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Overuse of chemical nitrogen (N) fertilizers leads to N leaching and soil degradation. Replacing chemical N fertilizers with organic fertilizers can enhance soil nutrition, reduce N loss, and improve soil productivity. However, the effects of combining organic and chemical fertilizers on soil N components and N transformation remain unclear. A 12-year field study included four treatments: no fertilizer (CK), chemical fertilizer alone (CF), 50% chemical N fertilizer combined with co-composted organic fertilizer (CFM), and composted (CFMC) organic fertilizer. The results showed that CFM and CFMC significantly enhanced SOC, TN, LFON, DON, NH4+-N, and MIN levels compared to CF. The CFM and CFMC treatments enhanced the soil N supply capacity and N pool stability by increasing the N mineralization potential (N0) and decreasing the N0/TN ratio. The CFM and CFMC treatments decreased net N ammonification rates by 108.03%–139.83% and 0.44%–64.91% and net mineralization rates by 60.60%–66.30% and 1.74%–30.38%, respectively. Changes in N transformation have been attributed to increased soil pH, enzyme activity, and substrate availability. These findings suggest that partial organic fertilizer substitution, particularly with co-composted organic fertilizers, is a viable strategy for enhancing soil fertility, improving soil N supply and stability, and reducing N loss in rubber plantations. [ABSTRACT FROM AUTHOR]

Agroforestry is known to significantly improve long-term land productivity, potentially enhancing the ability to cope with climate stress. However, there is limited information regarding the accurate monitoring of greenhouse gases (GHGs) in rubber-based agroforestry systems. Before GHGs can be accurately estimated, the diurnal variations and suitable sampling times must be studied to reduce the uncertainty of the manual static chamber method. In this study, the soil GHGs emitted from conventional single-row (SR) and improved double-row (DR) rubber plantations were compared across the dry and wet seasons in Hainan, China. A total of 1728 GHG samples from a field trial were collected, analyzed, and related to environmental factors. The results demonstrated that the diurnal fluxes of CO2 in rubber plantations were likely to remain fluctuating, with the maximum typically occurring during the night-time and daytime hours of the dry and wet seasons, respectively. A clearer double-peak (around 2:00 and 14:00) during the dry season and a daytime peak (14:00) during the wet season of the N2O were recorded. In addition to the commonalities, different seasons and different types of GHGs and rubber plantations also differed in their detailed fluctuation times and ranges; therefore, the determination of suitable sampling times should not ignore these factors in certain cases. Based on this study, it was determined that the late afternoon (16:00–18:00) was the suitable sampling time of soil GHGs in rubber plantations, instead of the most common morning times (with an underestimation of 25% on average). In addition, the air humidity during the dry season and the soil temperature during the wet season were both positively correlated with GHGs (p < 0.05). This study highlights the significance of accurately monitoring soil GHGs in rubber-based agroforestry systems, providing a basic reference for the development and management of climate-smart land use practices in rubber plantations. [ABSTRACT FROM AUTHOR]

Understanding the dynamic relationships between soil organic carbon (SOC) and stand age are essential to quantify and predict the terrestrial carbon sequestration potential. However, the spatial patterns in the response of rubber plantation SOC to stand age and their driving factors remain unclear. Based on SOC and its components measurement at different soil depths (0–40 cm) in rubber plantations under five different age classes (0–5, 5–10, 10–20, 20–30, and >30 years) in three major rubber cultivation regions in China, distribution pattern and controlling factors of SOC were investigated. We found that SOC and its components showed significant spatial variability vertically with soil depth and laterally across sampling sites. SOC contents in three major rubber cultivation regions range from 4.48 to 20.13 g kg−1 at a depth of 0–40 cm. Among the sampling sites, Jinghong had the highest SOC content at a depth of 0–10 cm (20.13 g kg−1). On a large‐scale, the relationship between SOC and stand age in rubber plantations did not show a consistent pattern among different sampling sites. Additionally, annual rainfall, soil moisture content, and soil pH had a stronger impact on SOC in rubber plantations compared to stand age. The results indicated that the spatial variability of SOC in rubber plantations with stand age could be influenced by specific soil properties and climate‐related variables at each sampling site. This study emphasized the significance of conducting multi‐site, multi‐scale studies to enhance our understanding of SOC dynamics and its influencing factors, and help to more accurately predict the dynamic changes of soil carbon storage in rubber plantations. [ABSTRACT FROM AUTHOR]

Introduction: Clonal fragmentation helps to assess clonal plants' growth resilience to human and environmental disturbance. Although clonal integration in epiphytes in tropical rubber plantations is important to understand their role in enhancing biodiversity and ecosystem services, research on this subject is limited. These plantations are typically monospecific economic forests that face increased anthropogenic disturbances. Methods: In this study, we selected the clonal fern Pyrrosia nuda to study its survival status, biomass, maximum quantum yield of photosystem II (Fv/Fm), and frond length in response to the level of clonal fragmentation in a tropical rubber plantation. Results and discussion: The results showed that (1) clonal fragmentation significantly negatively affected the survival rate, biomass, and frond length of clonal plants, but with minimal effects on Fv/Fm at different growth stages; (2) the performance of a ramet (e.g., biomass or frond length) increased with ramet developmental ages and decreased with the number of ramets in a clonal fragment. The age-dependent impacts of clonal fragmentation provide insights into the biodiversity conservation of epiphytes and forest management in man- made plantations. Therefore, to better conserve the biodiversity in tropical forests, especially in environment-friendly rubber plantations, there is a need to reduce anthropogenic disturbances and alleviate the level of fragmentation. [ABSTRACT FROM AUTHOR]

Background: Studying green manure decomposition in various returning methods can establish a scientific foundation for farmland nutrient management. Methods: In a rubber plantation on Hainan Island, China, utilized the nylon mesh bag method to imitate the decomposition of kudzu (whole plant, stem, and leaf) under two returning methods (mulching and burying) in two different sites (young and mature rubber plantations). The study examined the decomposition rate and nutrient release dynamics of kudzu, as well as the effects of kudzu reintroduction on several soil properties including soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), available phosphorus (AP), and enzyme activities. Results: Compared with mulching, the burying returning method significantly increased the kudzu decomposition rate and nutrient release proportions. After 270 days, more than 80% of the C, N, and P in different components of kudzu were released. The decomposition rate was found to be more affected by the initial soil factors than by the endogenous nutrients of kudzu. Compared with CK, all kudzu treatments led to significant increases in soil enzyme activities and soil pH, SOC, NO3−-N, and AP concentrations in two rubber plantations. The TN and NH4+-N concentrations were significantly increased in mature rubber plantations, while the TP was the opposite. Conclusion: The kudzu returned can effectively alleviate soil acidic, improve soil nutrient availability, regulating soil enzyme activities of the rubber plantation in the short-term. These results provide a scientific basis for the rational application of kudzu in rubber plantations. [ABSTRACT FROM AUTHOR]

The article explores the detrimental effects of expanding rubber plantations on the environment and local communities in Tripura, India. It highlights the conversion of natural forests, bamboo gardens, jhum cultivation, and farmland into rubber plantations, leading to deforestation and loss of biodiversity. The use of chemicals in rubber processing has resulted in soil degradation and contamination. Additionally, the rapid growth of rubber plantations has caused environmental degradation, including changes in temperature, rainfall, and soil quality. The study concludes that the negative impacts outweigh the benefits, as traditional livelihoods and biodiversity are at risk. [Extracted from the article]

