management of both native forests

and plantations. The industry employs almost 80

000 people, has a $15 billion annual turnover and

makes a 1% contribution to GDP. Annual wood

production exceeds 24 million m

of log, with 40%

from native forests and the remainder from

plantations (ABARE, 2004) which now exceed 1.6

million ha or approximately 0.2% of the total land

area.

Intensive management of plantations is carried out

to promote vigorous, healthy growth and to maximise

production per hectare. Standard practices during the

establishment phase include site cultivation,

vegetation control, and fertilisation, if required.

Effective vegetation management during this phase is

one of the major determinants of good early growth of

Southern African Forestry Journal – No. 207, July 2006 65

the tree crop under the majority of climate, site and

vegetation occurrence situations (Boomsma and

Hunter, 1990; Richardson, 1993). This is widely

recognised by many commercial plantation growers

in Australia and after more than three decades of

research has resulted in the development of successful

control methods based mainly on the use of herbicides.

The dominance of herbicide-based control methods is

due in large part to their effectiveness and ease of use

of in a wide variety of situations.

Historically, control of vegetation has changed

from manual, through mechanical to chemical control

by the 1970’s (Boomsma, 1982). In the 1960’s in South

Australia, chemical control of woody regrowth was

carried out with phenoxy herbicides (Boardman, 1988)

which enabled conversion of native forests and release

of newly established plantations from a wide range of

native and introduced woody species (Boomsma, 1982).

In the 1970’s glyphosate and hexazinone came into

prominence for control of grassy and woody vegetation

as plantations became increasingly established on ex-

pasture sites and second rotation plantations. Since

the mid-1970’s there has been intensive research and

development into all aspects of vegetation control with

the use of herbicides, including the testing of various

chemical combinations, formulations, application

techniques, new products, adjuvants and surfactants,

which provided forest managers with a wide range of

vegetation control options (Boomsma, 1982).

Since the early 1990’s there has been increased

environmental pressure and public scrutiny of forest

management and the use of herbicides, particularly

relating to catchment management and water quality.

The triazine group, particularly atrazine, has been

the major focus of attention with regards to off-site

movement and water quality. In some catchments

supplying drinking water to major towns and cities,

very strict controls have been enforced for the use of

herbicides during plantation management. This has

lead to serious reductions in survival and growth of

young trees. Research is being undertaken to quantify

the risk and find alternative herbicides that will not

move into water systems. There is an ongoing need,

therefore, to minimise the environmental impacts of

herbicides while making them more effective and

efficient, and appropriate to soil, site and species.

Many methods are being applied to improve the

efficiency of herbicide use, reduce the area treated

(spot or strip spraying), improve the application and

formulation technology, apply herbicides only to where

non-crop vegetation occurs, and improve vegetation

forecasting and timing of application.

In at least one case in Australia, a major plantation

grower has stopped using triazine herbicides during

establishment of eucalypt plantations and has been

actively seeking alternative approaches and more

integrated systems of management. This work has

included the evaluation of both pre- and post-plant

cultivation methods, manual slashing methods,

mulching and covercrops using oversowing techniques,

herbicide application techniques to reduce drift

(shrouded/shielded boomsprays) and hand application

equipment to improve herbicide application. Other

plantation growers are testing the efficacy of

alternative, non-triazine, residual herbicides. Biolo-

gical agents for the control of specific weeds such as

gorse and broom are also being investigated through

collaborative research between States and the

Commonwealth.

The implementation of non-herbicide alternatives

in industrial plantations has been low. Extra

cultivation methods that could be applied prior to

planting were limited to the amount of time available

prior to planting, terrain and soil conditions.

Cultivations carried out after planting are limited to

between the tree rows, have proved difficult, and in

some cases damaging to tree roots. Manual slashing

of vegetation can provide access for operations such

as pruning, and provides reasonable control on woody

vegetation, but is not satisfactory for herbaceous

species such as grasses that can rapidly regrow.

Multiple application of these mechanical methods

may be required which can become very uneconomic.

In the case of mulching, large amounts of material

are required, and it is very labour intensive and

therefore prohibitively expensive to apply. Covercrops

are difficult to establish and manage, and increase

management inputs. With grasses commonly being

a significant component of the covercrop, they can be

highly competitive to the tree crop, which means

herbicide control is required for each tree.

It is expected that further advances in vegetation

management, will require greater consideration of

the site quality, vegetation-tree interactions and the

processes or mechanisms involved (Wagner, 1993;

Cousens, 1996). An intensive study into competition

for soil water and nitrogen between a common grass

and young E. globulus (Adams, 2004) has improved

understanding of the timing, duration and intensity

of competition for these two important resources.

When applied to different site and resource levels,

this information allows managers to predict the

effects of competition on a site-specific basis and

target the management of vegetation more precisely.

Brazil

Reforestation, with pines and particularly eucalypts,

has occurred over the last 100 years in Brazil. Besides

the commercial importance of these plantations,

reforestation and subsequent silvicultural practices

are seen as important vectors for the sustainable

development of Brazil as a country. Technical

innovations from the 1940’s, combined with greater

public input from 1970, and increased efforts by

private companies in the 1990’s has promoted Brazil

from a net importer to a net exporter of a whole range

of forest products.

Although reforestation was initially carried out

over significant areas by large private companies,

recently there has been a shift towards the planting

of smaller blocks by private individuals or companies.

Southern African Forestry Journal – No. 207, July 2006

Currently, 4.8 million ha are established to

plantations, creating direct employment for 0.5

million people, and 1.5 million people indirectly.

The intensified use of herbicides together with the

development of appropriate equipment and rates of

application from the 1980’s has also allowed for more

cost-effective and better control of competitive

vegetation in eucalypt stands than would otherwise

be possible using more traditional, intensive soil

preparation techniques (Silva et al., 1997; Toledo et

al., 1999). Few herbicides are currently available for

use during reforestation in Brazil, with strict

legislation limiting the registration of new products.

In addition, pressure for the reduction of herbicide

use from certification bodies as well as from the

public sector will mean that this is unlikely to

change. Currently, registered products do not give

the same degree of control, are non-selective, or

control groups of vegetation that are not competitive.

This condition, together with the high price of

available herbicides and environmental concerns,

has meant that forest owners are investigating

alternative methods for the management of vegetation

The development of alternative vegetation

management systems has not received much

attention, although herbicide use has been reduced

through integration with other silvicultural

practices. Any method that decreases the time to

forest canopy closure, or reduces the development of

competitive vegetation is seen as important and

includes appropriate harvest residue management,

fertilisation, and planting density (Gonçalves et al.,

2002). More densely stocked stands capture the site

resources quicker and reduce the duration of

vegetation control operations, whereas more widely

spaced trees together with the retention of some

vegetation in the inter-row has a positive effect on

nutrient conservation, reducing losses through

leaching when the root system of the trees are not

fully established (Gonçalves et al., 2004). Significant

advances in developing new methods for eucalypt

sprout control through the reduction of herbicide

spraying have recently been achieved by the

application of imazapyr through the trunk injection

technique, a more environmentally sound and

effective methodology than spraying the foilage.

Canada

Canadian forests have been critical to Canadian life

for more than ten thousand years. Their plants and

animals provided the First Nations (Indigenous

peoples of North America), and those that followed,

essentials for sustenance and comfort. Canadian

First Nation communities practised vegetation

management (using fire and transplants) to

encourage desirable plants and animals and

discourage others, millennia before the term was

coined. Most Canadian landscapes remain forested,

although humans and related management have

altered historical disturbance patterns. They are

10% of the world’s forests and 30% of its boreal

forests. Of the 417.6 million ha, 183.1 million ha are

non-commercial forest (largely wilderness), while

234.5 million ha are commercial forest. Of the

commercial forest, during the last decade, approxi-

mately 0.4% has been harvested annually (Natural

Resources Canada, 2004).

Although vast tracts of forest remain largely

untouched, forest harvesting has changed the

structure and composition of harvested areas

(Lautenschlager and Sullivan, 2002). Almost without

exception, conifer content (“softwoods”) in post-

harvested forests is decreased, often dramatically. In

addition, forested areas are decreasing close to human

populations, agricultural production centres, mill

sites, and major transportation routes.

Forest plantations (mostly of native spruce and

pine) are presently contributing fibre to Canadian

mills, with the bulk of forest harvesting, and much

regeneration, based on natural regeneration. During

the last decade approximately 435 000 ha, less than

half of the area harvested, were planted with conifers

in Canada annually. Although many provinces have

legislation requiring forest companies to regenerate

harvested areas to pre-harvest cover percentages,

many provinces also have restrictions that make it

difficult to successfully regenerate conifers. Herbicide

release (chemical removal of unwanted vegetation

allowing) accounted for approximately 83% of all

post-planting release during the last decade, but on

average it has only been applied to 154 000 ha

annually, 15% of the annual harvest area. Even

these treatments, however, seldom yield post-harvest/

post-treatment conifer stocking levels similar to pre-

harvest conditions.

The majority of herbicide use in Canada is in

agriculture; forest herbicide applications are a minor

use. Five active ingredients (glyphosate; triclopyr;

2,4-D; hexazinone; simazine) are used for forest

vegetation management. Glyphosate, however,

dominated overall useage on 94.7% of the treated area

from 1998-2001 (Canadian Council of Forest Ministers,

2002). Despite the established record of efficacy and

safety associated with forest herbicide use,

considerable research into effects of alternative

management approaches have been conducted in

Canada. Thompson and Pitt (2003) provide a recent

overview of vegetation management research and

practice in Canada. One of the most significant efforts

to examine alternatives to aerially-applied herbicides

was undertaken by the Vegetation Management

Alternatives Program (VMAP), funded by the Ontario

government, in the mid-1990s (Wagner, 1993).

