Smallholder Oil Palm Plantations Research Articles

Microhabitat Characteristics of Myopopone Castanea (Hymenoptera: Formicidae) in Oil Palm Plantation

Ants are social insects which widespread and play many important roles in an ecosystem. Myopopone castanea ants are a predator for the pre-adult stage of pest Oryctes rhinoceros which is one of the important pests in oil palm plantations. At the oil palm plantations, M. castanea and pre-mature stadia from pests O. rhinoceros live on decaying palm oil stems. This study aimed to explore the presence and the microhabitat characteristics of M. castanea ant in oil palm plantation so that mass rearing of M. castanea ants can be carried out in the laboratory to support the natural enemy augmentation program in biological control of O. rhinoceros pest. The exploration of ant nests was carried out in two plantation locations: smallholder oil palm plantations in Tanah Merah sub-district, Binjai Selatan Subdistrict, Binjai and PTPN 2 and PTPN 4 in Deli Serdang and Serdang Bedagai districts, North Sumatra Province. The results showed that the colonies of M. castanea in both of plantations vary greatly in the size of the number and stage of the ant development stage. Average of abiotic factors in the microhabitat of M. castanea ants in PTPN plantation (t = 29.7 0C, Rh = 70%, pH = 6.03 and C / N ratio = 66.18%), while for smallholder plantation (t = 29.1 0C, Rh = 70.9%, pH = 6.39 and C / N ratio = 69.01%). A suitable abiotic environment will support life and mass rearing of M. castanea ant colonies.

Explaining the “Certification Gap” for Different Types of Oil Palm Smallholders in Riau Province, Indonesia

Indonesia is the world’s largest producer of palm oil, and its smallholder oil palm plantations involve more than 2.3 million farmers. The rapid expansion of the oil palm area, and resulting negative environmental and social impacts, has increased the demand for sustainability certification for palm oil products. This study investigates whether different types of smallholders face different barriers in complying with certification standards. The study uses survey data from 829 smallholders in Riau, Sumatra. First, an assessment is made of the gap between current management practices and practices required by Roundtable on Sustainable Palm Oil standards for different types of smallholders. Second, the article explores explanations for the gap between current and required practices. Finally, an investigation is made of the different starting points of different types of smallholders. Results indicate that the diversity between smallholders affects their prospects for certification. To date, this diversity in smallholders has not been taken into account in the application of Roundtable on Sustainable Palm Oil standards. This can help to explain the limited success of smallholder certifications in Indonesia.

Response of Immature Oil Palm Growth and CO2 emission on Intercropping System After Replanting

One of the problems in smallholder oil palm plantations was the financing for replanting and loss of revenues during immature oil palm period. One alternative to the problem was the development of an adaptive plant system through intercropping crops planted among immature oil palm crops. The research was conducted in banjar seminai village, dayun subdistrict, siak regency, Riau Province on May to October 2017. The study used a factorial randomized block design with three replications. Annual crops treatment consists of corn, soybean, eggplant and chili. The results showed that there was positive response of oil palm height on intercropping systems. Corn intercropping plants increased the height of oil palm crops. The intercropping plants had no significant effect on the number of leaf midrib and the width of oil palm canopy. Monoculture oil palm crops without intercropping produced average emissions of 8.78 t CO2 ha-1yr-1. Oil palm intercrop with eggplant and soybean produces the highest CO2 emissions of 10.4 and 10.2 t CO2 ha-¹yr-¹, while oil palm in intercrop with chili produced the lowest CO2 emissions of 8.66 t CO2 ha-1yr-¹.

