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The rhizosphere is a dynamic region influenced by complex interactions between plants and microbes that are closely linked to the metabolically active hotspots of the roots below the soil and participate in below-ground interactions. We must consider the roles of the rhizosphere to improve above-ground productivity and hence regulate the environment. Initially, the soil was measured to be stable only based on nutrient abundance, but the healthy soil is now seen with large microbial communities after rhizosphere evolution. In this regard, numerous strategies for manipulating the rhizosphere for better ecological functioning need to be developed. Based on current ecological evidence, we propose a new sketch in which future comparative research through sustainable agriculture and an environment is required to uncover the underlying mechanisms. Plant roots manage below-ground diversity by releasing exudates into the rhizosphere, due to their microbial growth capability. The microbes are attracted to the exudates, and in the rhizosphere, they developed communities. Roots play an important role in the microbial community establishment, having a major and primary energy channel in the ecosystem of the rhizosphere. Via the roots channel, the energy release then transfers to the microbial channel, eventually converted into microbial biomolecules, which are then returned to the above-ground in the form of volatile compounds and productivity. This review discusses the different energy channels in the rhizosphere that facilitate the development of the microbial community and the transfer of energy in a sequence in the form of productivity from above-ground to below-ground to above-ground. Importantly, such awareness may result in strategies for improving plant health and development in the context of future agricultural demand.

The largest continent, Asia, which harbored some of the world's oldest civilizations, constitutes one-third of the earths land area. The physiography of central Asia is dominated by the mightiest ranges: the Himalayas, Hindukush, Kunlun, and Tien Shan. The distribution and abundance of rodents in Asia indicate a broad pattern which, in a way, corresponds to the terrain physiography and bioclimate of the region. Periodic as well as sporadic outbreaks in the rodent populations enhance their numbers menacingly. Such outbreaks can be caused either by failure of monsoon, by favorable reproductive conditions after a fairly long spell of climates, or can be associated with flowering of bamboo in forests. Quantified information on actual damage caused by rodents to agricultural crops in China is not available; however, 10% loss in field crops is reported. Rodent damage to grasslands and fodder crops is very severe, especially in the arid tracts.

Results of experiments conducted in T-maze to probe the functional role of conspecific odours indicated that whereas the male Indian gerbil,Tatera indica indica invariably prefers odours (from their body, that of the sebum exudation of scent marking gland, urine and faecal matter) of strange males, the females with and devoid of the scent marking gland show slight preference for male odours. However, all the categories ofTatera indica placed their preference for their own odours at the lowest. This behaviour suggests that the role of scent marking to label the habitat for its own use or to signal ‘home’ to the marking animal may not be the sole function of scent marking in this species. It is quite possible that in the desert grassland, scent marking is being used for maintaining a minimum distance between two animals or pairs, as exhibited by the diversity in the occurrence of the scent gland in the field (pair-tolerant) and urban (gregarious social organisation) populations ofTatera indica. This type of spatial distribution, maintained by scent marking behaviour, may be important to withstand the low carrying capacity of the aridland which suffers from almost a perpetual paucity of food.

Four species of Indian desert rodents, viz. Tatera indica, Meriones hurrianae, Rattus meltada and Golunda ellioti have been found to have basal metabolic rates (BMR) lower than the values expected from the metabolic rate-body weight relationship for mammals. The low BMR in these species is evidently not due to any large accumulation of body fats, but is probably related to niche utilization. Of the four species examined, only T. indica and M. hurrianae have any appreciable body fat, presumably for use during summer when scarcity of both food and water prevail.

The two gerbils,Tatera indica andMeriones hurrianae, and the metad,Rattus meltada pallidior exhibit significant monthly variations in the dimension (maximum length X maximum breadth) of the ventral scent marking gland. Peaks in gland size occur late in winter and monsoon which generally correspond to the maximum breeding activity of these rodents during the year. However, the monthly averages of gland area and incidence of pregnancy in the three species do not follow the same trend. It is difficult, therefore, to conclude if the scent-marking behaviour and the breeding performance of the rodents are inter-related.

There are two different patterns of feeding rhythm of the diurnal gerbil, Meriones hurrianae during summer and winter seasons in the Indian desert. The feeding activity is restricted to two phases (6 to 11 a.m.; 4 to 7 p.m.) in summer with an intermediate phase (11 a.m. to 4 p.m.) of complete rest inside the burrow systems. In winter, feeding continues uninterrupted from 6.45 a.m. to 5.15 p.m. During summer, increase in air and or soil temprature suppresses the food intake and general activity of rodents, whereas the rise in these climatic parameters promotes feeding among gerbils during winter season. Two distinct peaks of the feeding cycle during summer (6–9 a.m.; 5–7 p.m.) as well as winter (8–10 a.m.; 3–5 p.m.) periods can be chosen as suitable timings for laying poison baits inside burrows of gerbils.