VMAP investigated all seemingly appropriate

alternatives to herbicides (animal grazing, prescribed

fire, mechanical and manual methods, biological

control, and mulches), and field-tested these along

with standard herbicide applications (Wagner et al.,

1995). Environmental consequences of the most

promising alternatives were often determined during

pre- and post-treatment field-test monitoring. One

Southern African Forestry Journal – No. 207, July 2006 67

proposed approach, using domestic sheep to control

competing vegetation in forest plantations, was

considered but because of concerns about disease and

parasite transport to native wildlife, and possible

attraction or displacement of large carnivores, this

was rejected before major field trials were initiated.

A milestone accomplishment in Canadian forest

research directed at developing new alternatives to

herbicides has been the development of

Chondrostereum purpureum, a common forest fungal

pathogen, as a biological control agent for re-sprouting

woody plant species (Thompson and Pitt, 2003). This

pathogen has recently received government

registration for forest use as the product Myco-Tech

Paste™ (Myco-Forestis Corp.). It is the first

commercial biocontrol agent for forestry in North

America. Development and registration of this

biocontrol agent represents a major breakthrough,

particularly in the province of Quebec, where

herbicide use in forestry has been recently suspended.

One of the most significant comparisons of

ecological effects between herbicides (glyphosate and

triclopyr) and non-herbicide competition control

(cutting with “brush-saws” or a tractor with a “brush-

saw”-like attachment), was conducted by the VMAP

during the mid-1990s. That interdisciplinary

“Fallingsnow Ecosystem Project” (Lautenschlager

et al., 1998) was a large-scale replicated block study

that examined responses by most major abiotic and

biotic environmental components. The authors

reported few short- or long-term differences, except

in cost, among the alternatives tested and concluded

that conifer release, regardless of the method used,

is relatively inconsequential for most environmental

components found in regenerating northern forests.

Post-harvest disturbances like conifer release are

minor compared with harvesting, but following

harvesting, planting, and conifer release plant and

animal species richness and diversity are commonly

as high as they will ever become in northern forests

(Lautenschlager and Sullivan, 2002). Still, public

perceptions about environmental and human health

risks associated with herbicide treatments are real.

Forest managers employing herbicides must

recognise that opposition to herbicide use in forestry

is high and increasing (Wagner et al., 1998), despite

accumulated scientific documentation of their safety

and relatively benign environmental effects. So, in

addition to supporting additional scientific

documentation of consequences of alternative

treatments, managers must understand that in the

future social input will be increasingly common if

not required (Lautenschlager et al., 1998).

Although broadcast conifer release treatments

are still the norm in Canada, one new development

has been the movement, at least in some western

forests, to the increased use of both ground- and

helicopter-applied “patch” release treatments. To

some degree this has been necessitated by the

significant biomass of non-conifer vegetation left on

site (often required by legislation) during harvesting.

Root sprouts from that residual, however, often

produce significant competitive biomass in and

around the residual areas. Because patch treatments

are new, it is unclear whether they will contribute to

survival and improved growth of the planted conifers.

Clearly micro-site quality is highly variable and

patch treatments focus on the most productive micro-

sites. For a variety of reasons site resources may be

equally or more limiting in areas where less

competitive biomass has developed.

Studies of alternative treatments commonly fail

to examine both the economic and ecological

consequences of the full range of alternatives,

including standard herbicide treatments. Therefore,

future examinations of alternatives should ensure

that economic and ecological consequences are

examined in detail. It is not clear that any alternative

will be more efficient, effective, or less environ-

mentally damaging than the herbicides presently

being used in Canada. However, it is clear that the

conifer component in post-harvested forest

ecosystems in Canada has been reduced, and although

herbicides may not be the only way to reverse that

trend, at this time herbicides provide the best hope

of restoring ecosystems changed dramatically by a

century of forest harvesting.

Herbicide use in forestry in Canada has decreased

slightly during the last decade, and efforts focused on

understanding effects of herbicides and alternatives

have also decreased, but some research concentrating

on understanding longer-term consequences of older

treatments continues. One key finding to emerge over

the last decade is the importance of early treatment if

the intention is to ensure conifer survival and maximise

growth. Evidence supporting this need, including the

advantage of pre-planting herbicide site-preparation,

continues to mount, while a variety of publics continue

to be concerned about the use of any herbicides for

forest vegetation management.

Although additional research in certain areas

may be necessary, at this time a national effort to

inform the public of the need for site-preparation,

timely planting, and release would benefit Canadian

forests and the Canadian economy in the long-run.

Additional research refining what is already known

will not convince a sceptical public of the value of

herbicides for managing these forests. If governments

hope to continue to benefit from forest production in

Canada, serious public education (not a propaganda

campaign), based on research that has already been

conducted, is the most desperate need.

China

Although deforestation has probably been the main

interaction between humans and forests, silvicultural

activities such as tree planting and tending have been

documented for more than two thousand years

(ECGPH, 1998). In response to an increase in natural

disasters such as floods and droughts, together with

wood shortages arising from the rapid decline in forest

Southern African Forestry Journal – No. 207, July 2006

resources and worsening ecosystems, extensive

government funded reforestation programs were

initiated within the last century (ECGPH, 1998). This

has resulted in the establishment of 46.7 million ha of

plantations and accounts for 29.4% of the forests in

China (26% of the world’s plantations). As these areas

were planted mainly for reforestation purposes, they

received low-level investment and management.

Subsequent to the availability of World Bank loans

from the early 1990’s, fast-growing trees have been

planted and intensively managed on a commercial

basis for the production of forest products (CSFA,

2003). Increased involvement from the private sector

from 1996, has also contributed to the establishment

of commercially managed plantations, which currently

account for 3.7% (1.7 million ha) of the total area of

plantations in the country (CSFA, 2003).

Throughout the history of forestry in China, the

management of competitive vegetation has always

been regarded as one of the most important of the

silvicultural practices. Regardless of the end-use,

the vegetation has been controlled as a form of site

preparation prior to planting, as well as for releasing

the tree from competition during establishment.

Current vegetation control methods include manual,

mechanical, burning, chemical, intercropping as

well as various combinations of the above. The most

common method used in plantations established for

wood production is burning prior to planting followed

by manual clearing.

Chemical control of vegetation was first considered

in 1959, subsequently resulting in extensive research

into herbicide use throughout the country (Wang et al.,

2001). Much of this research was aimed at screening

herbicides for application in forest nurseries, young

plantations (Feng, 2001; Xu et al., 2003), high-value

tree crops (He et al., 2000) and forest fire-breaks (Lu et

al., 1999; Zhang, 2003). This research had a positive

contribution on the management of forest vegetation

control (Wang et al., 2001). Among the many herbicides

available, only a few are recommended on a regular

basis. These include oxyfluorfen and haloxyfop-r-methyl

for use in forest nurseries, and glyphosate, hexazinone

and 2,4-D butylate for reducing competition in young

stands, or for the maintenance of forest fire-breaks

(Wang et al., 2001). The use of herbicides as an

alternative to other forms of vegetation control is now

well established, particularly in: forest nurseries;

economically well-developed regions such as the coastal

areas in the south and east of China; management of

high-value species such as teak, ginkgo and selected

woody herbs; plantations owned by well-established

forest farms (He et al., 2000); and for establishment of

forest fire-breaks (Lu et al., 1999).

Despite the successful use of herbicides for the

management of vegetation in the situations

mentioned above, they are not commonly used in

reforestation programs even for the establishment of

commercial eucalypt, poplar and pine plantations,

most of which were planted in the last decade and

involve intensive management. Reasons for this are

firstly, most of these plantations are located in the

poorer, rural regions of China where field operations

are carried out by low-paid, unskilled labourers from

local communities. Despite the gradual increase in

labour costs over time, and reduced costs associated

with manually applied herbicides, the small

differences between manual and chemical vegetation

control costs does not warrant a switch (Lu et al.,

1999; He et al., 2000; Wang et al., 2001). Secondly,

for the effective control of competing vegetation with

herbicides, a degree of skill and knowledge is required.

As most operations are carried out by seasonal and

unskilled labourers, frequent training would be

necessary if herbicide use were to be considered.

Thirdly, most of these plantations have been

established on long-disturbed, ex-agricultural fields

where any vegetation present is easily controlled by

burning followed by manual hoeing. Fourthly,

ecological, environmental and social concerns related

to herbicide use are also taken into account by the

majority of commercial plantations owners (Wei,

2003). This is particularly true for those plantations

established in the last decade by private companies,

or with funds obtained from the World Bank, which

required the inclusion of the above issues into their

management (Bai, 1993).

The potential exists for the increased use of

herbicides in fast-growing plantations that are aimed

at maximising production. However, existing control

measures are currently regarded as successful and

until such a time as the use of herbicides become

more cost-effective, it is unlikely that their use will

increase. On the other hand, the concept of integrated

forest vegetation management through which

herbicide use is reduced, and site productivity is

continuously maintained or improved, is nowadays

well accepted among plantation scientists, owners

and managers (CSFA, 2003; Wei, 2003). These

principles are actively practised by certain companies

or sectors (Wei, 2003) where different operations are

integrated, and included various combinations of

burning, mechanical or manual clearing of the site

prior to planting, manipulation of planting time,

density and spacing to allow for the shortest time for

the stand to capture the site, manual weeding or

chemical weed control at reduced rates, and the

inter-planting “green manures” or cash crops to

reduce or suppress unwanted vegetation. To be able

to expand these practices to be all encompassing, a

range of relevant issues need to researched and

developed, including the development of long-term

management plans, plantation type, land use history,

site accessibility and topography, investment budget,

feasibility of alternative vegetation management

practices, cost, and ecological, social or environmental

concerns.