Rubber tree plantations (Hevea brasiliensis) are expanding into the tropical regions of southwest China to ensure production to meet the growing demand for latex. The effects of long-term plantations on soil carbon processes are still unclear. Also, the effects of the plant's rhizosphere on the decomposition of soil organic matter (SOM) play a crucial role in predicting soil carbon dynamics. The rhizosphere and soils corresponding to a chronosequence of ages (4, 15 and 30 years) of rubber plantations were collected and incubated to determine the effect of the rhizosphere (RE) on SOM decomposition. We also examined the soil physicochemical properties; bacterial community structure; and root morphological, chemical, and physiological traits to further explore the underlying mechanisms of the RE on SOM decomposition. The REs on SOM decomposition varied significantly in the different age classes of the rubber plantations, and the higher the REs on SOM decomposition in an older plantation might limit the accumulation of organic carbon in the soil. Root traits, including the specific root length, root nitrogen content, and root carbon/nitrogen ratio, varied significantly in response to the plantation age and explained more of the variance in the RE on SOM decomposition than the soil and microbial properties. Due to the changing root morphological and chemical traits along the age chronosequence, the rhizosphere bacterial community composition tended to shift the carbon utilisation strategy and the bulk soil nitrogen content decreased. These variations also affected the RE on SOM decomposition. Our results indicate that the development of rubber plantations would prevent soil carbon accumulation, especially in the rhizosphere, by increasing the RE on SOM decomposition, which would be predicated by root morphological and chemical traits. [ABSTRACT FROM AUTHOR]

Soil quality is a critically important component of soil within ecosystems, and our understanding of soil quality variation and its driving factors in tropical forests is limited. This study collected soil samples at 0–20 cm depths from two typical tropical forests (tropical rainforest and rubber plantation) on Hainan Island, China's largest tropical island, during dry and rainy seasons. A soil quality index (SQI) using principal component analysis was applied to measure soil quality based on 21 soil properties. The soil properties' spatial and seasonal changes and their driving factors were simultaneously collected for a holistic analysis of the ecosystems. The results were summarized as follows: (i) The SQI of the rubber plantation decreased by 26.48% compared to the tropical rainforest on the island, while four soil properties investigated (soil pH, total phosphorus, cellulose decomposition, and actinomycetes) increased. (ii) The SQI of different soil types in the two tropical forests displayed an apparent discrepancy. Within the same soil type, the SQI of tropical rainforests showed no obvious differences, while there was a notable spatial discrepancy among rubber plantations in dispersed geographical positions belonging to varied climatic zones. (iii) The SQI of the tropical rainforest was significantly higher in the wet season than in the dry season. In contrast, there were no significant differences between the two seasons for rubber plantations, indicating that soil quality in the tropical rainforest was more sensitive to seasonal changes than soil quality in rubber plantations. Overall, we concluded that except for land use and soil type, spatial variability and seasonal pattern also played essential roles in soil quality on the tropical island. The results from the SQI are expected to provide novel information regarding the sustainable use of tropical forests on Hainan Island. [ABSTRACT FROM AUTHOR]

Soil management zoning can normally use weighted environmental variables to obtain the weight of environmental factors. This approach relies mainly on the crop yield to acquire the weights of environmental variables, in order to establish the relationship model between the crop yields and environmental variables. Thus, the current zoning cannot fully meet the requirement of modern agriculture in recent years, particularly when the crop yields are unavailable or there is no relationship between them. Fortunately, the normalized difference vegetation index (NDVI) can be expected to reflect the soil condition, which was significantly influenced by the environmental variables. In this study, an accurate and efficient approach was developed to obtain the weights of environmental variables using NDVI. The relation model between NDVI and environmental variables was then established in this case. Three steps consisted of this approach. Firstly, the key environmental variables were selected to significantly impose the influence on NDVI. The relation model was then established between NDVI and the selected key environmental variables. Finally, the weights of environmental variables were acquired from the established relation model. A case study was applied to test the effectiveness of the approach. Specifically, the weights of environmental variables were acquired for a rubber plantation in Danzhou County, Hainan Province, China. Among them, the candidates were taken as the 10 terrain attributes, 19 bioclimatic variables, and 5 parent materials types. Furthermore, 15 key environmental variables were determined to construct the relationship model with the NDVI using the random forests (RF). The importance index (IncMSE) was extracted from the fitted relation model, and then calculated the weight of each key environmental variable. These acquired weights were also used to weigh the environmental variables, and then to serve as the input variables for the K means clustering. Finally, six groups of soil management zones were generated for the rubber plantation. A total of 1296 top soil (0-20 cm) samples were employed to verify the soil management zones. Results indicated that the management zones better distinguished the abundance and deficiency levels of different soil nutrients (soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK)). Zone 1 presented the high AP content, the normal range of pH value and SOM content, as well as the TN and AK in deficiency. Zone 2 shared the high AP content, pH value suitable for the rubber tree growth, but the SOM, TN, and AK in deficiency. Zone 3 demonstrated a very high AP content and a pH value within the normal range. Nevertheless, the contents of SOM, TN, and AK were all lower than the normal range in Zone 3. More importantly, the contents of SOM, TN, and AK in Zone 4 were similar to those in Zone 3. However, the values of pH and AP were significantly lower than that in Zone 3. In Zone 5, the values of pH and AK were the highest in the normal range among the six zones, while the values of SOM and TN were the lowest in deficiency. In Zone 6, the soil TN content was the highest among the six zones within the normal range. The pH value and AP were also within the normal range, but the AP content was close to the lower limit of the normal range, indicating the insufficient content of SOM and AK. At the same time, the mean differences were all significant at P < 0.05 level in 15 selected environmental variables among different management zones. Consequently, the soil management zones further verified the effectiveness of the approach, where the weights of environmental variables were acquired by the NDVI. Anyway, the NDVI acquiring the weights of environmental variables can be applied to much wider ranges, because the NDVI can be much easier to access than the crop yields in practice. [ABSTRACT FROM AUTHOR]

Forest age, a critical variable for land-use decision makers, is known to change soil microbial communities. However, how such changes affect microbial metabolic strategy and the associated soil C mineralization processes in different forest ages remains unknown, especially in tropical region. To address this issue, three different aged rubber plantations, namely 4-year-old (Young, YRP), 15-year-old (Mature, MRP), and 31-year-old (Old, ORP), were studied to reveal the soil mineralization characteristics. Furthermore, to understand the mechanism from the coupled perspective of decomposers and substrate availability, the microbial metabolic strategy was deciphered by 2D-COS-Biolog assay, and linked with soil microbial composition and labile-/recalcitrant- organic pools. Results showed that YRP was characterized by having more copiotrophic taxa (e.g., actinobacteria) and the largest G(-)/G(+) ratio and invertase activity. Thus, YRP exhibited a preferential utilization for carbohydrate and the largest SOC mineralization rate. In contrast, regardless of abundant labile C and N pools in MRP, the soil microbial communities were shifted to oligotrophic taxa in utilizing resistant polymer, and MRP contained abundant G(+), fungi and arbuscular mycorrhizal fungi related to aggregate formation. As a result, the soil mineralization rate in MRP was reduced by 66 % compared with YRP. However, the SOC mineralization rate was unchanged from MRP to ORP, primarily because the increased proportion of recalcitrant nutrient pool, and soil microorganism had greater priority in utilizing relatively resistant amine. The structural equation modeling revealed that the variations in mineralization were mainly regulated by soil microbial composition and metabolic strategy, and partially affected by soil C and N pools. Furthermore, random forest model indicated that soil pH, NH 4 -N and C/N were also the crucial factor for mineralization by affecting soil microbial communities during stand development. In summary, these findings improve our understanding in soil C budget and contribute to the C accurate management during plantation development. [Display omitted] • SOC mineralization decreased from young to mature stage and then remained unchanged. • Young plantation contained more fungi and preferentially utilized carbohydrate. • More recalcitrant pool and amine utilization caused a lower SOC mineralization. [ABSTRACT FROM AUTHOR]