[With 4 Tables] A comparison of external body parts and cranial characters in three populations of Cutch rock-rat, Rattus c. cutchicus (Wroughton, 1912) and Soft furred field-rat, R. meltada pallidior (R y 1 e y, 1914) collected from their respective habitats in the Indian desert, has been made. In R. c. cutchicus, males are found to be larger in almost all the characters in Jalore and Jhunjhunu populations, whereas females tended to possess larger values in the Cutch sample. However, inter-population comparison indicated significant differences only for a few characters. In R. meltada pallidior, the male body parts are significantly larger in respect of head and body length and tail length (P

Measurement of the metabolic rates of eight species of Rajasthan desert rodents and of Rattus rattus at a moderately low temperature (21 °C) during winter has revealed that: there is a significant negative correlation (P

Basal metabolic rate (BMR), evaporative water loss (EWL) within the thermoneutral zone and minimal thermal conductance (C) of the Indian desert gerbil Meriones hurrianae Jerdon, were 0·79 cm3 O2/g/h, 1·89 mg H2O/cm3 O2 and 0·110 cm3 O2/g/h/°C respectively. Below the thermoneutral zone, gerbils regulated their body temperature within the normal limits of homeotherms. The relatively high body temperature (38·7 °C) recorded within the thermoneutral zone is, presumably, the result of an adaptive mechanism for reducing evaporative water loss. The gerbil's low BMR, low conductance (67 and 92 per cent of the values predicted on body weight basis respectively) and its comparatively high body temperature are considered to be physiological means of avoiding overheating.

In a choice test, the Indian gerbils,T. indica preferred urine-mixed food over ordinary millet indicating a phago-stimulant nature of conspecific urine. The experiments also revealed that addition of conspecific urine mitigates the poison aversion and bait shyness behaviour significantly, as a result of which zinc phosphide poisoning can be attempted a second time in a sequence, thus enhancing the control success.T. indica showed a clear preference for urine of the same sex which suggests that the active attractant in the urine has no sex attraction.

The responses of Meriones hurrianae deprived of food and food-cum-water were found to be similar in respect of time spent in feeding, exploration and drinking whereas water- deprived gerbils fed for a significantly (P < 0.01) shorter time. However, they explored twice (P < 0.01) as long as gerbils in the other two conditions of deprivation. These observations indicate that deprivation of water increases exploratory behaviour among M. hurrianae but food, and food-cum-water deprivation do not seem to influence it. The behaviour of M. hurrianae, when deprived of water, mostly alternated between exploration and drinking whereas feeding was the major behavioural component of the gerbils deprived of food, and food-cum-water. It appears that feeding behaviour among M. hurrianae is of a higher order than drinking behaviour since the animals depend chiefly on the available water content of the food in their natural invironment - the desert.

Held trials were conducted in 18 1‐ ha plots arranged as a 6×3 randomised block to evaluate brodifacoum (0.002%), chlorophacinone (0.0075%) and coumatetralyl (0.0375%) for the control of desert rodents, predominantly Meriones hurrianae Jerdon. Success was measured by counts of inhabited burrows before and four days after the treatment period of ten days. Average kills were 90.5, 83.2 and 81.1 % respectively. It is concluded that all three poisons are effective, but brodifacoum performed significantly better than either chlorophacinone or coumatetralyl.

The Indian Desert, situated on the eastern-most boundary of the Saharo-Rajasthan Desert, is of recent origin and offers considerable scope for ecological studies of fundamental and economic importance. RAO (1957) records evidence on the hunting of rhinoceros (which inhabits humid regions) in the Indus Valley by the Mugals as late as in 1519. At present, however, the prevailing climatic as well as the habitat conditions in this desert can only support predominantly xerophile and xerobiont fauna. Inspite of the interesting zoogeographical and evolutionary importance of the Indian Desert, adequate attention has not been paid so far to the zoology of the region. For instance, the Mammal Survey of India, Burma and Ceylon, conducted by the Bombay Natural History Society, did not include the Indian Desert. Realizing this lacuna in our knowledge of the fauna of the Indian desert, Dr. DAYA KRISHNA, formerly Professor of Zoology at the Jaswant College, Jodhpur, moved the UNESCO to finance a project on the ‘Ecological studies of vertebrates of the Indian Desert’. The author had the privilege to be associated with it from 1953 to 1955. These ecological studies were carried out mainly on reptiles and mammals and their findings were incorporated in university dissertations (DAVE, 1961; PRAKASH, 1957).

Rodents constitute one of the largest mammalian groups in the Rajasthan desert, India, both in total number and in the number of species represented. They exhibit a great plasticity in respect of their choice of a wide spectrum of desert habitats and their impact on the desert ecosystems is all too prominent. The rodents’ role in the intensification of desertic conditions may be comprehended from the fact that a single species, viz. Meriones hurrianae***, is able to excavate about 61,400 kg of stabilised soil per km2 per day during summer and deposit it outside its burrow openings in a loose formation. This dug-up soil is easily blown away by the strong desert winds. The rodents, thus, are a prime biotic factor for soil erosion. Their impact on the desert vegetation as a result of their gnawing, debarking, cutting and feeding propensities is easily discernible throughout the tract. In the desert region, orchards, crop fields and rangelands cannot attain their optimum productivity without a rodent control programme. The rodents are, therefore, regarded to be the most potent enemies of man in the desert in his endeavours for maximizing output from this inhospitable terrain. In view of the considerable economic importance of a large number of desert vertebrates, and especially rodents, a study was initiated in the Rajasthan desert in 1953 with financial assistance of the Unesco***. Later on, in 1959, the Central Arid Zone Research Institute at Jodhpur provided a small cell of workers to study the ecology of the rodents and to devise means of their control in the Rajasthan desert. A brief review of our work on the population structure of rodents, their ecological distribution, home ranges, food, predators and reproduction aspects has been presented here. The control aspects of our work have been deliberately left out of this review.

