Akhmad Rizali

Land-use choices follow profitability at the expense of ecological functions in Indonesian smallholder landscapes

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 quantification of land-use change and associated bundles of ecosystem functions, services and economic benefits to date, we show that Indonesian smallholders predominantly choose farm portfolios with high economic productivity but low ecological value. The more profitable oil palm and rubber monocultures replace forests and agroforests critical for maintaining above- and below-ground ecological functions and the diversity of most taxa. Between the monocultures, the higher economic performance of oil palm over rubber comes with the reliance on fertilizer inputs and with increased nutrient leaching losses. Strategies to achieve an ecological-economic balance and a sustainable management of tropical smallholder landscapes must be prioritized to avoid further environmental degradation.

Long-term change of ant community structure in cacao agroforestry landscapes in Indonesia

Land‐use change and agricultural intensification can strongly affect biodiversity in agricultural landscapes. Although many studies investigate management impacts, data on the long‐term change of species communities in agroecosystems are scarce. We analysed the long‐term change in diversity and composition of ant communities in cacao agroforestry systems in Central Sulawesi, Indonesia and attempted to disentangle the driving factors of this change. Ant communities were resampled in 2009 from sites for which previous surveys had been conducted either in 2001 (the rainforest‐poor Palolo region) or 2003 (the rainforest‐rich Kulawi region) using insecticide fogging. Ant community composition changed significantly over time in Palolo and Kulawi. The change in ant species richness differed between regions. Species richness increased in Kulawi, probably due to the increasing availability of nest sites and microhabitats as trees grow larger and older. In the Palolo region, species richness decreased, suggesting that the high local intensification and landscape‐wide changes may have counteracted the effects of tree age. Changes in ant communities over time were significant, but were more difficult to explain than expected, despite clear difference in management changes within and between regions. The findings suggest that the landscape‐scale differences between the two study regions play a more important role for species diversity and its composition than changes in local management. This highlights the importance of long‐term studies across contrasting landscapes for better understanding the consequences land‐use intensification has on tropical biodiversity.

Insect pollinator communities under changing land-use in tropical landscapes: implications for agricultural management in Indonesia

The destruction of rainforests can affect many ecosystem services, e.g pollination services for wild and crop plants in landscapes with high proportion of natural habitats. We discuss evidence of the impact of landuse change toward insect pollinator communities and pollination based in the tropics, with an emphasis on case-studies from Indonesia. Some studies showed that species richness of flower visiting bees, pollination, and fruit set were found to be negatively correlated with increasing rainforest isolation and land-use intensity. However, others demonstrated an opposite pattern. Species composition changes significantly between habitat types, which may be relevant in the context of environmental changes as species composition can be an important variable to ensure pollination services and fruit set.

Separating effects of species identity and species richness on predation, pathogen dissemination and resistance to invasive species in tropical ant communities

Ants are abundant in natural and managed tropical ecosystems and can have an impact on herbivorous arthropods, as well as plant pathogens. Although it has been shown for plants that the diversity of communities can result in improved ecosystem functioning, it remains uncertain how the species richness of ants affects multiple ecosystem services and disservices. In the present study, we used experimentally enhanced natural gradients in ant species richness on 100 cacao trees in a plantation aiming to analyze the effect of ant species identity and species richness on predation pressure and the incidence of cacao pod borer (CPB), as well as the spread of black pod disease (BPD). Ant species richness did not significantly improve predation of experimentally exposed insects, and was not associated with a reduction in the incidence of CPB. However, the incidence of BPD was higher in ant species rich trees, presumably because more ant species were pathogen vectors. The identity of the dominant ant species affected the incidence of CPB and BPD, as well as predation pressure. Although both ant species richness and identity affected ecosystem services and disservices delivered by the ant community, the results of the present study suggest that the identity of dominant ants is the main driver for ecosystem services in these systems.

Susceptibility of Maize Genotypes to Maize Weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

One possibility to protect the maize from storage pests is by developing genotypes that resistant to maize weevil (Sitophilus zeamais Motsch). The research was aimed to evaluate the susceptibility of several maize genotypes including local variety to the maize weevil. Six genotypes i.e. SJA, G10-12-20, G10-1-3, G10-1-7, G10-1-20 and G10-1-17 and Tosari as local variety were used. No-choice assay under laboratory condition with observed variables was laid an egg and F1 progeny number, the median time of development and weight loss of infested kernel. The susceptibility index was assessed using Dobie’s susceptibility index. Results showed that the number of eggs laid by five females and infested samples weight loss were not significantly different between six maize genotypes as well as local variety. In contrast, the number of F1 progeny emerged was significantly different. Based on the susceptibility index, the maize genotype of G10-1-3 and G10-1-17 were resistant to the weevil. While other maize genotypes and local variety were considered as moderate resistant. Based on analysis of chemical and physical characteristic revealed that maize genotypes with higher of the total phenolic compound and physical hardness tend to resist from weevil damaged.