Heat-tolerant maize for rainfed hot,dry environments in the lowland tropics:From breeding to improved seed delivery

Climate change-induced heat stress combines two challenges:high day-and nighttime temperatures,and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit.It is one of the major factors in low productivity of maize in rainfed stress-prone environments in South Asia,affecting a large population of smallholder farmers who depend on maize for their sustenance and livelihoods.The International Maize and Wheat Improvement Center(CIMMYT)maize program in Asia,in partnership with public-sector maize research institutes and private-sector seed companies in South Asian countries,is implementing an intensive initiative for developing and deploying heat-tolerant maize that combines high yield potential with resilience to heat and drought stresses.With the integration of novel breeding tools and methods,including genomics-assisted breeding,doubled haploidy,fieldbased precision phenotyping,and trait-based selection,new maize germplasm with increased tolerance to heat stress is being developed for the South Asian tropics.Over a decade of concerted effort has resulted in the successful development and release of 20 high-yielding heat-tolerant maize hybrids in CIMMYT genetic backgrounds.Via public–private partnerships,eight hybrids are presently being deployed on over 50,000 ha in South Asian countries,including Bangladesh,Bhutan,India,Nepal,and Pakistan.

Transformation and Option:A Spatial Study of Nilo Cruz’s Anna in the Tropics

Nilo Cruz is a Cuban-American playwright,whose Pulitzer-winning Anna in the Tropics has earned his national fame.Based on spatial theory proposed by Lefebvre and other scholars,this paper explores spatial transformations and characters’options from three aspects:social space,psychological space,and theatrical space.Social space is both a physical social product and a projection of social relations.Cruz focuses on spatial practice in the cigar factory and reflects the transformation of American society and production methods,which leads to the conflict between tradition and modernity.Psychological space shows the spatial subject’s psychological state in social relationships.Cruz portrays cultural displacement of Cuban immigrants and indicates their quest for identity and spatial belonging through memories and spatial transcending.Theatrical space presents a symbolic stage place.Cruz uses theatrical techniques such as juxtaposition along with sound and lighting.He goes beyond the context to make options predestined and attempts to reconstruct the spiritual order in the tragic ending,thus implying a possible eternity of memories.The interweaving of multi-dimensional transformations and options reveals Cruz’s reflection on social reality and his humanistic concern,extends beyond the stage via Tolstoy’s classic and provides a new perspective on the interpretation of this play.

Analysis of Differences in Productivity,Profitability and Soil Fertility Between Organic and Conventional Cropping Systems in the Tropics and Sub-tropics

Organic farming aims to stimulate soil fertility by avoiding the use of synthetic fertiliser inputs, relying instead on locally available natural resources. It is regarded by many as a sustainable alternative to conventional fanning because it ensures higher biodiversity, restricts environmental pollution, prevents land degradation and is easy to apply for smallholder and subsistence farmers. Although widely practiced and studied in temperate regions, little is known about the potential overall benefits of organic farming in the tropics and subtropics. This paper addresses this gap by undertaking an analysis of the differences between organic and conventional agriculture in the tropics and sub-tropics based on an extensive literature review including 88 papers with 458 data pairs. The comparison is based on three main indicators： yield, gross margin and soil organic carbon （SOC）. The differences between the organic and conventional systems for each of these main indicators is represented by the ratio of the value of the indicator in the organic system divided by the corresponding value in the conventional system. This was initially calculated for each data pair individually, and grouped by a variety of explanatory factors, such as precipitation, human development level, soil texture, crop type, organic input type, time after conversion and certification. The results demonstrate that under organic management, yields were on average 26% higher, gross margins 51% higher and soil organic carbon 53% higher than under conventional management. The highest yield increases in organic cropping systems were achieved in the least developed countries, in arid regions and on coarse soils. For gross margins, certification was the main reason for differences between organic and conventional systems. Certified farmers, mostly located in developed countries, receive significantly higher prices. Furthermore, organic farming in the driest regions results in higher profits than in other regions. Even though soil organic carbon was significantly higher overall under organic management, the results do not show significant differences when grouped by the explanatory factors. They do however suggest that the highest carbon sequestration potential occurs in systems that had a high level of inputs, in regions with 1000-1 500 mm of rainfall and on clayey soils.