Southern African Forestry Journal – No. 207, July 2006 69

France

Commercial forests, occupying an area of 14 million

ha, cover a quarter of the metropolitan territory in

France (Cazettes et al., 2002; IFN, 2003). The

majority of these forests consist of naturally

regenerated native forest species, such as pines, fir,

spruce, oak, beech and various broadleaves species,

with only 5% established to exotic trees (Douglas fir,

red oak and several poplar clones). The growing

stock is estimated at 2 000 million m

, with 60%

broadleaved species and 40% conifers.

The metropolitan forests consist of high forests

(54%), a mixture of high forests and coppice (31%), or

coppice alone (IFN, 2003). The high forest is mainly

mono-specific and is dominated by oaks (Quercus

petraea and Q. robur), by conifers such as maritime

pine (Pinus pinaster), common silver fir (Abies alba),

Norway spruce (Picea abies) and Scots pine (Pinus

sylvestris). The mixtures of high forests and coppice

are multi-specific, multi-storied and widely dominated

by broadleaves species such as beech (Fagus

sylvatica), Spanish chestnut (Castanea sativa),

common ash (Fraxinus excelsior) and others.

France is an industrialised nation with a population

that is predominantly urban. Increased public pressure

regarding ecologically sound management practices

and free access, have sometimes resulted in formal

charter agreements between owners and individuals

or territorial groups (Bessière et al., 2002).

Traditionally French forests fulfil multiple uses: wood

production; social function; protection of biodiversity;

and natural resources, although only wood production

and to a lesser extent hunting, provide sources of

income. Many of the forests are either currently

certified with PEFC (amongst others) or are committed

to certification in the near future (Colinot, 2003).

Some of these forests are also bound by charters,

which place an even higher emphasis on the

conservation of the environment (Natura 2000

network). Current management trends include mainly

those silvicultural practices that will enhance the

diversification of commercial species through assisted

natural regeneration. These practices arose from the

need to re-establish close to 450 000 ha of damaged

forests following catastrophic storm damage in 1999

(Wincèlius, 2002), about 6 or 7 times the annually

regenerated areas.

From the 1970’s, herbicides have been used to

enhance natural or artificial regeneration, and to a

far lesser extent to optimise yield in intensively

managed forests. Herbicide use varies with the

intensity of management, the degree of control

required, and the receptivity of forest manager

(Frochot et al., 2002a), and herbicides are rarely

used more than one or two times during a rotation,

if at all. The forest area treated annually is less than

0.35% and forest managers are encouraged to respect

any environmental constraints when using herbicides

(Gama et al., 1987; Barthod, 1994; Wehrlen et al.,

1994; Barthod and Landmann, 2002). Although there

has been a marginal increase in herbicide use in

intensively managed areas (as in maritime pine),

there has been a corresponding decrease in most

other areas. This decrease can be attributed to the

attitudes of forest managers regarding herbicide

use, ecological concerns, and restrictions placed on

the use of specific herbicides.

From 1995 there has been a further decline in the

number of herbicides used in French forests (Gama,

2002) due to a combination of recommendations from

government organisations to use only herbicides

specifically authorised for forestry, the EEC which

limits pesticide use (such as triazines, fosamine

ammonium, dalapon), the time taken to register

forest herbicides that are not seen as a priority due

to minor usage, and the lack of commitment from

pesticides companies to invest in the registration of

new herbicides with limited forest use.

Initiatives to reduce herbicide use are at present

varied and include the testing of replacement

herbicides that control only specific vegetation types

rather than eradicating all vegetation (Gama, 2002;

Frochot et al., 2002a), through the combination of its

usage with other forms of vegetation management

(manual and mechanical), and by reducing the area

that needs to be treated to that immediately

surrounding the seedlings (Frochot et al., 2002a).

The utilisation of high-quality seedlings (size, quality,

mycorhization) is practised in low-density

plantations. Research into alternative practices is

focused mainly on the replacement of competition,

and consists in modifying the composition of existing

vegetation (Frochot et al., 2002a), or in sowing a

fixed mixture of herbaceous species (Frochot et al.,

2002b). The first method is well accepted in forests,

but the second will need further research before it

can be practically and commercially viable.

India

Plantations are an important source of pulpwood and

fuel in India. Although teak (Tectona grandis), which

is native to India, was planted from 1842, the large

scale planting of eucalypts and acacias (both exotics)

commenced from the 1960’s. This expansion of area

under plantations has been driven by increased local

demand for wood and other products, and by

community pressure to diminish dependence on native

forests. The total area under plantations is

approximately 32.5 million ha (Brown and Durst,

2003). Of this, teak, which is used mainly as a source

of timber, occupies an area of 1 million ha, and

eucalypts which are used as a source of pulpwood,

around 4.6 million ha. Plantations were initially

planted into indigenous grasslands, or in areas cleared

of natural forests, the latter of which was halted by

the Government of India in 1982. Thereafter, new

plantations could only be re-established after

harvesting existing plantations.

Most of the natural forests and plantations are

owned by the government, with the majority of the

Southern African Forestry Journal – No. 207, July 2006

plantations grown for timber or pulp. Productivity of

these plantations is considerably lower when

compared to world standards (Sankaran, 1999).

Competing vegetation has been identified as a major

factor contributing to this low productivity, with an

increase in Eucalyptus tereticornis performance of

up to 138% possible through regular vegetation

control in plantations in Kerala (Sankaran, 2004 –

unpublished data). The major competitive species in

teak and eucalypt plantations are broadleaves and

include Chromolaena odorata, Lantana camara,

Mikania micrantha, Mimosa invisa and Ageratum

conyzoides.

Various control measures including mechanical,

cultural, chemical and biological have been researched

and recommended for the control of unwanted

vegetation (Singh, 2001), unfortunately none has

resulted in any substantial impact on either their

distribution or abundance. The first use of herbicides

dates back to 1937, with 2,4-D introduced in 1948.

Since then a large number of herbicides have been

used on an experimental scale in plantations, and

include glyphosate, paraquat, diuron and oxyflurofen

(Choudhury, 1972; Nair, 1973; Sankaran et al.,

2002). Despite this, herbicides are seldom used on a

regular basis for the management of vegetation due

to concerns related to their toxicity, the high cost of

the products, and the availability of cheap labour for

manual control.

Revenue earned by the government from the

plantations is negligible since products such as acacia

and eucalypt pulpwood is supplied to the industries

at a highly subsidised rate. This has compelled the

government to treat plantation management as low

priority. The decline in productivity over successive

rotations due to sub-optimal management has meant

that plantations in some states, for example Kerala,

are no longer able to provide the required quantity of

raw materials to the affected industries. Despite the

urgent need to increase productivity, attempts to use

herbicides to help achieve this have met with strong

resistance from the public due to perceived ecological

and environmental concerns. A similar situation

occurs in the smaller plantations under private

ownership where manual control of vegetation is

preferred over herbicides.

Plantation production of tea and coffee in north-

east India is highly dependent on herbicides (Barbora,

2001) and attempts to use alternative cultural weed

control in this and other agricultural sectors involving

local communities have so far proved to be

unsuccessful (Murphy, 2001). If similar methods

were to be applied in forest plantations, it is doubtful

they would be successful. Manual weeding is also not

a viable option in plantations due to the rapid

regeneration of the vegetation, combined with the

high costs involved. The control of specific species

using biological control are preferred over other

methods by all concerned. Costs are relatively small,

risks minimal and potential benefits considerable.

Although a number of biocontrol agents have been

introduced into India, mainly for the control of

Chromolaena, Lantana and Parthenium (Singh,

2001), these attempts have been largely unsuccessful,

or at best successful only at a local level (Evans,

2001). Reasons for recurrent failures are linked to

the genetic diversity of the species, their ability to

adapt to a range of ecosystems compared to the

biocontrol agents, lack of expertise in handling

biocontrol agents, absence of co-ordinated follow-up

actions after the introduction of the agents, and a

lack of information on the ecology and distribution of

the weeds. Little effort has been made to examine the

possibilities for exploiting indigenous or exotic host-

specific pathogens, even though recent studies in the

neotropics have indicated that for the latter, the

potential exists.

Integrated vegetation management programmes

involving mechanical, cultural and chemical methods

in conjunction with biocontrol agents have been

proposed and discussed on several occasions within

the country, but to date, concerted attempts have not

been made to implement any of these, and reasons for

this are unclear. Yet another suggestion is the

adoption of an effective natural resource management

strategy to enhance biodiversity in the landscape

and thus keep the biological invasion, including

unwanted vegetation, under check (Ramakrishnan,

2001). This suggestion again needs testing in the

field which may take several years for any observable

results.

To summarise, the management of vegetation

using herbicides in forest areas has not been an

option in India so far, a situation that is likely to

persist for some years to come. To avoid any future

misconceptions regarding herbicide use, efficient,

environmentally safe and sustainable methods need

urgent development. To achieve this, international

co-operation is needed by way of information sharing,

technology transfer and capacity building.

New Zealand

New Zealand is a resource-based, industrial nation

with a total land area of 27.1 million ha and a

population of 4 million. Plantation forests, utilising

exotic tree species (mainly Pinus radiata), cover 1.8

million ha (7% of the total land area) and contribute

4% (NZ$ 3 546 million) to the GDP (New Zealand

Forest Owners Association, 2004). The importance of

managing competitive vegetation in New Zealand

plantations has long been recognised. Herbicides are

the most widely used tool to control competing

vegetation, although non-chemical methods are

increasing in importance (Richardson, 1993). Ray

and Richardson (1995) stated that, “without good

weed control it is doubtful whether commercial

plantation forestry would be economically viable on

many sites”. Herbicides have long been the principlal

method for controlling unwanted vegetation, initially

with the use of agriculturally derived chemicals in

the 1960’s. Over the last 40 years many changes

Southern African Forestry Journal – No. 207, July 2006 71

have occurred. Prior to 1970, herbicides were rarely

utilised for site preparation, with manual and

mechanical vegetation control methods in conjunction

with prescribed burning being the preferred approach.

