Oil Palm Age Research Articles

GROWTH PROFILE ANALYSIS OF OIL PALM BY USING SPOT 6 THE CASE OF NORTH SUMATRA

Oil Palm (Elaeis guineensis Jack.) is one of the world’s most important tropical tree crops. Its expansion has been reported to cause widespread environment impacts. SPOT 6 data is one of high resolution satellite data that can give information more detail about vegetation and the age of oil palm plantation. The objective of this study was to analyze the growth profile of oil palm and to estimate the productivity age of oil palm. The study area is PTP N 3 in Tebing Tinggi North Sumatera Indonesia. The method that used is NDVI analysis and regression analysis for getting the model of oil palm growth profile. Data from the field were collected as the secondary data to build that model. The data that collected were age of oil palm and diameters of canopy for every age. Results indicate that oil palm growth can be explained by variation of NDVI with formula y = -0.0004x2 + 0.0107x + 0.3912, where x is oil palm age and Y is NDVI of SPOT, with R² = 0.657. This equation can be used to predict the age of oil palm for range 4 to 11 years with R2 around 0.89.

Controls of water and energy fluxes in oil palm plantations: Environmental variables and oil palm age

Oil palm is rapidly expanding, particularly in Indonesia, but there is still very limited information on water and energy fluxes in oil palm plantations, and on how those are affected by varying environmental conditions or plantation age. In our study, we measured turbulent fluxes of sensible (H) and latent (LE) heat and gross primary productivity (GPP) with the eddy covariance technique for 8 months each in a young oil palm plantation (1-year old) and subsequently in a mature plantation (12-year old) in Jambi Province, Sumatra, Indonesia. Simultaneous measurements of transpiration (T) were performed using the sap flux technique. We additionally estimated albedo, the maximum rate of carboxylation (Vcmax), the maximum rate of photosynthetic electron transport (Jmax) and water use efficiency (WUE). LE dominated the energy budget in both plantations, particularly in the mature one, where it accounted for up to 70% of the available energy. In the young oil palm plantation, evapotranspiration (ET) was significantly reduced and H fluxes were higher. The Bowen ratio was higher in the 1-year old plantation (0.67±0.33), where it remained constant during the day, than in the mature plantation (0.14±0.09), where it varied considerably over the day, suggesting the existence of water sources inside the canopy which evaporated during the day. Albedo was similar in both plantations (0.16±0.02 and 0.14±0.01 for the 1 and 12-year old plantation, respectively), while WUE differed with plantation age. Annual T estimates for oil palm were 64±3 and 826±34mmyr−1 for the 1 and 12-year old plantation, respectively. The corresponding annual ET was 918±46 and 1216±34mmyr−1, respectively. The Community Land Model (CLM), a process based land surface model that has been adapted to oil palm functional traits (i.e. CLM-Palm), was used to investigate the contribution of different water sources to the measured fluxes. CLM-Palm differentiates leaf and stem surfaces in modelling water interception and thus is able to diagnose the fraction of dry foliage that contributes to T and the wet fraction of all vegetation surfaces (leaf and stem) that contributes to evaporation. The results of the simulations performed are consistent with the storage of water within the canopy in the mature plantation, and suggest that oil palm trunk surfaces including epiphytes provide water reservoirs for intercepted rain which significantly contribute to ET. The decoupling between GPP and T in the morning and the early decreases of both fluxes at midday point to internal water storage mechanisms in oil palms both in the leaves and in the stem, which delayed the detection of water movement at the leaf petioles. Our measured data combined with the model simulations therefore suggest the existence of both external and internal trunk water storage mechanisms in mature oil palms contributing to ecosystem water fluxes. Oil palm plantations can lead to surface warming at early stages of development, but further assessments should be performed at landscape level. Our study provides data relevant for the parametrization of larger-scale models, which can contribute to understanding the climatic feedbacks of oil palm expansion.

Micro-habitats Utilizations, Feeding Niche Overlapping, and Management Systems Impacts on Community Tolerances of Wasp Species within Oil Palm Plantations.