Simple Summary: While studies based on the taxonomic facet of biodiversity have already proven their value in understanding soil functioning, studies focusing on the functional facet based on the traits of organisms are scarce in the Ivorian context. Among soil organisms, springtails play an important role in soil functioning and are a useful bioindicator for assessing the impact of land use change and agricultural practices on soil biodiversity. However, their taxonomy is very poorly known in Côte d'Ivoire. The functional trait approach is therefore a relevant alternative for assessing the response of springtails communities to organic matter management in tree plantations. The aim of this study was to determine how different input of organic matter in the form of logging residues and legumes influence the body size and functional diversity of springtails. Our results showed a high functional richness and body size of springtails in the practice with trunks and large branches (R2L1). Functional traits are useful to assess the effects of agricultural practices on springtails communities. We used trait-based approaches to reveal the functional responses of springtails communities to organic matter inputs in a rubber plantation in Côte d'Ivoire. Pitfall traps were used to sample springtails in each practice. The results showed that the total abundance of springtails increased significantly with the amount of organic matter (R0L0 < R2L1). Larger springtails (body length, furca and antennae) were observed in plots with high organic matter. Practices with logging residues and legume recorded the highest functional richness. The principal coordinate analysis showed different functional composition patterns between practices with logging residues (R1L1 and R2L1) and those without inputs (R0L0 and R0L1). This difference in functional composition (PERMANOVA analysis) was related to the effect of practices. These results highlight the pertinence of the functional trait approach in the characterization of springtail communities, a bioindicator of soil health, for organic matter management practice. [ABSTRACT FROM AUTHOR]

Intercropping is a labor-intensive practice largely adopted by smallholder farmers to increase yield per unit area, cope with crop failures and market fluctuations, meet food preferences and increase farm income. A field experiment was conducted to examine the yield performances and intercropping efficiencies of sweet corn and okra planted in a young rubber plantation. The treatments were arranged in Randomized Complete Block Design (RCBD) with three replications. The treatments ratios were 20% okra + 80% sweet corn (strip and strip relay intercropping) with sole okra and sweet corn as the control. This consisted of strips intercropping (okra and sweet corn planted on the same date), strip relay intercropping (sweet corn planted 4 weeks after okra planting), sole okra and sole sweet corn. The highest yield of okra was obtained from strip relay intercropping while the highest yield of sweet corn was produced from the pattern of strip intercropping. However, the economic analysis showed that the strip intercropping recorded the maximum gross margin and costbenefit ratio of RM 17,733.20 ha-1 and 2.09, respectively. Immature rubber growth was unaffected by intercropping with sweet corn and okra crops. Strip intercropping not only resulted in the higher land equivalent ratio (1.29), but also area time equivalent ratio, % land saved and monetary advantage index of 1.14, 22.28% and RM 7,583.50 ha-1, respectively compared with strip relay intercropping. The highest assessment of intercropping based on relative crowding coefficient was recorded by strip intercropping with 4.56. With regard to competition between the intercrops, okra was a more dominant species as measured by the positive value of aggressivity. However, strip intercropping was indicated the lowest competitive ratio than the strip relay intercropping. Thus, this intercropping pattern can be recommended to the farmers for adoption. [ABSTRACT FROM AUTHOR]

Rubber plantations have rapidly replaced natural forests (NFs) in Mainland Southeast Asia, yet the relevant impacts on the terrestrial carbon cycle remain uncertain especially with an increase in drought frequency. Our study compared eddy‐covariance measurements of carbon and water fluxes from two rubber monoculture plantations (at a northern marginal site and a southern traditional plantation site) with a second‐growth NF between 2015 and 2018, and their responses to a prolonged drought during 2015/2016. The NF had higher light use efficiency, water use efficiency and gross primary productivity (GPP, 2.94 ± 0.41 kg C m−2 yr−1) than the northern rubber (NR) monoculture (2.45 ± 0.17 kg C m−2 yr−1), while lower ecosystem carbon use efficiency (eCUE) caused a lower net ecosystem productivity (NEP, 0.75 ± 0.25 kg C m−2 yr−1) compared to the plantation (1.19 ± 0.22 kg C m−2 yr−1). Drought decreased the NF eCUE by 23% with significant carbon uptake restrictions across multiple seasons, while the rubber GPP reduction was only substantial in the warm‐dry season with an overall 17% decline in eCUE. The NR site's GPP was mainly controlled by soil water content throughout the year. Higher light availability offset the negative effect of drier conditions on the rubber GPP, resulting in larger carbon uptake compared to the southern plantation (GPP, 2.12 ± 0.12 kg C m−2 yr−1; NEP, 1.07 ± 0.14 kg C m−2 yr−1). In contrast, the NF GPP was mainly restricted by vapor pressure deficit, especially during the drought. Plain Language Summary: Both rubber expansion from south to north and increased drought events lead to large uncertainties in forest carbon and water cycles in Mainland Southeast Asia. To better understand their potential impacts, our study compared the carbon and water fluxes, and how they respond to drought in a marginal rubber planting area with a traditional planting area, and with a second‐growth natural forest (NF) near the marginal plantation over 4 years using eddy‐covariance technique. We found the NF absorbed more carbon with a higher use efficiency of light and water, while it was largely used for ecosystem respiration resulting in decreased carbon uptake than the rubber plantation. The decreased carbon uptake during drought was significant across multiple seasons in the NF, while it was only substantial in the warm‐dry season in the rubber plantations. Compared to the traditional planting area, carbon uptake in the marginal site was higher and mainly driven by soil moisture. The negative effect of drier conditions was offset by higher light availability during the rainy season. In contrast, the NF carbon uptake was mainly controlled by atmospheric water demand, especially during the drought. Key Points: Rubber plantations had a lower annual gross primary productivity yet higher carbon sequestration than a natural forest (NF)Higher light availability offset the negative effect of drier conditions on the rubber gross primary productivity in a marginal areaDrought increased the importance of soil moisture and vapor pressure deficit on the rubber and NF carbon uptake, respectively [ABSTRACT FROM AUTHOR]

The expansion of rubber (Hevea brasiliensis) cultivation plantation over the past few decades has been significantly explosive in Xishuangbanna, southwest China. More and more evidences concerning the expansion of rubber plantations lead to the negative influence to local regional hydrology. It is vital to explore the impact of climate change and rubber (Hevea brasiliensis) plantation expansion on reference evapotranspiration (ET0) for the sustainable and efficient use of regional water resources. In this study, the spatiotemporal variation of ET0 as well as its relationship in rubber plantations area in Xishuangbanna from 1970–2017 were analyzed by using trend, correlation and contribution analysis. The results showed that the rubber plantation was 12,768 ha yr–1 from 1990 to 2017 in Xishuangbanna, and nearly 40.8% of new rubber plantations expanded above 900 m in altitude from 2000 to 2017. Sunshine duration and average relative humidity were the key meteorological factors that affect ET0 in Xishuangbanna, with the sensitivity coefficient of 0.51 and 0.35, respectively. The multiyear relative change of ET0 in Xishuangbanna was 9.18%, and the total contribution of major climate factors was 7.87% during 1970 and 2017. The average relative humidity in the plantation area decreases, which directly leads to the increase of ET0. The amount of ET0 change from 2000 to 2017 affected by climate change increased at 3.13 mm/10a, whereas it was 2.17 mm/10a affected by the expansion of rubber plantations by quantitative separation. ET0 was significantly affected by climate change but intensified by the expansion of rubber plantation. [ABSTRACT FROM AUTHOR]

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 pudicd) 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. [ABSTRACT FROM AUTHOR]