During the 1970’s, there was a shift towards the use

of herbicides applied as a pre-plant spray followed by

a prescribed burn. These herbicides (mainly the

phenoxy type herbicides) with relatively high eco-

toxicity were applied using fixed wing aircraft at

high spray volumes (200 – 350 l ha

-1

). Diesel was

frequently used to enhance herbicide performance.

Since the mid-1980’s there has been a concerted

effort from within the forest industry to reduce the

use of herbicides, initially driven by the need to

reduce costs associated with the management of

vegetation, and more recently by public concern

regarding toxicity and requirements from forest

certification bodies.

Herbicide use and rates of application have been

reduced by a combination of the following; new

herbicides replacing some of the more toxic products

used in the past; the spraying of herbicides becoming

more affordable with helicopters, allowing also for

directed application; herbicides applied at lower rates

with improved efficacy by the addition of adjuvants;

improved application techniques; and reducing the

area that needs to be treated (spot release) as an

alternative to a complete cover spray (Richardson et

al., 1997a). Currently 26 herbicides, or herbicide

mixtures are registered for use in New Zealand

forestry. These herbicides are generally classified in

the least hazardous “non-scheduled” category based

on oral and dermal toxicity. Research has shown

that environmental impacts from using herbicides

in New Zealand are often lower than from alternative

options such as crushing and burning. In addition

the chemical control of competitive vegetation is

more cost-effective than manual operations, or with

the use of cover-crops alone (Richardson, 1993).

In the 1990’s New Zealand Forest Research

developed two software decision support systems,

Vegetation Manager (VMAN) and Spray Safe Manager

(SSM) in collaboration with the U.S.D.A. Forest

Service (Richardson et al., 1997b). VMAN is a decision

support system that assists the user in selecting

which vegetation management treatment should be

used to optimise vegetation control operations. SSM

calculates aerial spray deposition, drift and either

vegetation control efficacy or damage to non-target

plants. Both systems help reduce the quantity, as

well as area over which herbicides are applied.

The New Zealand “principles for commercial

plantation forest management” states that

environmental excellence in plantation forest

management is the primary objective (New Zealand

Forest Owners Association, 2004). Over the past 20

years the forest industry has significantly improved

all facets of vegetation management practices

including reducing herbicide rates, using products

with lower toxicity and less use of practices that

degrade site quality.

South Africa

Timber is a scarce resource in South Africa (SA)

where the area under natural forests is limited (<

0.5%). To address this, timber plantations were

established, from the late 1800’s onwards, on

previously un-afforested land using exotic tree species

(pines, eucalypts and Acacia mearnsii) (von Gadow

and Bredenkamp, 1992). The total area of plantations

is approximately 1.1% of the area of South Africa, yet

they contribute 9% to the gross value of agricultural

output in SA. Although most of the timber produced

is used as a source of sawlogs, pulpwood and mining

timber (94.5%), 5.5% is used for other purposes

including poles for building, and wood for fires and

charcoal. This is important in a developing country

where most of the population live in rural areas and

do not have access to any other form of building

material and energy. Of the 1.4 million ha planted,

75 000 ha are re-established annually (Forestry

Economic Services, 2002). Silvicultural practices

during re-establishment are designed to take full

advantage of the sites’ productive potential, and as a

result, intensive operations, including land

preparation techniques, appropriate spacing,

fertilisation and vegetation management are practised

widely during re-establishment.

Most of the plantations are privately owned (76%)

with the emphasis on maximising productivity on a

sustainable basis. Until the late 1980’s, herbicides

were not used extensively in SA forestry, with most

vegetation management operations carried out by

hand or with hand-held implements. Around this

period early competition trials demonstrated potential

yield benefits, and this together with the availability

of glyphosate, provided the forester with the means

of significantly improving yield, at a reduced cost,

and on a consistent and predictable basis. Although

there was a shift towards the use of herbicides, this

was not to the total exclusion of manual weeding, nor

did it become less labour intensive, with all herbicides

applied by hand either as a broadcast application or

a directed spray. Since the majority of the forest

owners in SA subscribe to the principles of sustainable

management, 80.5% of the total area afforested is

currently certified with FSC, ISO 14001, or both. As

these forest owners provide funding for most of their

silvicultural needs through private research

organisations, any recommendations made must

take into account the concepts of the relevant

certification bodies. This has seen the development of

research initiatives aimed at refining current

vegetation management standards without compro-

mising productivity. Work includes trials demon-

strating the viability for reducing areas around the

trees that need weeding as well as the frequency of

weeding operations, the target control of specific

vegetation types, the development of standards for

cover-cropping, the adjustment of weed control

standards according to site (on a regional level),

immediate and historical land use, methods of site

Southern African Forestry Journal – No. 207, July 2006

preparation and species to be planted (Little and

Schumann, 1996; Little and Rolando, 2001; Jarvel

and Pallett, 2002; Little et al., 2002; Little and

Rolando, 2004). All recommendations rely on the

integrated management of vegetation, incorporating

both a reduction in herbicide use, together with non-

herbicidal forms of vegetation control.

Although these results can be considered successful

from a research perspective, in that they provided

solutions to the questions asked, few have been

applied commercially (Little and Dyer, 2002). This

has raised concerns, especially in identifying issues

that prevent the implementation of vegetation

management recommendations, and include,

robustness of research findings, transfer of

technology, complexity of weed growth information,

institutionalisation of systems and economic and

political constraints (Little and Dyer, 2002). Key

elements that can constrain the successful transfer

of technology in SA forestry include: a resistance to

change (including the so-called “not invented here”

syndrome); an inability to consume the technology

(company structures are inflexible); an inability to

understand and therefore use the technology (too

complicated); inappropriate technology (not practical);

unrealistic expectations as to what can be obtained

from research; the changes proposed through the

application of technology do not impact the way the

manager is measured; and the fact that the economic

return for the company is not perceived to be worth

the additional resources to implement the

recommendations (Little and Dyer, 2002).

Sweden

About 60% (ca 23 million ha) of the land area in

Sweden is covered with forest, and consists of a

mixture of naturally regenerated and planted forests.

About 85% of the standing volume is Norway spruce

or Scots pine. Other important species are birch

(Betula sp.), oak (Quercus robur), and beech (Fagus

sylvatica). Most forests are a mixture of species, with

composition varying from north to south relative to

the many climatic zones, and as such monocultures

are uncommon. Current forest policy is against the

introduction of exotics and as such the only exotic

species of any importance is lodgepole pine (Pinus

contorta) that has been planted on approximately

2% of the area.

Sweden is a highly developed, industrial nation,

and although highly mechanised, the forest sector

provides direct employment for about 100 000 people.

Prior to 1975, large areas were treated with herbicides,

although environmental concerns around this period

led to the government placing restriction on future

herbicide use. Approximately 14 million ha of forests

are certified with either FSC or PEFC. The public

have access to all forests, and since 1993 forest policy

places equal emphasis on the environment and wood

production. Management of the forests for multiple-

use is therefore standard.

Vegetation occurring within forests is managed

on two occasions, prior to planting, and in young

stands when unwanted (mostly broadleaved) species

are removed. No herbicides are used for the re-

establishment of forests, with only limited herbicides

used when planting into ex-agricultural fields. Prior

to planting, the soil is scarified, providing effective

control of vegetation, similar to that provided by

herbicides on many sites (Nilsson and Örlander,

1999). About 70% of the areas regenerated in Sweden

are mechanically scarified before planting (Swedish

National Board of Forestry, 2003). Disc trenching,

patch scarification or mounding are the most common

method of scarification, although inverting might

allow for improved seedling establishment where

vegetation is particularly competitive (Örlander et

al., 1998; Hallsby and Örlander, 2004). Damage to

seedlings after planting by the pine weevil (Hylobius

abietis) is the most serious problem affecting

successful re-establishment. As a strong correlation

has been found between vegetation in scarified areas

and risk for damage (Örlander and Nordlander,

2003), the duration of vegetation control after

scarification is important. Planting as soon after

felling as possible, preferably within the same year,

reduces the negative impact any vegetation may

have on the seedlings (Nilsson and Örlander, 1999).

Other methods to reduce the impact of vegetation on

tree growth include, the selection of species less

sensitive to competition (such as Norway spruce),

and the planting of Norway spruce at a higher

density resulting in more rapid canopy closure.

Competition, especially from some broadleaved

species may have a negative impact on the production

of target species (usually Norway spruce or Scots

pine). Although these broadleaved species add to

species diversification and fill gaps in the canopy,

most of them are removed using pre-commercial

thinning that sometimes is costly. Pre-commercial

thinning is made on 200 000 – 300 000 ha of Swedish

forest annually (Swedish National Board of Forestry,

2003). During the last 10 years this pre-commercial

thinning has not been carried out according to need

and this has the potential to impair future economy.

In conclusion, competition from unwanted

vegetation following planting might be a problem,

but planting as soon as possible after scarification at

a high density can reduce any negative impact.

Currently, there is no need for removing broadleaves

with herbicides after re-establishment, provided pre-

commercial thinning is carried out correctly.

United Kingdom

Woodlands occupy 2.7 million ha, or 11.6% of the

land area of the United Kingdom (UK). No virgin

natural forests remain. Less than 1% of the land

area is occupied by ‘ancient semi-natural’ woodlands,

which are defined as sites which have been

continuously wooded since 1600 AD, and although

managed, still comprise predominantly native trees

Southern African Forestry Journal – No. 207, July 2006 73

that have not been planted. Of the remaining forest

area, 58% consists of mainly introduced exotic

coniferous species such as Picea sitchensis, Picea

abies, Pseudotsuga menziesii, Pinus spp., and Larix

spp. grown as plantations, and the balance native

broadleaves. Around 40% of woodlands are publicly

owned, and approximately 25 000 ha are planted or

restocked annually (Forestry Commission, 2003).

