Environment Of Southeast Asia Research Articles

Simulating rice and maize yield potential in the humid tropical environment of Indonesia

Little is known about the yield potential of modern rice and, particularly, maize cultivars in the tropical humid environment of Indonesia where farmers can grow 2–3 consecutive crops on the same piece of land per year. This study provides a first step to fill this knowledge gap by using two crop simulation models to estimate yield potential for rice and maize based on experiments conducted across multiple site-years and measured weather and soil data. Data collected from well-managed irrigated experiments, with observed yields ranging from 7.8 to 10 Mg ha−1 (rice) and 12 to 14.4 Mg ha−1 (maize), were used to calibrate phenology and growth coefficients for both a rice (OryzaV3) and maize crop model (Hybrid Maize). The calibration was performed for commercial, high-yielding irrigated rice and maize cultivars. Subsequently, calibrated models were evaluated on their ability to simulate yield potential using an independent database available from variety (irrigated rice) and fertilizer (irrigated and rainfed maize) trials conducted at multiple site-years across major rice and maize producing areas in Indonesia. Calibrated coefficients for rice were robust at reproducing observed leaf area, aboveground biomass, and biomass partitioning to different plant organs. In the case of maize, close agreement between simulated and observed yields suggests that the generic growth model coefficients originally derived for temperate maize performed well at simulating yield potential of modern tropical maize hybrids. The two models reproduced with acceptable performance the maximum observed yields across variety and fertilizer trials, except for rainfed maize grown in a region with very heavy clay soils. Across site-years, yield potential for irrigated rice and maize averaged 9.1 and 11.6 Mg ha−1, respectively, while rainfed maize averaged 11.5 Mg ha−1. Comparison between simulated yields and average national rice and maize yields (5.2 and 5 Mg ha−1, respectively) suggested that room exists to further increase average farmer yields in rice and maize-based crop systems. Our study also highlighted the high yield potential of modern maize hybrids grown in intensive crop sequences in the humid tropics (>10 Mg ha−1). The two models evaluated here can be used to benchmark productivity in rice and maize crop systems in the humid tropical environments of South East Asia and fine tune current management practices and inputs application.

Observations of particles at their formation sizes in Beijing, China

Abstract. New particle formation (NPF) has been observed in many highly polluted environments of South East Asia, including Beijing, where the extent of its contribution to intense haze events is still an open question. Estimated characteristics of NPF events, such as their starting times and formation and growth rates of particles, are more accurate when the detection range of particles extends to smaller sizes. In order to understand the very first steps of particle formation, we used a neutral cluster and air ion spectrometer (NAIS) to investigate particle characteristics at sizes exactly at which atmospheric nucleation and cluster activity occurs. Observations over a continuous 3-month period in Beijing showed 26 NPF events. These events generally coincided with periods with relatively clean air when the wind direction was from the less industrialised north. No NPF events were observed when the daily mean PM2. 5 concentration exceeded 43 µg m−3, which was the upper threshold for particle formation in Beijing. The fraction of particles that are charged in the size range 2–42 nm was normally about 15 %. However, this fraction increased to 20–30 % during haze events and decreased to below 10 % during NPF events. With the NAIS, we very precisely determined the starting times of NPF to a greater accuracy than has been possible in Beijing before and provided a temporal distribution of NPF events with a maximum at about 08:30 LT. Particle formation rates varied between 12 and 38 cm−3 s−1. Particle growth rates were estimated to be in the range of 0.5–9.0 nm h−1. These results are more reliable than previous studies in Beijing as the measurements were conducted for the first time at the exact sizes at which clusters form into particles and provide useful insight into the formation of haze events.

Urban tree growth and their dependency on infiltration rates in structural soil and structural cells

Expanding tree canopies can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation so engineered planting systems offer a potentially valuable tool for achieving sustainable urban forests. Tree water uptake, performance and root distribution were assessed in systems of structural soil and structural cell. Structural soil relies on stone and soil, it is highly porous and designed to support tree root growth and possess pavement strength. The structural cell is made up of rigid structural units with 90% void space which is to be filled with soil. To evaluate tree performance under the conditions of fill and drain regimes in structural soil and structural cell, these two systems were subjected to three simulated infiltration rates. This study was conducted in April 2015 to April 2016 in the tropical equatorial environment of South East Asia. Infiltration rate affected both biomass accumulation and rooting depth. Species and substrate effect was significant for biomass and rooting characteristics but less prominent for transpiration. Biomass was greater for trees in structural cells, and Pouteria obovata was particularly sensitive to prolonged inundation. Rooting depth was always higher in the rapid infiltration indicating the negative effects inundation had on this parameter. Root system in the structural cell was deeper while those in the structural soil were wider. Samanea saman had better adapted to the drain and fill regimes, and this was despite Pouteria obovata being a coastal species and was expected to be flood tolerant. Species and substrate effect was weak (R2 ranging from 0.20 to 0.28) but moderate drainage consistently led to higher transpiration. We conclude that structural soil and structural cell are potential solutions and provide a tool to overcome suboptimal urban growing conditions. The application of these solutions will allow for seamless integration of greenery with urban infrastructure.

Prevalence of azole-resistant Aspergillus fumigatus in the environment of Thailand.