Infiltrated Water and Runoff at Four Gradient Slopes at Smallholder Oil Palm Plantation in Dry Season in Jambi, Indonesia

Infiltrated Water and Runoff at Four Gradient Slopes at Smallholder Oil Palm Plantation in Dry Season in Jambi, Indonesia

Transpiration on the rebound in lowland Sumatra

Following large-scale conversion of rainforest, rubber and oil palm plantations dominate lowland Sumatra (Indonesia) and other parts of South East Asia today, with potentially far-reaching ecohydrological consequences. We assessed how such land-use change affects plant transpiration by sap flux measurements at 42 sites in selectively logged rainforests, agroforests and rubber and oil palm monoculture plantations in the lowlands of Sumatra. Site-to-site variability in stand-scale transpiration and tree-level water use were explained by stand structure, productivity, soil properties and plantation age. Along a land-use change trajectory forest-rubber-oil palm, time-averaged transpiration decreases by 43 ± 11% from forest to rubber monoculture plantations, but rebounds with conversion to smallholder oil palm plantations. We uncovered that particularly commercial, intensive oil palm cultivation leads to high transpiration (827 ± 77 mm yr−1), substantially surpassing rates at our forest sites (589 ± 52 mm yr−1). Compared to smallholder oil palm, land-use intensification leads to 1.7-times higher transpiration in commercial plantations. Combined with severe soil degradation, the high transpiration may cause periodical water scarcity for humans in oil palm-dominated landscapes. As oil palm is projected to further expand, severe shifts in water cycling after land-cover change and water scarcity due to land-use intensification may become more widespread.

Environmental impacts as affected by different oil palm cropping systems in tropical peatlands

Tropical peatlands are globally important for their high carbon storage and unique biodiversity, but are currently under severe threat in South East Asia from expansion of oil palm plantations. A large part of this expansion in Peninsular Malaysia arises from small-holder oil palm plantations that follow varied cropping practices, yet their impact on the environment is largely unexplored. This research aimed to study and evaluate the environmental and belowground microbial impacts of different smallholder cropping systems relative to forested peatlands in North Selangor, Peninsular Malaysia. Specifically, GHG measurements using closed chambers, and peat sampling were carried out in both wet and dry seasons. Microbial phenotypic community structure was determined using phospholipid fatty acid (PLFA) analysis. Relative to forested peatlands, the agricultural plantations had increased pH, temperature and bulk density, decreased organic content, and peat moisture, with a pineapple intercropping site as the only exception. These effects were most pronounced in 2nd generation mono-cropping systems. Soil microbial community structure, dominated by Gram-positive bacteria under all land-use types, differed significantly between agricultural sites and forest, and also showed significant seasonal variation. There was a general increase in non-specific fatty acids and a decrease in Gram-positive fatty acids in agricultural sites from forest, however microbial community structure were similar in most agricultural sites. CO2 emissions were greatest at the forest site and showed no seasonal variations, however most of the forest CO2 emissions were most likely due to high autotrophic contribution from roots. CH4 emissions were under 1 mg m−2 h−1 for all the agricultural sites, while forest peat surface absorbed similar low quantity of CH4. Overall, the changes in peat properties and loss of C was greatest in the 2nd generation mono-cropping, while the intercropping systems ameliorated these effects by maintaining most of the forest peat organic content and causing relatively smaller changes in pH, moisture and bulk density. It is clear that oil palm intercropping have an ameliorating effect on environmental impacts caused by the expansion of oil palm plantations into peatlands.

Readiness of oil palm smallholders in facing oil palm replanting in North Sumatra

This study aimed to determine the development of smallholder oil palm plantations and the performance of smallholder oil palm plantations, and to study the readiness of smallholders in facing the oil palm replanting (rejuvenation). Samples were taken using purposive sampling technique. The method used was qualitative method with descriptive approach. Data filtering instruments used was in-depth observation, documentation and interview. This study showed that there were actions to show readiness that had been done by oil palm smallholders in facing oil palm replanting, those were: by having another plantation area in rejuvenated (replanted) area, by having other jobs and other incomes. The impact was that there was a period of non-productive oil palm and farmers’ income was no longer there.

