African
Journals Online
Southern African Forestry Journal
Issue 191, July 2001
ABSTRACTS
Simultaneous growth and yield models for Eucalyptus
grandis (Hill) Maiden plantations in Zimbabwe
Mabvurira, Danaza; Miina, Jari
Abstract: Simultaneous stand-level growth and yield models
for Eucalyptus grandis in Zimbabwe were developed from
Correlated Curve Trend (CCT) and Nelder wheel experiments replicated
on five different sites. Nonlinear three-stage least squares method
was used to simultaneously fit prediction and projection equations for
stand basal area, volume and stand density (S/ha). The age-dominant
height model was fitted separately to the data to enable the
estimation of site indices for the plots. The data consisted of a
total of 313 growth periods of stands ranging in age from 1.3 years to
19.5 years, and site indices from 14 m to 37 m (at an index age of 7
years). The models were validated both quantitatively and
qualitatively. Correlation between error components for basal area and
volume was strong and significant while the correlation of stand
density with basal area and volume was either weak or non-significant.
Degree of determination was relatively high for all the models. The
mean biases for basal area, volume and stand density predictions were
negative. The use of these models in stands managed for pole or saw
log production was recommended.
Yield potential of selected Eucalyptus
genetic stock on the sandy soils of the South African Cape West Coast
Van Wyk, G.; Van Laar, A.; Theron, J.M.
Abstract: Land available for afforestation in the Western
Cape Region has largely been subordinate to agriculture. Eucalypt
species have never been tested intensively along the West Coast.
Climatic matching suggests planting of species from West Australia as
native habitat introductions, or from seed sources in the
Mediterranean region where eucalypt species have been tried
successfully, such as Morocco and Israel. Promising growth of eucalypt
hybrids on marginal sites in the summer rainfall areas of South Africa
prompted the inclusion of local as well as some hybrid seedlots
obtained from Morocco. The terrain of the trial site is an almost flat
old dune area (slopes < 3%) with a westerly aspect and 7 km from
the sea. The mean annual rainfall is about 400 mm, with most rain
falling during winter. The other months are usually windy and dry, and
the summer months are hot (maximum temperature > 35oC).
The sandy soils have a coarse texture within the normal rooting depth.
During winter water tables were observed on all soils within 2-3 m
from the soil surface. The trial was planted during the winter of
1991. It consisted of ten local hybrid families of different species
involving Eucalyptus grandis, 14 E. camaldulensis
seedlots from Australia, Morocco and Israel, 7 hybrid lots from
Morocco, 4 E. grandis ex Morocco and 11 other species including
E. gomphocephala and E. cladocalyx. The results indicate
the potential for correct species/provenance selection. Potential
yields of 8 to 10 m3 / annum / ha are predicted on the assumption that
good genetic stock and correct silvicultural procedures are used. Most
notable was the expected performance of the well known West Australian
species (E. gomphocephala, E. cladocalyx). The group of 14 E.
camaldulensis seedlots can be regarded as representing a series of
provenances from Australia, except for three from Israel and one from
Morocco. As expected, the different provenances survived well but
performed variably, generally ranking in the bottom 50 %. However, two
seedlots - the provenance from Lake Albacutya and the seedlot from
Morocco - are worth noting as they actually ranked among the top ten
for index score. Generally, the provenances from Queensland (e.g.
Petford) and New South Wales that normally do well in summer rainfall
regions did not do well. As the relevant parent species originate in
summer rainfall regions, the phenomenal growth rate of many of the
hybrid families came as a surprise in this trial. The yield of the
best E. grandis x E. camaldulensis (GXC) family would have been
equivalent to that of E. gomphocephala if the survival was
equally good. The E. grandis x E. tereticornis (GXT) family did
survive and performed equally well. The second best GXC family would
have yielded even better than the GXT if it had a better survival. The
GXC and GXT families were all within the top 50 % of the trial.
Assessment of wood density of seven clones of Eucalyptus
grandis
Lima, Jose T.; Rosado, Sebastiao C.S.; Trugilho, Paulo F.