The genus Moniligaster Perrier, 1872 is restricted to the Western Ghats mountain regions of the southern Peninsular India. A new species, Moniligaster julkai Narayanan & Paliwal, sp. nov., is described and illustrated using samples found in the Kerala districts of Kottayam and Pathanamthitta. Apart from that, the status of Moniligaster deshayesi minor Michaelsen, 1913 is critically reviewed, and it is upgraded to species rank as Moniligaster minor Michaelsen, 1913, based on a collection made near its type locality. Furthermore, new distributional records for other Moniligaster species are provided. With this discovery, the genus Moniligaster now has a total of 14 recognised species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Agroecosystems have been associated with risk of malaria. The aim of this study was to determine the relationship between three agroecosystems: (i) rubber plantation (RP); (ii) oil palm plantation (OPP); (iii) no cash crop plantation (NCCP) and the prevalence of Plasmodium falciparum infection among children living in the Aboisso region. In the three villages within (Ehania-V5) or close (N'zikro) or far from (Ayébo) to each agroecosystem (RP, OPP, and NCCP), two cross-sectional parasitological surveys were carried out during the dry and the peak of the long wet seasons. A total of 586 children aged 1–14 years were recruited in the three villages to determine the prevalence of malaria using conventional microscopy. Plasmodium falciparum was the dominant species with an overall infection prevalence of 40.8%. There was a significant difference in prevalence between agroecosystems, during both the dry (p = 0.002) and wet seasons (p < 0.001), which was higher in agricultural settings compared with the NCCP environment, whatever the season. The prevalence of P. falciparum infection increased from the dry to the wet season in agricultural settings (RP and OPP), whereas no difference was noted for NCCP. Less than 18% of children use insecticide-treated nets (ITNs) in the three villages, ranging from 6 (in RP) to 30% (in OPP). Multivariate analysis indicated that age (1–4; 5–9; and 10–14 years) was not associated with malaria risk, but the season and living in agricultural villages were associated with a greater risk of malaria infection. Risk of malaria exposure was fourfold higher in children from agricultural villages than their counterpart from the non-agricultural area. Our findings highlight significant variations in the prevalence of P. falciparum according to agroecosystem and season. The findings will be useful in designing and implementing malaria control interventions by the National Malaria Control Program. [ABSTRACT FROM AUTHOR]

Rubber powdery mildew disease (Oidium heveae) is a serious threat to natural rubber production (Hevea brasiliensis) in some rubber developing regions of the world. Both phenological- and meteorological-related factors have been reported influencing the powdery mildew disease. However, few studies have investigated the effects of both phenological- and meteorological-related factors on the disease. The objective of this study is to quantify the contributions of phenological- and meteorological-related factors to affect the disease. We used the partial least squares (PLS) regression method to comprehensively quantify the effects of thirty-five phenological related factors and six meteorological factors on the infection level of powdery mildew of rubber trees over 9-year records (2003–2011). The relative contributions of significant factors were further investigated by the variation partition analysis. We found that the most influential variables were the mean temperature during winter and the duration of leaf development to maturation which explained 32 and 26% of the variations in the infection level. We found the controlling role of winter mean temperature, for the first time, on the infection level of powdery mildew. The controlling role of winter temperature may have directly increase the infection level when winter temperature is high and indirectly increase the infection level through prolonging the duration of leaf development to maturation, although the duration itself had smaller influences. We detected a warming trend of the winter temperatures from 2003 to 2011, which indicates that the infection level of powdery mildew will be increased if the winter warming continues. [ABSTRACT FROM AUTHOR]

In recent years, rainfall-induced landslides along the Kerala segment of the Western Ghats have emerged as a recurrent natural hazard during the monsoon season. A significant number of these landslides are closely linked to rubber plantations. The official guidelines of the rubber board propound cutting the slopes into inwardly inclined contour benches for planting new saplings. The present investigation attempts to comprehend the adverse impact of this alteration practices adopted in terraced cultivated areas and its role in triggering landslides by employing a physically based landslide susceptibility model. The model combines infinite slope stability analysis with transient seepage analysis and determine the concomitant pore water pressure build-up on the terraced hillside slope during various rainfall rates. Further, the study assesses the adequacy of digital elevation model (DEM) resolution required to precisely capture the induced topographic modifications resulting from the terraced cultivation areas. DEM with different resolutions ranging from 0.25 m to 10 m is created using a terrestrial Light Detection and Ranging (LiDAR) survey data of a representative rubber plantation area located in the Western Ghats. The findings from the aforementioned DEMs were compared with DEM of an unmodified slope and those with horizontal contour benches. Our study reveals that terraced rubber cultivation facilitates an increase in pore pressure greater than twice to that of the unmodified slope with same attributes. Consequently, the practised modifications reduced the stability of an unmodified slope by 54 %. An important corollary of the present investigation is that the regional scale landslide hazard mapping using coarser resolutions DEM (> 2.5 m) cannot detect these detrimental anthropogenic topographical modifications, resulting in unreliable assessments of landslide hazard susceptibility. • Extensive slope modifications for terraced rubber cultivation raise landslide risks. • These terrain modifications promote rain infiltration, weakening slopes. • Numerical analyses show 50 % drop in slope stability under extremely heavy rainfall. • Analyses show 2 times increase of pore pressure compared to natural slopes. • DEM resolution < 2.5 m crucial to detect detrimental topographic variations [ABSTRACT FROM AUTHOR]

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Hunting and deforestation are the two biggest threats to vertebrates in Southeast Asia. In the last 50 years, monoculture rubber plantations replaced large areas of tropical rainforests in Xishuangbanna, southwest China. We set up camera traps at 109 stations (57 in forest reserves and 52 in rubber plantations) to determine the distribution of mammal species in Menglun, Xishuangbanna. We also interviewed 37 experienced hunters (mean age: 54) in the study area to understand their perceptions of species abundance trends. We used hierarchical multispecies occupancy modelling to determine the effect of distance to village, distance to forest edge and elevation on mammal occupancy after accounting for imperfect detection. We used non‐parametric tests for the rank data to evaluate perceived species trends. Using a combination of historical literature (1954–1985), hunter interviews, direct observations and camera‐trap surveys, we only recorded 56% (15 out of 27) of the medium‐to‐large sized (>1 kg) mammal species known previously from the study region. Interviews suggested that current population densities of all extant mammal species are below historical levels. Our camera traps captured 11 mammal species in the forest reserve and only two species in rubber plantations. Low capture rates (10 captures) in rubber mean we could only determine mammal occupancy in forests. Environmental variables did not affect community level mammal occupancy in forests, but common muntjac (Muntiacus muntjak) and the northern pig‐tailed macaque (Macaca leonina) avoided forest edges. At the time of the survey, hunting was still prevalent in the region. Therefore, conservation interventions that end both hunting and deforestation are urgently needed to stabilize and increase mammal populations in the region. [ABSTRACT FROM AUTHOR]

Rubber powdery mildew caused by the foliar fungi Oidium heveae is one of the main diseases affecting rubber plantations (Hevea brasiliensis) worldwide. It is particularly serious in sub-optimal growing areas, such as Xishuangbanna in SW China. To prevent and control this disease, fungicides causing serious environmental problems are widely used. Strong correlations between the infection level and the temperature variables were reported previously, but they were related to monthly data that did not allow unraveling the patterns during the entire sensitive period. We correlated the infection level of powdery mildew of rubber trees recorded over 2003–2011 with antecedent 365 days daily temperature variables using partial least squares (PLS) regression. Our PLS regression results showed that the infection level of powdery mildew responded differently to the temperature variables of the defoliation and refoliation periods. Further analysis with Kriging interpolation showed that the infection level increased by 20% and 11%, respectively, per 1 °C rise of the daily maximum and mean temperature in the defoliation season, while it decreased by 8% and 10%, respectively, per 1 °C rise of the daily maximum and temperature difference in the refoliation season. This pattern was likely linked to the effects of temperature on leaf phenology. It seems highly possible that the infection level of powdery mildew increases, as increasing trends of maximum temperature and mean temperature during the defoliation continue. [ABSTRACT FROM AUTHOR]

