Chapter- III Terrain, Soil Characteristics and Forest Types in the Study Area

Transcription

1 3.1 Terrain characteristics Chapter- III Terrain, Soil Characteristics and Forest Types in the Study Area Relief of any area plays a significant role in overall set up and designing hydrological make up of the area. Several aspects like altitude, slope, relative relief, absolute relief and dissection index are important to understand the actual picture and reality of the surface under investigation Altitude wise distribution of study area Altitude wise distribution of the study area with the help of specific contour interval has been computed and shown in table no 3.1. For this exercise, toposheets of the study area on 1:50,000 scale, at an interval of 100 m, are digitized with maximum accuracy. Altitudinal variation in the study area is noticed to range between to 1307 m ASL. It can be noticed that maximum study area lies below the 1100 m above MSL and it is admeasured to be km 2 i.e % of the study area. The area starts to steadily decrease after 1000 m contour and it is almost negligible up to 1300 m. Fig. 3.1 Altitude wise distribution of study area Absolute relief It is maximum elevation in a particular unit area, which provides an idea about the distribution and magnitude of relief over the surface in the study area (Fig 3.2). It can be clearly observed that, in the study area highest elevation lies towards the northern and southern edges and ridge lines and it gradually decreases towards the 44

2 KHADAKWASALA IRRIGATION PROJECT DIVISION ABSOLUTE RELIEF MAP 45 Fig 3.2

3 KHADAKWASALA IRRIGATION PROJECT DIVISION RELATIVE RELIEF MAP 46 Fig 3.3

4 KHADAKWASALA IRRIGATION PROJECT DIVISION DISSECTION INDEX MAP 47 (In %) Fig 3.4

5 valley. The range in variation is 626 to 1131m and the highest range is observed up to the m Relative relief Relative relief is also termed as amplitude of available relief or local relief and it can be defined as the difference in height between the highest and the lowest elevations or heights in a unit area. It is very important morphometric variable which is used for the overall assessment of morphological characteristics of terrain and degree of dissection (Fig. 3.3). In the selected study area values of relative relief are ranging from 46 to 422 m. The highest relative relief is 422 and it lies in south east and western part of the study area. These regions are well marked by ridge lines. Low relative relief however noted in the valleys of the study area Dissection index Dissection index express a ratio of the maximum relative relief to the maximum absolute relief. It is an important morphometric indicator of the nature and magnitude of dissection of terrain. Dov Nir (1957) has suggested the formula for the derivation of dissection index- DI= R R /A R, where R R is relative relief and A R is absolute relief (Fig 3.4). Percentage of dissection is ranging from the 5% to 57% and it can be observed that, western parts of study area is highly dissected as compare to the eastern parts. Very high dissected areas i.e. above 27% dissection is observed in western parts. Ridges of the entire study areas also show high dissection Slope Slope is defined as angular inclinations of terrain between hill tops (crest) and the valley bottoms. It results from the combinations of many causative factors like geological structure, climate vegetation cover, drainage texture and density, dissection index, relative reliefs and of course denudational processes. Slope of any area directly give the geomorphic impression of the terrain slopes which are significant morphometric attributes in the study of landforms of a drainage basin (Singh S. 1998). It plays a vital role in the life cycle of a landscape. It determines the drainage pattern and account for the transformation of terrain and thereby influence the flora and fauna of the land. Slope map of the study area has been prepared using GIS software Arc GIS 9.3. (Fig 3.5). The entire study area forms the parts of Sahyadri, characterized by hilly terrain, hence slope range is high and it 48