I. The Desert as a Habitat.- Distribution.- Soils.- Climate.- Vegetation.- References.- II. The Ecology of Rodents in the northern Sudan.- Desert Species.- Jebel Species.- Riverine Species.- Commensal Species.- Reproduction.- Other Adaptations for Life in the Desert.- Discussion.- Acknowledgements.- References.- III. The Rodents of the Iranian Deserts.- The Rodents: northern and southern Types.- Annual Rhythm.- Population Densities.- Some Peculiarities.- References.- IV. Comparative Ecological Notes on Afghan Rodents.- Results.- Discussion.- Summary.- References.- V. The Population Ecology of the Rodents of the Rajasthan Desert, India.- Population Structure.- Ranges of Movements.- Food.- Predator-Prey Relationship.- Breeding Season and Litter Size.- References.- VI. Outbreaks of Rodents in Semi-Arid and Arid Australia: Causes, Preventions, and Evolutionary Considerations.- Climates in Central Australia.- The Study-Area: Habitats and Rodents.- Populations.- Conclusions and Discussion.- Acknowledgements.- References.- VII Observations of Argentine Desert Rodent Ecology, with Emphasis on Water Relations of Eligmodontia typus.- The Argentine Monte and some of its Rodents.- Methods and Materials.- Results and Discussion.- Acknowledgements.- References.- VIII. La diversite des Gerbillides.- IX. Some Observations on Ecological Adaptations of Desert Rodents and Suggestions for further Research work.- The Desert Environment.- Ecological Adaptations.- Need for further Research.- References.- X. The Behavior Patterns of Desert Rodents.- The Evolution of Desert Adaptations.- A Comparison of Behavior Patterns.- A Comparison of Behavior Patterns in : Meriones, Gerbillus and Perognathus.- Spacing and Communication.- Acknowledgements.- References.- XI Activity Patterns of a Desert Rodent.- Methods.- The Microdosimeter and the Index of Activity.- Variation in Activity.- Climatological Variables and Animal Activity.- Analysis.- Discussion.- Summary.- References.- XII. Patterns of Food, Space and Diversity.- Resource Allocation by Seed Selection.- Habitat Selection in Space.- The Pattern of Local Species Diversity.- Acknowledgements.- References.- XIII. Desert Coloration in Rodents.- Desert Coloration.- Acknowledgements.- References.- XIV. The Biology of some Desert-Dwelling Ground Squirrels.- Reproduction.- Food Habits.- Population Characteristics.- Habitat Factors.- References.- XV. Reproductive Biology of North American Desert Rodents.- Reproductive Biology: Species Summaries.- References.- XVI. Rodent Faunas and Environmental Changes in the Pleistocene of Israel.- The Main Biogeographical Changes in the Near-East since the Miocene.- The Composition of the Rodents Faunas in the Pleistocene of Israel.- The Main Ecological Changes in the Quarternary of Israel.- Analysis of the Main Habitats Occupied by the Pleistocene Rodents of Israel.- Note on the Origin of the Israeli Desert Rodents.- References.- XVII. Prehistoric Rodents of the Middle East.- Prehistoric Rodents.- Discussion.- Acknowledgements.- References.- Addenda.- XVIII. Desert Rodents : Physiological Problems of Desert Life.- Problems of Temperature Regulation.- Water Balance, Intake and Loss.- References.- XIX. Ecophysiology of Water and Energy in Desert Marsupials and Rodents.- Methods.- Ecophysiology of Water and Energy.- Discussion.- References.- XX. Thermo-Regulation and Water Economy in Indian Desert Rodents.- Methods.- Thermo-Regulation.- Water Economy.- Conclusion.- References.- XXI. The Physiological Adaptations of Desert Rodents.- Water Conservation in Desert Rodents.- Structure and Concentrating Mechanisms in the Desert Rodent Kidney.- Tolerance to Heat and Thermo-Regulation of Desert Rodents.- Reproduction in Desert Rodents.- References.- XXII. Nematode Parasites of the Indian Desert Rodents.- Material and Methods.- Nematode Parasites of the Indian Desert Rodents.- Discussion.- References.- XXIII. Ecology of the Desert Rodents of the U.S.S.R. (Jerboas and Gerbils).- Jerboas.- Gerbils.- References.- Author Index.- Genus and Species Index.

SUMMARY Two rodents, Tatera indica indica Hardwicke and Meriones hurrianae Jerdon, developed aversion to zinc phosphide after one day's exposure to a sublethal dose. The poison shyness persisted for at least 115 and 35 days, respectively.