• Domestic land grab as a non-egalitarian process of control over the smallholders' land. • The positioning of domestic stated-owned investors in land grabbing literature. • SOE's domestic investment with more freedom, leverage, and power than similar firms investing abroad. • Domestic land grab as a process of re-territorialization and re-legalization for state formation. This paper examines the land grab processes dominated by a domestic state-owned enterprise in Vietnam. We examine the case of a rubber plantation in an ethnic minority area in the Northwest of the country. In doing so, the paper seeks to address how the Vietnamese socialist State – often considered a 'strong state' because it has pursued egalitarian land distribution policies over the past three decades – proceeds with domestic land grabbing in a context where the local people follow customary land use practices. The field research revealed the following. First, the Vietnamese government, while maintaining land distribution policies for its rural farming population, has increasingly sought to bring these policies more in line with the global trend of large-scale land acquisition at the expense of the traditional interests and livelihoods of the local population. By seeking to justify their essentially non-egalitarian land grab processes through the policy of post-land grab 'egalitarian land re-distributions' in areas with disembedded customary control, the domestic state actors deployed a cunning duplicity in their persistent adherence to agrarian egalitarianism. Second, with the supports from the local and central governments, a state-owned enterprise named Vietnam Rubber Group, carved out its land grab processes with more freedom, leverage, and power than similar firms investing abroad through land concessions. Last, the post-land grab redistribution of land rights materializes state formation through re-territorialization of and re-legalization within the frontier zone. [ABSTRACT FROM AUTHOR]

Natural environmental settings, in general, are considered by humans as the ideal ambience which makes them happy and reinvigorated especially within their mental realm. If this is the case, can we assume that all green spaces are synonymous to augmenting happiness? Biodiversity is expressed in terms of a system having number and abundance of different species. For resilience of various ecosystem services like food production, climate regulation, and pest management to take place, prevalence of such biodiversity is essential which can substantially contribute to sustained human well-being. In this study, we assessed the status of agrobiodiversity and subjective well-being of an indigenous community amidst the transition from shifting cultivation (SC) to monoculture of natural rubber (NR). Sampling the respondents from 18 villages of Dhalai, Tripura, a remotely located district in northeast India and bordered by Bangladesh, we used mixed methods research for in depth investigation. Findings revealed that in the SC landscape of study area, the cultivated crop species and livestock breeds were being largely replaced by encroachment from rubber plantation. We documented only 19 crop species on such a landscape which is otherwise known for its vast agrobiodiversity in the tropics. This kind of transition from SC to NR which is usually supported by the government development interventions, has severely affected the ecosystem services of such landscapes and banishing happiness from the indigenous communities, as perceived by them. Hence stabilization of rich agrobiodiversity and simultaneously ensuring the peoples' well-being is the only potential alternative for development in the region. [ABSTRACT FROM AUTHOR]

1. While it is clear that land‐use change significantly impacts the taxonomic dimension of soil biodiversity, how the functional dimension responds to land‐use change is less well understood. 2. This study examined how the transformation of primary forests into rubber tree monocultures impacts individual termite species and how this change is reflected in termite taxonomic and functional α‐diversity (within site) and β‐diversity (among sites). 3. Overall, individual species responded strongly to land‐use change, whereby only 11 of the 27 species found were able to tolerate both habitats. These differences caused a 27% reduction in termite taxonomic richness and reduced taxonomic β‐diversity in rubber plantations compared with primary forests. The study also revealed that the forest conversion led to a shift in some termite species with smaller body size, shorter legs and smaller mandibular traits. Primary forests exhibited higher functional richness and functional β‐diversity of termite species, indicating that functional traits of termite species in rubber plantations are more evenly distributed. 4. The present study suggests that forest conversion does not merely decrease taxonomic diversity of termites, but also exerts functional trait filtering within some termite species. The results affirm the need for biodiversity assessments that combine taxonomic and functional indicators when monitoring the impact of land‐use change. [ABSTRACT FROM AUTHOR]

Temperature change is an important environmental variable for global change sciences since it largely affects the physiology of plants in forest ecosystems. Canopy temperature depression (CTD) - the result of the deviation of the air temperature (Ta) from the plant canopy surface temperature (Tc) - varies depending on the meteorological and environmental conditions of the forests. Here, we evaluated the differences in CTD between a rubber plantation (RP) and a tropical rainforest (TR) in Xishuangbanna, southwestern China across the various time series of the period of 2011 to 2015. The mean maximum CTD values at the TR site and the RP site were 2.4°C and 0.6°C at diurnal level, 1.3°C and -0.5°C at monthly level, 0.6°C and -0.8°C at seasonal level and 5.6°C and 0.2°C at yearly time series level, respectively, while they were only significant (p < 0.01) in the diurnal time series. There was a significant (p < 0.01) negative linear relationship between CTD and global radiation (Q) in both sites at diurnal level and a significant (p < 0.05) negative linear relationship in the RP site at monthly time series level. A significant (p < 0.05) positive linear relationship between CTD and precipitation (P) at the RP site was found at diurnal level, as well as a significant (p < 0.01) positive linear relationship in the TR site at monthly time series level. The variation of CTD was critical for these two sites and largely depended on the amount of global radiation and the precipitation, while it will mainly affect the physiological variables. This study may prove useful for assessing the physiological response in terms of high temperature and drought conditions to regional and global change. [ABSTRACT FROM AUTHOR]

Large‐scale conversion of natural forest to rubber plantations has taken place for decades in Southeast Asia, help to make it a deforestation hot spot. Besides negative changes in biodiversity, ecosystem water, and carbon budgets, converting forests to plantations often reduced CH4 uptake by soils. The latter process, which might be partly responsible for resumed increase in the growth rate of CH4 atmospheric concentrations since 2006, has not been adequately investigated. We measured soil surface CH4 fluxes during 2014 and 2015 in natural forests and rubber plantations of different age and soil textures in Xishuangbanna, Southwest China—a representative area for this type of land‐use change. Natural forest soils were stronger CH4 sinks than rubber soils, with annual CH4 fluxes of −2.41 ± 0.28 and −1.01 ± 0.23 kg C ha−1 yr−1, respectively. Water‐filled pore space was the main factor explaining the differences between natural forests and rubber plantations, even reverting rubber soils temporarily from CH4 sink into a methane source during the rainy season in older plantations. Soil nitrate content was often lower under rubber plantations. Added as a model covariate, this factor improved explanation power of the CH4 flux—water‐filled pore space regression. Although soils under rubber plantation were more clayey than soils under natural forest, this was not the decisive factor driving higher soil moisture and lower CH4 uptake in rubber soils. Thus, the conversion of forests into rubber plantations exerts a negative impact on the CH4 balance in the tropics and likely contributes to global climate. [ABSTRACT FROM AUTHOR]

Despite the extensive, ongoing conversion of tropical forests to rubber plantation, the effects of this land-use change on soil fungal community diversity and composition are still poorly known. We compared a network of sites of tropical forest in southern Yunnan, China, with a network of rubber plantation sites originally derived from this forest. Soil DNA was amplified for ITS2 and sequenced using Illumina MiSeq. We found that there was a major shift in community composition across all phyla, including a large reduction in ectomycorrhizal fungi likely related to the absence of hosts. Conversion from forest to rubber plantation had no effect on total fungal α-diversity, but rubber plantation had lower β-diversity, resulting in lower overall gamma diversity. Networks based on co-occurrence of operational taxonomic unit in each land-use type showed that network complexity decreased with land-use change from forest to rubber plantation. Further investigation of soil functionality is needed to investigate whether this lower network complexity is related to reduced soil ecosystem resilience. [ABSTRACT FROM AUTHOR]

A species of laelapid mite, Ololaelaps formidabilis, is redescribed based on male and female adults from soil in Sumatra, Indonesia. This species is distinguished from other Ololaelaps species by its metapodal platelet narrowly fused with the parapodal plate and by its hologastric shield having two inverted-V-like ridges. The genus is redescribed based on a review of the literature and examination of specimens of some species. Valid species of Ololaelaps are listed and accompanied by notes on morphological characters to assist future revision of the genus. [ABSTRACT FROM AUTHOR]