The UK has an industrialised economy and a

largely urban based population. Since the 1920’s

successive governments have encouraged land owners

to create new woodlands, and to maximise the

productivity of existing forests through the scientific

application of intensive techniques such as

coniferisation, fertilisation, cultivation, improved

planting stock and the use of pesticides. However,

since the 1970’s there has been a shift in emphasis

away from establishing a strategic reserve of timber

towards providing multiple use woodlands. This

trend has been accelerated in recent years with the

real terms reduction in timber prices, such that non

market, intangible benefits have become increasingly

important. Most woodland management in the UK

now includes one or more of the following major

aims: to promote and conserve biological diversity; to

improve the landscape; to provide a recreational

resource; and to produce timber and hence encourage

rural development.

The pressure to maximise production from a site

to the exclusion of all other objectives has therefore

reduced. One result of this shift in the objective for

woodland management has been a reduction in the

amount of money owners are prepared to invest in

operations such as vegetation management. The use

of herbicides is easily the most cost effective method

of weed control in the UK, but even so, economic

pressures have encouraged mangers to limit spraying

only to areas where it is necessary to allow

establishment of trees. Economic pressures and

changing objective have therefore led to some reduction

in herbicide use in UK forestry.

In addition, UK Government and European Union

policy is to minimise pesticide use as far as possible.

Statutory codes of practice (HSC, 1995) oblige

managers to consider whether, in any given situation,

pesticide use is really necessary and if possible to

adopt either wholly non chemical methods, or

techniques based on reduced quantities of chemicals

used as part of an integrated approach to crop

management. The European Union Plant Protection

Products Directive is intended to harmonise member

states regulation of pesticide use. One consequence of

this legislation is a review of all European registered

pesticides to a common data standard (Whitehead,

2004). Those active ingredients with adverse impacts

on the environment or operators, along with older,

often generic, less profitable activities where

additional data generation is not economic, will have

their approvals revoked. This has led to a reduction

in the number of pesticides that are available to be

used in forests, and has further encouraged managers

to consider alternative chemical and non chemical

solutions to their vegetation management problems.

A voluntary certification initiative the United

Kingdom Woodland Assurance Standard (UKWAS,

2000), which is approved by both the FSC and PEFC,

gives standards for sustainable forest management

against which management units can be assessed.

The standard calls for managers to develop a strategy

which will lead to a reduction, and eventually

elimination, of synthetic pesticide use. Where there

is no practical alternative not entailing excessive

cost, the use of synthetic pesticides is still permitted.

Economic pressures have probably had the greatest

effect to date in reducing the amount of pesticides

used in UK woodlands. By comparison, so far

legislation and other initiatives such as UKWAS

have probably only had a limited impact on levels of

usage. This may again be due to economics. For the

majority of pest and weed problems in UK forestry a

non chemical method of management already exists,

but in most cases the alternative is at least a factor

of ten to a hundred times more expensive than using

pesticides.

However, the reduction in available products, and

the adoption of certification initiatives will result in

managers being faced with increasing pressure to

reduce pesticide usage in the future, whilst there is

little immediate likelihood of more resources becoming

available to fund this change in practices. Alternative

silvicultural approaches to the management of

woodlands such as continuous cover forestry (Mason

et al., 1999) and restoration of conifer plantations on

ancient woodland sites to native species (Thompson

et al., 2003) partly reflect changing objectives for

woodland management, but there is also the perception

amongst some mangers that these silvicultural

systems will offer a lower cost approach that may

require less intensive inputs. However, in reality

such approaches may still require the use of herbicides

in the transformation phase, so an immediate

reduction in inputs may not be possible.

For more conventional felling and replanting

systems, complete replacement of non chemical

options may be far less practical than using a

combination of techniques to reduce chemical use.

This may be one area where research in the UK

needs to focus, rather than striving for an elusive

direct replacement for cheap, effective chemical

regimes. However, some pressure groups might see

such an approach as a dilution of their eventual aim

of eliminating all synthetic chemical use in

woodlands, and managers with limited time may be

reluctant to replace a relatively straightforward

chemical regime with a more complex system

involving a combination of techniques.

Research into alternatives to pesticide use has

taken place over many years in the UK (Willoughby,

1999), but one barrier to the adoption of an integrated

approach may have been that information relating to

individual pest, disease, vegetation and wildlife

problems has often been published separately. New

Southern African Forestry Journal – No. 207, July 2006

guidance (Willoughby et al., 2004) aims to start to

address this by providing a decision framework to

allow managers to take an integrated approach to

reducing chemical use when dealing with these

damaging agents, and to determine the method of

management that will be likely to have the least

impact on the environment. Before widespread

adoption of an integrated approach to vegetation

management in the UK takes place, it is likely that

more research and technology transfer will be

required on the fundamental need to weed under

different silvicultural regimes and locations, as well

as investigations into novel lower cost, low impact,

socially acceptable techniques for pesticide reduction.

United States of America

About 33% of the land area in the United States of

America (US), or 302 million ha, is covered by forest

(Smith et al., 2001). The forest area is divided nearly

evenly east and west of the central plains. The

forests are diverse, containing over 800 species of

trees, 82 of which are exotic. About a third of the

forest was cleared for agriculture during the 19

century by European settlers. Of the total forest

area, about 204 million ha (67%) is classed as

timberland capable of producing more than 1.4 m

-1

and not legally restricted from timber

harvesting.

About 42% of U.S. forestland is publicly owned,

either by individual states or the federal government

(Smith et al., 2001). Public forestlands predominate

in the western states and privately owned forests

dominate in eastern states. About 21 million ha (7%)

of all U.S. forestland is reserved from commercial

timber harvest in wilderness, parks, and other legal

reserve classifications. The total area of timberland

has remained relatively stable during the last half of

the 20

century, with a net loss of only about 1% (12

million ha) since 1953. Most of these reductions have

come from withdrawals of public timberland for

wilderness or other non-timber uses.

A wide variety of silvicultural practices and

management intensities are used across the country.

About 11% of U.S. timberlands are plantations, with

two-thirds occurring in the southern states (Smith

et al., 2001). Nearly all tree species planted in

commercial forests are native to the regions in which

they are planted. About 58% of the volume of growing

stock is in softwoods, and the remaining 42% is in

hardwoods. Nearly all (90%) of the hardwood growing

stock is in the eastern states. About 68% of the

softwood growing stock is in western states, 22% in

the southern states, and 10% in northern states.

U.S. forests are an important part of the economy.

It is estimated that every forest-related job produces

an additional two jobs, therefore about 4 million jobs

are tied to the wood and paper industry. In addition,

recreational uses of the forest for hiking, camping,

fishing, hunting, and other non-timber uses continues

to grow, especially public lands, providing substantial

additional economic benefits in many parts of the

country (Loomis and Richardson, 2001).

The management of unwanted or competing

vegetation is vital to successful forest management

across the U.S. (Walstad and Kuch, 1987). Forests in

each region (Northwest, Southeast, Northeast, and

Lake States) have unique vegetation management

problems that can substantially reduce the growth

and survival of desired trees. Results from the longest

running studies (10–30 years) among these regions

suggest that gains in wood volume yield from

effectively managing forest vegetation are from 30 to

300% for major commercial tree species (Wagner et

al., 2004). Although there is no national tracking

system for the specific methods used to manage

forest vegetation, herbicides have been the primary

tool used to manage forest vegetation since the 1960’s

(Shepard et al., 2004; Wagner et al., 2004).

Despite their demonstrated safety, effectiveness,

and relatively low cost, the use of herbicides on

forestland has generated substantial public

controversy over the past several decades. Much of

the concern was initiated by the book “Silent Spring”

(Carson, 1962) and perpetuated with the use of

phenoxy herbicides (Agent Orange) by the U.S.

government during the Vietnam War (Walstad and

Dost, 1986). Perceived risks associated with using

herbicides in North American forests persist today,

and most of the other methods of vegetation

management are perceived as less risky and more

acceptable (Wagner et al., 1998). Pressure to reduce

or eliminate herbicide use has been most intense on

public forestlands, and as a result, relatively little

herbicide use occurs today on federal and state

forests for commercial timber production.

Controversy over the use of herbicides has

encouraged forest researchers and managers to develop

and use alternatives to herbicides, as well as develop

integrated approaches to forest vegetation manage-

ment (Wagner, 1993). Alternatives to herbicides for

managing forest vegetation include prescribed fire,

mechanical equipment, manual cutting, mulches,

grazing animals, and cover cropping (Harrington and

Parendes, 1993; Wagner, 1993; Comeau et al., 1996;

Wagner et al., 2001). These methods are often used

together with herbicides in many U.S. forests.

Depending on the circumstances, some of these

methods can be used in place of herbicides or reduce

the overall amount of herbicide use. Although not well

documented, experience suggests that when appro-

priately applied in some circumstances, alternative

methods can be just as effective as herbicides for

reducing competition and increasing stand growth,

but generally at substantially greater financial cost

than with herbicides. There also are many conditions

where alternatives to herbicides are not physically

possible, practical, available, or affordable. In addition,

many of the environmental and human health risks

of alternative methods are less well understood, and

are probably far worse in many situations, than for

herbicides.

Southern African Forestry Journal – No. 207, July 2006 75

In addition to the use of alternatives to herbicides,

there also has been a strong interest in developing

and promoting integrated forest vegetation

management (IFVM) approaches in U.S. forestry.

More recently efforts at promoting IFVM have come

from new systems of sustainable forest certification

established by various organisations. These systems

have been developed and are being promoted as a

means to improve the sustainability of forest

management practices across the U.S. and

internationally. The two most popular systems in

the U.S. are the Sustainable Forestry Initiative

(SFI) and the FSC. There are currently about 39

million ha certified under the SFI standard (SFI,

2003) and 3.8 million ha certified under the FSC

standard (FSC, 2004). SFI requires that forest

managers “minimise chemical use” and “use

integrated pest management where feasible” (SFI,

2002). FSC is more restrictive, stating that forest

managers are required “to adopt non-chemical

methods of pest management” and “to avoid and

move away from chemical pesticides wherever

possible,” and that “well-designed integrated pest

and vegetation management” be used an essential

part of their policy.

