African
Journals Online
Southern African Forestry Journal
Issue 192, November 2001
ABSTRACTS
Studies on ovulate strobili and seed production of Pinus
patula in KwaZulu-Natal: scientific paper
Hagedorn, S.F.
Abstract: Cone and seed production studies in Pinus patula
were conducted by the Institute for Commercial Forestry Research
(ICFR) in KwaZulu-Natal as part of the improvement programme of the
species. The optimum altitude for female strobilus and seed production
is approximately 1450 m in KwaZulu-Natal. At four years after
establishment of the Breeding Seedling Orchards (BSOs), male and
female flowering is high enough to make a commercial cone collection
two years later worthwhile. The seed potential is between 120 and 140
seeds per cone and seed efficiency about 50 percent.
The effects of remedial fertilizer treatments on
growth and pulp properties of Eucalyptus grandis stands
established on infertile soils of the Zululand coastal plain:
scientific paper
Du Toit, Ben; Arbuthnot, Athol; Oscroft, Denis; Job, R.
Anthony
Abstract: Remedial fertilizer applications were applied to
nutrient-poor stands of Eucalyptus grandis growing on infertile
(ex-agricultural) land of the Zululand coastal plain. Two
nitrogen-rich fertilizer mixtures were applied in one year-old stands
at rates ranging from zero to 160 kg N ha-1 . Foliar
nitrogen levels increased highly significantly at the higher levels of
fertilization. A highly significant response to height, diameter and
basal area growth was observed within 6 months of treatment initiation
which was sustained until clear felling (8.3 years). A comparison of
the unfertilized control with the optimum treatment (i.e. a single
fertilizer dose equivalent to 80 kg N ha-1 ) yielded the
following results: Utilizable wood volume increased from 136.7 to
264.3 m3 ha-1 . The wood density showed a weakly
significant increase from 448 to 472 kg m-3. The
pulpability factor (defined as the pulp yield / kappa number)
decreased significantly from 2.63 to 2.32. The net effect of
fertilization on pulping properties is a non- significant increase in
pulp yield per unit volume of timber (chiefly due to increases in wood
density). The combined effects of fertilization on both volume growth
and pulping properties resulted in an increase in the pulp yield on a
plantation area basis from 32.03 to 63.43 t pulp ha-1 in
the 8.3 year-old stand.
Quantifying the geographic range of Pinus patula
var. longipedunculata in Southern Mexico using morphologic and
RAPD marker data: scientific paper
Dvorak, W.S.; Jordan, A.P.; Romero, J.L.; Hodge, G.R.;
Furman, B.J.
Abstract: Pinus patula var. longipedunculata
occurs in southern Mexico, but the extent of its geographic range is
poorly defined. Trees from some populations are morphologically
similar to P. tecunumanii , which adds to the confusion over
the variety's geographic range. Recent field explorations have
identified six new populations of supposed P. patula var. longipedunculata
in the Sierra Madre del Sur of Oaxaca and Guerrero. In an effort to
determine the validity of these sightings, botanical samples were
collected from 79 trees in these six populations and were assessed for
ten cone and needle morphology traits. Random Amplified Polymorphic
DNA (RAPD) analyses were conducted on 73 trees from the six
populations, 38 of which were in common to 79 trees used in the
botanical study. Species control lots for both the botanical and RAPD
studies were P. herrerae, P. oocarpa, P. patula, P.
pringlei and P. tecunumanii. Morphologic assessment
indicated trees in the Manzanal population were predominantly patula
-related, but trees in the other five populations grouped into two
clusters that were significantly different from P. patula and P.
tecunumanii and not strongly related to the other control species.
