Effect of patches of woody vegetation on the role of fire in tropical grasslands and savannas

2014 ◽  
Vol 23 (3) ◽  
pp. 410 ◽  
Author(s):  
Frank van Langevelde ◽  
Casper de Groot ◽  
Thomas A. Groen ◽  
Ignas M. A. Heitkönig ◽  
Ian Gaigher
Keyword(s):  
Patch Size ◽  
Fire Effects ◽  
Climatic Conditions ◽  
Windward Side ◽  
Woody Vegetation ◽  
Leeward Side ◽  
Tree Seedlings ◽  
Tropical Grasslands ◽  
Vegetation Expansion

In tropical grasslands and savannas, fire is used to reduce woody vegetation expansion. Woody vegetation in these biomes is often patchily distributed, and micro-climatic conditions can largely vary locally with unknown consequences for fire effects. We hypothesised that (1) fire has higher temperature and maintains high temperatures for a longer period at the windward side than at the leeward side of wooded patches, (2) this difference increases with patch size, (3) fire has a larger effect on woody vegetation at the windward side than at the leeward side of wooded patches and (4) this effect increases with patch size. We planted tree seedlings around wooded patches in a grassland and burnt these plots. We found that fire had a lower temperature and had an elevated temperature for a shorter time period at the leeward side of wooded patches than at the windward side. Also, we found smaller effect of fire on the seedlings at the leeward side. We conclude that patches of woody vegetation can have a large effect on the role of fire in tropical grasslands and savannas. This effect suggests a ‘safe zone’ for seedlings at the leeward side, which consequently promotes woody vegetation expansion. This paper contributes to understanding of the effect of patchiness of woody vegetation on the role of fire in tropical grasslands and savannas in reducing woody vegetation expansion.

scholarly journals Topographical Influence on Precipitation Distribution in Different Ranges of Western Himalayas

1995 ◽  
Vol 26 (4-5) ◽  
pp. 259-284 ◽  
Author(s):  
Pratap Singh ◽  
K. S. Ramasastri ◽  
Naresh Kumar
Keyword(s):  
Precipitation Intensity ◽  
Windward Side ◽  
Leeward Side ◽  
Western Himalayas ◽  
Precipitation Distribution ◽  
Post Monsoon ◽  
Seasonal Characteristics ◽  
Annual Distribution

Seasonal and annual distribution of rainfall and snowfall with elevation has been studied for outer, middle and greater Himalayan ranges of Chenab basin in the western Himalayas. Rainfall and snowfall exhibited different trends with elevation on the windward and leeward slopes of the three ranges of Himalayas. Seasonal characteristics of rainfall have shown a spill over effect on leeward side during winter, pre-monsoon, and post-monsoon seasons in the outer Himalayas. The role of orography in the middle Himalayas was found to be more pronounced for both rainfall and snowfall in comparison to other ranges of Himalayas. Variation of snowfall with elevation was more prominent in comparison to variation of rainfall. In the greater Himalayan range it is found that rainfall descreases exponentially with elevation and snowfall increases linearly. Rainfall becomes negligible at elevations beyond 4,000 m on the windward side of the greater Himalayan range. Efforts have also been made to explain whether variation in precipitation is due to changes in precipitation intensity or number of precipitation days or a combination of both.

Role of Advection on the Evolution of Near-Surface Temperature and Wind in Urban-Aware Simulations

2020 ◽  
Author(s):  
Pallav Ray ◽  
Haochen Tan ◽  
Mukul Tewari ◽  
James Brownlee ◽  
R. S. Ajayamohan ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Urban Areas ◽  
Single Layer ◽  
Windward Side ◽  
Leeward Side ◽  
Land Use Patterns ◽  
Near Surface ◽  
Horizontal Advection ◽  
The City

AbstractThe role of advection of heat and momentum on the evolution of near-surface temperature and wind is evaluated in urban-aware simulations over Houston under dry conditions on a light-wind day. Two sets of experiments, each consisting of four simulations using different planetary boundary layer (PBL) schemes, were conducted over 48 hours using the default urban scheme (BULK) and the single-layer urban canopy model (SLUCM) available within the Weather Research and Forecasting (WRF) model. We focus on understanding and quantifying the role played by temperature and momentum advection, particularly on the windward and leeward sides of the city. Previous studies have largely ignored any quantitative analysis of impacts from the advection of momentum over an urban area.The horizontal advection of temperature was found to be more important in the BULK because of the larger surface temperature gradient caused by warmer surface temperatures over urban areas than in the SLUCM. An analysis of the momentum budget shows that horizontal advection of zonal and meridional momentum plays a prominent role during the period of peak near-surface winds, and this effect is more pronounced in the windward side of the city. The local tendency in peak winds in the leeward side lags that in the windward side by about 1-2 hours, similar to the lag found in horizontal momentum advection. The sensitivity of the results to different urban and PBL schemes was explored. The results imply that representation and influence of land-use patterns via sophisticated urban parameterizations generates locally driven winds that best resemble observations.

scholarly journals Diversity and Altitudinal Distribution of Understorey Corticolous Lichens in a Tropical Montane Forest in Kenya (East Africa)

