Aiyen Tjoa

Universitas Tadulako · Faculty of Agriculture

Sustainability standards, such as the Roundtable for Sustainable Palm Oil (RSPO), can potentially mitigate the trade-offs between economic benefits and environmental harm of oil palm expansion. Using unique primary household and farm level panel data collected from Jambi Province, Indonesia, we first document the differences in agricultural inputs...

The expansion of the oil palm industry in Indonesia has improved livelihoods in rural communities, but comes at the cost of biodiversity and ecosystem degradation. Here, we investigated ways to balance ecological and economic outcomes of oil palm cultivation. We compared a wide range of production systems, including smallholder plantations, industr...

Tropical forests occupy small coral atolls to the vast Amazon basin. They occur across bioregions with different geological and climatic history. Differences in area and bioregional history shape species immigration, extinction and diversification. How this effects local diversity is unclear. The Indonesian archipelago hosts thousands of tree speci...

Tropical forests occupy small coral atolls to the vast Amazon basin. They occur across bioregions with different geological and climatic history. Differences in area and bioregional history shape species immigration, extinction and diversification. How this effects local diversity is unclear. The Indonesian archipelago hosts thousands of tree speci...

Conventional management of oil palm plantations, involving high fertilization rate and herbicide application, results in high yield but with large soil greenhouse gas (GHG) emissions. This study aimed to assess a practical alternative to conventional management, namely reduced fertilization with mechanical weeding, to decrease soil GHG emissions wi...

Conventional management of oil palm plantations, involving high fertilization rate and herbicide application, result in high yield but with large soil greenhouse gas (GHG) emissions. This study aimed to assess a practical alternative to conventional management, namely reduced fertilization with mechanical weeding, to decrease soil GHG emissions wit...

The rapidly growing areal extent of oil palm (Elaeis guineensis Jacq.) plantations and their high fertilizer input raises concerns about their role as substantial N2O sources. In this study, we present the first eddy covariance (EC) measurements of ecosystem‐scale N2O fluxes in an oil palm plantation and combine them with vented soil chamber measur...

Mangrove forests, benefitting millions of people, experience significant degradation. Global recognition of the urgency of halting and reversing this trend have initiated numerous restoration activities. Restoration success is typically evaluated by estimating mangrove survival and area restored, while diversity and structure of vegetation, as prox...

Nickel (Ni) and associated minerals (Cr and Mn) are naturally occurring substances in ultramafic laterites soil. It may be found in our vegetables and grains when agriculture is grown in ultramafic laterites. This study aimed to assess the contamination of Ni in edible crops affected by soil volume in mono- and mixed cropping on limonitic laterite...

Potential effects of land-use/land-cover (LULC) transformation from lowland rainforest into oil-palm plantations on silicon (Si) pools in tropical soils remain poorly understood, although appropriate levels of plant-available Si in soils may contribute to maintain high crop yields and increase the vitality and drought resistance of oil palms. There...

Mangroves are complex, unique, and dynamic ecosystems that host organisms that have special physiological adaptations to fluctuations in salinity, temperature, and pH. Gastropods have an important role in the mangrove ecosystem for food cycles and webs by helping to provide nutrients and micro-habitats for microbes. Micro-fungi isolated from mangro...

Most plant-available Si in strongly desilicated soils is provided through litter decomposition and subsequent phytolith dissolution. The importance of silicon (Si) cycling in tropical soil–plant systems raised the question of whether oil-palm (Elaeis guineensis Jacq.) cultivation alters Si cycling. As oil palms are considered Si hyper-accumulators,...

Effects of oil-palm (Elaeis guineensis Jacq.) management on silicon (Si) cycling under smallholder oil-palm plantations have hardly been investigated. As oil palms are Si accumulators, we hypothesized that management practices and topsoil erosion may cause Si losses and changes in spatial Si concentration patterns in topsoils under oil-palm cultiva...

Oil palm is the most productive oil crop, but its high productivity is associated with conventional management (that is, high fertilization rates and herbicide application), causing deleterious environmental impacts. Using a 2² factorial experiment, we assessed the effects of conventional vs reduced (equal to nutrients removed by fruit harvest) fer...

Feed quality is a very important factor in shrimp farming because it will affect shrimp growth, water quality and even the emergence of pathogenic bacteria. High quality feed can be well digested by shrimp so that it can improve the growth and do not leave plenty of residue. Mold is capable of producing cellulase which can be used to improve feed q...

Wallacea—the meeting point between the Asian and Australian fauna—is one of the world's largest centers of endemism. Twenty-three million years of complex geological history have given rise to a living laboratory for the study of evolution and biodiversity, highly vulnerable to anthropogenic pressures. In the present article, we review the historic...

Silicon (Si) is known to have multiple beneficial effects on crops. Most plant-available Si in soils is provided through litter decomposition and subsequent phytolith dissolution, especially in strongly desilicated tropical soils. The importance of Si cycling in tropical soil-plant systems raised the question if oil-palm cultivation, the oil palm b...