The response of soil respiration to climatic drivers in undrained forest and drained oil palm plantations in an Indonesian peatland

To accurately quantify tropical peatlands’ contribution to global greenhouse gas emissions, and to understand how emissions from peat may change in the future, long-term measurements over seasons and years are needed. Sampling soil respiration over a range of temperature and moisture conditions in the field is valuable for understanding how peat soil emissions may respond to climate change. We collected monthly measurements of total soil respiration, moisture and temperature from forest and smallholder oil palm plantations on peat in Central Kalimantan, Indonesia. Our study period, from January 2014 through September 2015, covered wet–dry transitions during 1 year with relatively normal precipitation and one El Nino year. Oil palm plots, with lower water table, had 22% higher total soil respiration (0.71 ± 0.04 g CO2 m−2 h−1) than forest plots (0.58 ± 0.04 g CO2 m−2 h−1) over the entire monitoring period. However, during the El Nino event in September 2015, despite overall lower water table levels in oil palm plots, total soil respiration was higher in forest (1.24 ± 0.20 g CO2 m−2 h−1) than in oil palm (0.90 ± 0.09 g CO2 m−2 h−1). Land-use change continues to be an important driver of carbon dioxide (CO2) emissions from Indonesian peatlands. However, the stronger response of total soil respiration to extreme drought in forest indicates the potential importance of climate regime in determining future net carbon (C) emissions from these ecosystems. Future warming and increased intensity of seasonal drying may increase C emissions from Indonesian peatlands, regardless of land-use.

Linking soil respiration and water table depth in tropical peatlands with remotely sensed changes in water storage from the gravity recovery and climate experiment

Carbon dioxide (CO2) emissions from Southeast Asia peatlands are contributing substantially to global anthropogenic emissions to the atmosphere. Peatland emissions associated with land-use change, and fires are closely related to changes in the water table level. Remote sensing is a powerful tool that is potentially useful for estimating peat CO2 emissions over large spatial and temporal scales. We related ground measurements of total soil respiration and water table depth collected over 19 months in an Indonesian peatland to remotely sensed gravity recovery and climate experiment (GRACE) terrestrial water storage anomoly (TWSA) data. GRACE TWSA can be used to predict changes in water storage on land. We combined ground observations from undrained forest and drained smallholder oil palm plantations on peat in Central Kalimantan to produce a representation of the peatland landscape in one 0.5° × 0.5° GRACE grid cell. In both ecosystem types, total soil respiration increased with increasing water table depth. Across the landscape grid, monthly changes in water table depth were significantly related to fluctuations in GRACE TWSA. GRACE TWSA explained 76% of variation in water table depth and 75% of variation in total soil respiration measured on the ground. By facilitating regular sampling across broad spatial scales that captures essential variation in a major driver of soil respiration and peat fires, our approach could improve information available to decision makers to monitor changes in water table depth and peat CO2 emissions. This would enable measures better targeted in space and time to more effectively mitigate CO2 emissions from tropical peat drainage and fires. Testing over larger regions is needed to operationalize this exploratory approach.

SELECTION OF FRESH FRUIT BUNCH MARKETING CHANNEL IN SMALLHOLDER OIL PALM PLANTATION IN ACEH PROVINCE

This research was conducted at smallholder plantation in Aceh Province in January- March 2015. The purpose of this research is to analyze the factors that influence farmers in choosing marketing channel in smallholder oil palm plantation in Aceh Province. The analytical method used in this study was multinomial logit. The result of the analysis shows that several factors, namely the age of farmers, production volume, loan capital, and the price of fresh fruit bunch (FFB) are the factors that become the basis of consideration of farmers in choosing marketing channel of large traders. Based on the result of regression coefficient, it is known that production volume was the most dominant factor affecting the farmers in choosing marketing channel of large traders. Meanwhile, all independent variables which were analyzed did not have a significant effect on the selection of marketing channels of Palm Oil Factory (POF).