A study on micro-habitats utilizations, feeding niche overlapping, and management systems impacts pertaining to hymenopteran community were evaluated at five chosen oil palm age stands within FELDA Sungai Tekam oil palm plantations, Pahang. Samplings were done within the duration of one year, employing the standard Malaise traps, starting from February 2013 till February 2014, involving both hot and wet seasons. 60 species, from 17 families and 35 subfamilies were successfully collected during the sampling periods. Eight defined micro-habitats were elaborated, with the subdivisions of major, minor, stable, and risky micro-habitat types. Management systems impacts were associated with the applications of chemical herbicides and fertilizers. Species groups were formed using Two-Way Hierarchical Cluster Dendrogram, following 75% of information remaining. Three species groups were formed for hot and wet seasons respectively, with the first group involved nearly half of the overall hymenopteran community. Beneficial nectariferous plants, heaps of chipped rotting oil palm trunks, and remnants of rotting forest logs were all the prominent micro-habitats associated will all cases of hymenopteran species groups, for both cases of major and minor micro-habitat types. Application of BASTA, Glyphosate-Type-A and Type-B herbicides, as well as NK-Mix, Borax, and GML chemical fertilizers were all highly correlated with hymenopteran species groups, showing the high tolerance of most hymenopteran species towards the employed management systems, with reference to minor micro-habitats. Strong feeding ecological niches and plexus values between species of similar species groups formed were specifically associated with discrete but connected minor micro-habitats with weaker food chains, collectively forming larger stable food webs within major micro-habitats. Suggestions on maintaining minor micro-habitats for the survival of most hymenopteran community, as well as the sustenance of their food sources were also discussed.

Micro-habitats Utilizations, Feeding Niche Overlapping, and Management Systems Impacts on Community Tolerances of Wasp Species within Oil Palm Plantations.

A study on micro-habitats utilizations, feeding niche overlapping, and management systems impacts pertaining to hymenopteran community were evaluated at five chosen oil palm age stands within FELDA Sungai Tekam oil palm plantations, Pahang. Samplings were done within the duration of one year, employing the standard Malaise traps, starting from February 2013 till February 2014, involving both hot and wet seasons. 60 species, from 17 families and 35 subfamilies were successfully collected during the sampling periods. Eight defined micro-habitats were elaborated, with the subdivisions of major, minor, stable, and risky micro-habitat types. Management systems impacts were associated with the applications of chemical herbicides and fertilizers. Species groups were formed using Two-Way Hierarchical Cluster Dendrogram, following 75% of information remaining. Three species groups were formed for hot and wet seasons respectively, with the first group involved nearly half of the overall hymenopteran community. Beneficial nectariferous plants, heaps of chipped rotting oil palm trunks, and remnants of rotting forest logs were all the prominent micro-habitats associated will all cases of hymenopteran species groups, for both cases of major and minor micro-habitat types. Application of BASTA, Glyphosate-Type-A and Type-B herbicides, as well as NK-Mix, Borax, and GML chemical fertilizers were all highly correlated with hymenopteran species groups, showing the high tolerance of most hymenopteran species towards the employed management systems, with reference to minor micro-habitats. Strong feeding ecological niches and plexus values between species of similar species groups formed were specifically associated with discrete but connected minor micro-habitats with weaker food chains, collectively forming larger stable food webs within major micro-habitats. Suggestions on maintaining minor micro-habitats for the survival of most hymenopteran community, as well as the sustenance of their food sources were also discussed.Â

An investigation of age and yield of fresh fruit bunches of oil palm based on ALOS PALSAR 2

The objective on this study is to investigate age and yield of FFB of oil palms based on ALOS PALSAR 2. Study areas in oil palm plantations areas of Jerantut, Pahang Malaysia. Methodology consists collecting of ALOS PALSAR 2 and tabular data on the study area, processing of ALOS PALSAR 2 including of converting digital numbers to normalize radar cross sections (NRCS), topography correction and filtering, making of regions of interest according to areas of age and yield of FFB of oil palms and making of relationship analysis between backscatter value of HH, HV and age and yield of FFB of oil palm. The results have showed relationship between HH, HV and age of oil palm which R2 of 0.63 for HH and 0.42 for HV that indicated increasing of age of oil palm as increasing of HH and HV value. Also relationship between HH, HV and yield of FFB of oil palm which R2 of 0.26 for HH and 0.15 for HV, that indicated increasing of yield of FFB as decreasing of HH and HV value.