Conversely, molecular marker results indicated that four of the
populations, Manzanal, San Mateo, Tlacuache (Oaxaca) and Yextla
(Guerrero) were genetically indistinguishable or closely related to P.
patula. The remaining two populations, Juquila (Oaxaca) and Palo
Blanco (Guerrero), were closely related genetically to P. herrerae
/ P. pringlei. The morphologic study indicated that 5% of the
trees in the six populations were indistinguishable from P.
tecunumanii, but marker analyses indicated that the trees in
question were of either P. patula or P. herrerae / P.
pringlei origin. Pinus tecunumanii does not appear to occur
in the Sierra Madre del Sur of Oaxaca and Guerrero, but a four-needle
type of P. herrerae that can be very easily confused with P.
patula var. longipedunculata does. The geographic range of P.
patula var. longipedunculata is defined as occurring from
northeastern Oaxaca to central Guerrero. The existence of populations
of the variety in Chiapas needs to be verified using molecular
techniques. The genetic relationship between P. pringlei and P.
herrerae is much closer than heretofore thought, even though the
morphology of each species is very distinctive.
The impact of vegetation control on the
establishment of pine at four sites in the summer rainfall region of
South Africa: scientific paper
Little, K.M.; Rolando, C.A.
Abstract: Four trials designed to study the impact of
intensive, selective and commercial vegetation control (operational)
practices on pine establishment were implemented across an altitudinal
and climatic range of sites in the summer rainfall region of South
Africa. The trial sites incorporated one high altitude (1650 m a.s.l.)
cool temperate site, two mid-altitude (1000 m a.s.l.) warm temperate
sites and a low altitude (60 m a.s.l.) sub-tropical site. Treatments
implemented at each trial included a weedy and a weedfree control,
operational weed control, selective control of herbaceous or woody
vegetation types as well as a ringweeding treatment at three sites.
The results indicate that the abundance and type of vegetation at a
site varies as a function of the local physiographic and environmental
conditions as well as historical land-use. At the high altitude site
the competitive vegetation was less abundant than at the mid-low
altitude sites where vigorous woody vegetation dominated. Due to the
differential growth of vegetation across the sites, tree growth
responses to intensive and selective vegetation control were site
dependent. There were no significant tree growth responses to
vegetation management at the high altitude site. Relative to the
weedfree control, tree growth suppression was highest on the weedy and
woody treatment plots at the warmer, mid-low altitude sites. No
significant suppression of tree growth occurred where the vegetation
was kept away from the trees, on the ring-weeded and operational
treatment plots. Herbaceous vegetation caused significant tree growth
suppression only where climatic conditions were conducive to extended
seasonal growth.
A comparison of the impacts of winter versus summer
burning of slash fuel in alien-invaded fynbos areas in the Western
Cape: scientific paper
Holmes, Patricia
Abstract: Dense slash from cleared stands of invasive alien
trees in mountain catchment areas poses a hazard to fynbos recovery
and soil stability, if it burns under extreme summer weather
conditions. Experimental burning of alien slash fuel was done to
investigate whether winter burning of fuel may be used as a practical
alternative to risking a summer wild fire. Fire intensity, heat
release at the soil surface and indigenous post-fire plant recruitment
were compared between different blocks of the same felled alien stand,
which burnt during a controlled winter burn and a summer wild fire.
Both fires consumed nearly all the fuel, but fire intensity and heat
penetration into the soil were much greater for the summer wild fire
than the winter control burn. Fynbos plant recruitment following the
main winter establishment season was extremely low in the summer burn,
and indicated that propagules in the upper soil had been killed in the
fire. Species that emerged following the summer burn were
predominantly resprouters or species with larger seeds that could
emerge from deeper in the soil. Plant recruitment, species richness
and cover were much higher following the winter burn. Half the species
(mainly forbs, resprouters and legumes) appeared during the summer
after the fire, but the remainder appeared only after the main winter
establishment season. Small-seeded species were few and indicated that
all germination cues were not optimized by burning in winter.