Despite the demand for IFVM, the principles,

methods, approaches, technologies, and scientific

information needed to implement IFVM are still in

their infancy. Considerable research is needed to

make IFVM, as it is currently conceived, a reality in

U.S. forests. Unfortunately, the same government,

industry, environmental, and forest certification

organisations demanding that reduced herbicide use

and IFVM be a firm policy on U.S. forestlands, are

doing little to support needed research this area. As

a result, herbicide use continues to be the primary

technology for managing forest vegetation (Shepard,

et al., 2004; Wagner et al., 2004), and many of the

principles of IFVM described above lack the scientific

and practical underpinnings required to put them

into practice.

DISCUSSION

Forestry is vital to each country reviewed, with the

type practised and forest products produced varying

according to the internal and external social,

ecological and economic needs of that country. Active

management of these forests is seen as critical to

ensure the sustained maintenance of both timber

and non-timber products. The management of

vegetation, whether for optimising growth,

eradication of exotics, or the maintenance of

biodiversity, is regarded as one of the most important

components of this process, and as such, has become

fully integrated within forest management as a

whole. This increased emphasis on the active

management of vegetation has resulted in changes

in the methods employed.

Despite the obvious attractions of utilising

herbicides, most countries have at some stage been

under pressure to regulate and reduce their use. The

degree of progress in finding research solutions and

their adoption varies from country to country. The

importance attached to reducing herbicide use also

varies, and is reflected in the steps taken to bring

change. For example, in Sweden and France there

has been limited herbicide use from the 1970’s,

whereas in South Africa, India and China,

opportunities exist to increase herbicide use,

particularly where the continued availability of

subsidised, or rural-based labour for manual

vegetation control operations is uncertain.

Among the countries reviewed, there appear to

have been three general approaches adopted to reduce

the use of herbicides. These are the continued use of

appropriate herbicides alone, but at lowered rates;

the use of alternative weed control methods to the

total exclusion of herbicides; or the continued use of

appropriate herbicides at lowered rates in combination

with alternative weed control methods.

Regardless of external pressure from governments

and non governmental pressure groups, a reduction

in herbicide use has occurred in many parts of the

world (for those countries where herbicides are still

used), through close co-operation between timber

growers, chemical companies and the country’s

regulatory bodies. Most countries have regulatory

processes in place that prevent using new herbicides

with harmful biological effects, for example high

mobility combined with long persistence and

significant health or ecological risk. Increasingly,

older active ingredients that pose a threat of

significant adverse environmental impact are also

being reviewed. In addition, the chemical industry

has continued to develop chemicals with more

attractive environmental profiles. The following

modifications have also reduced the amounts of

herbicides used: a reduction in the area treated; a

switch from high to low dosage products; the

introduction of highly active herbicides; reducing

application rates; removal of inactive isomers from

racemic mixtures; increased sprayer precision;

regulation of maximum dosage rates and maximum

number of applications. Similar modifications have

also occurred within the agricultural sector (Bellinder

et al., 1994; Lawson, 1994).

Although the basic principles of the need for

vegetation management when establishing trees

stretch back to at least the seventeenth century

(Evelyn, 1670; ECGPH, 1998), in modern times

research into understanding the underlying principles

behind weeding decisions may have been delayed due

to the development of herbicides which provided a

cheap, effective solution to the problem of competing

vegetation. Most knowledge on weed interference in

young plantations has come from empirical research

with herbicides (Richardson, 1993), focusing mainly

on tree crop response, herbicide type, application

rate, and degree of vegetation removal. Alternatives

to herbicides that have been developed and practised

include manual (hoeing/grubbing, slashing),

Southern African Forestry Journal – No. 207, July 2006

mechanical (rotovating, scalping), physical (organic

and inorganic mulches, thermal, inter- and smother-

cropping), biological and cultural methods. However,

these various vegetation control methods have, to a

large extent, been developed independently of each

other and consequently the technology of non-

herbicide treatments is not as advanced as that for

herbicides. Burnside (1993) suggests weed scientists

need to be pro-active and develop mechanical, cultural,

biological, and integrated weed management

research, otherwise they will continue to waste time

on defensive research and debating with environ-

mentalists. The practice of forest vegetation

management without herbicides requires more skill

than that with herbicides and tends to be less effective

and more difficult to prescribe, largely because a

forester must understand more of the biology of the

system (Harrington, 1993). Aspects such as

interference from competing vegetation, their ecology,

growth and behaviour have received less attention

(Nambiar, 1990; Collet et al., 1996). To match

appropriate vegetation control practices to soil, site

and species requirements, greater consideration needs

to be given to site quality and vegetation-tree

interactions (Neilsen and Wilkinson, 1990; Lowery

et al., 1993; Richardson et al., 1996). It is also

unlikely that any non-herbicide method applied in

isolation will bring about the desired effect, but

rather a combination of two or more methods, and

may even require the adoption of a totally new

species selection or silvicultural system.

Elmore (1992) suggests that scientists need to

advocate weed science by presenting the various

alternatives for controlling weeds, including both

non-chemical and chemical methods. Implicit within

these approaches is the principle associated with

integration, whereby appropriate technologies are

combined into an integral whole. It may be that the

greater the variety of techniques employed, the

smaller their individual importance and, by the

same token, the smaller their potential for

accumulation in or impact on the environment or the

development of resistance (Harr, 1992). Wagner

(1994) defines integrated forest vegetation

management (IFVM) as “managing the course and

rate of forest vegetation succession to achieve

silvicultural objectives by integrating knowledge of

plant ecology with a wide variety of complementary

methods that are ecosystem based, economical, and

socially acceptable.” Key elements of IFVM described

by Wagner (1994) involve forest managers 1) adopting

new perspectives about forest management, 2)

incorporating autecological information into

management strategies as a means of prevention, 3)

using economic or other thresholds before taking

management action, 4) enlisting a wider array of

complementary methods for vegetation control, and

5) more fully considering public concerns in the

design of vegetation management programs. Comeau

et al. (1996) suggest that IFVM (like Integrated Pest

Management) involves five steps: 1) problem

identification or diagnosis, 2) specifying injury and

treatment thresholds, 3) monitoring and predicting

vegetation development and young stand dynamics,

4) selecting treatment options, and, 5) evaluating

treatment effectiveness and impacts. Although many

countries have subscribed to the general principles of

IFVM, more research into specific strategies is

required. At present, where IFVM is practised, it

may be occurring by default rather than as part of

any formalised plan, or there may only be partial

integration at various levels, rather than total

integration, with the forestry system as a whole.

CONCLUSIONS

Challenges facing reduced herbicide use in

forest vegetation management

This review suggests that further work is required

on the following aspects:

• Accurate quantification of changes in herbicide

use over time (increased or decreased product

number and quantities used).

• Determination of the fate of herbicides currently

used in forestry, and the significance thereof

(rather than using agriculturally based data).

• Enhanced research developing alternatives to

herbicides, and assessing the ecological and

economic impact of these alternatives.

• Innovation regarding the dissemination of current

FVM information such that holistic and informed

decisions regarding the importance of different

vegetation practices (including herbicides) can

be made.

• Where appropriate, innovation is also needed

regarding the implementation of viable

alternatives to herbicides through IFVM.

• Refinement of the underlying principles of IFVM

within different silvicultural systems and

enhanced research of the highest priority

components of IFVM.

• Refinement of vegetation management standards,

the use of alternatives, and limitations on the

use of herbicides in evolving forest certification

systems being implemented in various parts of

the world.

• Education of the public, based on research that

has already been conducted, regarding the role

of appropriate herbicide use for managing

vegetation.

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Distinguishing Carotene and Xanthophyll Contents in the Leaves of Riparian Forest Species by Applying Machine Learning Algorithms to Field Reflectance Data

Chapter

Oct 2022

Carotenoid pigments are deeply involved in forests’ response to environmental stressors. Imaging spectroscopy has been widely applied for predicting leaf total carotenoid content. However, distinguishing carotene and xanthophylls, which is essential for monitoring plants’ stress at a broad-scale, remains challenging. To achieve this, calibrating models using field spectroscopy is necessary for applications to drone, airborne, and satellite imagery. In this respect, this chapter presents a novel approach based on Machine Learning (ML), which involves comparing various algorithms applied to continuum-removed field reflectance data for estimating carotenoid contents in leaves of riparian forest species. The first section of the chapter outlines recent advances and pitfalls in carotenoid retrieval using remote sensing. The next section describes the proposed approach, including the description of the dataset, the principles of commonly-used ML algorithms, as well as their performance in distinguishing carotene and xanthophylls. Finally, the last section discusses the perspectives of upscaling the approach to imaging spectrometers towards broad-scale, operational monitoring of forests’ response to environmental stressors.