A newly innovated UV-Pit-Light trap efficacy for sampling beetles within oil palm plantations of various age stand types

A newly innovated UV-Pit-Light trap specific for trapping beetle species within oil palm plantations is described and the results of experiments on its efficacies that were carried out within different oil palm age stands are presented. The UV-Pit-Light trap is made of two parts: a lower located 1-L plastic collection container inserted into the ground, 6V fast recharging lead-acid battery and 4-W miniature UV-bulb attached to electronic device with wire clips, with the upper located plastic stool for the basic stand and the wide plastic basin for rain and light shield. The UV-Pit-Light trap caught significantly higher beetle specimens, which also included several morphospecies from the common beetle families found in oil palm plantations with 1.5 to 2 times higher in abundances including Nitidulidae, Curculionidae, Scarabaeidae, and Tenebrionidae. Rare beetle families of Aderidae, Cerambycidae, Histeridae, and Lagriidae, which not to be found in passive pitfall trap, were caught in considerable abundances in the UV-Pit-Light trap. The short electro-magnetic wavelengths of UV-light source included many closely packed epigeal related micro-habitats, which makes the UV-Pit-Light trap specific for sampling beetles specifically related within micro-habitats of various oil palm age stand types. The use of only four units of UV-Pit-Light trap compared with 100 units of passive pitfall trap is adequate for sampling beetle species community which includes both the common and uncommon families, and include two times higher for the most abundant and common species than the passive pitfall trap. Thus, the UV-Pit-Light trap allows accurate and unbiased diversity and ecological evaluations of beetle species and proposed to be the specific trapping system for insect species dwelling within the epigeal related micro-habitats oil palm plantations.Â

In-situ data collection for oil palm tree height determination using synthetic aperture radar

The oil palm is recognized as the “golden crop,” producing the highest oil yield among oil seed crops. Malaysia, the world's second largest producer of palm oil, has 16 per cent of its territory planted with oil palms. To cope with the increasing global demand on edible oil, additional areas of oil palm are forecast to increase globally by 12 to 19 million hectares by 2050. Due to the limited land bank in Malaysia, new strategies have to be developed to avoid unauthorized clearing of primary forest for the use of oil palm cultivation. Microwave remote sensing could play a part by providing relevant, timely and accurate information for a plantation monitoring system. The use of synthetic aperture radar (SAR) has the advantage of daylight- and weather-independence, a criterion that is very relevant in constantly cloud-covered tropical regions, such as Malaysia. Using interferometric SAR, (InSAR) topographical and tree height profiles of oil palm plantations can be created; such information is useful for mapping oil palm age profiles of the plantations in the country. This paper reports on the use of SAR and InSAR in a multisensory context to provide up-to-date information at plantation level. Remote sensing and in-situ data collection for tree height determination are described. Further research to be carried out over the next two years is outlined.