Alternatively, soil-heating during the winter burn was sufficient to
kill small seeds located close to the surface. Comparisons between
summer slash fires on granite versus sandstone parent materials
suggest that the impacts are much greater on the granite. The impacts
were also greater where fuel loads are high. It is recommended that
summer burning of slash fuel be avoided in all areas supporting old
(>8 yr), dense (>75% cover) alien stands. Furthermore, summer
slash fires also should be avoided for moderately dense (>50%)
alien stands on shale bands or granite-derived soils. As an interim
strategy in these areas, winter burning of fuel should be considered
to prevent excessive soil and propagule damage during a summer wild
fire. However, future alternatives, such as the immediate targeting of
low-density stands and the implementation of biological control
agents, urgently should be sought.
The wood quality of Pinus chiapensis (Mart.)
Andresen grown in the Mpumalanga forest region: scientific paper
Malan, F.S.
Abstract: The ten best performing families selected in a Pinus
chiapensis trial at Tweefontein forest near Sabie have been
evaluated for wood and saw timber properties. The wood was found to be
soft, remarkably uniform both within and between annual rings, stable,
with a well-defined heartwood zone. The latewood proportion of the
annual rings was extremely small, resulting in a poorly defined ring
structure.
The fifty trees studied had an average air-dry density of 0,420 g /
cm3 (extracted and at 12 % moisture content) with
individual tree densities varying from 0,380 to 0,465 g / cm3
at 0,8 m height level. Differences between families were highly
significant, suggesting that there is a strong potential to increase
the density of the wood through tree breeding.
Knots were relatively small and well shaped, and normally occurred
in small clusters. Knot occlusions following pruning were accompanied
by little grain distortion. When present, the amounts of included
resin, pieces of bark and other debris at the occluded pruning cuts,
were small and of little practical significance.
The wood machined without any difficulty in the wet and dry
condition. Boards dried without any significant drying degrade, but
moisture loss during drying from the heartwood zone was markedly
slower compared to what is normally experienced with the pith zone of
other South African commercial pines.
Some sawn pieces may not be suitable for some structural purposes
where strength is important, while tests on Colombian and Brazilian
grown P. chiapensis have shown that the species may not be
acceptable for pulp production because of low pulp yields and high
alkali consumption. Owing to its high degree of uniformity it might be
well suited for special products such as for internal construction
purposes, panelling and other decorative work, woodcarving and some
applications in the furniture manufacturing industry. It might also be
suitable for the manufacturing of items such as match sticks,
toothpicks, clothes-pegs and other small wooden objects.
Mechanical Feller-buncher felling: an example study
on timber value recovery in South Africa: management paper
Kewley, Steven; Kollegg, Loren (Kellogg, Loren)
Abstract: Timber breakage during felling reduced the value
of timber harvested from a stand. This is especially evident in the
larger saw timber stands where large trees are being harvested. A
field study was completed with the objective of quantifying and
comparing the timber value recovery between conventional chainsaw
felling, and mechanical feller-buncher felling, using two pine species
- Pinus elliottii and Pinus taeda.
Although there was no significant difference in mean volume
recovery, felling with the feller-buncher yielded a 2.4% higher volume
recovery than chainsaw felling. Mean value recovery, however, for
felling with the feller-buncher was significantly higher than chainsaw
felling. Study results showed that feller-buncher felling had a 6.8%
lower tree value recovery than chainsaw felling. The difference is
attributed to a decrease in breakage and improved sawlog recovery when
felling with the feller-buncher.
Woodlands or wastelands: examining the value of
South Africa's woodlands: management paper
Shackleton, C.M.; Willis, C.B.; Scholes, R.J.
