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Is the Sind-Rajasthan desert the result of a recent climatic change?
No full textThe author reviews the problem whether the Sind-Rajasthan desert of the Indo-Pakistan sub-continent is of recent origin and which factors are responsible for its creation: climatic change, shifting of rivers, floods, or yet social causes such as wars and man's abuse of his environment resulting in ecological imbalance
A phytoclimatic approach to the problem of mediterraneity in the Indo-Pakistan sub-continent
No full textIn the N. W. part of the sub-continent winter-spring rains coupled with low temperature and dry, hot summer create mediterranean conditions. Variants may be recognised in relation to aridity, temperature of the coldest month and intensity of summer dryness based on the contribution of average summer rainfall and rainy days to the annual total, percentage frequency of estival rainfall and rainy days, percentage number of years showing mediterranean regime. The degrees of mediterraneity (pure, moderate, attenuated) recognised according to the above criteria are supported by phytogeographic evidence. Dry evergreen sclerophyllous forests, with one ore more of the typical mediterranean species like Olea cuspidata, Pistacia khinjuk, P. mutica, Quercus baloot, Punica granatum, Cedrus deodara occur under moderate degree of mediterraneity. Some of these and few others of mediterranean stock persist under attenuated degree though the forest physiognomy is not well developed. The floristic elements viz. mediterranean, tropical, arid zone and general, show close correlations with the degrees of mediterraneity, aridity and temperature regimes
A diagram for depicting the interyearly variability in bioclimatic factors
No full textIn cases of unstable climates like that of Peshawar (West Pakistan) which exhibit variations in rainfall amount, length of distribution and season of occurrence from year to year, averages have little meaning in bioclimatic studies. Range and coefficient of variation are indicated as well as average and median values of annual precipitation, the number of rainy days in the year, the length of the dry season in months and the xerothermic index, in order to give an idea of the magnitude of variability. A diagram to illustrate the variability in the bioclimatic elements has been designed
Tropical dry deciduous forests of Peninsular India
No full textThe paper deals with structure, composition, floristic elements, bio-climatic conditions and palaeoecology of the dry deciduous forests. On the basis of dominance, these forests are divided into the teak, sal and miscellaneous types and the latter into Anogeissus latifolia-Terminalia, Hardwickia binata and Anogeissus pendula sub-types. Teak forest is the richest in the number of species followed by sal; A. pendula is the poorest type. Undergrowth contains the largest number of species, followed by upper canopy, understorey and liana in all the types exept in A. latifolia-Terminalia where upper canopy takes the first place. Of the 14 floristic elements, Indian and Indo-Malaysian dominate all the strata but Sudano-Rajasthanian has certain importance in A. pendula forest. Fossil record from the Deccan Intertrappean series indicates marshy and coastal conditions which go in favour of Upper Cretaceous age. Fossils of evergreen and moist deciduous formations from this series and from W. Rajasthan Kutch suggest a wetter climate during Upper Cretaceous-Mid Tertiary for which probable causes are outlined. Trends of progression of the dry teak forest has been discussed in relation to bio-climatic factors
Some phytogeographic aspects of Rajasthan, India
No full textThe literature on the demarcation line between the "Indo-Malayan" and the "Perso-Arabian" floras is reviewed and it is proposed to base the delimitation on the vegetation types. In the forests of teak or miscellaneous species generally located on the hills, the Indo-Malayan and the Indian elements predominate but in the thicket or scattered shrubby vegetation ofProsopis, Salvadora, Acacia, Capparis, Euphorbia of the sandy alluvial plains of North Gujarat and Rajasthan the western element is conspicuous. Geologically, Rajasthan west of the Aravallis possesses a mingling of the distinctive characters of the Peninsula and the extra-Peninsula and cannot be referred to as either. It is shown that plantgeography does not provide any evidence to consider the area as probably peninsular as suggested previously
Buttress like Structures on the Upper Part of the Trunk of Ceiba Pentandra (L.) Gaertn
No full textVolume: 71Start Page: 336End Page: 33
Repercussions of deforestation on precipitation in Western Karnataka, India
No full textPresent investigation involving 28 stations of Western Karnataka and one of Kerala produces at least some evidence of the impact of deforestation on declining trends of rainfall and rainy days. Twelve climatic parameters have been chosen; 6 of annual rainfall, 6 of rainy days (see Table 1). As a rule higher the deforested area, larger is the number of climatic criteria showing diminishing trend of rainfall-rainy days. Exceptions are the coastal stations where the humidity due to the proximity of the sea seems to compensate for the loss of forest cover. The potential evergreen forest belt appears to be subject to decreasing trend in higher number of criteria because of reduction of forest area than the zone of deciduous forest. Introduction of deciduous trees in the evergreen forests do not seem to affect the precipitation pattern. Generally, the rainy days are more prone to decline than the rainfall
On the mediterranean climatic regime of West Pakistan
No full textTaking mediterranean climate as one having mild winter, rainfall during the cool seasons of the year and summer drought, the stations of West Pakistan subject to this climate are listed. Degrees of mediterraneity are recognized on the basis of intensity of estival dryness (summer rainfall as percentage of the total). Three categories are recognised and mapped out: pure mediterranean (e. g. Nokkundi: no summer rain), moderate mediterraneity (<40% summer rains on an average, e. g. Quetta, Kalat), attenuated mediterraneity (>40% rainfall in hot season) marking a transition towards tropical or bixeric climates (e. g. Fort Sandeman, Dera Ismail Khan). Whereas the stations of tropical regime have the highest coefficient of variation of rainfall and number of rainy days during cool seasons and the least during summer, contrary is the case for the stations having moderate degree of mediterraneity. For those of attenuated character, the position is more or less intermediate but leaning towards tropical regime. In tropical and bixeric climates, it is the summer rainfall (and number of rainy days during summer) expressed as percentage of the annual total that occupies the dominant position; in the moderate mediterranean regime, winter has the most prominent position followed by spring-autumn and then by summer. Further attenuation in the degree of mediterraneity is marked by corresponding increase in summer rainfall
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