Replanting reduces frog diversity in oil palm

AbstractA growing body of literature has demonstrated significant biodiversity losses for many taxa when forest is converted to oil palm. However, no studies have directly investigated changes to biodiversity throughout the oil palm life cycle, in which oil palm matures for 25–30 yr before replanting. This process leads to major changes in the oil palm landscape that likely influence species assemblages and ecosystem function. We compare frog assemblages between mature (21–27‐yr old) and recently replanted (1–2‐yr old) oil palm in Sumatra, Indonesia. Across eighteen 2.25‐ha oil palm plots, we found 719 frogs from 14 species. Frog richness was 31 percent lower in replanted oil palm (nine species) than mature oil palm (13 species). Total frog abundance was 47 percent lower in replanted oil palm, and frog assemblage composition differed significantly between the two ages of oil palm. The majority of frog species were disturbance‐tolerant, although we encountered four forest‐associated frog species within mature oil palm despite a distance of 28 km between our study sites and the nearest extensive tract of forest. Although it is clear that protection of forest is of paramount importance for the conservation of tropical fauna, our results indicate that management decisions within tropical agricultural landscapes also have a profound impact on biodiversity. Practices such as staggered replanting or maintenance of connectivity among mature oil palm patches could help maintain frog diversity in the oil palm landscape.

Optimization and Kinetic Modeling of Ethanol Production from Oil Palm Frond Juice in Batch Fermentation

Ethanol was produced from oil palm frond juice (OPFJ) by using Saccharomyces cerevisiae yeast cells. Experiments were operated in a batch mode by varying the oil palm age between 3-4, 4-7, 7-10, 10-20 and 20-25 years. Experimental results showed that OPFJ at 3-4 years gave the highest concentrations of glucose and ethanol as 31.26 and 11.50g/l. Ethanol yield was 0.39 g-ethanol/g-glucose, which estimated as 76.47% of the theoretical yield (0.51 g-ethanol/g-glucose). Additionally, the Monod and modified Gompertz equations were used to describe the kinetics of substrate utilizationand product formation. The values of the kinetic parameters in Monod and modified Gompertz equations of OPFJ extracted from oil palm aged 3-4 years were evaluated: maximum specific growth rate (μmax) was 0.29g/g-VSS.hr, saturation concentration (Ks) 47.05g/l, maximum ethanol concentration (Pm) 11.50g/l, maximum ethanol production rate (rp,m) 0.24g./l.hr and lag phase 0.12 hr. Both models fitted well to the experimental data, which had the high regression coefficient values (R2>0.95).

Ground-foraging ant communities vary with oil palm age

The conversion of natural habitats to croplands is a major cause of the global loss of species diversity and ecosystem services. One potentially effective method for enhancing the biodiversity of important groups such as insects, and their associated ecosystem services within croplands, is to increase the environmental complexity of the agricultural matrix. This can be achieved in perennial tree crops by planting mixed-age stands. There is, however, very little evidence for the effects of stand age on biodiversity in tropical tree crops. In this study, we assess how ground-foraging ant communities differ in relation to oil palm stand age, currently the dominant tree crop across tropical Southeast Asia. Oil palm age did not affect overall ant species richness. However, the numbers of species that were either common or numerically-dominant decreased with increases in canopy cover, which positively correlated with oil palm age, suggesting greater species evenness in older oil palm. In mature, but not young, oil palm, ant species co-occurred non-randomly, suggesting competitive exclusion and species segregation. Species responses to variables associated with oil palm age depended on their functional group. Generally, opportunists and generalized myrmicines were less abundant and less diverse, whereas specialist predators were more abundant and diverse, in older oil palm. Our results show that ground-foraging ant communities in oil palm change significantly in composition, but not in species richness, with crop age. These results suggest that mixed-age stands could support compositionally variable communities and help boost insect diversity in otherwise homogeneous perennial monocultures.

Availability of Forage Under Oil Palm Plantation for Cattle Grazing

Increasing rate of oil palm plantation in Indonesia since 2008-2011 was 6.92%, that increased from 7,363,703 to 7,873,384 ha. Vegetation grown in the area of oil palm plantation is weed for its main crop. There is potential source of oil palm plantation area for livestock industry. Oil palm-cattle integration system is well known and it has been applied in many oil palm plantations, by the use of waste from oil palm plantation, oil palm by-product, the fronds for feed and feces from cattle as organic fertilizer for the plant. Management of oil palm plantation, including plant maintainance, weeding, providing organic and chemical fertilizer is costly. Grazing system under oil palm would minimize cost problem and oil palm production input can be reduced. One of the systems in oil palm-cattle integration that prospective to be developed is grazing by rotation system. Types of plants under oil palm plantation consist of grasses, legumes, other narrow and broad leaves, some are palatable and some are unpalatable or toxic for cattle. Species of vegetation under oil palm vary among the plantation depending on the age of oil palm plant. Introduction of superior forage into oil palm plantation is promising effort to increase the production and quality of feed. Carrying capacity for cattle varies among the oil palm plantation and depends on vegetation under oil palm plantation and age of oil palm. Studies showed that integration oil palm-livestock by grazing system has been proven economically feasible. Key words: Plantation, oil palm, forage, cattle, grazing