Anomalies in the Tropics Associated with the Heavy Rainfall in East Asia during the Summer of 1998

The summer of 1998 was characterised by a severe flood in East Asia. The possible linkages were examined among the anomalies in the tropics that may be associated with the severe flood. The anomalies of 1998 are obtained by removing the climatology, which is the average of the ECMWF (European Centre for Medium Range Weather Forecasts) Re—Analysis (ERA) data over 15 years from 1979 to 1993, from the corresponding fields of 1998, which are obtained from the ECMWF operational analyses. In comparison to the results of Nitta (1990), it was found that there are considerable similarities in the atmospheric circulation anomalies between the summers of 1998 and 1988, in the tropics as well as in middle—high latitudes. It was shown that the atmospheric convection is slightly suppressed over the tropical western Pacific. In general, the suppressed convection corresponds to a negative anomaly of SST in the warm pool region. In the summers of 1998 and 1988, however, there are positive anomalies of SSTs in the tropical western Pacific, corresponding to the suppressed convection over there. This slightly suppressed convection may not provide a viable forcing mechanism for the severe flood in East Asia. It was postulated that the zonal wind anomalies in the tropics, in addition to the atmospheric convection over the tropical western Pacific, influence the position and intensity of the North Pacific subtropical high. In both summers of 1998 and 1988, while the stronger convection occurs over the warmer tropical Indian Ocean, the suppressed convection corresponds to the positive anomalies of SSTs in the tropical western Pacific. A possible explanation was given for the broken relationship between SSTs and OLR, (Outgoing Longwave Radiation) by analyzing the large—scale atmospheric circulation anomalies in the tropics. The heat fluxes at the surface in the warm pool of the tropical western Pacific and tropical Indian Ocean were also examined by using the ERA–15 data. To avoid the inconsistency between the ERA–15 and the operational analyses, the anomalies of the heat fluxes at the surface in the warm pool region in the summer of 1988, instead of the summer of 1998, were examined. The anomalous latent heat flux and the net solar radiation flux are the main reason for the positive anomalies of SSTs in the tropical Indian Ocean and in the tropical western Pacific, respectively. The suppressed convection over the tropical western Pacific allows more solar radiation fluxes downward at the surface, which would increase the SSTs. Key words Anomalies in the tropics - Comparison between 1998 and 1988 - Surface heat flux This study was supported by the National Natural Science Foundation of China (No. 49605065) and “National Key Programme for Developing Basic Sciences” G1998040900 part 1.Part of this study was carried out during the visit of the author to the Department of Meteorology, University of Reading, which was supported by the Royal Society. The author would like to thank Drs. Buwen Dong and Paul Berrisford in the Department, and Dr. Xu Li, who was seconded to ECMWF from Institute of Atmospheric Physics, Chinese Academy of Sciences, for their help. All the figures in this paper were drawn by using the Visualization and Computation System (VCS) designed by PCMDI (Program for Climate Model Diagnosis and Intercomparison).

CISK-rossby wave and the 30-60 Day Oscillation in the Tropics

The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it appear to resemble the observed 30-60 day oscillation mode in many aspects, such,as vertical structures, zonal and meridional propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric 30-60 oscillation. It is considered that CISK-Rossby mode should not be neglected.

The Structure of Low Frequency Phenomena in the Tropics and Its Interaction with the Extratropics

The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics, it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean, when the Southern Oscillation Index is negative, almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile, the second logitudinal mode almost disappears. On the other hand, the meridional wind field possesses maximum amplitude at higher wave numbers. However, near the equator,the amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving mechanisms.Correlation analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact, stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this 'remote' correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a 'corridor' of communication between the low and high latitudes. The regionality of the correlations confirms, to some extent, recent theoretical development regarding trapped equatorial modes. Finally, time lagged correlations from plus and minus six months between variations of U and OLR indicate that the interactions between the extratropics and low latitudes possess an organized sequence. The extratropical influence appears to propagate into the tropics followed by an eastward propagation along the equator. Finally, a propagation from the tropics to the extratropics in the upper troposphere occurs in the eastern Pacific Ocean. The time-lagged correlation sequence does not appear to be symmetric about the equator.