Phytoliths make up the predominant fraction of biogenic silica in plant litter and soils. Thus, they represent a major source of dissolved silicon (Si) in soil-plant systems. Dissolution of phytoliths from Si-accumulating crops such as rice has been well studied in recent years. However, phytolith dissolution in oil-palm plantations remains largely...

Effects of oil-palm (Elaeis guineensis Jacq.) management on silicon (Si) cycling under smallholder oil-palm plantations have hardly been investigated. As oil palms are Si accumulators, we hypothesized that management practices and topsoil erosion may cause Si losses and changes in spatial Si concentration patterns in topsoils under oil-palm cultiva...

To secure high yield, tropical oil palm plantations are fertilized, and understory vegetation is controlled by chemical clearing with herbicides. These treatments cause a drastic turnover of soil microbes and cause loss of beneficial mycorrhizal fungi. Here, we tested if reduced fertilization and weeding instead of conventional treatments restored...

The effects of land use and fire on ecosystem silicon (Si) cycling has been largely disregarded so far. We investigated the impacts of land use and fire on Si release from topsoils and litter of lowland rainforest and oil-palm plantations in Jambi Province, Indonesia. Lower concentrations of Si in amorphous silica (ASi) were found in oil-palm plantati...

Mangroves are uniquely important ecosystems, for preserving biodiversity, sustaining livelihoods and mitigating against climate change. However they are degraded globally and are therefore a priority for ecosystem restoration. To date, the assessment of mangrove restoration outcomes is generally poor, and the limited studies that do exist are focus...

Intensive management practices in large-scale oil palm plantations can slow down nutrient cycling and alter other soil functions. Thus, there is a need to reduce management intensity without sacrificing productivity. The aim of our study was to investigate the effect of management practices on gross rates of soil N cycling and soil fertility. In Ja...

Cocoa (Theobroma cacao L.), a major commodity globally, depends on insects for pollination. However, the cocoa pollinator identity is largely unknown and there are important knowledge gaps regarding landscape and farm-level management driving pollinators. Here we analyzed flower visitation with two approaches to quantify how landscape and farm-leve...

The high and relatively unexplored diversity of fungi present in the mangrove ecosystem represents a source of novel biotechnological importance. This study explored the potential of fungi isolated from the mangrove ecosystems to produce proteases and cellulases (commercially important enzymes) and their ability to inhibit pathogenic Vibrio species...

At the oil palm landscape, conserving biodiversity and ecosystem processes can range from continuous adjacent forest remnant to tree patches (agroforestry) maintained within the oil palm landscape on steep slopes and riparian margins. The objective of the research was to analyze patched of tree planting inside monoculture oil palm plantation (agrof...

The efficiency of the water transport system in trees sets physical limits to their productivity and water use. Although the coordination of carbon assimilation and hydraulic functions has long been documented, the mutual inter-relationships between wood anatomy, water use and productivity have not yet been jointly addressed in comprehensive field...

Nutrient leaching in intensively managed oil palm plantations can diminish soil fertility and water quality. There is a need to reduce this environmental footprint without sacrificing yield. In a large-scale oil palm plantation in Acrisol soil, we quantified nutrient leaching using a full factorial experiment with two fertilization rates (260 kg N,...

Increasing demand for cocoa and climate-related yield declines have sparked a multi-stakeholder debate on cocoa production strategies. Agrochemical inputs and pollination enhancement through hand pollination are two strategies to increase yields. Here, we test both strategies with field experiments in Indonesia. We show that even partial hand polli...

The purpose of this study was to evaluate the plant growth performance of top grafted young cacao cultivated in various elevations. This research was conducted from January-August 2019 in South Sulawesi and Central Sulawesi. A total of 54 plants were taken randomly from 6 locations with 3 altitudes (<300, 300-600, >600 meter above sea level, as.)....

Root and soil interactions will alter the biochemical status of the rhizosphere, the acquisition of nutrients and impacted to plant growth. The biochemical of the rhizosphere is strongly influenced by the agriculture input e.g. fertilizer, herbicides and farm management system. Application of fertilizers, their effects are robust and difficult tobe...

Nutrient leaching in intensively managed oil palm plantations can diminish soil fertility and water quality. There is a need to reduce this environmental footprint without sacrificing yield. We quantified nutrient leaching in a large-scale oil palm plantation on Acrisol soil with factorial treatment combinations of two fertilization rates (260 N, 5...

Nickel hyperaccumulators are plants that can absorb a large amount of Ni in their tissues. Nickel hyperaccumulators have a strong potential to be used as bioindicators in mineral explorations. Previous studies show that analysis of magnetic susceptibility has a potential to accelerate the screening of Ni hyperaccumulators. In this study, we investi...

