African
Journals Online
Southern African Forestry Journal
Issue 195, October 2002
Abstracts
Southern Africa : woodbasket of the future : guest
editorial
Job, John L.
5-10
Abstract: With increasing political and economic stability
in prospect, the region's potential as a grower of plantations is
explored. Along with the potential afforestation, the region's
ability to exploit the resources so generated is considered
across a variety of manufacturing industries. The need for
political alignment, as well as stability, as prerequisites for
success are discussed. Concerted efforts within the region are
needed to create the potential and much-needed wealth.
Deployment strategies to maximise value recovery from tree
improvement : the experience of two South African companies :
operational deployment of technology
Bayley, Arlene D.Blakeway, Flic
11-22
Abstract: Current strategies for deployment of improved
material from the tree breeding programmes of two South African
forestry companies are reviewed for all commercial species,
including both hardwoods and softwoods. How high site variability
and propagation constraints restrict this are examined and
illustrated with examples. The multiplication techniques are
viewed not just as a means of amplifying improved material, but
also from a plant quality perspective and the effect this can
have on the establishment of the crop. Lastly, two important
questions are posed. Is enough known about the sexual
reproduction of the commercial species in South African forestry?
What developments in vegetative propagation techniques are
necessary to allow the exploitation of the gains being offered
from advanced generation breeding in the tree improvement
programmes within the two companies?
Some issues associated with the commercial implementation
of weed management recommendations : operational deployment of
technology
Little, Keith M.Dyer, Colin
23-32
Abstract: The Institute for Commercial Forestry Research
(ICFR) is owned by the South African forestry industry and
undertakes research on applied aspects of commercial timber
growing. The type of research conducted depends, to a large
extent, on a combination of our areas of expertise and the needs
as determined by our sponsors. By way of a case study (one single
trial) in the field of weed management research, an attempt is
made to show the processes of research and development and how
these lead to knowledge that is transferred to the end user. From
this single trial with clear objectives, a number of tentative
recommendations were made based upon early results. The
commercial implementation of these results was only partially
successful, with questions being raised that could only be
addressed through additional trial work. Even though subsequent
research efforts can be considered a success from a research
perspective, in that they provided solutions to the questions
asked, few have been applied commercially. This raises concerns,
especially as to what the issues are that prevent the
implementation of weed management recommendations. Some of the
issues discussed include: researcher competence, whether the
industry knows what it wants, robustness of research findings,
how technology is transferred, complexity of weed growth
information, institutionalisation of systems and economic and
political constraints. By way of discussing the mixed successes
in technology transfer, a hypothesis is developed as to where the
barriers to effective technology transfer are and how these can
be overcome. We believe that the most effective way of overcoming
this is through the establishment and strengthening of the
research-consumer interface. This needs to be included as a
research activity, and to be enabled and resourced by end-users.
Operational gain : measuring the capture of genetic gain :
operational deployment of technology
Pallett, Robert N.Sale, Giovanni
33-38
Abstract: The southern African forestry and forest
products industry contributes two percent of the countries gross
domestic product, yet is one of the most globalised industrial
sectors. Forest product exports make up eight percent of the
countries total exports and produce an annual net trade surplus
of R5 billion. To remain globally competitive, the southern
African forestry industry must continue to produce low cost wood
of the required quality for processors. Increasing yield per
hectare is a significant means to achieving this aim and is
actively pursued by industry players, particularly through
genetic improvement of planting stock. To maximise future
productivity from plantations, it is important to consider and
measure a number of components within the deployment process. The
concept of operational gain is more than the weighted average of
the genetic quality of planted hectares, and encompasses tree
breeding efficiencies, propagation efficiencies, matching of
species and genotype to site, plant use efficiency and early
measures of stand density and growth. To test the operational
gain concept, trials have been planted to eucalypts in the
Kwa-Zulu Natal midlands. Two and a half year volume measurements
from two of these trials are presented. The trials test a
factorial combination of species, genetic level, stand density
and level of silvicultural input. Results at two and a half years
demonstrate the additive nature of yield gains associated with
each of these factors. The results confirm the need to measure
efficiencies in all the components of the deployment process in
order to maximise productivity. It is suggested that the
measurement of operational gain, should include the measure of
genetic gain against established benchmarks, conformance to
site/species matching best practice, plant use efficiency and the
assessment of stand density and variation in height at one year,
for eucalypt pulpwood crops.
