Globose cacti (Mammillaria) living on cliffs avoid high temperatures in a hot dryland of Southern Mexico     

《Journal of Arid Environments》2007,68(4):541-552

Succulent plants are prone to overheating due to their massive organs and lack of daytime transpiration. Thus, they frequently grow in cool microenvironments. Due to their verticality, cliffs avoid sunlight at noon, providing a cool refuge during the hottest hours of the day. We test the hypothesis that species in the genus Mammillaria (Cactaceae) are associated with cliffs in hot areas. We compared the temperatures and light interception of Mammillaria crucigera experimentally placed on a cliff and on the plateau above it. Through comparative analysis of 10 species we tested if those living in warmer areas inhabit steeper slopes. We found that plants and soil on the cliff were 9.9 and 14.4 °C cooler than their counterparts in the plateau at noon. While the temperatures on the plateau were within the range that has been found to inhibit photosynthetic activity, those on the cliff were closer to the optimal ones for CO₂ fixation in other cacti. Living on the cliff may be costly because radiation is reduced by 38.2%. A comparative analysis revealed an evolutionary trend toward living on steeper slopes when the climate is hot. This may contribute to explain why cliff-dwellers have evolved in so many succulent-plant families.  相似文献   

Balancing deformation in NW Borneo: Quantifying plate-scale vs. gravitational tectonics in a delta and deepwater fold-thrust belt system     

Rosalind C. King  Guillaume Backé  Christopher K. Morley  Richard R. Hillis  Mark R.P. Tingay 《Marine and Petroleum Geology》2010

Recent GPS measurements demonstrate that NW Borneo undergoes 4–6 mm of plate-scale shortening a year, which is not accommodated by plate-scale structures. The only geological structure in NW Borneo described to accommodate on-going shortening is the Baram Delta System located on the outer shelf to basin floor. Delta toe fold-thrust belts are commonly thought to be caused by margin-normal compressional stresses generated by margin-parallel upslope gravitational extension.  相似文献   

Forest cover change assessment in conflict-affected areas of northwest Pakistan: the case of swat and shangla districts   总被引：2，自引：2，他引：0  

Faisal Mueen QAMER  Sawaid ABBAS  Rashid SALEEM  Khurram SHEHZAD  Hassan ALI  Hammad GILANI 《山地科学学报》2012,9(3):297-306

This study examines the spatial and temporal forest cover changes in Swat and Shangla districts to understand the deforestation pattern in context of the recent security conflict in these districts. We used multi-resolution satellite images to assess the long term deforestation from 2001 to 2009 and also to identify episodic forest cutting areas appeared during the conflict period of Oct. 2007 - Oct. 2008. There are only 58 ha of deforestation identified during the conflict period while 1268 ha of gross annual deforestation were assessed during last eight years. Most of the deforestation patches persist around the administrative boundaries at sub-district levels (tehsils) which can be attributed to ambiguity in unclear jurisdiction between the forest official. The results highlight that the forest cutting appeared in Swat and Shangla during the conflict period is not as significant when compared with the long term deforestation pattern in the area. On the one side the results of the study are supportive to the picture that emerges from international studies which report high rate of deforestation in the country and on the other side it negates any relation between the security situation and the increasing deforestation in the north western Pakistan. The study concludes that deforestation assessments require verification by independent sources of data, such as satellite imagery to improve our understanding of deforestation processes.  相似文献   

Sources of sedimentary PAHs in tropical Asian waters: Differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance   总被引：2，自引：0，他引：2  

Mahua Saha  Kaoruko Mizukawa  Hideshige Takada  Mohamad P. Zakaria  Bui Cach Tuyen  Ruchaya Boonyatumanond  Badal Bhattacharya  Touch Seang Tana 《Marine pollution bulletin》2009,58(2):189-200