Soil quality and pollution assessment around Jumar watershed of Jharkhand, India

Article

Full-text available

Dec 2021

This work aimed to analyze the soil quality and heavy metal contamination in the Jumar watershed of Jharkhand and suggests possible measures that could be taken to guarantee suitable management practices. Therefore, in the present work, the soil sampling was done at 8 locations, selected based on site visit. The GPS coordinates of the sampling sites were noted. The soil samples were collected during pre-monsoon and post-monsoon seasons for 2017 and 2018 at a depth of 20 cm from the top. Water samples were collected from the river flowing closer to the sampling points. Then, soil quality parameters such as pH; electrical conductivity; bulk density; moisture content; and surface water quality parameters such as pH, EC, TDS, DO, COD, BOD, alkalinity, turbidity, and nutrients (N & P) were studied. For heavy metal analysis (Pb, Zn, Cu, As, Ni), both soil and water samples were analyzed using an inductive coupled plasma-optical emission spectrophotometer (ICP-OES). Statistical tools like descriptive statistics, multivariate analysis, principal component analysis, correlation coefficient, and ANOVA were applied using SPSS version 21. The data indicate that the values of moisture content varied between 22.06 and 45.7%, soil bulk density varied between 1.20 and 1.55 g/cm 3 , pH varied between 7.79 and 8.17, and EC varied between 116.66 and 207.08 μS/cm. The concentrations of heavy metals in the pre-monsoon season were higher (Zn 0.183 mg/l, Cu 0.09 mg/l, Ni 0.061 mg/l) than those in the post-monsoon season (Zn 0.17 mg/l, Cu 0.076 mg/l, Ni 0.138 mg/l). The water quality index found using pH, EC, TDS, DO, COD, BOD, alkalinity, turbidity, BOD, COD, nutrients, and heavy metals indicated that most sites had excellent water quality, especially in the pre-monsoon period. But in the post-monsoon period of 2017, the water quality index showed that water was in poor condition. Overall water quality was found to be good. It was found that the soil had very slight traces of heavy metals and was slightly alkaline indicating the need for better watershed management practices for the future. PCA showed that the component variables like pH and EC were principal components specially for both pre-monsoon seasons, whereas through ANOVA, it was found that the variable has strong relationship among themselves.

A comprehensive experimental assessment of glyphosate ecological impacts in riparian forest restoration

Article

Oct 2021

Competition with invasive grasses is one of the most important drivers of tree planting failures, especially in tropical forests. A widely disseminated weeding approach has been glyphosate spraying, the most used herbicide globally in forestry and ecosystem restoration. However, glyphosate use in restoration is highly controversial and requires further studies to elucidate its effects on restoration processes and the environment. We evaluated the use of glyphosate in riparian forest restoration and its impacts on tree planting costs, weed control efficiency, planted seedling performance, herbaceous and woody species regeneration, soil bacteria, and environmental contamination, using mowing treatments as a reference and based on a controlled experiment established in the Brazilian Atlantic Forest. Glyphosate spraying reduced by half and a third the accumulated aboveground biomass of, respectively, weeds in general and of the invasive grass Urochloa decumbens compared to mowing treatments, and it reduced the cost by half. The performance of planted tree seedlings was markedly favored by glyphosate spraying compared to mowing treatments, as expressed by improved seedling height (~twice higher), crown area (~5× higher), and basal area (~5× higher); the regeneration of both native woody and ruderal herbaceous plants were also enhanced. Neither glyphosate nor its metabolite Aminomethylphosphonic acid (AMPA) residues were detected in either water runoff or soil samples, but they were found at relatively high concentrations in the runoff sediments (from 1.32 to 24.75 mg kg‐1 for glyphosate and from 1.75 to 76.13 mg kg‐1 for AMPA). Soil bacteria communities differed before and after glyphosate spraying in comparison to mowing plots (without glyphosate). Glyphosate spraying was far more cost‐effective than mowing for controlling U. decumbens and greatly improved the performance of planted tree seedlings and natural regeneration, while not leaving residues in soil and water. However, the changes in the structure of bacterial communities and high concentration of glyphosate and AMPA residues in runoff sediments highlight the need for caution when using this herbicide in riparian buffers. We present alternatives for reducing glyphosate use and minimizing its risks in tree planting initiatives.

Advances in the Mechanization of Regenerating Plantation Forests: a Review

Article

Full-text available

Jun 2020

Purpose of Review The mechanization of silvicultural work on forest plantations is usually driven by a decreasing supply of motivated labour which increases its relative cost. Mechanization can also result in other advantages like increased effectiveness, higher efficiency, and improved working conditions. The purpose of our review is to examine the last few decades’ endeavours to mechanize the regeneration activities of plantation forestry in the southern and northern hemisphere. In this case, regeneration activities include (1) site preparation; (2) tree planting; and (3) stand tending until the crop trees are free from vegetative competition. Recent Findings Originally, the mechanization of silvicultural work commenced in the northern hemisphere, but over the past decades, the most notable progress has been made in the southern hemisphere plantation forests. Although soil preparation is largely mechanized across the globe, tree planting and stand tending activities lag behind because of factors such as global variations in the manner in which they are performed, higher level of complexity, and low-cost competitiveness compared with existing labour-intensive methods. Summary For mechanization of regeneration/silvicultural activities to progress, productive and adaptable machines will be required where economies of scale permit cost-efficient operations. These machines will probably have to be modified to the specific forestry context of different countries. Knowledge of the existing and state-of-the-art regeneration technologies available in both the northern and southern hemispheres is important for foresters to make informed decisions about the selection and application of mechanized regeneration systems.

Species choice, planting and establishment in temperate and boreal forests: meeting the challenge of global change

Chapter

Full-text available

Nov 2019

Comparação entre dois métodos de eliminação de Eucalyptus sp. em Área de Preservação Permanente

Article

Dec 2014

O objetivo deste trabalho foi comparar a atividade de eliminação de Eucalyptus sp. em uma área de preservação permanente de margem de rio, realizada pelos métodos mecânico, por meio de anelamento, e químico, com uso de uma cavadeira química. A área de estudo pertence a uma empresa florestal localizada no estado de São Paulo. Foram amostradas 15 árvores em cada método, sendo cinco por trabalhador, e cada trabalhador executou a atividade em ambos os métodos de trabalho. A análise técnica foi realizada por meio de um estudo de tempos, contemplando a fase propriamente dita da atividade, de modo a se verificar o tempo médio demandado em cada método. A análise de custos foi realizada por meio da determinação dos custos fixos e variáveis, bem como do custo de produção. A análise da eficácia foi realizada pela observação visual das árvores amostradas, a fim de se verificar possíveis sintomas indicativos de morte dos indivíduos. Os resultados mostraram que o método químico apresentou menor tempo demandado, onde a relação entre os dois métodos foi de 4,3 árvores inoculadas com o produto químico para cada 1 árvore anelada. O método químico apresentou maior custo operacional em relação ao método mecânico, devido principalmente à depreciação da cavadeira química e aos custos com o herbicida. Entretanto, devido à maior produtividade, o custo de produção no método químico se mostrou menor. Por fim, durante o período de quatro semanas de observação, foi comprovada a eficácia do método químico, devido à existência de sintomas indicativos de morte, como coloração marrom das folhas e sua queda parcial. No entanto, não se deve tomar a decisão final sem antes verificar o impacto ambiental do produto químico.

Challenges and Monitoring Methods of Forest Management Through Geospatial Application: A Review

Chapter

Oct 2022

Life is dependent on forest cover. Many ecosystem services such as mitigation of climate change, protection of the watershed, maintenance of biogeochemical cycles, and control of environmental pollution may be achieved by a good forest cover. Because of the demands of a growing population, some devastating changes have occurred in land use, land cover, and resources utilization. Due to anthropogenic interference such as deforestation, overgrazing, cultivation with more fertilizers, urbanization, and industrialization, extreme climatic changes have occurred. Loss of wildlife species, extinction of microbial diversities, drought, eutrophication, sedimentation, and flash floods have become common. To manage resources sustainably and effectively, advanced technology of geospatial application is being utilized worldwide. Geospatial applications such as GIS and remote sensing methods, use of sensors, geostatic methods, spectral indices, and neural networking methods have made the processes from data collecting to developing plans for better greenery management much easier. This chapter aims to review the sustainable management strategies of vegetation cover and the challenges faced in this process. We review how remote sensing and GIS applications help in overcoming the various challenges of sustainable monitoring and management of vegetation and forest resources.

Estimated herbicide use in the commercial forest sector in South Africa

Article

Full-text available

Jul 2021

This paper examines herbicide use in South African commercial plantations in 2017/18 across three climate zones (cool temperate − CT, warm temperate − WT and subtropical − ST) for three genera (eucalypts, pines and acacias) grown for two end-products (sawn timber and pulpwood). Herbicide information was obtained from 46 timber plantations owned by six forestry companies, comprising 343 872 ha surveyed. The herbicide survey was divided into three climate zones due to increased vegetation growth (and hence more herbicide use) on more productive ST sites compared to moderately productive WT sites, with the lowest vegetation growth on CT sites (lower productivity). The survey was further divided into three distinct vegetation management phases associated with plantation forestry (pre-establishment, re-establishment and post-establishment) to compare herbicide use bet ween genera grown on an annual basis. A total of 188 288 kg (or 0.55 kg ha⁻¹) of herbicide active ingredient (a.i.) was applied in the area surveyed. Glyphosate-based products accounted for 97% of all the herbicides applied, and metazachlor and triclopyr butoxy ethyl ester accounted for 2%. Overall, herbicide use per hectare on an annual basis was highest in the ST zone, followed by the WT and CT zones. For both the CT and WT zones, the general trend was that the pre-establishment phase received noticeably more herbicides, followed by the re- and post-establishment phases (pre>re>post). This trend remained similar for the genera grown (pre>re>post), with hardwoods receiving more herbicides than softwoods. In contrast, there was little difference in herbicide use between the re- and pre-establishment phases for the ST zone, with the post-establishment phase being noticeably less. Besides providing benchmark data related to herbicide use in South African plantations, future research should investigate the potential for a reduction in herbicide use in those regions, vegetation management phases and management regimes where it is highest.