Management of insect pests : have the goalposts changed
with certification? : operational deployment of technology
Govender, Prem
39-46
Abstract: The certification of commercial forestry
according to the Forest Stewardship Council specifications has
successfully occurred in many South African plantations and this
trend is set to increase in the future. Various principles and
criteria govern the management of insect pests in certified
forests, which differ from traditional control measures.
Regulations on the use of insecticides, biocontrol agents,
monitoring, assessment and management of insect pests have become
more specific. World Health Organisation type 1a and 1b,
chlorinated hydrocarbons and persistent, toxic and
bioaccumulative insecticides are prohibited. Only Bacillus
thuringiensis is acceptable from the about twelve insecticides
used in forestry. The use of biological control agents need to be
documented, minimised and monitored. Flora and fauna in general
and insect pest species must be regularly monitored and the
results incorporated into an ongoing management plan. A summary
of monitoring indicators should be made available to the public.
An integrated pest management approach for the control of insect
pests is advocated but with restrictions on the use of
insecticides and biological control. Although the FSC management
plan for the control of insect pests would certainly contribute
to the sustainability of commercial plantations in the future, it
poses many challenges in the short term.
Growth and yield as an indication of sustainable forest
management in industrial plantations : evidence for sustainable
plantation forestry
Morris, A.R.Smith, C.W.
47-56
Abstract: Evidence from growth and yield measurements of
successive rotations of industrial plantations is reviewed. The
objectives, methodologies and limitations of the evidence is
discussed and suggestions made concerning appropriate aims and
methods for such work. Reported comparisons of forest
productivity between successive rotations of Pinus radiata,
P. patula, P. taeda and P. elliottii
demonstrate that yield declines can occur when inappropriate
forestry practices are applied to specific sites. Identification
and understanding of these effects appear to have been initiated
by data from simple growth comparisons between rotations. In
these studies the observation of decline in successive rotations
was followed by empirical and process studies to establish a
cause. This in turn leads to modification of forestry practice to
correct the decline. These experiences suggest two important
objectives for monitoring of growth and yield in successive
rotations; firstly, as a physical check that the actual trend in
yield between rotations is consistent with expectation and
secondly, as a tool to elucidate the cause of observed change in
productivity between rotations. The chosen methodology must
relate to the specific objective of the study. The lack of
comparative data from successive rotations of fast-grown Eucalyptus
plantations is highlighted.
Biological processes as indicators of sustainable
plantation forestry : evidence for sustainable plantation
forestry
Scholes, Mary C.
57-62
Abstract: This paper discusses the use of an ecosystems
approach in the management of plantations and the concept of
plantations in providing goods and services. Ecological
indicators are compared for the CIFOR and South African systems.
The CIFOR system focuses on three criteria, which involve the
maintenance of a) biodiversity, b) ecosystem function and c)
genetic variation. The South African system has chosen six
criteria: a) the protection of natural forests, b) conservation
of biodiversity, c) conservation of ecosystem structures and
processes, d) protection of forests from fire, pests, diseases
and alien plants, d) maintenance of production potential and e)
the conservation of soil and water resources. Ideas are presented
on indicators and measures, which may be useful in the
sustainable management of nutrient cycling, yield production,
pest outbreaks and water use and quality. Indices of nitrogen
mineralization rates, soil carbon stocks and ongoing mensuration
of biomass are key measurements. Under global change conditions
it is predicted that the outbreaks of pests will be more severe
and the industry must be prepared to invest in appropriate
monitoring and technologies. It is emphasized that a framework
needs to be provided into which the indicator measures can be
placed. This would best be accomplished by the simultaneous
development of a number of relatively simple ecosystem and
plant-physiological based models.
Nutritional sustainability of Eucalyptus plantations : a
case study at Karkloof, South Africa : evidence for sustainable
plantation forestry
Du Toit, BenScholes, Mary C.
