B. K. Subba Rao , Laxmi Rawat

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The paper reviews the recent research advances in forest microclimatology in India. Most of tbe studies have been carried out in forest plantations at F.R.I., Dehra Dun and natural sal forests nearby. Salient results of the studies have been brought out.

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T. C. Pokhriyal , B. K. Subba Rao

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The role of forest in soil and water conservation is well recognised. This paper examines the role of forests from a new point of view viz. in mitigating air pollution. A list oC pollution tolerant free specics has also been given.

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A. S. Raturi , B. K. Subba Rao

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no abstract

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B. K. Subba Rao , B. C. Ramola , V. N. Sharda

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The paper deals with the effect of thinning (20%) on peak flow and fort-nightly runoff in a forested mountainous watershed near Dehra Dun, U.P. India. It has been found that the peak rate of flow increased by 8.6% in the first year (significant at 5% level) but the effect was insignificant in the second year after thinning. There was no significant effect on the total volume of fort-nightly runoff either in the first year or in the second year after thinning.

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R. C. Ghosh , B. K. Subba Rao , B. C. Ramola

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This paper presents the results of interception studies carried out during 1977 in coppice sal forest at Rajput Forest Experiment Station, (Rajpur Forest Block, West Dehra Dun Division) to evaluate the effect of thinning on the interception loss. This study is one of a series of hydrological studies that are being carried out at Forest Research Institute, Dehra Dun. It is proposed develop mathematical models by using the results of these studies, to predict hydrological behaviour of forested watersheds. These models also enable us to predict the effect of management operations and biotic influences on the hydrological behaviour. Present study has shown that the interception loss decreases with increasing amount of rainfall and that a reduction of crown density by 22% has resulted in a reduction of interception by 5% in coppice sal forest. Also, it has been observed that interception loss depends upon rainfall and vegetation characteristics.

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R. C. Ghosh , O. N. Kaul , B. K. Subba Rao

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This is a brief survey of the information available on the effects of Eucalytpus plantations with particular reference to water relation and soil nutrition. It appears that their benificial effects out-weigh any possible adverse effects and the complaints regarding the adverse effects of Eucalyptus plantations on water supply is rather exaggerated.

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I. M. Qureshi , J. S. P. Yadav , B. K. Subba Rao , B. G. Dabral

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Soil and water constitute by far the two most valuable natural resources and need to be protected from every loss. The various factors like inadequate vegetative cover, indiscriminate deforestation, excessive grazing, faulty cultivation, unsound agronomical practices, burning, defective land use, and neglect of soil conservation in the catchment areas of many rivers cause severe floods and run-off which result in tremendous damage. Excessive run-off whether it results in floods or not is by itself a wasteful phenomenon involving loss of both soil and utilisable water yield. The water balance of a watershed involving the various losses and gains has been explained. The importance of infiltration, percolation and storage capacity of the soil in governing the surface flow, sub-surface flow and base flow of precipitation has been dealt with. An account has been given of the effect of various soil characteristics on infiltration, percolation and storage capacity as well as water movement and hydrology of a given area. The harmful effects of burning, grazing and other faulty practices on the soil properties and hydrological conditions of a tract have been described. Important features of some common soil groups found in India having a bearing on their moisture relations have been mentioned. The value of soil moisture studies in understanding the water balance and in deciding suitable management practices to prevent floods and run-off has been emphasized. The effect of different vegetative covers on the soil properties, water movement and storage, interception, evapotranspiration, water yield, intensity of run-off and floods and such other aspects which are fundamental to the hydrological cycle of watersheds has been elucidated. The importance of the quality of water yield has been emphasized and has been correlated with the vegetative cover and with soil conditions. The beneficial role of the maintenance of a suitable vegetative cover in the control and prevention of floods has been examined. The protective and ameliorative functions of forests on steep slopes and undulating lands which are highly susceptible to quick run-off and easy soil wash have been emphasized. It has been stated that there is scarcity of scientific data on many such aspects in India. In view of the magnitude and complexity of the problem of run-off and floods the urgent necessity for a correct assessment of the exact requirements of each watershed in the light of varying climatic, edaphic and biotic conditions has been stressed so as to evolve most suitable management practices. An integrated approach to the study of hydro-meteorological elements with the cooperation of different research and administrative organisations in the country has been proposed.