2018 ◽  
Author(s):  
Paul M. Kirika ◽  
George G. Ndiritu ◽  
George K. Mugambi ◽  
Leonard E. Newton ◽  
H. Thorsten Lumbsch
Keyword(s):  
East Africa ◽  
Structural Heterogeneity ◽  
Climatic Conditions ◽  
Windward Side ◽  
Leeward Side ◽  
Sampling Effort ◽  
Forest Types ◽  
Altitudinal Distribution ◽  
Adequate Sampling ◽  
Study Sites

Lichens constitute an important component of tropical forest biodiversity. This study inventoried corticolous lichens and examined their variation in various forest types with varying climatic conditions in Mt. Kenya, East Africa. Specifically we evaluated variation of lichen assemblages in relation to forest types and tree diversity along an altitudinal gradient (1800-3100m). Ten study sites were established on two contrasting sides of Mt. Kenya in the indigenous forest: six of them at Chogoria which is on the humid southeastern windward side of the mountain and four sites on the Sirimon side located on the drier northwestern leeward side. Overall 242 lichen taxa were documented; with Chogoria and Sirimon forests having 148 and 94 species that translated to an adequate sampling effort of 74 % and 68 %, respectively. The two contrasting forest types (Chogoria and Sirimon) supported slightly different lichens assemblages. Meanwhile lichen assemblages were found to significantly vary with elevation (or forest types) and with tree host. Posterior analyses showed that the differences were significant among sampling sites (or forest types) on the Chogoria side and insignificant on the Sirimon side. Similarly the number of lichens differed significantly among the host tree species. This study stresses the urgent need to upscale the sustainable management of the presently threatened tropical forests in order to preserve their structural heterogeneity.

scholarly journals Characteristics of Phomopsis juglandina (Sacc.) Hohn. Associated with Dieback of Walnut in the Climatic Conditions of Southern Romania

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 46
Author(s):  
Cristina Mihaescu ◽  
Daniel Dunea ◽  
Adrian Gheorghe Bășa ◽  
Loredana Neagu Frasin
Keyword(s):  
Growth Temperature ◽  
Potential Evapotranspiration ◽  
Optimal Growth ◽  
Climatic Conditions ◽  
Cultural Characteristics ◽  
Optimal Growth Temperature ◽  
Conidial State ◽  
Optimal Ph

Phomopsis juglandina (Sacc.) Höhn., which is the conidial state of Diaporthe juglandina (Fuckel) Nitschke, and the main pathogen causing the dieback of branches and twigs of walnut was recently detected in many orchards from Romania. The symptomatological, morphological, ultrastructural, and cultural characteristics, as well as the pathogenicity of an isolate of this lignicolous fungus, were described and illustrated. The optimum periods for infection, under the conditions prevailing in Southern Romania, mainly occur in the spring (April) and autumn months (late September-beginning of October). Strong inverse correlations (p < 0.001) were found between potential evapotranspiration and lesion lengths on walnut branches in 2019. The pathogen forms two types of phialospores: alpha and beta; the role of beta phialospores is not well known in pathogenesis. In Vitro, the optimal growth temperature of mycelial hyphae was in the range of 22–26 °C, and the optimal pH is 4.4–7. This pathogen should be monitored continuously due to its potential for damaging infestations of intensive plantations.

Investigation on the drag effect of a rolling element confined in the cavity of a cylindrical roller bearing

2021 ◽  
pp. 135065012110260
Author(s):  
Wenjun Gao ◽  
Shuo Zhang ◽  
Xiaohang Li ◽  
Zhenxia Liu
Keyword(s):  
Open Space ◽  
Roller Bearing ◽  
Flow Characteristics ◽  
Experimental Tests ◽  
Windward Side ◽  
Leeward Side ◽  
Drag Effect ◽  
Rolling Element ◽  
Cylindrical Roller Bearing ◽  
Cylindrical Roller

In cylindrical roller bearings, the drag effect may be induced by the rolling element translating in a fluid environment of the bearing cavity. In this article, the computational fluid dynamics method and experimental tests are employed to analyse its flow characteristics and pressure distribution. The results indicate that the pressure difference between the windward side and the leeward side of the cylinder is raised in view of it blocking the flow field. Four whirl vortexes are formed in four outlets of two wedge-shaped areas between the front part of the cylindrical surface and adjacent walls for the cylinder of L/ D = 1.5 at Re = 4.5 × 103. Vortex shedding is found in the direction of cylinder axis at Re = 4.5 × 104. The relationship between drag coefficient and Reynolds number is illustrated, obviously higher than that of the two-dimensional cylinder in open space.

scholarly journals 2.5D Flexible Wind Sensor Using Differential Plate Capacitors

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3101
Author(s):  
Yu Wan ◽  
Zhenxiang Yi
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Parallel Plate ◽  
Electrode Array ◽  
Copper Electrode ◽  
Windward Side ◽  
Leeward Side ◽  
Electrode Layer ◽  
Young’S Moduli ◽  
Speed Up