Soil Biochemical Properties and Nutrient Leaching from Smallholder Oil Palm Plantations, Sumatra-Indonesia

The study aimed to assess soil biochemical properties and nutrient leaching in palm oil plantation. The research was conducted in smallholder oil palm plantations which were located in Jambi Province - Indonesia. Nutrient leaching was determined by measuring nutrient concentration in soil solution bi-weekly and monthly in the frond stacked and fertilized areas; soil water samples were collected by using suction cup lysimeter. The result showed that the application of mineral fertilizer (e.g. NPK) and dolomite resulted higher base saturation, exchangeable Ca, and available P in the fertilized than frond stacked and inter row areas (p ≤ 0.05). Stacking palm oil frond increased the soil macro-porosity, hence decreased leaching of K, Mg, Na, P, and total Al in the frond stacked than in the fertilized areas. The lower leaching losses and the higher soil macroporosity in the frond stacked than in the fertilized areas indicated that either the water did not dilute nutrient in the soil due to bypass flow, or the nutrient release from mineralization did not surpass nutrient demand which is quickly uptaken by palm root. Proper soil management through synchronizing rate of fertilizer application with nutrient output or frequency of fertilizer application may potentially minimize leaching losses.

Mapping of smallholder oil palm plantation and development of a growth model

Smallholder plantation accounts for 39% of total oil palm plantation in Indonesia, which is currently estimated at 12 million ha. Limited information on spatial distribution of smallholder oil palm and the growth of plantation pose a great challenge for providing information in scientific based. Therefore, information on smallholder oil palm plantation are necessary and they will give valuable input for policy maker and related stakeholders. This study is aimed to generate smallholder oil palm distribution map using optical satellite data of SPOT 7 and investigate the backscatter values of ALOS PALSAR-2 with height and age of oil palm in mineral soil and peatland. We mapped 46,756 ha of smallholder plantation or about 18% of total oil palm plantation in district of Kotawaringin Barat, Central Kalimantan province and 14% of which is located on peatland area. From the result, height to age mineral soil has a strong relationship with R2 value 0.80 but weak in peatland with R2 value 0.31. Relationship between height and backscatter in mineral soil has R2 value 0.43 for HH and 0.30 for HV and in peatland 0.28 for HH and 0.15. Relationship between age and backscatter in mineral soil has moderately strong correlation with R2 value 0.55 for HH and 0.37 for HV and in peatland 0.36 for HH and 0.28. In all relationship, independent variables are statistically significant with Significance-F value lower than 0.05. In general, height, age, and backscatter relationship in peatland is lower than in mineral soil. Backscatter value can be useful for studying height and age of smallholder oil palm. Further studies are suggested to involve more potential variables and utilize multi temporal datasets in determining height and age of oil palm trees using backscatter values.

FERTILISER APPLICATION PRACTICES AND NUTRIENT DEFICIENCIES IN SMALLHOLDER OIL PALM PLANTATIONS IN INDONESIA

SUMMARYOil palm has become an important source of revenue for smallholders in Indonesia, but productivity of smallholder plantations is generally poor. Nutrient limitations have been suggested as an important agronomic constraint to yield. Our research aimed to quantify fertiliser use, soil and tissue nutrient status, and palm growth and yield in a sample of independent smallholder plantations. We selected 49 plantations in Indonesia in two provinces with contrasting soils. For all plantations, we obtained self-reported fertiliser use and yield data, collected soil and tissue samples, and analysed vegetative growth. More than 170 kg N ha−1year−1was applied in one site, and P was applied in excess of recommended quantities in both sites, but on average farmers applied less than 100 kg K ha−1year−1. Soils in the palm circle were poor in N, P and K in 29, 40 and 82% of the plantations, and deficiencies were measured in 57, 61 and 80% of the leaflet samples, respectively. We found statistically significant correlations between tissue nutrient concentrations and vegetative growth, but a large part of the variation in the data remained unaccounted for. Single leaf area was reduced in >80% of the plantations. Average yields were estimated to be 50‒70% of the water-limited potential. Our results demonstrate that widespread nutrient imbalances and deficiencies, especially potassium and phosphorus, occur in smallholder oil palm plantations, due to inadequate and unbalanced fertiliser application practices. These deficiencies may be an important underlying cause of the overall poor productivity, which threatens the economic and environmental sustainability of the smallholder sector.

