Growth Strategies of Eucalyptus camaldulensis Dehnh. At Three Sites in Northern Australia

1994 ◽  
Vol 21 (5) ◽  
pp. 653 ◽  
Author(s):  
A Gibson ◽  
EP Bachelard ◽  
KT Hubick
Keyword(s):  
Gas Exchange ◽  
Shoot Growth ◽  
Eucalyptus Camaldulensis ◽  
Dry Season ◽  
Growth Strategies ◽  
Wet Season ◽  
Wind Speeds ◽  
The North ◽  
Air Temperatures ◽  
Semi Arid

The morphology and physiology of trees of Eucalyptus camaldulensis growing in the field at two monsoonal and one semi-arid location were compared. In the wet season, shoot growth at the monsoonal locations was similar and larger than that at the semi-arid location. In the dry season, new shoot growth at the more humid monsoonal location (Petford) was similar to growth in the wet season while at the less humid (Katherine) and the semi-arid (Tennant Creek) locations, shoot growth was foreshortened and the leaves had larger dry weights per unit area. In the summer wet season, leaves on both the north and south sides of the trees were maintained at or below (by up to 5�C) air temperatures throughout the day except for north facing leaves at Petford which were consistently above (by up to 3�C) air temperatures. Midday gas exchange in the dry season at both monsoonal localities was restricted to trees at the water's edge, whereas most trees, including those at drier sites, at the semi-arid location exhibited significant rates of gas exchange. The results, which are discussed in relation to environmental variables (vapour pressure deficits, wind speeds) to which the trees are exposed, and to previous results obtained in the glasshouse, indicate that the differences in shoot growth and physiology are adaptations to the environment in which the trees have evolved.

scholarly journals Epidemiology of gastrointestinal helminths infections in Dorper sheep in a semi-arid area of Kenya

2004 ◽  
Vol 71 (3) ◽  
Author(s):  
C.J. Ng'ang'a ◽  
N. Maingi ◽  
W.K. Munyua ◽  
P.W.N. Kanyari
Keyword(s):  
Age Groups ◽  
Dry Season ◽  
Arid Area ◽  
Wet Season ◽  
Weather Factors ◽  
Gastrointestinal Helminths ◽  
Faecal Samples ◽  
Dorper Sheep ◽  
Short Rains ◽  
Semi Arid

A survey on the prevalence and intensity of infection with gastrointestinal helminths of Dorper sheep in relation to age and weather factors was carried out on a ranch in Kajiado district, a semi-arid area of Kenya for a period of 13 months (May 1999 to May 2000). Faecal samples from lambs (3 months to 1 year), yearlings (1-2 years) and adult breeding ewes (2-4 years) were examined for helminth egg output and helminth genus composition at 3-week intervals. The results indicated that the prevalence of strongyle and tapeworms infections were highest for lambs, followed by the adult breeding ewes and then for the yearlings. In all age groups the proportions of infected animals were higher during the wet season than in the dry season for both nematodes and tapeworms. The mean strongyle egg counts were higher during the dry season for lambs, but were higher during the wet season for the other age groups. Mixed strongyle infections were detected, with Trichostrongylus (55 %), Haemonchus (28 %), Cooperia (10.5 %) and Oesophagostomum (6.5 %) being the most frequently encountered genera throughout the study period. The trends in strongyle faecal egg counts indicated the occurrence of hypobiosis, with resumption of development towards the end of the dry season and at the onset of the short rains in October and November. Self-cure was also observed in September and November in all age groups, although less frequently in lactating ewes. The prevalence and intensities of infection with gastrointestinal helminths in this area appeared to be influenced by the age of the host and weather factors.