In this paper, a novel 2.5-dimensional (2.5D) flexible wind sensor is proposed based on four differential plate capacitors. This design consists of a windward pillar, two electrode layers, and a support layer, which are all made of polydimethylsiloxane (PDMS) with different Young’s moduli. A 2 mm × 2 mm copper electrode array is located on each electrode layer, forming four parallel plate capacitors as the sensitive elements. The wind in the xy-plane tilts the windward pillar, decreasing two capacitances on the windward side and increasing two capacitances on the leeward side. The wind in the z-axis depresses the windward pillar, resulting in an increase of all four capacitances. Experiments demonstrate that this sensor can measure the wind speed up to 23.9 m/s and the wind direction over the full 360° range of the xy-plane. The sensitivities of wind speed are close to 4 fF·m−1·s and 3 fF·m−1·s in the xy-plane and z-axis, respectively.

Air movement and heat loss from sheep. II. Thermal insulation of fleece in wind

1980 ◽  
Vol 209 (1175) ◽  
pp. 209-217 ◽  
Keyword(s):  
Thermal Diffusivity ◽  
Heat Loss ◽  
Thermal Insulation ◽  
General Relation ◽  
Windward Side ◽  
Leeward Side ◽  
Sensible Heat ◽  
Bulk Resistance ◽  
Air Movement ◽  
Dimensionless Constant

Penetration of an animal’s coat by wind reduces its thermal insulation and increases heat loss to the environment. From studies of the sensible heat loss from a life-sized model sheep covered with fleece, the average fleece resistance r¯ f (s cm -1 ) was related to windspeed u (m s -1 ) by 1/ r¯ f ( u ) = l/ r¯ f (0) + cu , where c is a dimensionless constant. As c is expected to be inversely proportional to coat depth Î , the more general relation k¯ ( u ) = k¯ (0) + c'u was evaluated, where k¯ = Î / r¯ f is the thermal diffusivity (cm 2 s -1 ) of the fleece and c' = cÎ is another constant (cm). The orientation of the model to the wind had little effect on the bulk resistance of the fleece, but the resistance on the windward side was substantially lower than on the leeward side.

HAS PSYCHOLOGIC MALNUTRITION TAKEN THE PLACE OF RICKETS AND SCURVY IN CONTEMPORARY PEDIATRIC PRACTICE?

PEDIATRICS ◽  
1963 ◽  
Vol 31 (6) ◽  
pp. 909-918
Author(s):  
Nathan B. Talbot
Keyword(s):  
Sixteenth Century ◽  
Lemon Juice ◽  
Climatic Conditions ◽  
Northern Europe ◽  
Scientific Medicine ◽  
Pediatric Practice ◽  
Therapeutic Value ◽  
High Prevalence ◽  
The Baltic

WHILE MEDICAL HISTORIANS cannot provide us with accurate statistics concerning the incidence of rickets and scurvy in centuries past, they leave little room for doubt about the high prevalence of these disorders prior to the advent of modern scientific medicine. Thus, Castiglione has written that in the sixteenth century scurvy raged throughout northern Europe, in Scandinavia, on the shores of the Baltic, and in the interior of Germany. It is interesting to note, however, that Jacques Cartier, whose sailors had been ravaged by scurvy, learned in 1536 from the Indians that the malady could be cured by juices of the almeda tree. This was 200 years before James Lind demonstrated the curative effects of lemon juice in his treatise on scurvy published in 1753 and almost 400 years before ascorbic acid, which was isolated by Szent-Gyorgi in 1928, was recognized to be vitamin C by Waugh and King in 1932. Rickets, likewise, was occurring in a large portion of children prior to the discovery of the existence of vitamin D by Hess, Steinbock, and Windaus in 1918, of its therapeutic value by Mellanby in 1919, of the equivalent role of sunlight by Hess in 1921, and of the chemical composition of the vitamins by Windaus in 1922. But 200 years earlier Friedrick Hoffman had the answer to the control of this disease almost in hand. He attached much importance to climatic conditions as a factor in rickets, noting that if anything is specially powerful in producing this affliction, it is a surrounding atmosphere of cold foggy air. He cited as striking evidence of this the famous emporium of England, London, which he found to be specially apt to produce and foster this disease.

On Approaches to Taking into Account the Risks of Changing Climatic Conditions when Planning and Implementing Oil and Gas Projects

2021 ◽  
Vol 18 (1) ◽  
pp. 52-65
Author(s):  
P. N. Mikheev
Keyword(s):  
Climate Change ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Climatic Conditions ◽  
Qualitative Assessment ◽  
Physical Factors ◽  
Gas Industry ◽  
Climate Risks ◽  
The Impact

The article discusses issues related to the impact of climate change on the objects of the oil and gas industry. The main trends in climate change on a global and regional (on the territory of Russian Federation) scale are outlined. Possible approaches to the identification and assessment of climate risks are discussed. The role of climatic risks as physical factors at various stages of development and implementation of oil and gas projects is shown. Based on the example of oil and gas facilities in the Tomsk region, a qualitative assessment of the level of potential risk from a weather and climatic perspective is given. Approaches to creating a risk management and adaptation system to climate change are presented.

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