Land cover changes reduce net primary production in tropical coastal peatlands of West Kalimantan, Indonesia

Tropical peat swamp forests are carbon-rich ecosystems that have been threatened by high rates of land use change (LUC). Despite the ecosystem’s shifts from sequestering carbon (C) to emitting carbon, few studies have quantified the changes in ecosystem productivity associated with LUC in tropical peatlands. This study quantified net primary production (NPP) in intact peat swamp forests (PSF), logged forests (LPSF), early seral sites (ES), and smallholder oil palm plantations (OP) in a peat dome of West Kalimantan, Indonesia. All sites were dominated by peat forest prior to deforestation. The NPP of intact forests was 13.2 Mg C ha−1 year−1 making it among the world’s most productive terrestrial ecosystems, exceeding that of many tropical rainforests and similar to the most productive mangrove ecosystems (12.9 Mg C ha−1 year−1). Land cover change resulted in large shifts in NPP. Logged forest and early seral sites were < 11.1 Mg C ha−1 year−1. The NPP of oil palm plantations was 3.7 Mg C ha−1 year−1. Aboveground NPP was recorded at 10.5 Mg C ha−1 year−1 in forests, exceeding the NPP of LPSF, ES, and OP (8.9, 5.1, and 3.5 Mg C ha−1 year−1, respectively). Early seral sites (5.7 Mg C ha−1 year−1) were estimated to have the highest belowground NPP (p = 0.05). Root productivity in PSF, LPSF, and OP was 2.7, 2.1, and 0.2 Mg C ha−1 year−1, respectively. Land use change and forest degradation have reduced the productivity of tropical peatlands.

Canopy soil of oil palm plantations emits methane and nitrous oxide

Due to an increasing global demand in cheap oils and biofuels, forest conversion to oil palm plantations is rapidly increasing in Indonesia. Oil palm canopy soil, or the soil lodged between the stems and leaf axils of oil palms, is one ecosystem compartment that has yet to be investigated as to its importance on the soil greenhouse gas budget. Our objectives were 1) to quantify nitrous oxide (N2O) and methane (CH4) fluxes from oil palm canopy soil, and 2) to determine the factors controlling these fluxes. Our study was conducted in Jambi Province, Indonesia, an area of rapid oil palm expansion. Trace gas fluxes were measured in eight smallholder oil palm plantations (9–16 years old). In each plantation, oil palms were delineated into three 1-m height sections (low, middle, and top) to represent possible gradients of canopy soil conditions that influence N2O and CH4 fluxes. Trace gas fluxes were measured by collecting canopy soil from each stem section and immediately incubating in the field in an air-tight glass jar. Canopy soils from all oil palm stem sections emitted N2O and CH4. The top stem section had higher N2O and CH4 emissions than the lower sections, and this pattern was paralleled by nitrogen availability and water content, which strongly influenced these fluxes. Greenhouse gas emissions per unit dry mass of canopy soil were considerable, but on a hectare basis these emissions were small due to the low amount of canopy soil per hectare (170 kg ha−1). Annual canopy soil N2O and CH4 emissions were 10.7 ± 3.3 g N2O-N ha−1 yr−1 and 1.9 ± 0.5 g CH4-C ha−1 yr−1, respectively, which contributed only 1% of the total soil (canopy soil + ground soil) N2O fluxes and 0.2% of the ground soil net CH4 consumption. Our estimate of oil palm canopy soil emissions in Jambi Province were 7.7 Mg N2O-N yr−1 and 1.3 Mg CH4-C yr−1. Considering the increasing areal coverage of oil palm plantations in Southeast Asia, these fluxes may substantially contribute to soil greenhouse gas budgets.