Abstract: With the objective of evaluating the correlation
of wood basic density with age in seven Eucalyptus grandis
clones planted in Brazil, five trees in each clone were sampled at the
ages of 0, 5, 1, 5, 2, 5, 3, 5, 4, 5 and 7, 5 years. The analysis of
these samples showed that the intraclonal variation of the basic
density (except for 0, 5 year-old) was very low, while the interclonal
variation was moderately high (from 7, 5 % at 0, 5 year-old to 4, 1 %
at 7, 5 year old) for all ages. The analysis of variance indicated
that the variation between clones, between ages and the clone ( age
interaction were all significant (P < 0, 01), but the
variation of the basic density of the trees within-clones were
non-significant. The study of temporal stability of the basic density
showed that most of the clones behave similarly to the mean clone for
all ages. According to the analysis of regression of the mean basic
density per clone using temporal-index as predictor it was found that
for this group of clones is it possible to predict the basic density
of wood produced at one age from its value at another age. Indeed, the
correlation of the basic density at different ages within a clone
showed that, except for the correlations for wood of 0, 5 year-old,
all other correlations were statistically significant. However, it can
be noted that correlations based on more recent ages presented higher
values of coefficient of correlation, even if the same time span has
been considered. Also, it was shown that was it possible to estimate
the basic density using the age of the tree as independent variable
through the logarithmic model both for individual clones (R2
from 75 % to 96 %) and for all seven clones analysed together (R2
= 92 %).
Responses of Eucalyptus species to fertilizer
applications made at planting on granitic parent materials in the
Mpumalanga and Northern Provinces of South Africa
Carlson, Colleen A.; Allan, Ross; Soko, Samuel
Abstract: Early research trials in South Africa have shown
that Eucalyptus species generally respond positively to the
addition of nutrients at planting. However, as most of these research
trials were located in KwaZulu-Natal, it was important to investigate
the nature of the response in other afforested regions of the country
where this genus is planted. Consequently, a number of fertilizer
trials were established in the late 1980's and early 90's in
Mpumalanga and the Northern Province to investigate the nature of
fertilizer responses in Eucalyptus species. Three of these
trials form a series and were established to investigate the impact of
nitrogen (N), phosphorus (P) and potassium (K) additions made both
individually and in combination. In addition, two trials in Mpumalanga
were initiated to investigate genotype by fertilizer interactions.
Viewed as a whole, the results indicate that growth improvements in
response to the nutrient additions are readily obtainable. Highly
significant positive responses to N and P, each applied individually,
occurred immediately after planting. The response to N appeared more
sustained than the response to P. The best growth was observed when N
and P were applied together. The ratio of N to P that gave the best
response ranged from 3:1 to 3:2. No genotype by fertilizer
interactions were observed in the trials investigating this aspect.
The influence of fire on a southern Cape mountain
forest
Watson, L.H.; Cameron, M.J.
Abstract: Afromontane forests in the southern Cape are
surrounded by fire-prone fynbos. Although the presence of charcoal in
Afromontane forests indicate that they do burn, little is known about
the influence of fire on the dynamics of these forests. We compared
the species composition and diversity of tree species in the margin
and core of recently burned mountain forest. The species composition
and diversity of tree species differed between the forest margin and
core, with the core being more species rich and comprising trees not
recorded in the margin. Although small trees of a number of species
accumulated in the forest margin and core, fire killed most small
trees in the margin but only a few in the core. In the margin,
comparatively low numbers of small Ocotea bullata and Cunonia
capensis were killed, and these two species formed > 90 % of
the large trees recorded in the margin, but lower proportions in the
forest core. Fire is thus an important factor influencing species
composition and diversity in mountain forest.
Valuing South Africa's savannas: methodological
issues
Ballance, A.; Shackleton, C.M.; Shackleton, S.E.; Geach, B.;
Crookes, D.; De Wit, M.; Evans, J.; Von Maltitz, G.; Willis, C.;
Kelatwang, S.; Havemann, J.
Abstract: Natural resource valuation techniques have been
applied in recent years to savannas and savanna resources in South and
southern Africa. Results from these studies have been used to
demonstrate the importance of savannas, and to assist in resource-use
planning. Because these studies have been conducted to meet different
research objectives a large number of disparities exist between
studies. This makes comparison of results difficult and identification
of underlying drivers of value is problematic. This paper discusses
issues which can lead to differences in estimates of resource value,
and makes recommendations for future studies to reduce
incompatibilities. In particular, this paper recommends that future
studies make full descriptions of the objectives of the study, the
background characteristics of the study area (including the social,
political, economic, cultural, and biophysical characteristics), the
methods used, and assumptions made. In this way, the values reported
from case studies may be used in other research and decision-making
exercises
Modelling growth and water use in four Pinus
patula stands with the 3-PG model
Dye, Peter J.