We collected surface sediment samples from 174 locations in India, Indonesia, Malaysia, Thailand, Vietnam, Cambodia, Laos, and the Philippines and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. PAHs were widely distributed in the sediments, with comparatively higher concentrations in urban areas (∑PAHs: ∼1000 to ∼100 000 ng/g-dry) than in rural areas (∼10 to ∼100 g-dry), indicating large sources of PAHs in urban areas. To distinguish petrogenic and pyrogenic sources of PAHs, we calculated the ratios of alkyl PAHs to parent PAHs: methylphenanthrenes to phenanthrene (MP/P), methylpyrenes + methylfluoranthenes to pyrene + fluoranthene (MPy/Py), and methylchrysenes + methylbenz[a]anthracenes to chrysene + benz[a]anthracene (MC/C). Analysis of source materials (crude oil, automobile exhaust, and coal and wood combustion products) gave thresholds of MP/P = 0.4, MPy/Py = 0.5, and MC/C = 1.0 for exclusive combustion origin. All the combustion product samples had the ratios of alkyl PAHs to parent PAHs below these threshold values. Contributions of petrogenic and pyrogenic sources to the sedimentary PAHs were uneven among the homologs: the phenanthrene series had a greater petrogenic contribution, whereas the chrysene series had a greater pyrogenic contribution. All the Indian sediments showed a strong pyrogenic signature with MP/P ≈ 0.5, MPy/Py ≈ 0.1, and MC/C ≈ 0.2, together with depletion of hopanes indicating intensive inputs of combustion products of coal and/or wood, probably due to the heavy dependence on these fuels as sources of energy. In contrast, sedimentary PAHs from all other tropical Asian cities were abundant in alkylated PAHs with MP/P ≈ 1-4, MPy/Py ≈ 0.3-1, and MC/C ≈ 0.2-1.0, suggesting a ubiquitous input of petrogenic PAHs. Petrogenic contributions to PAH homologs varied among the countries: largest in Malaysia whereas inferior in Laos. The higher abundance of alkylated PAHs together with constant hopane profiles suggests widespread inputs of automobile-derived petrogenic PAHs to Asian waters.  相似文献   

Observed and simulated sea breeze characteristics over Rayong coastal area, Thailand   总被引：1，自引：0，他引：1  

Tung Thanh Phan  Kasemsan Manomaiphiboon 《Meteorology and Atmospheric Physics》2012,116(3-4):95-111

This work presents the detailed characterization of sea breeze (SB) over the Rayong coastal area, one of the most rapidly developed and highly industrialized areas during the last decade in Thailand, using observation data analysis and fine-resolution (2?km) mesoscale meteorological modeling with incorporation of new land cover and satellite-derived vegetation fraction data sets. The key characteristics considered include frequency of SB occurrence, sea-breeze day (SBD) identification, degree of inland penetration, and boundary layer development. It was found that SBs occur frequently in the winter due mainly to relatively large land–sea temperature contrasts and minimally in the wet season. Monthly mean SB onset and cessation times are at around 12–15 local time (LT) and 18–21 LT, respectively, and its strength peaks during the early- to mid-afternoon. Monthly SB hodographs generally exhibit clockwise rotations, and SB inland penetration (at PCD-T tower) ranges widely with the monthly means of 25–55?km from the coast. Mesoscale MM5 modeling was performed on two selected SBDs (13 January and 16 March 2006), on which the SBs are under weak and onshore strong influences from background winds, respectively. Simulated near-surface winds and temperature were found to be in fair-to-acceptable agreement with the observations. The SB circulation along the Rayong coast is clearly defined with a return flow aloft and a front on 13 January, while it is enhanced by the onshore background winds on 16 March. Another SB along the Chonburi coast also develops separately, but their fronts merge into one in the mid-afternoon, resulting in large area coverage by the SB. Simulated planetary boundary layer height over the land area is significantly affected by a thermal internal boundary layer (TIBL) induced by an SB, which is found to be low near the coast and increases toward the front (up to 800–1,000?m along the Rayong coast).  相似文献   

After the 1997 financial crisis in Bangkok: The behaviour and implications of a new cohort of street vendors     

John Walsh  Chuthatip Maneepong 《Singapore journal of tropical geography》2012,33(2):255-269

After the 1997 financial crisis, many retrenched workers preferred not to return to provincial homes but remained in Bangkok to establish informal retail businesses in branded and other consumer products. In contrast to traditional street vendors, who specialized in food items primarily catering for low‐income customers, and focused on high volume, these ‘new generation’ street vendors also adopted more formal business practices. Given their greater sophistication and better education, we hypothesized that they would be more organized advocates of vendors' rights and thus more prone to conflicts with municipal authorities. Based on interviews, however, we found that new generation vendors are adaptive to location and business strategy, and prefer a low profile in dealing with officialdom. By contrast, traditional vendors remained more tied to particular spaces, are more likely to stand up for their rights to use public space and, because they expect more from government, are more prone to conflicts with municipal authorities. Our findings relate to ongoing discussion on the rights and needs of street vendors to access urban public space and the responsibilities of authorities to meet and provide for these informal sector livelihoods that make up a significant share of the national economy in Thailand, as elsewhere in the global South.  相似文献   

Responses to the 2011 floods in Central Thailand: Perpetuating the vulnerability of small and medium enterprises?     