Land cover change interacts with drought severity to change fire regimes in Western Amazonia.

Fire is becoming a pervasive driver of environmental change in Amazonia and is expected to intensify, given projected reductions in precipitation and forest cover. Understanding of the influence of post-deforestation land cover change on fires in Amazonia is limited, even though fires in cleared lands constitute a threat for ecosystems, agriculture, and human health. We used MODIS satellite data to map burned areas annually between 2001 and 2010. We then combined these maps with land cover and climate information to understand the influence of land cover change in cleared lands and dry-season severity on fire occurrence and spread in a focus area in the Peruvian Amazon. Fire occurrence, quantified as the probability of burning of individual 232-m spatial resolution MODIS pixels, was modeled as a function of the area of land cover types within each pixel, drought severity, and distance to roads. Fire spread, quantified as the number of pixels burned in 3 × 3 pixel windows around each focal burned pixel, was modeled as a function of land cover configuration and area, dry-season severity, and distance to roads. We found that vegetation regrowth and oil palm expansion are significantly correlated with fire occurrence, but that the magnitude and sign of the correlation depend on drought severity, successional stage of regrowing vegetation, and oil palm age. Burning probability increased with the area of nondegraded pastures, fallow, and young oil palm and decreased with larger extents of degraded pastures, secondary forests, and adult oil palm plantations. Drought severity had the strongest influence on fire occurrence, overriding the effectiveness of secondary forests, but not of adult plantations, to reduce fire occurrence in severely dry years. Overall, irregular and scattered land cover patches reduced fire spread but irregular and dispersed fallows and secondary forests increased fire spread during dry years. Results underscore the importance of land cover management for reducing fire proliferation in this landscape. Incentives for promoting natural regeneration and perennial crops in cleared lands might help to reduce fire risk if those areas are protected against burning in early stages of development and during severely dry years.

Determination of the age of oil palm from crown projection area detected from WorldView-2 multispectral remote sensing data: The case of Ejisu-Juaben district, Ghana

Information about age of oil palm is important in sustainability assessments, carbon mapping, yield projections and precision agriculture. The aim of this study was to develop and test an approach to determine the age of oil palm plantations (years after planting) by combining high resolution multispectral remote sensing data and regression techniques using a case study of Ejisu-Juaben district of Ghana. Firstly, we determined the relationship between age and crown projection area of oil palms from sample fields. Secondly, we did hierarchical classification using object based image analysis techniques on WorldView-2 multispectral data to determine the crown projection areas of oil palms from remote sensing data. Finally, the crown projection areas obtained from the hierarchical classification were combined with the field-developed regression model to determine the age of oil palms at field level for a wider area. Field collected data showed a strong linear relationship between age and crown area of oil palm up to 13years beyond which no relationship was observed. A user’s accuracy of 80.6% and a producer’s accuracy of 68.4% were obtained for the delineation of oil palm crowns while for delineation of non-crown objects a user’s accuracy of 65.6% and a producer’s accuracy of 78.6% were obtained, with an overall accuracy of 72.8% for the OBIA delineation. Automatic crown projection area delineation from remote sensing data produced crown projection areas which closely matched the field measured crown areas except for older oil palms (13+ years) where the error was greatest. Combining the remote sensing detected crown projection area and the regression model accurately estimated oil palm ages for 27.9% of the fields and had an estimation error of 1year or less for 74.6% of the fields and an error of a maximum 2years for 92.4% of the fields. The results showed that 6 and 11year old oil palm stands were dominating age categories in the study area. Although the method could be reliably applied for estimating oil palm age at field level, more attention is required in improving crown area delineation to improve the accuracy of the approach.