Nutritional imbalance in smallholder oil palm plantations in Indonesia

In Indonesia more than 40% of the area under oil palm is owned by smallholders. The productivity in smallholder plantations is usually less than in large plantations, and limited fertiliser applications may be one of the key reasons. We investigated the use of fertilisers by > 300 smallholder farmers in Sumatra and Kalimantan, some of whom were involved in training programmes aimed at yield improvement. In our sample, the total applications of N were largest (166 kg ha−1 year−1), followed by K (122 kg) and P (56 kg). The applications of K were insufficient to compensate for the off-take with a production of 20 tonne fruit bunches ha−1 year−1, while N applications were excessive. On average, farmers applied 1130 kg fertiliser ha−1 year−1, and relied strongly on subsidised fertilisers, especially NPK Ponska (66%) and urea (39%). The average costs for fertiliser application were USD 225 ha−1 year−1. Trained farmers applied significantly more P in one research area, but for the other nutrients and research areas, there was no significant difference between trained and untrained farmers. Plantation size and nutrient application were weakly correlated in some areas, but not in the sample as a whole. Previously reported nutrient application rates were mostly less than our findings indicated, suggesting that actual nutrient limitations may be more severe. To overcome nutrient limitations and enhance nutrient use efficiency, we recommend that fertilisers are used in the correct balance; a ground cover vegetation is maintained to protect against erosion; and the application of empty fruit bunches is encouraged.

Bird Diversity in Smallholders Oil Palm Plantation in Riau Province

Within the last few decades, oil palm (Elaeis guine) has become one of the most rapid crop plantations being widely cultivated in Indonesia. Land clearing for stallholder plantation is made by people, either individually or in group. Forest clearing for planting activities may cause changes to the composition of the ecosystem. Birds have a signifcant role in the ecosystem, such as pollinators, seed spreader and pest control. It was claimed that bird richness decreases at least 60% due to changes in land cover into plantations. This claim needs to be further verifed. The objective of this study is to identify bird diversity and determine thesimilarity of the bird community in some smallholder oil palm plantations in Kuantan Singingi, Pelalawan and Siak District in Riau Province. Data collection had been conducted using transect method with length of 1 km and width of 50 m. Observations were done at 8 smallholder oil palm plantations in the morning from 6:00 to 8:30 pm and in the afternoon from 15:30 to 18:00 pm with 3 times repetition. Data in the study were analyzed by Margalef Index (Dmg), evenness (E) and community similarity (IS). This research showed that there are 22 species of birds from 15 families. The highest value of diversity and richness was in the plantation 1 while the highest evenness was in the plantation 5. The lowest diversity was in SH5 (H '= 1.79), the lowest richness was plantation 6 (Dmg = 2.50) and the lowest evenness value was in the plantation 4 (E = 0.90). The highest value of community similarity recorded between plantation 1-plantation 4 (IS = 0.92) while the lowest was seen between plantation 5-plantation 7 (IS =0.44). Similar habitat conditions affect the value of the bird community similarity.

Soil nitrogen oxide fluxes from lowland forests converted to smallholder rubber and oil palm plantations in Sumatra, Indonesia

Abstract. Oil palm (Elaeis guineensis) and rubber (Hevea brasiliensis) plantations cover large areas of former rainforest in Sumatra, Indonesia, supplying the global demand for these crops. Although forest conversion is known to influence soil nitrous oxide (N2O) and nitric oxide (NO) fluxes, measurements from oil palm and rubber plantations are scarce (for N2O) or nonexistent (for NO). Our study aimed to (1) quantify changes in soil–atmosphere fluxes of N oxides with forest conversion to rubber and oil palm plantations and (2) determine their controlling factors. In Jambi, Sumatra, we selected two landscapes that mainly differed in texture but were both on heavily weathered soils: loam and clay Acrisol soils. Within each landscape, we investigated lowland forests, rubber trees interspersed in secondary forest (termed as jungle rubber), both as reference land uses and smallholder rubber and oil palm plantations as converted land uses. In the loam Acrisol landscape, we conducted a follow-on study in a large-scale oil palm plantation (called PTPN VI) for comparison of soil N2O fluxes with smallholder oil palm plantations. Land-use conversion to smallholder plantations had no effect on soil N-oxide fluxes (P = 0. 58 to 0.76) due to the generally low soil N availability in the reference land uses that further decreased with land-use conversion. Soil N2O fluxes from the large-scale oil palm plantation did not differ with those from smallholder plantations (P = 0. 15). Over 1-year measurements, the temporal patterns of soil N-oxide fluxes were influenced by soil mineral N and water contents. Across landscapes, annual soil N2O emissions were controlled by gross nitrification and sand content, which also suggest the influence of soil N and water availability. Soil N2O fluxes (µg N m−2 h−1) were 7 ± 2 to 14 ± 7 (reference land uses), 6 ± 3 to 9 ± 2 (rubber), 12 ± 3 to 12 ± 6 (smallholder oil palm) and 42 ± 24 (large-scale oil palm). Soil NO fluxes (µg N m−2 h−1) were −0.6 ± 0.7 to 5.7 ± 5.8 (reference land uses), −1.2 ± 0.5 to −1.0 ± 0.2 (rubber) and −0.2 ± 1.2 to 0.7 ± 0.7 (smallholder oil palm). To improve the estimate of soil N-oxide fluxes from oil palm plantations in this region, studies should focus on large-scale plantations (which usually have 2 to 4 times higher N fertilization rates than smallholders) with frequent measurements following fertilizer application.