Changes in land use and improper soil management have led to severe land degradation around the globe through the modification in soil physicochemical and biological processes. This study aimed to assess the soil properties of different land use system types. Soil samples (0-15 cm depth) were collected from five land uses; Rubber Plantation (RP), Oil Palm Plantation (OPP), Bamboo Forest (BF), Fallow Land (FL) and Natural Forest (NF) and analyzed for bulk density, soil texture, soil pH, soil moisture, soil carbon, total nitrogen, ammonium, nitrate, soil microbial biomass carbon, soil respiration. Soil pH was lower than 4.9 in all the sites indicating that the surface soil was highly acidic. Soil organic carbon (SOC) and total nitrogen (TN) values ranged from 2.02% to 2.81% and 0.22% to 0.3% respectively. Soil organic carbon (SOC), total nitrogen (TN) and soil microbial biomass (SMBC) were highly affected by soil moisture. NH4 +-N and NO3 --N ranged from 5.6 mg kg-1 to 10.2 mg kg-1 and 1.15 mg kg-1 to 2.81 mg kg-1 respectively. NF soils showed the maximum soil microbial biomass carbon (SMBC) whereas the minimum was observed in BF with values ranging from 340 mg kg-1 to 345 mg kg-1. Basal respiration was highest in RP (375 mg CO2 m-2 hr-1) and lowest in BF (224 mg CO2 m-2 hr-1). The findings demonstrated significant effect (p<0.05) of land use change on soil nutrient status and organic matter. Findings also indicated that land use change deteriorated native soil physicochemical and biological properties, but that land restoration practices through longer fallow period (>10 years) likely are successful in promoting the recovery of some soil characteristics. [ABSTRACT FROM AUTHOR]

Graphical abstract: Highlights: • A new soil quality index aggregating the set of Biofunctool® indicators was created. • The Biofunctool® index was applied in rubber tree-based cropping systems. • The Biofunctool® index proved to be sensitive to land uses and management practices. • The Biofunctool® index proved to be robust against various pedo-climatic contexts. • The Biofunctool® index allows to characterize a gradient of soil disturbance. Abstract Biofunctool® is a new framework for assessing the impact of land management on soil quality – defined as the capacity of the soil to function. Biofunctool® uses a set of twelve indicators to monitor changes in three key soil functions: carbon transformation, nutrient cycling and structure maintenance (part A). Information from all the indicators is integrated in a Soil Quality Index using multivariate analysis (PCA) weighting. We used Biofunctool® to assess the impact of land use, land use change and agricultural practices on soil quality. The Biofunctool® index was measured for soils in Thailand within rubber plantations, forests and intensive cash crops (cassava and sugar cane). The results demonstrate that the Biofunctool® index provides an aggregated synthetic soil functioning score that is sensitive to land management and is robust in various pedo-climatic contexts. Firstly, the index revealed the impact on soil of land conversion from annual cropping to rubber plantations and ranked the effect on soil with respect to a natural forest reference. Secondly, it showed the positive effect of legume cover-crops on soil functioning. Thirdly, it highlighted a trend of improving soil quality with increasing age of rubber plantations, in contrasted pedo-climatic contexts. It is concluded that the Biofunctool® index is a reliable and relevant descriptor of integrated soil functioning (i.e. soil quality) that could be useful for environmental impact assessment at regional to global scales. [ABSTRACT FROM AUTHOR]

In recent years, rubber plantations have been strongly promoted in the northern uplands of Vietnam–especially in the northwest, where it is an ill agro-ecological fit–with an aim to improve ethnic minority livelihoods and to modernize peasants by transforming them into rubber workers. A large area of land has been taken away from farmers to make way for rubber plantations. This land acquisition and agrarian transformation have impacted local people and their livelihoods in various ways. Drawing on ethnographic research, in combination with interviews with authorities and studying related documents, this article focuses on the gendered consequences of rubber plantation in northern uplands Vietnam. It argues that the process of becoming a rubber worker and adapting to the new way of living has indeed added new roles and responsibilities for women. At the same time, it has undermined men's values and reshaped gender relations both within and outside the home. [ABSTRACT FROM AUTHOR]

With the current trend of land use/land cover (LULC) change taking place globally, several parts of northeast India are also showing signs of change in LULC pattern leading to forest loss. This study focusses on the expansion of monoculture rubber plantation (Hevea brasiliensis) in selected sub-watersheds in northeast India, and distributed in parts of north Tripura, Mizoram and a major portion in the Karimganj district of Assam. Remote sensing and GIS technique has been used to map and analyse the extent of rubber plantation using temporal IRS LISS III satellite data from 1997 to 2013. It has been observed that rubber plantation increased from 4.47 sq. km to 28.42 sq. km in various parts of the study area. The expansion was more rapid during recent times, i.e. during 2010 to 2013. The plantation took place in dense forest, open forest and degraded forest areas. The spread of the plantation was also observed in one reserved forest located within the study area. There are several instances of negative impacts of rubber plantation expansion in Southeast Asia. Similar expansion of rubber plantation has been observed in northeast India as well. Further spread of rubber plantations in the region needs to be regulated to avoid conversion of dense and reserved forest areas by fostering use of mixed cropping methods instead of rubber monocultures, and by adopting more sustainable land use and management practices. [ABSTRACT FROM AUTHOR]

Soil respiration (SR) plays an important role in the global carbon cycle. The widespread and continued conversion of tropical forests to plantations is expected to drastically alter CO 2 production in soil, with significant consequences for atmospheric concentrations of this crucial greenhouse gas. In Southeast Asia, rubber plantations are among the most widespread monoculture tree plantations. However, knowledge of how SR differs in rubber plantations compared to natural forests is scarce. In this study, surface CO 2 fluxes and soil CO 2 concentrations (at 5 cm, 10 cm, 30 cm and 70 cm depths) were measured at regular intervals over a one-year period along slopes at three sites in paired natural tropical forests and mature rubber plantations. Annual surface soil CO 2 fluxes were 15% lower in the rubber plantations than in natural forest. This difference was due to substantially lower SR during the dry season in rubber plantations compared to natural forest. During the wet season, SR did not differ significantly between rubber plantations and natural forests. In rubber plantations, soil moisture increased from lower and middle to upper slope positions, but this did not significantly impact SR. Throughout the year, net CO 2 production per unit volume in the topsoil (2.5–7.5 cm) exceeded by 2–3 orders of magnitude net CO 2 production in the subsoil (7.5–50 cm). However, CO 2 originating from 5 cm depth and below in both land cover types could only explain up to 30% of the aboveground measured CO 2 flux, indicating that >70% of the total CO 2 respired and emitted to the atmosphere originated from the uppermost few cm of the soil. Net CO 2 production at different soil depths did not differ significantly between rubber plantations and natural forests. Our results indicate that SR characteristics in mature rubber plantation and natural forest were broadly similar, although dry season soil surface CO 2 fluxes were lower in rubber plantations. However, further information on the drivers of CO 2 production in the uppermost topsoil layers which are responsible for most CO 2 emissions is needed to understand the extent to which these results are generalisable. [ABSTRACT FROM AUTHOR]

Canopy temperature is a result of the canopy energy balance and is driven by climate conditions, plant architecture, and plant-controlled transpiration. Here, we evaluated canopy temperature in a rubber plantation (RP) and tropical rainforest (TR) in Xishuangbanna, southwestern China. An infrared temperature sensor was installed at each site to measure canopy temperature. In the dry season, the maximum differences (T − T) between canopy temperature (T) and air temperature (T) in the RP and TR were 2.6 and 0.1 K, respectively. In the rainy season, the maximum (T − T) values in the RP and TR were 1.0 and −1.1 K, respectively. There were consistent differences between the two forests, with the RP having higher (T − T) than the TR throughout the entire year. Infrared measurements of T can be used to calculate canopy stomatal conductance in both forests. The difference in (T − T) at three g levels with increasing direct radiation in the RP was larger than in the TR, indicating that change in (T − T) in the RP was relatively sensitive to the degree of stomatal closure. [ABSTRACT FROM AUTHOR]