Migratory Labour from North-Wester Nigeria

Africa ◽  
1957 ◽  
Vol 27 (3) ◽  
pp. 251-261 ◽  
Author(s):  
R. Mansell Prothero
Keyword(s):  
Large Scale ◽  
Source Area ◽  
Dry Season ◽  
Labour Migration ◽  
Agricultural Activity ◽  
Wet Season ◽  
The North ◽  
The People ◽  
Limited Scale ◽  
Opening Paragraph

Opening ParagraphReaders of Africa will be well aware of population migration as a characteristic feature of a continent where movement between one part and another is largely unrestricted as compared with the more settled parts of the world. There is much evidence of large-scale tribal migrations in the past, of the age-old seasonal wanderings of herders, and of recent labour migration to centres of mineral and industrial production, the last particularly in Central and South Africa. Information is more limited concerning the features of labour migration in West Africa at the present day. In general it is thought that migrants leave their home areas, after the harvest at the commencement of the dry season, to seek work elsewhere for a period of from three to six months and then return to take up farming with the commencement of the next rains. The major source area for these migrants is to the north of the tenth parallel where the wet season is concentrated into a period of about four months, thus severely restricting agricultural activity. Cultivation during the dry season is possible only on a very limited scale. There is thus a considerable period of the year when the primary economic activity of the people is not possible. It is logical that they should seek work elsewhere.

scholarly journals Impacts of the dry season on the gas exchange of oil palm (Elaeis guineensis) and interspecific hybrid (Elaeis oleífera x Elaeis guineensis) progenies under field conditions in eastern Colombia

2016 ◽  
Vol 34 (3) ◽  
pp. 329-335 ◽  
Author(s):  
Cristihian Jarri Bayona-Rodríguez ◽  
Iván Ochoa-Cadavid ◽  
Hernán Mauricio Romero
Keyword(s):  
Water Stress ◽  
Gas Exchange ◽  
Water Potential ◽  
Oil Palm ◽  
Interspecific Hybrid ◽  
Elaeis Guineensis ◽  
Dry Season ◽  
Wet Season ◽  
Elaeis Oleifera ◽  
Photosyn Thesis

Elaeis guineensis palms and its interspecific hybrid (E. oleifera x E. guineensis) were planted in 2004 in the Cuernavaca farm of Unipalma S.A., located in the municipality of Paratebueno (Cundinamarca, Colombia). The palms were planted in two fields: Mecasaragua and Aurora. The first field has never been irrigated, and the second one (Aurora) has always been flood-irrigated during the dry season according to the parameters of the plantation. In this study, physiological parameters (gas exchange and water potential) were assessed in three seasons of the year 2013 (dry season, dry-to-wet transition season and wet season). Significant gas exchange differences were found among the seasons in the field with no irrigation (Mecasaragua). Likewise, differences between the genetic materials were observed during the dry season. For example, the photosyn thesis decreased by 75% compared with the palms planted in the irrigated field. No differences among seasons or materials were found in the irrigated field (Aurora). E. guineensis palms were more sensitive to water stress compared with the OxG interspecific hybrid. Both genetic materials responded rapidly to the first rains by leveling their photosynthetic rates and demonstrated an excellent capacity to recover from water stress.

Occurrence of the grasshopper pest Zonocerus variegatus (L.) (Orthoptera: Pyrgomorphidae) in south-western Nigeria in relation to the wet and dry seasons

1980 ◽  
Vol 70 (4) ◽  
pp. 621-633 ◽  
Author(s):  
W. W. Page
Keyword(s):  
Dry Season ◽  
Seasonal Abundance ◽  
Secondary Peak ◽  
Rapid Decline ◽  
Arid Zones ◽  
Zonocerus Variegatus ◽  
Wet Season ◽  
The North ◽  
Dry Seasons ◽  
Peak Abundance