63-72
Abstract: The nutritional sustainability of a
short-rotation Eucalyptus grandis plantation system was
evaluated in a trial located at Karkloof, KwaZulu-Natal, South
Africa, by determining nutrient pools and fluxes. Nutrient pools
in the forest floor and biomass (above- and below-ground) were
assessed by destructive sampling. The size of nutrient pools in
the soil that approximate to readily available and potentially
available fractions was estimated from chemical extractions. An
approximate nutrient input-output budget was constructed. The
study has shown that large nutrient pools occur in the forest
floor and below-ground biomass when compared to most
short-rotation eucalypt cropping systems overseas. The readily
available soil pools are moderately large (100 to 800 kg ha-1)
when compared to similar systems in the tropics (Brazil &
Congo). The potentially available nutrient pools are particularly
rich in potassium (2.5) and magnesium (1.1 t ha-1).
This indicates that the system is well buffered against nutrient
depletion in the short and long term. Estimates of nutrient
fluxes revealed that fertilization and mineral weathering
constitute small inputs, while atmospheric deposition makes a
major contribution to the system (95% of total N inputs, 92% of
total Ca and Mg and 82% of total K inputs). Sizeable nutrient
losses were caused by slash burning (N), leaching (Ca & Mg),
and both wood harvesting and firewood collection (N, K & Ca).
The management regime and intensity of operations both have a
pronounced effect on nutrient fluxes to and from the system, and
hence, the net balance of the budget was calculated for different
management regimes at representative intensities. Net fluxes were
positive or near zero for most elements in the absence of
firewood collection or slash burning and changed to losses of
between ca. 5 to 10 kg ha-1 a-1 per
individual nutrient when slash burning was incorporated in the
regime. Despite the increases in nutrient loss with more
intensive management, the indices of nutritional sustainability
for all regimes tested still indicated a stable system with
respect to nutrition. Nutritional sustainability has been gauged
by other researchers using the ratio (nutrient export in
harvesting) / (available nutrient pool size). An index of
nutritional stability (pINS) is proposed, based on the negative
logarithm of the ratio (net nutrient loss) / (nutrient pool)
where the nutrient pool can be readily available soil pools or
(long term) potentially available system pools. Although this
index has intensive data requirements, it evaluates management
intensity effects as well as the "buffer capacity" of
the system more rigorously than previously proposed indices.
Water use efficiency : what are the implications for
plantation forestry? : evidence for sustainable plantation
forestry
Pammenter, N.W.
73-78
Abstract: Water use efficiency (WUE) is the ratio of some
measure of growth or carbon assimilation to water utilization. It
can be considered at the level of the leaf, whole plant or stand,
and can be expressed in terms of total plant biomass or that of
harvestable stems. It is a ratio and will be influenced by
changes in either or both of the components. WUE is extremely
variable with climatic and local weather conditions, soil type
and plant age. Increases in yield of harvestable stem would
increase WUE, but breeding practices have probably already
maximised stem yield. Reductions in transpiration are considered
unlikely to be achievable in plants growing in well-watered
soils, and any such reductions would probably also bring about
reductions in productivity. 'Water conservation' strategies are
also unlikely in plants in water-limited soils, as competing
neighbours would utilise the conserved water. It is not known
whether there are differences among genotypes in intrinsic WUE,
but if there are, these are more likely to become apparent under
conditions of low, rather than high water availability. However,
high WUE may not be a good selection criterion for plants
suitable for water-limited conditions; the ability to acquire
water and the ability to survive periods without water may be
more important than the efficiency with which water is utilised.
The future of exotic plantation forestry in the tropics and
southern hemisphere : lessons from pitch canker : evidence for
sustainable plantation forestry
Wingfield, Michael J.Coutinho, Teresa A.Roux,
JolandaWingfield, Brenda D.
79-82
Abstract: Exotic plantation forestry, particularly with Pinus
and Eucalyptus species in the tropics and southern
Hemisphere, has expanded dramatically during the course of the
last Century. Success of these intensively managed plantations is
largely attributed to the fact that trees have been separated
from their natural enemies. Due to increasing rates of
introduction of pests and pathogens, this is a situation that is
changing relatively rapidly. There is also growing evidence that
unexpected native pests and pathogens are developing the capacity
to infect exotic plantation trees. Clearly, highly productive,
and intensively managed fibre farms are threatened and their
future is likely to be more complicated than it has been in the
past. The appearance of the pitch canker pathogen, Fusarium
circinatum in South Africa, provides a contemporary example
of new problems relating to a pathogen, previously absent from a
country. This pathogen was first found in a single nursery and it
has rapidly spread to all South African pine nurseries. It has
significantly complicated pine propagation and is resulting in
substantial losses in plantation establishment. Whether the
fungus will manifest itself as a pathogen of adult trees as is
the case elsewhere, is unknown. But this prospect is a matter of
serious concern. Research aimed at a better understanding of the
biology of F. circinatum in South Africa is essential.