This paper introduces a mixed method approach for analyzing the determinants of natural latex yields and the associated spatial variations and identifying the most suitable regions for producing latex. GeographicallyWeighted Regressions (GWR) and Iterative Self-Organizing Data Analysis Technique (ISODATA) are jointly applied to the georeferenced data points collected from the rubber plantations in Xishuangbanna (in Yunnan province, south China) and other remotely-sensed spatial data. According to the GWR models, Age of rubber tree, Percent of clay in soil, Elevation, Solar radiation, Population, Distance from road, Distance from stream, Precipitation, and Mean temperature turn out statistically significant, indicating that these are the major determinants shaping latex yields at the prefecture level. However, the signs and magnitudes of the parameter estimates at the aggregate level are different from those at the lower spatial level, and the differences are due to diverse reasons. The ISODATA classifies the landscape into three categories: high, medium, and low potential yields. The map reveals that Mengla County has the majority of land with high potential yield, while Jinghong City and Menghai County show lower potential yield. In short, the mixed method can offer a means of providing greater insights in the prediction of agricultural production. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of the litter layer and undergrowth intercrops on surface runoff and soil erosion, experimental field plots were monitored over one rainy season in a rubber monoculture and a rubber/tea agroforestry system. Results indicated that the cumulative runoff from plots with bare soil was 1.7 and 2.3 times higher than plots with a litter layer, and with a litter layer plus undergrowth, respectively. Overall, soil erosion from plots with bare soil, plots with a litter layer, and plots with a litter layer plus undergrowth was 4.73, 1.92 and 0.91 t ha − 1 , respectively. This suggests that rubber/tea agroforestry was more effective in runoff and erosion control than rubber monoculture. In contrast to runoff, soil erosion was found to be highly correlated with rainfall intensity, but weakly correlated with rainfall volumes. In the early rainy season when litterfall was considerably abundant (litter coverage > 70%), runoff and soil erosion in both the litter plots and litter plus undergrowth plots were significantly lower compared to the bare soil plots, or plots with only undergrowth. In the late rainy season when litter coverage < 40%, runoff and soil erosion in plots with litter layer or litter plus undergrowth were no longer significantly lower than those in the bare soil or undergrowth plots. These imply that the thick, intact leaf litter layer is an important soil protection agent. In addition, the results demonstrate that the direct influence of precipitation on surface erosion becomes less important as the number of protective layers increase. Solely from the point of view of erosion control, particular attention in practical soil conservation activities should be given to the capacity of tree litter to maintaining soil cover in a rubber plantation. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation on strategies for rubber plantation mapping employing SAR data coupled with Random Forest (RF) and Support Vector Machine (SVM). Linear backscatter coefficients achieved saturation point at about 10 years, making this form of polarimetric data being robust only for young to mature stands. This research found that the performance of both algorithms was comparable. The addition of texture features gave substantial impact to the overall accuracy. As indicated by the analysis of variable importance, only some texture features have contributed to higher overall accuracy. Classification using a subset of texture features pointed out that accuracy could be improved using dual polarimetric data, while trivial enhancement was seen in combined HH, HV and VV backscatter intensities. The research showed that classification accuracy could be further augmented by setting proper classification parameters. Nonetheless, it is argued that the level of improvement would greatly depend on selecting a proper dataset fed into classifier, rather than tuning classifier parameters. [ABSTRACT FROM PUBLISHER]

Rubber plantations are strongly increasing in Xishuangbanna, Southwest China. Herbicide applications controlling the undergrowth may increase erosion potential and carbon export by decreasing plant and litter cover. Quantitative evaluation of the erodibility of rubber systems and the impact of herbicides has not been studied. This study aimed at assessing the impact of herbicide application on soil loss and the induced carbon export in a rubber plantation. Runoff, sediment yield, and total organic carbon (TOC) content in sediments were measured under natural rainfall for one year in a 12-year old rubber plantation subjected to three different herbicide treatments: i) standard application twice per year practiced by the majority of farmers (Hs); (ii) no application to maintain a high understory plant cover (H −); and (iii) bimonthly application (adopted by some farmers) in order to largely avoid understory plant cover (H +). The infiltration rate under different treatments was measured with a rainfall simulator. Monthly measurements of fine root density using soil coring, surface cover, and understory plant cover making photography were carried out. The highest soil and TOC in sediment losses (425 g m − 2 , 15 g C m − 2 respectively) were observed under H + treatment, while under H − treatment they were strongly reduced (50 g m − 2 and 2 g C m − 2 respectively). Compared to Hs, H + increased soil and sediment TOC loss by 34 and 52%, while H − reduced soil and TOC loss, both by 82%. Notably, H − presented high conservation efficiency, reducing sediment yields by 86% for highly erosive rainfall events. The cover and management ( C ) factor and support practice factor ( P ) are essential components of the common Universal Soil Loss Equation (USLE) model. We combined the C and P factors into a single value ( CP ) and, for the first time, derived estimations of annual CP values for a rubber plantation (0.005–0.04) using our data. The dynamic change of the CP factor of plantations during the rainy season was quantified by relating relative soil loss to changes in understory plant cover (PC), which can be expressed as CP = 0.04e − 0.028PC ( R 2 = 0.88, P < 0.0001). Understory plant cover as affected by herbicide application was thus a key factor controlling the soil loss of established rubber systems. This suggests options to improve the soil conservation and biodiversity through reduced herbicide management. [ABSTRACT FROM AUTHOR]

Large areas of rainforest in Asia have been converted to plantations, with uncertain effects on soil biodiversity. Using standard metagenetic methods, we compared the soil biota of bacteria, fungi, and nematodes at three rainforest sites in Malaysia with two rubber plantation sites with similar soils and geology. We predicted the following: (1) that the rubber sites would have a lower α- and β-diversity than the rainforest sites, due to the monospecific canopy cover and intensive management with herbicides, pesticides, and fertilizers, and (2) that due to differences in the physical and biotic environment associated with cultivation, there would be distinct communities of bacteria, fungi, and nematodes. However, regarding (1), the results showed no consistent difference in α- and β-diversity of bacteria, fungi, or nematodes between rainforest and rubber plantation sites. It appears that conversion of rainforest to rubber plantations does not necessarily result in a decrease in diversity of soil biota. It may be that heterogeneity associated with the cultivation regimen compensates for loss of biotically imposed heterogeneity of the original rainforest. Regarding (2), as predicted there were statistically significant differences in community composition between rainforest and rubber plantation for bacteria, fungi, and nematodes. These differences could be related to a range of factors including light level, litter fall composition, pH, C and N, selecting a distinct set of soil taxa, and it is possible that this in itself would affect long-term soil function. [ABSTRACT FROM AUTHOR]

Agricultural activity associated with habitat conversion is a major driver of biodiversity loss across the tropics. The decline of species richness is a common outcome of conversion to agricultural land use, but the associated changes in functional and phylogenetic diversities, and spatial patterns of beta diversity, are not well understood. These patterns may shed light on underlying ecological processes that are of both basic and applied interest; for example the relative roles of stochastic assembly, ecological filtering, and competition in structuring ecological communities as well as broader consequences for ecological functioning in agroecosystems. Here we investigate the effects of conversion to rubber plantation ( Hevea brasiliensis), a rapidly spreading agroecosystem in Southeast Asia, on leaf-litter ant taxonomic, functional, and phylogenetic diversities at local and among-sites scales in Xishuangbanna, Southeast China. We found a sharp decline of ant species richness in rubber plantations compared with nearby forest habitat, with low beta diversity indicating spatial homogeneity of communities in rubber plantations. In addition, patterns of both functional alpha and beta diversities suggested the emergence of a functionally distinct ant community in the agroecosystem compared to the forest habitats. These results support a role of ecological filtering in structuring the taxonomic and functional composition of both rubber and forest habitats. In contrast, changes in phylogenetic diversity were modest and not significantly different from random expectations despite strong phylogenetic signal of functional traits. This study highlights the need for a pluralistic approach to characterizing the loss of biodiversity in agroecosystems, as well as understanding the underlying mechanisms of community assembly driving this biodiversity loss. [ABSTRACT FROM AUTHOR]