Risk factors for peripheral arterial disease in the tropics and its comparison with the western population

Objective:To identify and compare the existence of similar and other risk factors in the perspective of an Indian population.Methods:It was designed as a case control study and was conducted in the Department of General and Vascular Surgery Unit 2 of Christian Medical College,Vellore,India between the periods July 2003 to June 2005.100 patients with an ABPI【 0.9 and 100 controls were studied.Results:Peripheral arterial disease(PAD) was found to be commoner among males(87%).While atherosclerosis was the commonest aetiology(54%),the incidence of Thromboangiitis Obliterans was also not uncommon(38%).Smoking was the main risk factor in the Indian context(83%) as compared to hypercholesterolemia(60%) in the West. The patients with atherosclerotic PAD were middle-aged and had concomitant diabetes(50%) and hypertension(30%).Conclusions:Peripheral arterial disease occurs in a relatively younger age group in India as compared to their Western counterparts.Thromboangiitis Obliterans was found to be a significant aetiology for arterial occlusive disease,with smoking as the primary risk factor followed by diabetes,hypertension and hypercholesterolemia.

The relative stability of prehistorical geographic environment in China's tropics on the basis of archaeology

According to archaeological data from about sixty samples the relative stability of physical and human geographical environment in the tropical zone of China is discussed in this paper. Because of the superior natural environment, sufficient food resources and a sparse population resulting in the absence of social requirement to transform the productive forces, the advancement of economy and society was stagnated during prehistorical period in China's tropics. Compared with northern China, the appearance of ground stone tool stagnated about 3,000 years, the beginning of Bronze Age, about 1,000 years, and the agriculture, 2,500-3,000 years. The no ceramics age continued till the early Neolithic Age and the appearance of colour or white ceramics was 2,000 years later than that in northern China. The life form of migration to gather and to hunt continued till the middle Neolithic Age, and the fixed settlement based on agriculture 1,000-2,000 years stagnated. The clan commune just appeared at the end of the Neolithic Age which was 2,000-3,000 years later than that in northern China.

Multivariate Objective Analysis of Wind and Height Fields in the Tropics

The commollly used objective analysis scheme(Scheme-A) for the analysis Of wind and geopotential height smoothen the divergent component of the wind which is rather important in the tropics,specifically over convective regions.To overcome this deficiellcy, a new analysis SCheme in which divergent component is included in the statistical model of the wind forecast errors,has been proposed by Daley(1985).Following this scheme,a new set of correlahon functions of forecast errors for the indian region during monsoon season which are suitable for analysing the tropical wind are obtained.This analysis scheme(Scheme--B) as well as Scheme-A were used to make analyses for the period from 4 July to & July 1979(12 GMT) at 850,700 and 200 hpa levels over an area bounded by l.875'N to 39.375'N and 41.250'E to 108.750'E and subsequently divergent component,velocity potential are computed for both schemes.Results from both these schemes show that in the monsoon depression region the velocity potential and divergence have increased in the later case(Scheme-B).This suggests that the divergent component has been enhanced in Scheme-B and that the objechve of this study is realized to some extent.

Geomorphological effects of plate movement during Quaternary in China' s tropics

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China's tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 110 o E.

Quantitative Review of Ecosystem Services and Disservices Studies in the Tropics

The tropics host about 80% of the planet’s terrestrial species and over 95% of its corals. A well-known tropical forest ecosystem to provide significant global regulating services has declined at a rate of 5.5 M ha per year from 1990-2015, while another region noted an increase per year. There is evidence that tropical region ecosystem services and disservices are the least studied in the world. This study quantified peer-review papers in the tropics, then explored the neglected ecosystem type, service category, assessment mode, applied techniques and choice dependence between ecosystem type, service category, assessment mode and applied techniques. The Google Scholar and Web of Science database were used to collect all ES & ED studies available online from 1960 to December 2017. This review covered 102 countries with 578 articles. The study showed dramatic articles increase in the last three years as more than 50% of articles were published after the year of 2014. The top countries in high articles were Mexico (n = 53), India (n = 43), and Brazil (n = 35). The ES & ED assessment tools/techniques are barely applied in tropics as only social based techniques such as interviews and questionnaire take over 45%, while biophysical tools like remote sensing and GIS appeared only in 20%, InVEST only in 3% while the rest tools are less than 1% even none such as ARIES model. Urban and marine ecosystem types, disservices category and trade-off assessment mode were the least studied. The review concluded that policy analysis ES & ED studies do not reflect the trade-offs and synergy analysis between different services which hinder the development of pragmatic policy and decisions toward ES sustainable management in the tropics. The rampant urbanization in the tropics is subjected to destroy existing ES. Thus, this review highly suggested a high concern of urbanization ecosystem. This study also calls for great academic research to give attention to the tropical rainforest region as most African countries to host such forest have not even a single article on ES & ED.