Marks  Danny  Thomalla  Frank 《Natural Hazards》2017,87(2):1147-1165

Natural Hazards - The 2011 flood was the worst in Thailand in decades. Many of the impacts occurred in the Bangkok Metropolitan Region. The floods negatively affected small and medium enterprises...  相似文献   

Nutrients,light and phytoplankton production in the shallow,tropical coastal waters of Bandon Bay,Southern Thailand          下载免费PDF全文

Takashi Yoshikawa  Kosuke Tomizawa  Yuki Okamoto  Kazuya Watanabe  Jintana Salaenoi  Kenichi Hayashizaki  Hisashi Kurokura  Satoshi Ishikawa 《Marine Ecology》2017,38(6)

Phytoplankton primary production and its regulation by light and nutrient availability were investigated in the shallow, tropical coastal waters of Bandon Bay, Southern Thailand. The bay was meso‐eutrophicated and highly turbid, receiving river water discharge. Water column stratification was consistently weak during both rainy and dry seasons. Dissolved inorganic nitrogen (DIN) was higher off the river mouth than in the other regions, suggesting that river water discharge was a main source of DIN. By contrast, dissolved inorganic phosphorus (DIP) showed a significant negative correlation with total water depth, implying that regeneration around the sea floor was an important source of DIP. Surface DIN and DIP showed positive correlations with surface primary production (PP) and water column primary productivity (ΣPP*), respectively. The combined correlation and model analyses indicate that total water depth had an ambivalent influence on water column primary production (ΣPP); shallower water depth induced more active regeneration of nutrients, but it also caused higher turbidity and lower light availability as a result of enhanced resuspension of sediments. Furthermore, there was a vertical constraint for phytoplankton during the rainy season: total water depth tended to be shallower than euphotic zone depth. In conclusion, light limitation and vertical constraint owing to shallow water depth appear to be more important than nutrient limitation for water column primary production in Bandon Bay.  相似文献   

Effects of rainfall intensity and slope gradient on the application of vetiver grass mulch in soil and water conservation   总被引：3，自引：1，他引：2  

Somchai DONJADEE  Chaiyuth CHINNARASRI 《国际泥沙研究》2012,27(2):168-177

The objective of this study is to investigate the effect of rainfall intensity and slope gradient on the performance ofvetiver grass mulch (VGM) in soil and water conservation.The study involved field ...  相似文献   

‘Thailand was a desert' during the mid‐Cretaceous: Equatorward shift of the subtropical high‐pressure belt indicated by eolian deposits (Phu Thok Formation) in the Khorat Basin,northeastern Thailand     

Hitoshi Hasegawa  Suvapak Imsamut  Punya Charusiri  Ryuji Tada  Yu Horiuchi  Ken‐Ichiro Hisada 《Island Arc》2010,19(4):605-621

The Tibetan Plateau is a key factor in controlling the present‐day climate and atmospheric circulation pattern in Asia. The pattern of atmospheric circulation after the uplift of the plateau is well known, whereas direct evidence is lacking regarding the nature of the circulation pattern prior to the uplift. The distribution of desert directly reflects the position of the subtropical high‐pressure belt, and the prevailing surface‐wind pattern recorded in desert deposits reveals the position of its divergence axis. Cretaceous eolian sandstone of the Phu Thok Formation is extensively exposed in the northern Khorat Basin, northeastern Thailand. We conducted a sedimentological study on this formation to reconstruct temporal changes in the latitude of the subtropical high‐pressure belt in low‐latitude Asia during the Cretaceous. Spatio‐temporal changes in the paleo‐wind directions recorded in the Phu Thok Formation reveal that the Khorat Basin mainly belonged to the northeast trade wind belt and subtropical high‐pressure belt was situated to the north of the Khorat Basin during the initial stages of deposition, shifted southward to immediately above the basin during the main phase of deposition, and then shifted northward again to the north of the basin during the final stages of deposition. The paleomagnetic polarity sequence obtained for the Phu Thok Formation comprises three zones of normal polarity and two of reversed polarity, correlating to chrons M1n to C34n of the geomagnetic polarity time scale. This result suggests that the Phu Thok Formation is mid‐Cretaceous in age (from c. 126 Ma to c. 99–93 Ma), similar to the age of eolian sandstone in the Sichuan Basin, southern China (the Jiaguan Formation). These results, in combination with paleo‐wind direction data, suggest the development of low‐latitude desert and an equatorward shift of the subtropical high‐pressure belt (relative to the present‐day) in Asia during the mid‐Cretaceous.  相似文献