Furthermore, development of disease tolerant planting stock, in
advance of a potentially deteriorating situation, would appear to
be crucially important.
Harvesting genetics for productive plantations : creating
new germplasm
Verryn, S.D.
83-88
Abstract: Tree breeding has had significant impacts on the
success of the South Africa forest industry. Examples are cited
for tree growth rate, where for instance, a mean genetic
improvement of 39% has been measured in F2 E.grandis over
unimproved controls over various sites. The mean improvement of
F1 over P0 was recorded as 15% in the genetic gains trials, which
compares with the realised reduction of rotation length by 10-15%
in sawtimber crops. In E.grandis sawtimber, the impact of
wood splitting has been reduced by approximately 29%. Similarly,
substantial progress has been made in stem form, and species
selection against pest and diseases. Selection of species with
suitable properties for pulp yield is currently gaining momentum,
with the increasing use of E.smithii, and the initiation
of Project Pulp. Tree breeding will have to harness increasingly
sophisticated technologies to make advances in the traits which
have already undergone some improvement, such as tree growth.
This is due to the gradual fixing of the genes which are easily
captured, leaving the more challenging inheritance for advanced
breeding techniques. There is a constant change in the market
needs from trees (and tree breeders), as technologies change,
markets change, and the environment changes. Tree breeding will
continue to be a critical tool in maintaining a healthy forestry
industry.
"New" pine species and hybrids: is there still
potential? : creating new germplasm
Kietzka, Eric
89-92
Abstract: Many tree breeding programs are moving into
advanced generation breeding, and breeders need to ensure
continued gains from these programs. The potential of infusing
genetic material into existing breeding programs, the
introduction of "new" species, and hybridisation are
discussed as options available to the tree breeder to increase
variability and gain. Pinus patula is the most important
pine species in South Africa. The provenance origin of the first
introductions of P. patula seed is unknown. The results of
a series of P. patula provenance / progeny trials
established from wide range collections made by CAMCORE indicate
that the original importations did not come from the best
sources. Infusion of this new material into local breeding
populations will result in generating new variation in the base
populations and resultant added gains. Mondi Forests main
processor requirements are for pulp and paper and P. patula
is the preferred species. Recent expansions in afforestation have
tended towards marginal land with regard to rainfall, temperature
and soils. Results from a series of CAMCORE P. greggii
trials established on these site types indicate that P.
greggii shows potential as an alternative to P. patula
. Species hybridisation is another option for breeders to
generate new variability, to take advantage of hybrid vigour or
to combine specific traits from different species. Hybrid work in
South Africa was initiated by SAFRI in 1968 and the P.
elliottii x P. caribaea hybrid showed excellent growth
potential. Mondi has concentrated its efforts on the P.greggii
x P.patula hybrid and results of the first trial established
with this hybrid has shown it to have potential.
Somatic embryogenesis as a tool to capture genetic gain
from tree breeding strategies : risks and benefits : creating new
germplasm
Jones, Nicky 93-102
Abstract: For clonal testing and ultimate
commercialization of selected clonal lines, breeding programmes
are reliant on vegetative propagation techniques. Somatic
embryogenesis is a propagation technique that has the potential
to assist with the deployment of pine clones. By virtue of its
amenability to cryopreservation, it offers the opportunity to
overcome the constraints associated with conventional vegetative
propagation (hedge maturation), which hamper the advancement of
clonal forestry in woody tree species. The limitations of somatic
embyogenesis in pines include poor induction and maturation
frequencies and the potential for somaclonal variation. These
restrict the number of families or genotypes that can be
processed. Methods of overcoming these restrictions are discussed
together with the associated long-term potential of somatic
embryogenesis, including genetic engineering and synthetic seed
production.
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