AbstractAn investigation into the seasonal abundance of Zonocerus variegatus (L.) around Ibadan, Nigeria, showed that hatching occurs between October and March and peak abundance is in late November. Adults occur almost throughout the year. Oviposition takes place between March and October or possibly November, with a peak in April. Eggs laid in March and April hatch in October and November after a diapause, while those laid from June onwards do not appear to enter diapause. Thus eggs laid in June and July hatch at the same time as those laid in March and April. Parasitism by the sargophagid fly Blaesoxipha filipjevi (Rod.) during March and April results in a rapid decline in adult numbers which may be followed by a secondary peak in adult numbers when nymphs, which are present at the same time and are rarely parasitised, reach adult stage. Oviposition resulting from such a peak does not produce a secondary peak in hatching as this coincides with hatching from earlier layings. The fungus Entomophthora grylli plays an important role in controlling the abundance of nymphs and adults during the dry season despite the intermittent nature of the attacks. During the wet season, the fungus is able to germinate and disperse more readily, thus keeping the numbers of the insects low. It is concluded that there is one generation of Z. variegatus a year, with a peak in population coinciding with the dry season (November-March). It is suggested from the results that the grasshopper may have originated in the semi-arid zones of the north.

scholarly journals Calibration of Methods to Estimate Solar Irradiance in Northeastern Pará

2020 ◽  
Vol 35 (2) ◽  
pp. 345-355
Author(s):  
João Vitor de Nóvoa Pinto ◽  
Hildo Giuseppe Garcia Caldas Nunes ◽  
Daniely Florencia Silva de Souza ◽  
Deborah Luciany Pires Costa ◽  
Paulo Jorge de Oliveira Ponte de Souza
Keyword(s):  
Solar Radiation ◽  
Performance Index ◽  
Solar Irradiance ◽  
Sunshine Duration ◽  
Dry Season ◽  
Daily Maximum ◽  
Wet Season ◽  
Average Performance ◽  
Daily Minimum ◽  
Air Temperatures

Abstract Two models aimed to estimate solar irradiance were calibrated in six locations in Northeastern Pará (Belém, Cametá, Conceição do Araguaia, Marabá, Soure, and Tucuruí). The first one is the equation of Angström-Prescott (AP), which requires observations of sunshine duration hours. The second model is a modified version of Hargreaves' radiation formula (MH), which requires observations of daily maximum and daily minimum air temperatures. Both models were calibrated to estimate daily and monthly solar radiation. The calibration of both equations for each season (i.e., dry season and wet season) in each location was also tested. AP has an average performance about 74% higher than MH for daily estimates (excluding Soure) and 83% higher than MH for monthly estimates (excluding Soure and Tucuruí). The use of seasonally calibrated equations slightly improves the performance of AP, measured by the performance index, by 0.68% and improves the performance of MH in most locations, when estimating daily solar radiation. The performance of both models is much higher when estimating monthly solar radiation than daily solar radiation, with an increase of the performance index of 10.95% for AP.

Enhancing food security in semi-arid eastern Indonesia through permanent raised-bed cropping: a review

1999 ◽  
Vol 39 (8) ◽  
pp. 1035 ◽  
Author(s):  
D. E. Van Cooten ◽  
A. K. Borrell
Keyword(s):  
Water Supply ◽  
Food Production ◽  
Crop Production ◽  
Ground Cover ◽  
Dry Season ◽  
Wet Season ◽  
Additional Food ◽  
Eastern Indonesia ◽  
Raised Bed ◽  
Semi Arid

Summary. Much of south-eastern Indonesia is mountainous and characterised by a semi-arid tropical environment. Soil erosion is a significant environmental problem facing the region, affecting both productivity of the land and water quality. The challenge for the region is to secure year-round food production in such a fragile environment. More than 90% of rain falls in a distinct wet season between November and April. Therefore, cropping in this region is dependent on matching crop growth with water supply. In particular, crop production depends on the efficient use of rainfall during the wet season, including avoidance of waterlogging, and efficient use of stored soil water during the dry season. This paper summarises the results of a series of experiments undertaken in West Timor, Indonesia, between 1993 and 1999 aimed at developing a raised-bed cropping system. The objective of these studies was to better utilise the more fertile alluvial soils that are often susceptible to waterlogging during the wet season, allowing a range of crops to be grown in addition to rice. Raised beds of height 0.2 m and width 1.5 m were constructed either manually or with an 8.5 hp two-wheeled hand tractor. A range of crops including soybeans, sorghum, maize, pigeon pea, yam bean and cassava were successfully grown on raised beds in the wet season in addition to rice, indicating that raised-bed technology overcomes the constraints of waterlogging in the wet season. Soybeans grew particularly well on raised beds, with December-sown crops producing almost twice the yield of January-sown crops (2.6 v. 1.4 t/ha). For rice and soybeans, early sown crops were better able to match growth with water supply, thereby avoiding end-of-season drought. Early sowing and harvesting of wet season crops enables a drought-resistant crop such as sorghum to be planted in lateMarch or early April, utilising the stored soil moisture for grain production and also maintaining ground cover in the dry season. It is argued that cropping systems based on permanent raised beds can reduce erosion in 2 ways. First, raised beds are a permanent structure and, with the inter-cropping and relay-cropping proposed, crops can provide all-year ground cover in lowland areas. Second, if sufficient food and cash crops are grown on raised beds to meet the basic needs of subsistence farmers, then upland cropping on steep slopes can be replaced by a variety of tree species, providing additional food, fodder, firewood and medicines. Together, these strategies have the capacity to enhance food production and security in the semi-arid areas of eastern Indonesia.

