| 總結: | The Forest Rehabilitation Program is one of the most effective ways to address
the forest and soil degradation problem. This research is critical in understanding
the ecological roles of the most important environmental effluents: soils,
particularly on land that has undergone various types of land use change. The
specific objectives of the study were: (1) to determine the status of soil
compaction impacts on different land used types (rehabilitated forest – trees was
planted in year 1991), secondary forest, oil palm plantation and rubber
cultivation) and determined the soil compaction effects on soil conditions among
of the rehabilitated forest sites; (2) to investigate and understand the relation of
physico-chemical properties of the soil under different land used types or under
several management, and under different years of planting of rehabilitated
forests; (3) to emphasis placed on finding significant soil properties or soil
parameters based on correlation and Principal Component Analysis (PCA)
analyses for soil under different land used types and among of the rehabilitated
forest plots; and (4) to assess the soil fertility status using the applicability of the
proposed indices, the Soil Fertility Index (SFI) and the Soil Evaluation Factor
(SEF) as an alternative approach of indicator for estimating soil fertility and site
quality of the soil under different land used types and soil under rehabilitated
forests comparison among of the rehabilitated forest plots.
The soil compaction at RF, SR, OP and RP for topsoil ranges from 0 to 5 cm
cumulative depths and very soft regarding ODP values, which means the topsoil
at all sites was less compacted. Toward deeper soil layer, the soil became very
hard towards the end from point of 12 to 49 cm cumulative depth. The study of
assessment on soil compaction, soil fertility and site quality among of the
rehabilitated forest plots (planting in different year for topsoil 0-15 cm depth) has
been done. The soil compaction rate among the rehabilitated forest plots was
increasing from topsoil to subsoil. The compaction rate for plot 1991 to 2000
show the increasing of compaction rate toward the depth of soil. The total
cumulative depth for plots from 2001 to 2008 has a longer graft compared to the
previous one. Indicate that the soil within this year’s more compacted.
Generally, the soil chemical properties or soil fertility for all sites are considered
low. With low in pH value less than 5.5, low in OM and CEC content, low in
exchangeable bases and available P content and high in exchangeable Al
content. The soil nutrients content for all rehabilitated plots were low and did not
reach the optimum condition. The organic matter (OM) content in the soil ranges
from 2.27 g kg-1 to 5.52 g kg-1. CEC is an important predictor of soil fertility since
it evaluates a soil's ability to store nutrients. The highest CEC content was at plot
1998 with 5.48 g kg-1. The exchangeable cations calcium (Ca2+), magnesium
(Mg2+), sodium (Na+), and potassium (K+) are the primary ions linked with CEC
in soils. The pH values below 5.5 limit P-availability to plants due to aluminium,
iron, or calcium fixation. Organic matter, pH, available P, exchangeable Mg, and
cation exchange capacity all show a significant positive association, indicating
that most nutrients are stored in surface soils, according to Principal Component
Analysis (PCA). Soil organic matter has a significant connection with CEC and
exchangeable Mg.
The SFI and SEF indices exhibit strong correlations with soil chemical and
biological properties, indicating that they can be used as soil quality indicators.
The SFI and SEF data may be used to create fertility maps and generate fertility
management recommendations based on soil spatial variability. More extensive
research on other environmental variables, such as soil biological
characteristics, that may impact tree development performance, should be
carried out in the future. The data of the soil and tree growth performance can
provide fundamental resource or information for other researchers or studies
regarding in carbon sequestration and greenhouse gases (GHG) emission
intensity (emission from land use, land use change and forestry; LULUCF) in
Malaysia.
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