Main drivers of plant diversity patterns of rubber plantations in the Greater Mekong Sub-region

The Greater Mekong Sub-region (GMS) is one the global biodiversity hotspots. However, the diversity has been seriously threatened due to environmental degradation and deforestation, especially by expansion of rubber plantations. Yet, little is known about the impact of rubber plantations on plant diversity. In this study, we analyzed plant diversity patterns of rubber plantations in the GMS based on a ground survey of a large number of samples. We found that diversity varied across countries due to varying agricultural intensities. Laos had the highest diversity, then followed China, Myanmar, Cambodia. Thailand and Vietnam were the lowest among them. Plant species richness of Laos was about 1.5 times that of Vietnam. We uncovered latitudinal and longitudinal gradients in plant diversity across these artificial forests of rubber plantations. These gradients could be explained by the traditional ecological theories. Furthermore, null deviation of observed community to the randomly assembled communities were larger than zero indicating deterministic process were more important for structuring the community. Meanwhile, the results also showed that higher dominance of some exotic species (such as Chromolaena odorata and Mimosa pudica) were associated with a loss of plant diversity within rubber plantations. In conclusion, not only environmental factors (such as elevation and latitude), but also exotic species were the main factors affecting diversity of these artificial stands. Much more effort should be made to balance agricultural production with conservation goals in this region, particularly to minimize the diversity loss in Vietnam and Cambodia.

Report of Lissachatina fulica (Bowdich, 1822) (Stylommatophora: Achatinidae) in rubber plantations of Western Ghats, Kerala

The giant African snail Lissachatina fulica (Bowdich, 1822) is reported as a pest in rubber plantations adjoining forest fringes in the Western Ghats region of Kerala. The snail was causing damage to rubber (Hevea brasiliensis) and nutmeg (Myristica fragrans) trees, by feeding on rubber latex and nutmeg twigs and leaves. L. fulica infestation on M. fragrans is a new record. The snail infestation in rubber plantations is the first report from the Western Ghats region in Kerala.

Developing Multi-Source Indices to Discriminate between Native Tropical Forests, Oil Palm and Rubber Plantations in Indonesia

Over the last 18 years, Indonesia has experienced significant deforestation due to the expansion of oil palm and rubber plantations. Accurate land cover maps are essential for policymakers to track and manage land change to support sustainable forest management and investment decisions. An automatic digital processing (ADP) method is currently used to develop land cover change maps for Indonesia, based on optical imaging (Landsat). Such maps produce only forest and non-forest classes, and often oil palm and rubber plantations are misclassified as native forests. To improve accuracy of these land cover maps, this study developed oil palm and rubber plantation discrimination indices using the integration of Landsat-8 and synthetic aperture radar Sentinel-1 images. Sentinel-1 VH and VV difference (>7.5 dB) and VH backscatter intensity were used to discriminate oil palm plantations. A combination of Landsat-8 NDVI, NDMI with Sentinel-1 VV and VH were used to discriminate rubber plantations. The improved map produced four land cover classes: native forest, oil palm plantation, rubber plantation, and non-forest. High-resolution SPOT 6/7 imagery and ground truth data were used for validation of the new classified maps. The map had an overall accuracy of 92%; producer’s accuracy for all classes was higher than 90%, except for rubber (65%), and user’s accuracy was over 80% for all classes. These results demonstrate that indices developed from a combination of optical and radar images can improve our ability to discriminate between native forest and oil palm and rubber plantations in the tropics. The new mapping method will help to support Indonesia’s national forest monitoring system and inform monitoring of plantation expansion.

Soil Properties Variability Under Various Agroecosystems In Ultisols Of Bengkulu

Understanding the relation of agroecosystem types, ages, and soil properties are vital in maintaining good quality soil. This study aims to explore the variation of selected soil properties with agroecosystem types and ages. The research has been conducted in North Bengkulu, Indonesia. Soil properties on agroecosystems of 5-yr, 10-yr, 15-yr oil palm plantation, 5-yr, 10-yr, 15-yr rubber plantation, food cropland, and scrubland were evaluated. The study found that soil in oil palm and rubber plantations of any age have a similar texture, bulk density (BD), and actual soil moisture (ASM). All plantation agroecosystems and scrubland have higher clay and lower silt content than that in food cropland. In addition, the scrubland has the highest ASM content among the agroecosystems. On the other hand, both agroecosystems enhances soil chemical properties than food cropland and scrubland as indicated by the improvement of organic-C, total-N, available P, exchangeable K and CEC of Ultisols. Older plantation also provides higher soil chemical improvement than younger one. This finding is significant for management of sub optimal soil mainly Ultisols for oil palm and rubber plantation.