scholarly journals Seasonal leaf gas exchange and water potential in a woody cerrado species community

2004 ◽  
Vol 16 (1) ◽  
pp. 7-16 ◽  
Author(s):  
Carlos Henrique Britto de Assis Prado ◽  
Zhang Wenhui ◽  
Manuel Humberto Cardoza Rojas ◽  
Gustavo Maia Souza
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Gas Exchange ◽  
Water Status ◽  
Dry Season ◽  
Leaf Water ◽  
Wet Season ◽  
Leaf Water Status ◽  
Mean Values

Predawn leaf water potential (psipd) and morning values of leaf gas exchange, as net photosynthesis (A), stomatal conductance (gs), transpiration (E), and morning leaf water potential (psimn) were determined seasonally in 22 woody cerrado species growing under natural conditions. Despite the lower mean values of psipd in the dry season (-0.35 ± 0.23 MPa) compared to the wet season (-0.08 ± 0.03 MPa), the lowest psipd in the dry season (-0.90 ± 0.00 MPa) still showed a good nocturnal leaf water status recovery for all species studied through out the year. Mean gs values dropped 78 % in the dry season, when the vapor pressure of the air was 80% greater than in the wet season. This reduction in gs led to an average reduction of 33% in both A and E, enabling the maintainance of water use efficiency (WUE) during the dry season. Network connectance analysis detected a change in the relationship between leaf gas exchange and psimn in the dry season, mainly between gs-E and E-WUE. A slight global connectance value increase (7.25 %) suggested there was no severe water stress during the dry season. Multivariate analysis showed no link between seasonal response and species deciduousness, suggesting similar behavior in remaining leaves for most of the studied species concerning leaf gas exchange and psimn under natural drought.

scholarly journals Water and Salt Transports in the Hengsha Channel of Changjiang Estuary

2022 ◽  
Vol 10 (1) ◽  
pp. 72
Author(s):  
Rui Ma ◽  
Jianrong Zhu
Keyword(s):  
Water Transport ◽  
Neap Tide ◽  
Spring Tide ◽  
Dry Season ◽  
Changjiang Estuary ◽  
Dynamic Mechanism ◽  
Gradient Force ◽  
Residual Water ◽  
Wet Season ◽  
The North

In a multilevel bifurcated estuary, the channels between the bifurcated branches play important roles in the exchanges of water and salt. In the Changjiang Estuary, the Hengsha Channel (HC) connects the North Channel (NC) and the North Passage (NP). In this paper, based on a two-way nesting unstructured quadrilateral grid, finite-differencing, three-dimensional estuarine and coastal ocean model, the tidal and seasonal variations in the water and salt transports in the HC were simulated, and their dynamic mechanism was analyzed. The residual water and salt transports in the HC both flow southward from the NC to the NP. In wet season, the residual water transport in the HC is 677 m3/s during neap tide and 245 m3/s during spring tide, and the residual salt transport is 0. In dry season, the residual water and salt transports in the HC are 1278 m3/s and 0.38 t/s during neap tide, respectively, and 1328 m3/s and 12.61 t/s during spring tide. Affected by the northerly wind and the southeastward baroclinic gradient force, the water and salt fluxes in dry season are much larger than those in wet season. The dynamic mechanism responsible for the water transport in the HC was numerically simulated and analyzed.