Sustainable Management in Crop Monocultures: The Impact of Retaining Forest on Oil Palm Yield

Tropical agriculture is expanding rapidly at the expense of forest, driving a global extinction crisis. How to create agricultural landscapes that minimise the clearance of forest and maximise sustainability is thus a key issue. One possibility is protecting natural forest within or adjacent to crop monocultures to harness important ecosystem services provided by biodiversity spill-over that may facilitate production. Yet this contrasts with the conflicting potential that the retention of forest exports dis-services, such as agricultural pests. We focus on oil palm and obtained yields from 499 plantation parcels spanning a total of ≈23,000 ha of oil palm plantation in Sabah, Malaysian Borneo. We investigate the relationship between the extent and proximity of both contiguous and fragmented dipterocarp forest cover and oil palm yield, controlling for variation in oil palm age and for environmental heterogeneity by incorporating proximity to non-native forestry plantations, other oil palm plantations, and large rivers, elevation and soil type in our models. The extent of forest cover and proximity to dipterocarp forest were not significant predictors of oil palm yield. Similarly, proximity to large rivers and other oil palm plantations, as well as soil type had no significant effect. Instead, lower elevation and closer proximity to forestry plantations had significant positive impacts on oil palm yield. These findings suggest that if dipterocarp forests are exporting ecosystem service benefits or ecosystem dis-services, that the net effect on yield is neutral. There is thus no evidence to support arguments that forest should be retained within or adjacent to oil palm monocultures for the provision of ecosystem services that benefit yield. We urge for more nuanced assessments of the impacts of forest and biodiversity on yields in crop monocultures to better understand their role in sustainable agriculture.

Permodelan Pertumbuhan dan Produksi Kelapa Sawit pada Berbagai Taraf Penunasan Pelepah

ABSTRACT The numbers of leaf frond influence oil palm yield, especially fresh fruit bunch weight and fresh fruit bunch production. The objective of this research was to obtain oil palm growth and production model for different levels of frond pruning. The experiment was conducted at PT. Astra Agro Lestari, Pangkalan Bun, Central Kalimantan, from August 2010 to February 2012. The experiment was arranged in a randomized block design with two factors and three replications for each oil palm age. The first factor was numbers of unpruned frond and the second factors was pruning seasons. The frond treatment consisted of 41-48, 49-56, and 57-64 fronds. The pruning seasons consisted of first period (early to mid rainy season: September-December), second period (mid to end of rainy season: Januari-April), and third period (dry season: May-August). Stella production model was created based on pruning experiment and weather data. The constructed production model was able to estimate 75% variable of oil palm production and fresh fruit bunch weight at different levels of pruning. Keywords: oil palm, pruning management, Stella model

Measurement of Oil Palm LAI by Manual and LAI-2000 Method*

In this study, accurate Leaf Area Index (LAI) of different palm age groups were determined by manual (direct) method. Optical methods for quantifying variation in LAI of different palm ages were evaluated using LAI-2000 Plant Canopy Analyser (PCA) as an indirect method. In the manual method, LAI values obtained were 0.69, 1.11, 2.38, 2.49, 3.41, 3.83, 4.05 and in the indirect method LAI values obtained were 1.75, 1.4, 1.14, 1.42, 2.87, 1.89, 3.05 for 2, 3, 6, 7, 9, 12 and 16 year old palms, respectively. Results showed that the PCA LAI values were overestimated for immature palms but underestimated for mature palms. The PCA LAI values were overestimated by 30.8-153% for 2 to 3-year old palms and underestimated by 24-52% for beyond 6-year old palms as compared to manual measurement. The relationship between palm age and LAI was also established in this study. A strong linear relationship between direct LAI and palm age was observed with a correlation coefficient, R = 0.90. However, the relationship between PCA LAI and palm age was weak and not significant. A relationship was observed between PCA LAI and direct LAI with a correlation coefficient of R = 0.57. The study shows that it was possible to rapidly determine LAI using the LAI-2000 Plant Canopy Analyser. This rapid and non-destructive method saves labour when compared to manual measurements. However, this instrument gave inconsistent of LAI values in respect to oil palm age.