Abstract: Accurate prediction of growth and yield of forest
plantations remains important to the forestry industry for such
purposes as assessing the benefits of silvicultural practices,
matching species to site, understanding economic risks, predicting
profitability and scheduling harvests. Conventional methodology is
based on statistically-derived stand growth curves used to define a
site index reflecting growth potential. Limitations of the method are
widely acknowledged: factors constraining productivity are not
identified; changes in environmental conditions affecting growth may
not be taken into account; and growth predictions at sites not
previously afforested may be poorly predicted. The hydrological impact
of forest plantations remains a controversial issue. Existing
prediction models do not take sufficient stand and site detail into
account to usefully predict water use patterns on a scale that is
practical to forest managers. Several relatively simple simulation
models based on the major physiological processes behind growth and
water use of forest stands have emerged recently, and are claimed to
be useful tools for forest managers and water resource planners. One
of these, the 3-PG model (Physiological Principles in Predicting
Growth) is assessed here for its ability to predict growth and water
use of Pinus patula at four widely separated test sites. Model
parameter values are fixed according to available field data, reported
data for other species of pines, or as a result of a fitting process
to match simulated to observed patterns of growth and water use in
four diverse stands of this species. Simulation results are very
encouraging, and a further phase of model testing on a wider range of
test sites is recommended to improve parameter estimates and
demonstrate the usefulness of the model.
Community forestry resources: a case study of
selected woodlots in the Eastern Cape Province
Ham, Cori; Theron, Francois
Abstract: Community surveys were conducted through the use
of participatory community meetings and a questionnaire in the
Butterworth area of the Eastern Cape. The objectives of these surveys
were to determine the needs and perceptions of communities regarding
woodlots and wood utilisation. From the surveys it is clear that
woodlots do play an important role in the livelihoods of communities
in the Butterworth area, but that the role varies according to
geographic location of the woodlot and urbanisation levels of the
community. Sociological / anthropological socio-economic differences
must be considered in community forestry extension work and future
strategic and policy considerations.
Farmers' tree planting and access to germplasm in
the southern highlands of Tanzania
Aalbaek, Anders
Abstract: This article examines the effects of insufficient
availability of planting material on farmers' tree planting in the
southern highlands of Tanzania. Patterns in scale of farmers' tree
planting, species preferences, and experienced availability of
planting material are investigated and compared with past sources of
germplasm and with existing local nursery capacity. Different aspects
of insufficient access to germplasm and possibilities for improving
the germplasm supply situation are discussed. The study is based on
interviews in 38 villages of 356 farmers and 161 key-informants and
visits to nine nurseries. Most farmers in the southern highlands of
Tanzania plant significant numbers of trees and tree planting is an
integral part of farming systems. Main purposes of tree planting are
fuelwood, timber in a broad sense, and fruit production. People want
to plant well-known species, which in most cases are exotics, and many
species, popular among professionals, e.g. indigenous and multipurpose
trees, are not requested by farmers. Lack of planting material is the
main constraint to tree planting, and although small private or
village-based nurseries are now being established, they are still few
and capacities are far below demands. Nurseries mainly raise species
with seed locally available, and many species, preferred by farmers,
especially fruit trees, are not produced. Currently, most nursery
owners are not able or willing to pay for seed. An improved supply of
seedlings and seed must be economically sustainable at local level and
there is a need for widespread promotion of low-tech, low-input
nursery production and an improved seed supply based on local seed
sources.
Role of supply chain management in the wise use of
wood resources
Pulkki, Reino
Abstract:
One of the cornerstones of sustainable forestry is the wise use of
wood resources to achieve maximum value or benefit for society, while
not jeopardizing the future. At the same time forest companies must
compete on an international scale, otherwise they themselves risk
becoming non-sustainable. Supply chain management (SCM) is a business
management approach which strives to achieve the wise use of inputs,
while ensuring the health of a company in tough international
competition, through breaking down barriers of communication and
information flow within and between organizations and companies. In
SCM the decision focus is the entire supply chain stretching from the
raw materials, right through to final consumption. In this way
sub-optimization of lower-level operations and processes does not put
the overall objectives of the organization at risk or limit future
opportunities. The concept of SCM is not new and is also known, for
example, as logistical management, total system costing, holistic
approach and total production management. The objectives of this paper
are to outline what SCM is, show why SCM has emerged as an important
field in wood procurement and finally give some examples of how a
wider view of wood procurement can influence the wise use of wood
resources
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