scholarly journals General procedure to initialize the cyclic soil water balance by the Thornthwaite and Mather method

2010 ◽  
Vol 67 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Durval Dourado-Neto ◽  
Quirijn de Jong van Lier ◽  
Klaas Metselaar ◽  
Klaus Reichardt ◽  
Donald R. Nielsen
Keyword(s):  
Water Balance ◽  
Soil Water ◽  
General Procedure ◽  
Water Storage ◽  
Dry Season ◽  
Soil Water Balance ◽  
Soil Water Storage ◽  
Wet Season ◽  
Water Balance Components ◽  
Semi Arid

The original Thornthwaite and Mather method, proposed in 1955 to calculate a climatic monthly cyclic soil water balance, is frequently used as an iterative procedure due to its low input requirements and coherent estimates of water balance components. Using long term data sets to establish a characteristic water balance of a location, the initial soil water storage is generally assumed to be at field capacity at the end of the last month of the wet season, unless the climate is (semi-) arid when the soil water storage is lower than the soil water holding capacity. To close the water balance, several iterations might be necessary, which can be troublesome in many situations. For (semi-) arid climates with one dry season, Mendonça derived in 1958 an equation to quantify the soil water storage monthly at the end of the last month of the wet season, which avoids iteration procedures and closes the balance in one calculation. The cyclic daily water balance application is needed to obtain more accurate water balance output estimates. In this note, an equation to express the water storage for the case of the occurrence of more than one dry season per year is presented as a generalization of Mendonça's equation, also avoiding iteration procedures.

Activity Cycles ofGlossina pallidipesAust.,G. palpalis fuscipesNewst. andG. brevipalpisNewst

1965 ◽  
Vol 56 (1) ◽  
pp. 141-160 ◽  
Author(s):  
J. M. B. Harley
Keyword(s):  
Lake Victoria ◽  
Glossina Pallidipes ◽  
Physical Factor ◽  
Dry Season ◽  
Physical Factors ◽  
Wet Season ◽  
North East ◽  
The North ◽  
Morning Peak ◽  
Hot Dry Season

A series of 24-hr catches ofGlossina pallidipesAust.,G. palpalis fuscipesNewst. andG. brevipalpisNewst. was carried out on the north-east shore of Lake Victoria over a period of 11 months in 1962–63. The object was to define and compare the daily pattern of activity of the three species as indicated by the numbers caught hourly on three black cattle that were used as bait. Catching during the hours of darkness was done by the light of dimmed hurricane lamps. The period of observation covered successively a dry season, a wet season, a cool dry season and a hot dry season.At all seasons, males ofG. pallidipeswere caught in gradually increasing numbers from just before dawn until shortly before sunset, after which a rapid decrease took place. Females ofG. pallidipesexhibited a different pattern, with a gradual rise in activity in the morning until about midday, after which activity remained more or less constant until shortly before sunset, when a rapid fall occurred. There was never any indication of a morning peak in activity such as has been described for this species elsewhere. Activity during the night was at an extremely low level.Activity of both males and females ofG. p. fuscipesstarted about dawn, increased to a peak in the middle hours of the day, and then fell fairly rapidly in the evening; the exact time of the peak was variable. None was caught during the night.There was some activity ofG. brevipalpisthroughout the diel, but marked peaks of activity were exhibited by both sexes. In the open, these took place immediately after sunset and immediately before sunrise, the latter being the smaller. In the shade, the morning peak in both sexes was an hour later than in the open, and the evening peak in males alone was an hour earlier.These results are compared with those of other workers, and the influence of physical factors is discussed. Particular values of temperature and saturation deficit were not closely associated with particular levels of activity of any of the three species, and light intensity is probably the physical factor that is most consistently the same at times of particular levels of activity at all seasons.

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