Perspectives and drivers of modernisation of silviculture re-establishment in South Africa

Article

Full-text available

Apr 2021
SOUTH FORESTS

Efficient and cost-effective re-establishment practices are important parts of any sustainable forest re-establishment programme. Re-establishment activities include residue management (post-harvest slash), preparation of a planting position, planting, fertilisation and vegetation management. In South Africa, these activities are largely labour intensive, time-consuming and relatively costly. Although mechanisation of site preparation during afforestation was achieved in the mid to late 1990s, plantation re-establishment operations in South Africa have remained manually oriented. However, there have been notable technology developments over the past decade. Semi-structured interviews were conducted with 66 experts (grower company specialists, foresters, contractors and machine manufacturers) to get their perspectives on modernisation of re-establishment activities in South Africa. Frequency distribution and chi-square test analysis found that two-thirds of the experts believed that re-establishment activities had progressed in terms of technology over the past decade. This development was reported as primarily due to the need to improve health and safety (91%), increase production whilst reducing costs (89%), improve stand productivity (quality) (86%), mitigate social (mainly labour) risks (80%) and reduce prevalent negative environmental impacts (50%). Key barriers to modernisation were identified as the capital cost of equipment (65%), reduction in employment opportunities (44%) and low utilisation of equipment due to seasonality of silviculture work (18%). Experts indicated that the efficiency of mechanised re-establishment equipment can be affected negatively by residues, high stumps and compaction of the site after harvesting. The results of this study will assist forestry stakeholders to make informed decisions when planning and implementing modernised silviculture operations.

Post-fire forest restoration in the humid tropics: A synthesis of available strategies and knowledge gaps for effective restoration

Article

Full-text available

Jan 2021
SCI TOTAL ENVIRON

Humid tropical forests are increasingly exposed to devastating wildfires. Major efforts are needed to prevent fire-related tipping points and to enable the effective recovery of fire-affected areas. Here, we provide a synthesis of the most common forest restoration strategies, thereby focusing on post-fire forest dynamics in the humid tropics. A variety of restoration strategies can be adopted in restoring humid tropical forests, including natural regeneration, assisted natural regeneration (i.e. fire breaks, weed control, erosion control, topsoil replacement, peatland rewetting), enrichment planting (i.e. planting nursery-raised seedlings, direct seeding) and commercial restoration (i.e. plantation forests, agroforestry). Our analysis shows that while natural regeneration can be effective under favourable ecological conditions, humid tropical forests are often ill-adapted to fire, and therefore less likely to recover unassisted after a wildfire event. Active restoration practices may be more effective, but can be costly and challenging to implement. We also identify gaps in knowledge needed for effective restoration of humid tropical forests after fire, hereby taking into account the ecosystems and socio-economic conditions in which these fires occur. We suggest to incorporate fire severity in future studies, to better understand and predict post-fire ecosystem responses. In addition, as fire poses a recurring and intensifying threat throughout the recovery process, more emphasis should be placed on post-restoration management and the prevention of fire throughout the different phases of the restoration process. Furthermore, as tropical wildfires are increasing in scale, establishing collaborative capacity and setting priorities for efficient resource allocation should become a major priority for restoration practitioners in the humid tropics. Finally, as global fire regimes are changing and expected to intensify in the context of climate change, land use and land cover change, we suggest to put continuous effort into fire monitoring and modelling to inform the development of effective restoration strategies in the long-run.

Herbicides et débroussaillants forêt : évolutions prochaines des homologations

Article

Jan 2002

A. Gama

Il est paru au Journal Officiel du 18 août 2002 un avis qui présente la "liste des substances actives entrant dans la composition des préparations dont l'autorisation de mise sur le marché est retirée". Concernant les herbicides pour la forêt, on y trouve : dalapon, dichloprop, fosamine et hexazinone. Cette décision implique le retrait de l'autorisation de vente. Les dates sont variables selon les spécialités.

Weed Science Extension in Transition

Article

Mar 1992

Clyde L. Elmore

Weed Science Extension is in a period of change. Though there is decreased funding for extension in the United States and Europe, the number of programs including extension activities is increasing in developing countries as shown by World Bank funding. There is a perception problem with the name weed science; we need a strong, recognizable science name. Decreases in one-on-one contact method for teaching, fewer extension weed specialists, and the increased need for interdisciplinary projects to support Integrated Pest Management and Sustainable Agriculture will increase stresses on our positions. These factors also increase the challenge for weed specialists and extension advisors (agents) to become leaders in current programs, initiate new multidisciplinary programs, and choose those programs that will benefit our discipline. Our clientele and the method of communicating with them will change, presenting yet another challenge.

The Role of Industry in the Future of Weed Science

Article

Mar 1992

Jost Harr

The agricultural-chemical industry has been offering solutions in plant protection for several decades. The primary role of Industry in weed control has mainly been to provide chemicals with increasingly attractive profiles regarding safe handling, ecological acceptance, and economical attractiveness. These objectives have been reached by significant developments, e.g. in rates, persistence, and specificity for non-target organisms. It is therefore safe to assume that in the year 2015 and beyond chemicals will continue to maintain a major role in weed control. However, as cropping systems and criteria for desirable control levels change, industry will have to change from a re-active to a pro-active participant in the development of integrated systems. Chemical solutions will be complemented by biological and agronomical methods and will be further supported by biotechnological successes in the crop area. In addition, it is anticipated that sophisticated computer models now in development will help exploit the potential of products as well as of integrated systems. Thus, fully integrated companies active in chemical, biological, and molecular-biological research and having branches in the agro-chemical as well as in the seed business will be especially suited to be driving forces in the changing world of modern weed control. The practice will ask for services much more than for single products. Industry will not only have to offer those services but at the same time assist in the education of growers to enable efficient use of the increasingly intricate methods of future weed control.

Weed Science—The Step Child

Article

Jun 1993

Orvin C. Burnside

A brief evolutionary description is given of the development of the discipline of weed science in the United States. Topics discussed include public recognition of weed science, losses from weeds, allocation of resources, herbicide usage, and future predictions of the development of the discipline. Weed scientists have had a major impact during the past four decades in increasing crop yields and reducing labor requirements for controlling weeds in crop production systems. Weed scientists have been so effective that recognition of their contributions and impact have often been overlooked in academic institutions but not in private industries that have staffed for herbicide development.

Changes in Pesticide Usage in the United Kingdom: Policies, Results, and Long-term Implications

Article

Jun 1994

Harry M. Lawson

Current United Kingdom (UK) government policy on pesticides is aimed at minimizing rather than arbitrarily reducing usage. It is to be achieved through a rigorous Approvals process, the setting of statutory maximum residue limits, regular monitoring, legislation on the safe use of pesticides on farms, and a core-funded research program on topics such as improved forecasting of pest infestations, more effective application techniques, alternative control strategies, integrated pest management and sustainable farming systems. Over the longer term these measures are expected to bring about substantial real decreases in pesticide usage, without the need to impose arbitrary reduction targets, such as have been implemented by several other European countries. Reductions in the usage of particular chemicals will also occur as a result of the implementation of European Community (EC) environmental legislation on pesticide levels in ground and drinking water and pesticide discharges into the North Sea. With herbicides, the tonnage of active ingredient applied in the UK declined substantially during the 1980s, due mainly to the increased use of products which were more biologically active at lower dosage rates than those they replaced. The actual percentage of crops sprayed remained at 95 to 100. Further reductions are likely in the 1990s, enhanced by factors such as dose-cutting by farmers in response to economic rather than environmental pressures and an increase in set-aside. Weed scientists are currently studying the long-term effects on weed population dynamics of reduced herbicide inputs in cereals, set-aside management, and more environmentally friendly, lower input rotations, as part of a wider program of research designed to provide government with scientifically based information upon which to decide future policies.

Reductions in Herbicide use for Forest Vegetation Management

Article

Jun 1994

Maxwell L. McCormack

There is distinct regional variation in forestry uses of herbicides. Different land ownership patterns affect policies and practices, and crop tree species characteristics differ within and among regions. Recent decreases in land areas treated have been attributed to budget reductions, changes in operating conditions, and pressures from the general public. Factors affecting future reductions in amounts of herbicides used will include new chemistry, improved delivery technologies, incorporating vegetation management into all aspects of young stand silviculture, and employment of alternative methods.

Alien weeds in Moist tropical zones: Banes and Benefits

Conference Paper

Jan 2001

Silent spring

Book

Jan 1962

Rachel Carson

"An important, controversial account ... of the way in which man's use of poisons to control insect pests and unwanted vegetation is changing the balance of nature." Booklist.

Forestry herbicides in the United States: an overview

Article

Dec 2004
Wildl Soc Bull

The role of herbicides for enhancing forest productivity and conserving land for biodiversity in North America

Article

Dec 2004
Wildl Soc Bull

Herbicide technology has evolved with forest management in North America over the past 60 years and has become an integral part of modern forestry practice. Forest managers have prescribed herbicides to increase reforestation success and long-term timber yields. Wildlife managers and others interested in conserving biodiversity, however, have often viewed herbicide use as conflicting with their objectives. Do herbicides increase forest productivity, and are they compatible with the objectives of wildlife management and biodiversity conservation? Results from the longest-term studies (10–30 years) in North America suggest that the range of wood volume yield gains from effectively managing forest vegetation (primarily using herbicides) is 30–450% in Pacific Northwest forests, 10–150% in the southeastern forests, and 50–450% in northern forests. Most of the 23 studies examined indicated 30–300% increases in wood volume yield for major commercial tree species and that gains were relatively consistent for a wide range of site conditions. Meeting future demands for wildlife habitat and biodiversity conservation will require that society's growing demand for wood be satisfied on a shrinking forestland base. Increased fiber yields from intensively managed plantations, which include the use of herbicides, will be a crucial part of the solution. If herbicides are properly used, current research indicates that the negative effects on wildlife usually are short-term and that herbicides can be used to meet wildlife habitat objectives.

Towards reduced herbicide use in forest vegetation management

Abstract

Recommendations

Chemical use in forestry

Vegetation Management

South African commercial forestry

Tree Classification System

The required herbicide application frequency for controlling Echinochloa crus-galli and Aeschynomene...

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