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I. M. Qureshi , B. K. Subba Rao , B. G. Dabral

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A study towards establishing the rdationship of frost deposition and the prevailing metrorological phenomena in open and sal cover conditions (2 to 600 cm height) during the cold spell of 1963-64, was made at NoW Forest. In the open it was observed that lower minimum temperatures and vapour pressure followed the frosty nights. Mulches were conducive in inducing frost depcsiticn. No frost deposition occurred under sal cover. Although frost caused damage to the standing vegetation, the established shrubs, poles and trees got reclothed with foliage on the return of favourable weather. As frost occurence is a microclimatic phenomenon, it is suggested that the microclimatic effects produced by the forestry operations in vogue be studied in detail and factual scientific data be collected.

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B. G. Dabral , B. K. Subba Rao

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The paper presents the results of studies made on stemflow, throughfall and interception losses in a chir and teak plantation at Forest Research Institute Reserve Forest. It was seen that chir pine conducted 3.6, 74.3 and 22.1 per cent of gross rainfall as stemflow, throughfall and interception losses respectively for rainfall groups up to 2". The corresponding figures for all rainfall groups considered together were 8.8,69.7 and 27.0 per cent of gross rainfall. In teak 6.0, 73.2 and 20.8 per cent and 7.1, 64.1 and 28.8 per cent of rainfall were conducted as stemflow, throughfall and interception losses in respect of all rainfall groups combined together and for 0"-2" rainfall groups respectively. Since maximum number of trees in chir plantation fell within the diameter range 7.6 mm to 22.9 mm (3" to 9") it may be assumed that stemflow and interception losses ranged between 2 to 3.9 and 22-24% respectively of the total rainfall. The corresponding figures in respect of the teak plantation, where maximum. Number of trees were within diameter range of 15.2 mm to 30.5 mm (6" to 12") were 2.5 to 7.9 and 18:9 to 24.4 per cent of the total rainfall

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B. G. Dabral , B. K. Subba Rao

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The paper presents results of interception studies conducted in sal and khair plantations raised at this Institute. It is seen that sal conducted 7.2, 54.6 and 88.2 percent of rainfall and khair 4.2, 67.8 and 28.5 percent of rainfall as stemflow, through-fall and interception, respectively Maximum number of trees ranged between 17.8 cm to 30.5 cm diameter class in sal and the stemflow, through-fall and interception ranged between 5-10%, 48-58% and 35-40% of rainfall respectively. In khair masimum number of trees were in 10.2 to 20.8 cm diameter range and the corresponding values of stemflow, through-fall and interception were between 2.5-7.0, 64-67 and 27-82% of rainfall respectively. The results are applicable to a dense canopied stand in which maximum interception may take place.

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B. G. Dabral , B. K. Subba Rao , I. M. Qureshi

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A preliminary study of the extremes of weather elements, (temperature and humidity) inside the forest plantations of chir (Pinus roxburghii) and bamboo (Dendrocalamus strictus) has been made, observations being made at different heights from ground surface to five feet. It was observed that both the air temperature and humidity were modified by the sheltering as well as the blanketing effects of vegetation cover. It was also observed that fair weather conditions induced the maximum differences in the temperature behaviour.

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B. K. Subba Rao , A. N. Chaturvedi

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Several relationships between the foliage weight (oven dry) and other tree dimensions have been developed based on the actual measurementl of various parameters during the clearfelling of 22 years old sal coppice crop. Best relationship was found between the square ischolar_main of foliage weight and the d.b.h.

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B. K. Subba Rao , B. G. Dabral , B. C. Ramola

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Regular hydrological studies are in progress since 1967 in the two experimental watersheds in the hill sal coppice forest of Rajpur Forest Block in the Debra Dun Forest Division. This paper presents the preliminary observations on runoff, sediment discharge and guality of water, made in one of the experimental watersheds (watershed No. 1) during 1967-70. It has been observed that the water flowing out is of high purity, pH was 7, tending to be slightly acidic. Among the dissolved chemicals CaO ranged highest. The total silt washed out during the monsoon months varied from 49 to 153 tonnes/km².

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