Variations in photosynthetic rate and associated parameters with age of oil palm leaves under irrigation

Net photosynthetic rate (P N), transpiration rate (E), and stomatal conductance (g s) in an adult oil palm (Elaeis guineensis) canopy were highest in the 9th leaf and progressively declined with leaf age. Larger leaf area (LA) and leaf dry mass (LDM) were recorded in middle leaves. P N showed a significant positive correlation with g s and a negative relationship with leaf mass per area (ALM). The oil palm leaf remains photosynthetically active for a longer time in the canopy which contributes significantly to larger dry matter production in general and greater fresh fruit bunch yields in particular.

Nonlinear Growth Models for Modeling Oil Palm Yield Growth

This study provided the basic needs of parameters estimation for nonlinear growth model such as partial derivatives of each model, determination of initial values for each parameter and statistical tests of industrial usage. Twelve nonlinear growth models and its partial derivatives for oil palm yield growth are presented in this study. The parameters are estimated using the Marquardt iterative method of nonlinear regression relating oil palm yield growth data. The best model was selected based on the model performance and it can be used to estimate the oil palm yield at any age of oil palm. This study found that the Gompertz, logistic, log-logistic, Morgan-Mercer-Flodin and Chapman-Richard growth models have the ability for quantifying a growth phenomenon that exhibit a sigmoid pattern over time. Based on the statistical testing and goodness of fit, the best model is the Logistic model and followed by the Gompertz model, Morgan-Mercer-Flodin, Chapman-Richard (with initial stage) and Log-logistic growth models.

Linear regression modelling for the estimation of oil palm age from Landsat TM

Linear regression modelling for the estimation of oil palm age from Landsat TM

Linear regression modelling for the estimation of oil palm age from Landsat TM

This paper investigates the accuracy with which the age since field planting of oil palm (Elaeis guineensis Jacq.) can be estimated from Landsat Thematic Mapper (TM) radiance at pixel and stand scales. The study site, a commercial plantation 30 km south-east of Kuala Lumpur in Selangor, Malaysia, consisted of even-aged blocks from 4 to 21 years old. Spectral data were the six reflective TM bands and three spectral indices. Nonlinear negative relationships between spectral variables and age are compared to published trends in leaf area, stem height and per cent canopy cover for oil palm and other tree plantations. Correlation coefficients between log age and log radiance are moderate and highly significant (p<0.01) for bands 2-5 and 7 (-0.214 to-0.776) at the pixel scale, and increase at the stand scale (r 2=0.985 for log band 5, p<0.01). Relationships are strongest for the mid-infrared bands, especially band 5 (r 2=0.585, p <0.01) and the infrared index (IRI), a normalized difference index of bands 4 and 5 (r 2= 0.48, p<0.01). Direct and inverse linear regression models for log age with log band and log age with IRI squared (IRIsq) were constructed at both scales. Equivalent age was estimated from the models using independent test sets for differing scales and degrees of aggregation of the age classes. Single age classes cannot be estimated accurately at the pixel or stand scales; the lowest RMS error was obtained from the direct model using all bands (RMS error=3.9 years at pixel scale, 2.7 at stand scale). A posteriori aggregation into generalized age classes (<5, 6-10, 11-15, 16-21 years) improved the RMS error but the results were still unacceptably high (2.2, 2.3, 2.7, 6.0 years respectively for direct model 3 using all bands). Acceptable RMS errors down to 0.58 years were obtained for models using IRIsq with generalized age classes developed and applied at the stand scale when variations in ground cover and other variables were averaged out. The spatial pattern of error in equivalent age deserves investigation for precision crop management.