Pacific Tropics Are Warmer than Atlantic

Pacific tropics are warmer than Atlantic tropics. This can be seen immediately from a world’s sea surface temperature atlas, but readings from it of the latitudinal bandwidths between 80 F isotherms in the open waters of both oceans make this result very clear. Explanations are offered by introducing what has already been proposed for the large-scale surface circulations of the Pacific and incorporating conjectures for the circulation of the upper layer of the South Atlantic.

Overcoming seasonality in the tropics by growing tomato (<i>Lycopersicon esculentum Mill.</i>) varieties under cooled conditions

The main objective of this work was to overcome seasonality in tomato production under hot tropical summer conditions, as well as to evaluate the adaptability and productivity of cherry and normal size indeterminate tomato varieties. The tested varieties were the standard varieties, Chanoa, Merel, Sensie and Yusra and the cherry varieties, Tomi and Elitrro. The cherry variety Elitrro recorded the highest plant height followed by the normal Merel. The cherry varieties over-numbered the classic varieties for mean number of fruits per cluster and mean number of fruits per meter square. There was no significant difference between the best yielders, the classic varieties Chanoa (25.63 kg/m2) and Yusra (24.13 kg/m2) and the cherry variety Elitrro (24.00 kg/m2). Yusra recorded the highest fruit diameter (60-70 mm). The classic type tomatoes are well known and of high demand in Sudan that give Chanoa and Yusra better adoption chances. Our results clearly indicated that production of summer tomato under cooled plastic house conditions is a new technique that has the potential to overcome the seasonality of tomato production under Sudan and similar tropical condition.

Plant Traits for Phytoremediation in the Tropics

Water is a limited and valuable resource.Singapore has four national sources of water supply,one of which is natural precipitation.Pollutants collected in stormwater runoff are deposited into drainage systems and reservoirs.Major nutrient pollutants found in local stormwater runoff include nitrate and phosphate,which may cause eutrophication.Bioretention systems are efficient in removing these pollutants in the presence of plants.This paper discusses plant traits that can enhance the phytoremediation of nutrient pollutants in stormwater runoff for application in bioretention systems.The plant species studied showed variations in chlorophyll florescence,leaf greenness,biomass production,and nitrate and phosphate removal.In general,dry biomass was moderately correlated to nitrate and phosphate removal(r=0.339–0.501).Root,leaf,and total dry biomass of the native tree species showed a moderate to strong correlation with nitrate removal(r=0.811,0.657,and 0.727,respectively).Leaf dry biomass of fastgrowing plants also showed a moderate to strong relationship with the removal of both pollutants(r=0.707 and 0.609,respectively).Root dry biomass of slow-growing plants showed a strong relationship with phosphate removal(r=0.707),but the correlation was weaker for nitrate removal(r=0.557).These results are valuable for choosing plants for application in bioretention systems.

Growth response of three plantation species of the tropics exposed to elevated CO_2 levels

The response of forest trees, the largest carbon sinks on the earth, to continuing rise in atmospheric carbon levels is unknown. Re- ports state that increasing levels of atmospheric CO2 will stimulate pho- tosynthesis and productivity in most ecosystems. However, the duration and magnitude of this stimulation, particularly in the tropics, remains a question. To investigate the effects of CO2 fertilization on plant growth, seedlings of three common plantation species, Casuarina equisetifolia, Ailanthus excelsa and Tectona grandis were grown in closed chambers enriched with CO2. After 180 days of treatment, morphological traits of seedling height, biomass of root and shoot and root-shoot allometric co-efficient were measured. The activity of carbonic anhydrase and con- tents of chlorophylls, total carbohydrates and soluble proteins were de- termined. In Tectona grandis, significant effects of CO2 supply were found on chlorophylls, root-shoot allometric ratio and seedling quality index. Ailanthus excelsa showed significant effect on only the shoot characteristics on exposure to elevated CO2 but the root characteristics and concentrations of chlorophylls were not significantly different. Ca- suarina equisetifolia also showed significant effects on exposure to ele- vated CO2 in terms of shoot characteristics and concentrations of chlo- rophylls. Total sugars, the major photosynthates, did not show any sig- nificant variation to elevated CO2 in any of the three species. Carbonic anhydrase, the key enzyme responsible for transfer of CO2 into the tis- sues significantly increased in all three species. Overall, all the variables responded to elevated CO2, reflecting the positive effects of one parame- ter of climate change conditions on seedling quality. A positive response of these three plantation species to elevated CO2 content is a good indi- cation for their future existence in potentially changed climatic eonditions.

