Evaluation of tree performance, site conditions and silvicultural procedures in forest plantations at high altitude sites in Lesotho.
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Date
2005
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Abstract
The permanent sample plots (PSP) and silvicultural trial plots established by the Forestry
Research Section of the Forestry Department of the Ministry of Forestry and Land
Reclamation in Lesotho were used as a source of information for this study. The study
area is located in the forest plantations on high altitude sites in Lesotho which have the
aim to determine important aspects of timber production for commercial use and to
address the problem of fuel wood scarcity and energy crisis. The major objective of the
study was to describe performance (survival, growth and timber volume) of exotic tree
species introduced in Lesotho.
The height and diameter relationships for trees in the 33 plots of Eucalyptus rubida and
44 plots of Pinus radiata were determined by a simple linear regression. There are four
plots of Eucalyptus macarthurii, three plots of Pinus halepensis, one plot of Eucalyptus
nitens and one plot of Pinus pinaster. The permanent sample plots data were analysed
with the use of a statistical package Genstat (7th edition). Categorical analysis were used
to detect the number of live and dead trees. The correlation analysis was used to study
association between site and performance variables, while multiple regression analysis
was utilised to analyse relationships between site index and site variables. The growth
curves developed for E. rubida and P. radiata tended to indicate a sigmoidal shape.
Analysis of variance was utilised to analyse the performance of species in terms of
survival and growth (HT and DBH) for the four species and provenance trials.
The early mortality rate was 2% for E. macarthurii, 14% for E. rubida, 0% for E. nitens.
Later, it was found that the percentage of dead trees is as follows: 7% for E. macarthurii,
15% for E. rubida, 29% for E. nitens. It was detected that the mortality rate for eucalypts
was 14% at last assessments. Similarly, it was detected that the final mortality rate for P.
halepensis, P. pinaster and P. radiata was 2%, 19% and 20% respectively.
The mean diameter for P. radiata ranged between 1,87 cm at age 3,75 years and 24,49
cm at age 18 years. The mean height ranged from 1,51 m at age 0,75 yrs and 13,51 m at
16 years. It was discovered that the mean diameter is found between 8,0 cm at age
4,83 yrs and 14,41 cm at age 8,83 yrs for P. halepensis. The mean height was 2,1 m at
age 4,83 years and 16,48 m at age 13,50 years. The mean diameter ranged from 7,41 cm
at age 6,42 years and 15,92 cm at age 10,42 years for P. pinaster. Similarly, the mean
height was detected to be between 5 m at age 6,42 years and 7,75 m at age 12,42 years
for P. pinaster. It was noted that the mean diameter for E. rubida ranged from 2,04 cm at
age 2,25 years to15,87 cm at age 11,75 years. On the same line the mean height started at
4,55 m at age 2,42 years and ended at 16,15 m at age 11,75 years. The mean diameter for
E. macarthurii was noted to be 13,64 cm at age 10 years. It was noticed that mean height
is found between 3,8 m at age 2,17 years and 16,03 m at age 10 years. It was also
detected that the mean diameter started from 4,45 cm at age 2,50 years and 10,78 cm at
age 6,50 years for E. nitens. The mean diameter ranged from 5,98 cm at age 2,50 years
and from 12,05 m at age 6,50 years for E. nitens.
The mean annual increment (MAI) for P. radiata is found between 0,15 m3/ha/yr at age
2,25 years and 21,91 m3/ha/yr at age 6,50 years. The MAI ranged from 0,58 m3/ha/yr at
age 3,42 years and 10,81 m3/ha/yr at age 10,42 years for E. rubida. It was determined that
the MAI started from 0,25 m3/ha/yr at age 2,17 years to 9,99 m3/ha/yr at age 4,17 years
for E. macarthurii. The MAI started from 1,59 m3/ha/yr at age 2,50 years and to 7,54
m3/ha/yr at age 6,50 years for E. nitens. It was noted that the MAI for P. halepensis began
from 0,01 m3/ha/yr at age 4,83 years and 3,52 m3/ha/yr at age 13,50 years. Similarly, the
MAI began from 0,73 m3/ha/yr at age 6,42 years and 2,70 m3/ha/yr at age 10,42 years for
P. pinaster.
The Site indices for E. rubida and P. radiata were calculated. They ranged from 6,72 to
14,40 m and from 12,05 to 18,43 m for E. rubida and P. radiata at age 6 years and 15
years respectively.
The MAI and SI of different species justify that a viable commercial forestry can be
implemented in Lesotho, if advanced selection of genetic material, improved silviculture
and appropriate site species matching can be followed. It was noticed that various
silvicultural practices like proper land preparation methods, weed management and deep
planting have a large impact on tree performance. Based on these results, larger
afforestation projects for commercial timber production and bioenergy are recommended.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
Keywords
Forests and forestry--Lesotho., Forest management--Lesotho., Trees--Growth., Pine--Lesotho., Eucalyptus--Lesotho., Theses--Forestry.