Occurrence of azole-resistant Aspergillus fumigatus (ARAF) in the environment is an emerging problem worldwide, likely impacting on patient treatment. Several resistance mutations are thought to have initially arisen through triazole-based fungicide use in agriculture and subsequently being propagated in a similar manner. Here we investigated the prevalence of ARAF in the environment of Thailand and characterized their susceptibility profiles toward clinically used azole compounds along with underlying resistance mutations. Three hundred and eight soil samples were collected and analyzed, out of which 3.25% (n = 10) were positive for ARAF. All isolates obtained were resistant to itraconazole (MIC ≥ 8μg/ml), two showed additional increased MIC values toward posaconazole (MIC = 0.5μg/ml), and one other toward voriconazole (MIC = 2μg/ml). Sequencing of the respective cyp51A genes revealed that eight of the isolates carried the TR34/L98H allele and those two with elevated MIC values to posaconazole the G54R substitution. Although a clear correlation between the use of triazole-based fungicides and isolation of ARAF strains from agricultural lands could not be established for Thailand, but this study clearly demonstrates the spread of globally observed ARAF strains to the environment of South East Asia.

National legitimacy and overseas Chinese mobilization

This paper examines the Chinese Nationalists’ overseas Chinese policies during the early War of Resistance and the early Cold War. The strategies, organizations and problems of huaqiao mobilization during the Anti-Japanese War set patterns for Cold War anti-Communist efforts. In both struggles, the Nationalists emphasized that they represented China's legitimate government and that support from overseas Chinese was part of a crusade dating back to Sun Yat-sen, the father of the nation. As mothers of the revolution, huaqiao were to remain loyal to Sun's legacy by backing Chiang. Southeast Asia, home to the majority of overseas Chinese, became the focus of Nationalist attention and is the most appropriate arena to examine the vicissitudes of huaqiao policies. Obstacles to huaqiao mobilization did not simply result from Japanese, then Communist, machinations. The Nationalists encountered difficulties due to overseas Chinese apathy and disunity. Further, the complex political environment of Southeast Asia, before and after decolonization, stymied mobilization. Nevertheless, after each military defeat, whether at the hands of the Japanese or the Communists, huaqiao support became more important, not for the material benefits they offered, but for the legitimacy they conferred.

Air-sea interactions of semi-volatile organic compounds in the tropical environment of Southeast Asia

Major urban and industrial centers increase loadings of semi-volatile organic compounds (SVOCs) to proximate sea waters through riverine transport, atmospheric deposition via dry particle deposition, wet deposition, and air-sea gas exchange. In addition to acting as sinks for SVOCs, oceans can act as sources of SVOCs to coastal atmospheres and play important roles in the global biogeochemistry of SVOCs. Particle-sorbed SVOCs can settle to the ocean surface by dry particle deposition, a uni-directional advective transport process from the atmosphere to the water, the removal rate by which is a function of the physical and chemical properties of the aerosols and bound pollutants, meteorological conditions and surface characteristics. In addition, SVOCs are removed from the atmosphere and transported to the waters by precipitation scavenging of atmospheric vapors and particles, which are incorporated into the rain within or below the clouds. After SVOCs are deposited into the bulk seawater, water-column partitioning can affect the distribution of pollutants between the dissolved aqueous and the solid phases and eventually impact the fate of these compounds in oceans. Other than the abovementioned processes, air-sea exchange can make SVOCs diffuse across the air-sea interface; however, the sea surface microlayer (SML), a unique compartment at the air-sea boundary defined operationally as the upper millimeter (1 ∼ 1000 μm) of the sea surface, has large storage capacity to delay the transport of SVOCs across the interface.This article reports the dry particle deposition and wet deposition of selected SVOCs based on an extensive set of yearly data collected in Singapore. Singapore, a representative country of Southeast Asia (SEA), is a small but highly developed island with dense industrial parks in the Southwestern part, where the terrestrial sources affect the surrounding coasts. In this study, Singapore’s Southern coastline was chosen during the Northeast monsoon season to evaluate if this coastal area acts a sink or source for selected SVOCs via air-sea diffusive exchange as well as to investigate the SML enrichment effect.

Japan's Role in Southeast Asian Security: "Plus ca Change ..."

HE SOUTHEAST ASIAN SECURITY environment is in a transitional period. 1 Recent regional and global developments notably east-west detente, the improvement of Sino-Soviet relations, and Vietnam's withdrawal from Cambodia, incomplete though it may be have reduced tension in the Southeast Asian regional order. Despite the current easing of tensions, there is no guarantee that the future of Southeast Asia will be either more stable or more peaceful. Moreover, while the economic importance of security has increasingly gained in significance, it is premature to think that military factors are no longer present in international relations in Southeast Asia or elsewhere. The war in Cambodia is not yet over and elsewhere the contest for position, power and influence continues, although not always in an openly antagonistic manner. Japan has vital interests in the stability and security of Southeast Asia. Southeast Asia is a major source of essential raw materials forJapan, a sizable market forJapanese manufactured goods, and the site of substantial Japanese investment. In addition, the waterways of Southeast Asia are increasingly vital forJapan's international transport system. About 60 percent ofJapan's oil imports and 40 percent of its foreign trade are transported via the Straits of Malacca, and the Lombok Straits. Not surprisinglyJapanese leaders take considerable interest, from both an economic and geopolitical point of view, in maintaining stability and security in Southeast Asia. Since World War II, Japan has played a predominantly economic role in this region, avoiding political and military entanglements. Japan's present and future role is less clear: what kind of role isJapan likely to play in the shifting security environment of Southeast Asia in order to meet its economic needs and goals? With the recent waning Soviet posture and with the U.S. seeking to reduce its presence in this region,

Construction Planning in South East Asia

Successful construction operations in Southeast Asia require comprehensive, flexible plans based upon the best possible information. A section or purpose and scope describes the general operating environment of Southeast Asia to include geography, business system and weather. Another section describes preplanning considerations to include sources of local expertise, the metric system, and various communication systems. A section on manpower describes the various aspects of both the local and foreign labor markets. Project supervision is also reviewed. Other sections review some aspects of equipment selection, power supplies, and equipment maintenance, and the proper selection, storage and uses of materials. The last section describes the various construction methods and management tools peculiar to construction in Southeast Asia.