Abstract: The savanna woodlands are the largest biome in the
country, constituting one-third of South Africa. They are also home to
one-quarter of the population, with 70 % of the former homelands being
in the savanna biome. Consequently, they have the potential to make a
marked contribution to the national economy, both in the formal and
informal sector. They are also valuable on a national scale in terms
of the ecosystem services they provide, such as carbon storage,
biodiversity and water yield. Until recently the real and potential
values attached to South Africa's savannas have not been recognised in
policy fora and government institutions. Recent policy changes,
especially the National Forestry Action Programme and the National
Forest Act, have attempted to remedy this situation. These policies
have not filtered down to land owners and managers, nor have they
resulted in a redirection of government resources. Thus, large areas
remain subject to unsustainable use. It is necessary that the true
value of woodlands be determined and acknowledged as a stimulus to
government agencies, the private sector and local users to use this
valuable resource sustainably.
Solar-assisted drying of timber at industrial
scale: management paper
Bux, M.; Bauer, K.; Mühlbauer, W.; Conrad, T.
Abstract: The production of high quality timber from
hardwood requires a gentle and controlled drying to a low wood
moisture content. While ambient air drying depends on the weather
conditions, conventional hightemperature dryers cause high investments
and energy costs. Up to now, solar dryers could not be established in
industrial timber production, due to their insufficient drying
capacity and the lack of an adequate control of the drying conditions.
Therefore, a new solar dryer was developed, which allows a
controlled drying of up to 250 m3 of timber per load. The
frame of the dryer is covered with a transparent, highly UV-stabilised
and well isolating air bubble foil. A specially developed
microprocessor control regulates air flow, temperature, humidity and a
back up wood chip furnace, which provides the heat during night and
unfavourable weather conditions. The drying regime is adjusted
automatically according to the type of wood, the board thickness and
the ambient air temperature.
The paper presents the experiences gained during the operation of
the two worlds largest solar timber dryers, drying up to 35000 m3
of eucalypt annually. The investigations showed, that investments,
drying costs and energy consumption could be reduced by 50 % compared
to conventional high-temperature drying systems. At the same time the
quality of the timber was improved considerably.
Exotic pine forestry in the Southern Hemisphere: a
brief history of establishment and quarantine practices: review paper
Burgess, Treena; Wingfield, Michael J.
Abstract: Afforestation with exotic softwoods commenced in
the Southern Hemisphere at the end of the 19th century. Initially the
areas under afforestation were small, but today, exotic plantation
species are the basis of huge forestry industries, forming a crucial
component of the economies of many countries. Early plantations were
relatively free of pests and diseases. However, as the industry
expanded, so did pest and disease problems. Initially, quarantine
regulations were non-existent or poorly enforced, but in the later
part of the 20th century rigorous quarantine regulations were
implemented. More recently, the opening of global markets and the
increase in trade has increased the risk of introducing new pests and
pathogens. The potential losses to the forestry industry are
immeasurable and vigilance is required from importers, exporters and
even tree breeders moving germplasm, to prevent the spread of
pathogens around the world. This review considers the history of
softwood forestry and quarantine in some of the most important
producers of forest products in the Southern Hemisphere, namely South
Africa, Australia and New Zealand.
Interspecific hybrids in Zimbabwe: status review
and future challenges: review paper
Gwaze, D.P.
Abstract: Several F1 eucalypt and pine interspecific hybrids
have been tested in Zimbabwe. The first hybrids tests were of pine
species, and these were established in 1973. The results from these
early tests were not spectacular and interest in hybrids was lost
until the 1990's when impressive eucalypt and pine hybrid performances
were reported in South Africa and Australia, respectively. During the
period 1990-1993 pine hybrids were imported from Australia and
eucalypt hybrids from South Africa, and tested on various sites around
Zimbabwe. Detailed analyses in 1999 / 2000 showed that many of the
tested hybrids outperformed the pure species on specific sites. The
reports based on these analyses highlighted the need to test local
hybrids, the need to determine wood qualities and the need to
determine cost-effective methods to mass-produce the most promising
hybrids. Currently, local pine and eucalypt hybrids are being
developed for field-testing. These developments and further research
needed to realise the full economic potential of hybrids are
discussed.
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