Gender Inequality and the Oppression of Women within Minangkabau Matrilineal Society

Gender inequality within the Melayu clan of a Minangkabau matrilineal community in Dharmasraya District, West Sumatra Province in Indonesia, leads to the clan’s women experiencing injustice when it comes to the management of communal forest land (ulayat). This inequality is most clearly shown in situations in which men sell communal forest land for their own personal interests. Moreover, the distribution of nucleus estate smallholder oil palm plantation (NESHP) plots disadvantages women. Although these plots are supposed to be distributed fairly among community members, the system used is controlled by the male communal ruler, who holds rights over the community as a whole. The practices used to manage ulayat forestland within the Melayu clan prove that women within the matrilineal system used by the Minangkabau group, of which the Melayu clan is a part, are not treated equally in terms of the management of natural resources. This inequality arises due to an imbalance that exists between men and women over the rights they have to manage the ulayat forest. The findings of this study challenge previous studies which have suggested that gender inequality is mainly an issue within patrilineal societies; the finding suggests that it also occurs within matrilineal systems such as within the Melayu clan in Bonjol village.

Soil degradation in oil palm and rubber plantations under land resource scarcity

Tropical regions, such as Sumatra, experiencing extensive transformation of natural ecosystems, are close to complete exhaustion of available land. Agroecosystems strongly modify water and nutrient cycles, leading to losses of soil fertility, C sequestration and biodiversity. Although large companies are the main drivers of deforestation and plantation establishment, smallholders account for 40% of the oil palm and the majority of the rubber production in Indonesia. Here, we assess the extent and mechanisms of soil degradation under smallholder oil palm and rubber plantations in a context of land scarcity. The topsoil properties (C and N contents, C stocks, C/N ratio, bulk density) in 207 oil palm and rubber plantations in the Jambi province of Sumatra were determined beside trees, inside rows and interrows. Soils under oil palms were on average more degraded than under rubber, showing lower C content and stocks, lower N and higher bulk density. While soil properties were homogenous under rubber, two opposite trends were observed under oil palm plantations: the majority of soils had C content <2.2%, but about one fifth of the plantations had >9% C. This resulted from the establishment of oil palms under conditions of land scarcity. Because the oil palm boom started when rubber was already well-established, oil palms were frequently planted in marginal areas, such as peatlands or riparian areas (high C) or soils degraded by previous use (low C). The management of oil palms led to subsequent soil degradation, especially in interrows: C content decreased and bulk density increased in older oil palm plantations. This was not observed in rubber plantations because of a C input from leaf litter spread homogeneously all over the plantation, higher ground cover and a limited use of motorized vehicles. Considering that 10% of soils under oil palms had very low C content (<1%), we conclude that intensive cultivation can lead to intensive soil degradation and expect future degradation of soils under young oil palms. This challenges the sustainability of agricultural intensification in Sumatra. Because Sumatra is a pioneer of tropical land-use change, this should be regarded as potential threats that other tropical regions may face in future.