Stretching the Habitat Envelope: Insectivorous Bat Guilds Can Use Rubber Plantations, but Need Understorey Vegetation and Forest Buffers

Effects of land-cover change on insectivorous bat activity can be negative, neutral or positive, depending on foraging strategies of bats. In tropical agroforestry systems with high bat diversity, these effects can be complex to assess. We investigated foraging habitat use by three insectivorous bat guilds in forests and rubber plantations in the southern Western Ghats of India. Specifically, we monitored acoustic activity of bats in relation to (1) land-cover types and vegetation structure, and (2) plantation management practices. We hypothesized that activity of open-space aerial (OSA) and edge-space aerial (ESA) bat guilds would not differ; but narrow-space, flutter-detecting (NSFD) bat guild activity would be higher, in structurally heterogeneous forest habitats than monoculture rubber plantations. We found that bat activity of all guilds was highest in areas with high forest cover and lowest in rubber plantations. Higher bat activity was associated with understorey vegetation in forests and plantations, which was expected for NSFD bats, but was a surprise finding for OSA and ESA bats. Within land-cover types, open areas and edge-habitats had higher OSA and ESA activity respectively, while NSFD bats completely avoided open habitats. In terms of management practices, intensively managed rubber plantations with regular removal of understorey vegetation had the lowest bat activity for all guilds. Intensive management can undermine potential ecosystem services of insectivorous bats (e.g., insect pest-control in rubber plantations and surrounding agro-ecosystems), and magnify threats to bats from human disturbances. Low-intensity management and maintenance of forest buffers around plantations can enable persistence of insectivorous bats in tropical forest-plantation landscapes.

Effects of tropical rainforest conversion to rubber plantation on soil quality in Hainan Island, China

Land-use changes can alter soil properties and thus affect soil quality. Our understanding of how forest conversion (from tropical rainforest to rubber plantations) affects soil properties and soil quality is limited. An ideal testing ground for analyzing such land-use change and its impacts is Hainan Island, the largest tropical island in China. Based on 21 soil physicochemical and biological properties, a soil quality index (SQI) employed principal component analysis to assess soil quality changes from the conversion of tropical rainforests to rubber plantations. The results showed that (i) soil available potassium, available phosphorus, microbial biomass carbon, cellulose decomposition, acid phosphatase, and urease were vital soil properties for soil quality assessment on Hainan Island. (ii) The SQI of rubber plantations decreased by 26.48 % compared to tropical rainforests, while four investigated soil properties (soil pH, total phosphorus, cellulose decomposition, and actinomyces) increased. (iii) The SQI of both the tropical rainforests and rubber plantations showed significant spatial differences, which, under tropical rainforests, was more sensitive to seasonal changes than those under rubber plantations. (iv) Structural equation modeling suggested that forest conversion directly impacted soil quality and, indirectly impacted soil qualities' spatial variation by their interaction with soil types and geographical positions. Overall, though the conversion of tropical rainforest to rubber plantation did not decrease all soil properties, the tropical rainforest with its high soil quality should be protected.

Livelihood Impacts of Smallholder Rubber Plantations: Case Studies of Two Communities in Vientiane Province, Lao PDR

<p>In Laos rubber plantation investment has increased significantly in recent years, supported by the Government. Farmers decide to cultivate rubber trees in order to generate greater income and diversify their agricultural activities. However, rubber planting also creates impacts on the livelihoods of farmers. This research aims to examine the impacts of rubber plantations on two communities in Vientiane Province. Utilising the sustainable livelihood framework, this research seeks to understand how the introduction of rubber plantations affect livelihood activities, the local land use system, and the environment in the case study communities. Key positive impacts include increased income and job opportunities. However, increased rubber planting reduces the availability of land for crops and livestock rearing and also creates some adverse environmental impacts. Overall, rubber production significantly modifies local agricultural production systems and resource use decision making in communities.</p>

Livelihood Impacts of Smallholder Rubber Plantations: Case Studies of Two Communities in Vientiane Province, Lao PDR

<p>In Laos rubber plantation investment has increased significantly in recent years, supported by the Government. Farmers decide to cultivate rubber trees in order to generate greater income and diversify their agricultural activities. However, rubber planting also creates impacts on the livelihoods of farmers. This research aims to examine the impacts of rubber plantations on two communities in Vientiane Province. Utilising the sustainable livelihood framework, this research seeks to understand how the introduction of rubber plantations affect livelihood activities, the local land use system, and the environment in the case study communities. Key positive impacts include increased income and job opportunities. However, increased rubber planting reduces the availability of land for crops and livestock rearing and also creates some adverse environmental impacts. Overall, rubber production significantly modifies local agricultural production systems and resource use decision making in communities.</p>