Land-use transitions can enhance the livelihoods of smallholder farmers but potential economic-ecological trade-offs remain poorly understood. Here, we present an interdisciplinary study of the environmental, social and economic consequences of land-use transitions in a tropical smallholder landscape on Sumatra, Indonesia. We find widespread biodiv...

The potential of palm-oil biofuels to reduce greenhouse gas (GHG) emissions compared with fossil fuels is increasingly questioned. So far, no measurement-based GHG budgets were available, and plantation age was ignored in Life Cycle Analyses (LCA). Here, we conduct LCA based on measured CO2, CH4 and N2O fluxes in young and mature Indonesian oil pal...

Inclusion of ecosystem-based approaches in the governmental masterplan for tsunami mitigation in Palu, Indonesia may make the city a rare case study for ecological disaster risk reduction in tropical biodiversity hotspots. Such case studies are a key pillar of the United Nations (UN) Sendai Framework to protect coastal societies globally.

Aim Massive biota mixing due to plate‐tectonic movement has shaped the biogeography of Malesia and during the colonization process, Asian plant lineages have presumably been more successful than their Australian counterparts. We aim to gain a deeper understanding of this colonization asymmetry and its underlying mechanisms by analysing how species...

Oil palm plantations are intensively managed agricultural systems that increasingly dominate certain tropical regions. Oil palm monocultures have been criticized because of their reduced biodiversity compared to the forests they historically replaced, and because of their negative impact on soils, water, and climate. We experimentally test whether...

Input such as fertilizer highly affects the root response, and can change the root morphology and architecture, which will have an impact on the nutrient uptake and biomass production. This research investigates changes in root architecture and morphology, nitrogen uptake and biomass production of the Noko rattan seed in the treatment of inorganic...

Cocoa (Theobroma cacao L.) is a cross-pollinated plant that is dependent on insect pollination. Despite this plant-pollinator dependency and the large economic value of cocoa, there are still important knowledge gaps in the identity of flower visitors, plantation management to enhance their habitats, and overall potential of pollination services to...

The original version of this Article contained an error in the third sentence of the abstract and incorrectly read "Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha-1 year-1 (95% CI 0.14-0.72, mean period 1988-2010) above-ground live biomass", rather than the correct "H...

Background and Aims To increase yield, cacao is planted increasingly in unshaded monocultures, replacing a more traditional cultivation under shade. We investigated how shade tree cover and species diversity affect the root system and its dynamics. Methods In a replicated study in Sulawesi (Indonesia), we studied the fine and coarse root system do...

This book is based on close and multi-year communication between ecologists and local cacao farmers and can therefore serve as a valuable tool to build a bridge of communications between farmers and scientists about ecosystems, biodiversity and land use strategies. As described in the book, birds and bats can make an economically beneficial contrib...

Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43...

Explaining the diversity and distribution of tree taxa in the isolated tropical mountain forests (TMF) of the Malesian archipelago remains one of the great challenges of tropical biogeographical research. We investigated tree diversity, endemism and community composition in 13 plots of 0.24 ha between 700 and 2400 m in the TMF of Central Sulawesi’s...

Smallholder-dominated agricultural mosaic landscapes are highlighted as model production systems that deliver both economic and ecological goods in tropical agricultural landscapes, but trade-offs underlying current land-use dynamics are poorly known. Here, using the most comprehensive quan-tification of land-use change and associated bundles of ec...

Primer pair sequences for plants, bacteria, and archaea

Supplementary Figures 1 - 9, Supplementary Tables 1 - 5, Supplementary Note 1 and Supplementary References

Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and the extraction of natural resources. In Jambi Province, Indonesia, the interdisciplinary EFForTS project focuses on the ecological and socio-economic dimensions of rainforest conversion to jungle rubber agroforests and monoculture plantations of rubber and...

One of the main drivers of tropical forest loss is their conversion to oil palm, soy or cacao plantations with low biodiversity and greatly reduced carbon storage. Southeast Asian cacao plantations are often established under shade tree cover, but are later converted to non-shaded monocultures to avoid resource competition. We compared three co-occ...

Above- and belowground biomass stocks. Above- and belowground biomass stocks and the shoot:root ratio of the nine study sites of the three cultivation systems in the Kulawi valley (means per plot). Only for the group ‘all’ fine root data is included. (PDF)

Net primary production (NPP). Components of annual net primary production (NPP) (in Mg ha-1 yr-1) of the nine study sites of the three cultivation systems in the Kulawi valley (means per plot). Note that coarse root biomass production includes production of root stocks as well. (PDF)

Above- and belowground carbon stocks. Above- and belowground carbon stocks and the shoot:root carbon ratio of the nine study sites of the three cultivation systems in the Kulawi valley (means per plot). Only for the group ‘all’ fine root data is included. (PDF)

Carbon pools in net primary production (NPP). Associated carbon pools (in Mg C ha-1 yr-1) in annual net primary production (NPP) of the nine study sites of the three cultivation systems in the Kulawi valley (means per plot). Note that coarse root biomass production includes production of root stocks as well. (PDF)