Climatological characteristics of the tropics in China:climate classification schemes between German scientists and Huang Bingwei

Reviewing some important German scientists who have developed climatic regionalization schemes either on a global or Chinese scale, their various definitions of the tropical climate characteristics in China are discussed and compared with Huang Bingwei's climate classification scheme and the identification of the tropical climate therein. It can be seen that, due to different methodological approaches of the climatic regionalization schemes, the definitions of the tropics vary and hence also their spatial distribution in China. However, it is found that the tropical climate type occupies only a peripheral part of southern China, though it firmly represents a distinctive type of climate that is subsequently associated with a great economic importance for China. As such, the tropical climate type was mostly identified with its agro-climatological significance, that is by giving favourable growing conditions all-year round for perennial crops with a great heat demand. Tropical climate is, hence, conventionally regarded to be governed by all-year round summer conditions 'where winter never comes'.

NONLINEAR CHARACTERISTICS OF THE ATMOSPHERIC PLANETARY BOUNDARY LAYER IN THE TROPICS

The nonlinear governing equations and its solutions for the tropical atmospheric planetary boundary layer are derived by means of scale analysis and vertical coordinate transformation. It is shown that the nonlinear momentum advection may alter the critical latitude. The restrictive requirement for the solutions to have continuity both in the free atmosphere and in the planetary boundary layer is derived. The context provides theoretical basis for numerical calculation of the wind field within the tropic atmospheric planetary boundary layer.

Common Medical Problems in the Tropics

Common Medical Problems in the Tropics has been expanded to provide a comprehensive reference book on adult internal medicine for use in tropical developing countries.It is intended for use by senior paramedical workers,such as clinical officers,health officers,medical assistants,health extension officers, senior nurses and others.It will be particularly useful for students and those newly qualified;and for those who have other specialisms or who do not usually deal with medical problems in tropical developing countries.

Carbon stocks in a highly fragmented landscape with seasonally dry tropical forest in the Neotropics

Background:Global modeling of carbon storage and sequestration often mischaracterizes unique ecosystems such as the seasonally dry tropical forest of the central region of the Gulf of Mexico,because species diversity is usually underestimated,as is their carbon content.In this study,aboveground and soil carbon stocks were estimated to determine the climate mitigation potential of this highly degraded landscape(<25%of forest cover).Results:Tree species in the study area had carbon content values that were 30%–40%higher than the standard value proposed by the IPCC(i.e.,50%).Tropical oak forest in the region,despite its restricted distribution and low species richness,accounted for the highest mean carbon stocks per unit area.The main factors driving spatial variability in carbon stocks were:maximum precipitation,soil organic matter,clay and silt content.No strong relationship was found between aboveground carbon stocks and soil organic carbon in the study area.Quanti-fication of carbon stocks is an important consideration in the assessment of the conservation value of remnants of native vegetation in human-modified landscapes.Conclusions:This study demonstrates the importance of the highly fragmented tropical dry regions of the Neo-tropics in maintaining landscape functionality and providing key ecosystem services such as carbon sequestration.Our results also highlight how crucial field-based studies are for strengthening the accuracy of global models.Furthermore,this approach reveals the real contribution of ecosystems that are not commonly taken into account in the mitigation of climate change effects.

Photodegradation for Nutrient Management in the Dry Tropics

Nutrient limitation in agriculture is a big problem in many tropical areas. Much research has focused on the optimal use of crop residues in agriculture. Recent work indicates that plant residue decomposition rates, including nutrient release rates can be increased by pre-exposure to sunlight. This has potential as a technology to manipulate nutrient release from residues to match crop demands. The possible development and use of this technology is discussed. There is some evidence that this could increase emissions of trace gases, but the increase is thought to be small. Research needs are discussed.