Unprecedented economic growth in Southeast Asia (SEA) has encouraged the expansion of rubber plantations. This land-use transformation is changing the risk of mosquito-borne diseases. Mature plantations provide ideal habitats for the mosquito vectors of malaria, dengue, and chikungunya. Migrant workers may introduce pathogens into plantation areas, most worryingly artemisinin-resistant malaria parasites. The close proximity of rubber plantations to natural forest also increases the threat from zoonoses, where new vector-borne pathogens spill over from wild animals into humans. There is therefore an urgent need to scale up vector control and access to health care for rubber workers. This requires an intersectoral approach with strong collaboration between the health sector, rubber industry, and local communities. [ABSTRACT FROM AUTHOR]

This research aimed to determine the best land and water management by arrangement of plant spacing, irrigation, and drainage of rubber plantation in order to improve rubber plantation productivity. This research was done using The WaNuLCAS (Water, Nutrient and Light Capture in Agroforestry System) model to determine the best land and water management under several scenario combinations of two factors. The first factor was rubber plant spacing arrangement system, which consisted of three levels, i.e. single row (3×7 m), single row (3×6 m) and double row (2×6×14 m). The second factor was water management treatment, which consisted of four levels, i.e. without irrigation and drainage, irrigation in dry season, drainage in wet season, and irrigation and drainage in dry and wet season respectively. The results showed that drainage treatment could enhance rubber plantation productivity. Moreover, rubber plantations which were using single row (3×7 m), single row (3 × 6 m) and double row (2×6×14 m) had no significant difference on latex production per hectare. [ABSTRACT FROM AUTHOR]

Tropical landscapes are not only rapidly transformed by ongoing land-use change, but are additionally confronted by increasing seasonal climate variation. There is an increasing demand for studies analyzing the effects and feedbacks on ecosystem functioning of large-scale conversions of tropical natural forest into intensively managed cash crop agriculture. We analyzed the seasonality of aboveground litterfall, fine root litter production, and aboveground woody biomass production (ANPP) in natural lowland forests, rubber agroforests under natural tree cover ('jungle rubber'), rubber and oil palm monocultures along a forest-to-agriculture transformation gradient in Sumatra. We hypothesized that the temporal fluctuation of litter production increases with increasing land-use intensity, while the associated nutrient fluxes and nutrient use efficiency (NUE) decrease. Indeed, the seasonal variation of aboveground litter production and ANPP increased from the natural forest to the plantations, while aboveground litterfall generally decreased. Nutrient return through aboveground litter was mostly highest in the natural forest; however, it was significantly lower only in rubber plantations. NUE of N, P and K was lowest in the oil palm plantations, with natural forest and the rubber systems showing comparably high values. Root litter production was generally lower than leaf litter production in all systems, while the root-to-leaf ratio of litter C flux increased along the land-use intensity gradient. Our results suggest that nutrient and C cycles are more directly affected by climate seasonality in species-poor agricultural systems than in species-rich forests, and therefore might be more susceptible to inter-annual climate fluctuation and climate change. [ABSTRACT FROM AUTHOR]

This article examines changing contexts and emerging processes related to “land grabbing.” In particular, it uses the case of Laos to analyze the driving forces behind land takings, how such drivers are implied in land policies, and how affected people respond depending on their socio-economic assets and political connections. We argue that understanding the multiple strategies farmers use to deal with actual land loss and the risk of losing land is crucial to understanding the hidden effects of land grabbing and its potential consequences for agricultural development and the overall process of agrarian transformation. From a policy perspective, understanding the hidden effects of land grabbing is critical to assess costs and benefits of land concessions, in Laos and elsewhere, especially in relation to current approaches to turn land into capital as a policy strategy to promote economic growth and reduce poverty. [ABSTRACT FROM AUTHOR]

Tropical acid soil used for rubber planting has usually low fertility due to continuous loss of plant nutrient elements by crop removal and leaching. Thus, proper soil improvement in tapping rubber is very essential. This study aimed to measure the growth and yield of 17-year-old rubber trees, chemical properties of soil, and plant nutrient status in the leaf and latex after two years of soil improvement. A randomized complete block of seven treatments: No fertilizer (Control treatment), Chemical fertilizer based on soil analysis according to the recommendation of the Rubber Research Institute (Ch.F), Ch.F+ Dolomite to raise pH up to 6.0 (D), 3 kg per plant of compost (C), Ch.F+C, ½ Ch.F+C and ½ Ch.F+C+D, with three replicates was designed. After two years of giving treatments, it was found that adding full rate of chemical fertilizer based on soil test together with compost or dolomite increased the tree girth increment from the first year to the second year. Rubber yield after soil improvements tended to increase from the beginning to the end of the year, especially with compost application. Increasing of soil fertility was found after soil improvement treatments. However, total N, available P and available K were still lower than optimum levels as well as leaf N and K. Nitrogen in rubber latex after soil improvement treatments was higher than those in the control treatment, which contrasted to those of Ca and Mg. However, fertilizer and dolomite effect on micronutrient elements in rubber leaf and latex were not clear. Thus, fertilizer should be continuously applied at least with the full rate of chemical fertilizer based on soil analysis, and organic fertilizer should be applied to gain some trace elements. Dolomite could also be applied in a very strong acid soil. [ABSTRACT FROM AUTHOR]

In the Southeast Asian uplands including Tripura, a North Eastern state of India, agricultural transition is underway from subsistence production of shifting cultivation to commercial plantation of rubber (Hevea brasiliensis). Though there are reports of positive impacts of this transition both on the socio-economic conditions of the concerned people and on the ecology of the concerned area, still it is questionable as there are certain adverse reports and assumption. In the light of studies in different Southeast Asian Countries including Tripura of India, the prospects and concerns of its impact have been reviewed in this paper in Tripura perspective. [ABSTRACT FROM AUTHOR]

Rubber ( Hevea brasiliensis ) plantations are one of the most important economic forest in tropical area. Retrieving leaf area index (LAI) and its dynamics by remote sensing is of great significance in ecological study and production management, such as yield prediction and post-hurricane damage evaluation. Thirteen HJ-1A/1B CCD images, which possess the spatial advantage of Landsat TM/ETM+ and 2-days temporal resolution of MODIS, were introduced to predict the spatial–temporal LAI of rubber plantation on Hainan Island by Nonlinear AutoRegressive networks with eXogenous inputs (NARX) model. Monthly measured LAIs at 30 stands by LAI-2000 between 2012 and 2013 were used to explore the LAI dynamics and their relationship with spectral bands and seven vegetation indices, and to develop and validate model. The NARX model, which was built base on input variables of day of year (DOY), four spectral bands and weight difference vegetation index (WDVI), possessed good accuracies during the model building for the data set of training ( N = 202, R 2 = 0.98, RMSE = 0.13), validation ( N = 43, R 2 = 0.93, RMSE = 0.24) and testing ( N = 43, R 2 = 0.87, RMSE = 0.31), respectively. The model performed well during field validation ( N = 24, R 2 = 0.88, RMSE = 0.24) and most of its mapping results showed better agreement ( R 2 = 0.54–0.58, RMSE = 0.47–0.71) with the field data than the results of corresponding stepwise regression models ( R 2 = 0.43–0.51, RMSE = 0.52–0.82). Besides, the LAI statistical values from the spatio-temporal LAI maps and their dynamics, which increased dramatically from late March (2.36 ± 0.59) to early May (3.22 ± 0.64) and then gradually slow down until reached the maximum value in early October (4.21 ± 0.87), were quite consistent with the statistical results of the field data. The study demonstrates the feasibility and reliability of retrieving spatio-temporal LAI of rubber plantations by an artificial neural network (ANN) approach, and provides some insight on the application of HJ-1A/1B CCD images, and data and methods for productivity study of rubber plantation in future. [ABSTRACT FROM AUTHOR]