6 Khadakwasala Irrigation Project Division SLOPE MAP (%) 49 Fig 3.5

7 ranges between 0 to 57. Steep slope is observed towards the ridge line and decreases towards the valley bottom Transverse profiles A profile of relief is a visual aid in its description and interpretation. Hence it is of particular interest for Geomorphologists, who is engaged in the analysis of landforms and their processes of aggradation and degradation. In the present study a series of profiles at an interval of 1 from east to west direction has been prepared using DEM procured from ASTER GDEM data (Fig 3.6). Overall 21 profiles have been considered in the present analysis. These profiles clearly depict the variation in land surface, undulating nature of the study area and also visualize the variation in topography (Fig 3.7a & 3.7b). Profiles also indicate abrupt and sharp breaks in altitude particularly in western parts of the study area. It can be observed from the set of profiles that entire area exhibits a mountainous topography. The pediment spread in foothills showing extensive appearance. The summit surfaces in the study area can be identified along marginal areas of the catchments, whereas plateau fringe surfaces shows marked steep sided slopes Aspect map Aspect is usually defined as azimuth, which is a horizontal angle expressed in degrees included between geographic north and slope. Aspect distributes the incident sunlight. Depending on the orientation of the earth surface in respect of the cardinal points and slope energy and moisture is redistributed, which generates wide range of processes and affects their course and duration. Flat areas and valley depth have no aspect as they receives very small amount of incident sunlight. It is also possible to apply appropriate colors according to the cartographic and environmental standards of the study area under consideration (Fig 3.8). 3.2 Soil characteristics Acquisition of basic inventory data is fundamental to forests resource management and has utmost important in conservation planning. Data including soil type, soil texture, soil drainage, soil depth, as well as parameters of vegetation like size, class, structure, crown closure, density etc are very significant. Data collection techniques for forest inventories range from selecting sample plots for ground surveys to using topographical maps, remote sensing techniques and Global positioning 50

8 KHADAKWASALA IRRIGATION PROJECT DIVISION KHADAKWASALA IRRIGATION PROJECT DIVISION TRANSVERSE PROFILE (DEM) SLOPE MAP 51 Fig 3.5 Fig 3.6

9 P1 KHADAKWASALA IRRIGATION PROJECT DIVISION TRANSVERSE PROFILE P7 P2 P8 P3 P9 52 P4 P5 P6 P10 P11 P12 Fig 3.7(a)

10 P13 KHADAKWASALA IRRIGATION PROJECT DIVISION TRANSVERSE PROFILE P18 P14 P19 P15 P20 53 P16 P17 P21 Fig 3.7(b)

11 KHADAKWASALA IRRIGATION PROJECT DIVISION ASPECT MAP 54 Fig 3.8

12 systems. In the present study all these methods have been used in forests inventory as they are interrelated to each other. Soil plays a significant role in determination of vegetation type and pattern of any area and vice versa. Soil is more or less loose and crumby part of the earth crust in which, by means of their roots, plant may or do find foot hold and nourishment as well all other conditions essential to their growth (Hilgard E.W. 1906). Soils are the product of chemical, physical and biochemical processes which act upon the earth s material under various climatic conditions. Local climatic conditions, topography and vegetation are fundamental factors due to which soils differ in color, texture and depth from region to region. Black soils, laterite and lateritic soils, saline-alkali soils, mixed red and black soil are some of the common soil type found in the district of Pune. On the basis of rainfall, geographical conditions and land type, agriculture department has divided Maharashtra into nine agro-climatic zones. Most of the part of study area falls in the group IV and that is transition zone (TR-1), where rainfall is comparatively high and basalt is found. Data related to soil type is collected from the district soil survey and soil testing department, Agriculture department, Pune Soil texture Soil texture is determined by identifying the proportions of the sand, silt, clay and organic matter. Soil texture usually depends on the type of bedrock, climatic condition and denudation processes. In the western part of Pune district, two distinct types of soil are observed: red to reddish brown, silty soils (alfisols) and black clayey soils (vertisols). The basalt forms the bed rock to both types of soils. The alfisols represents high alumina and iron content. Majority of the soils in the study area is covered by gravelly sandy loam which is % followed by clayey soils and it is about 29.25% (Fig 3.9 & 3.11). Gravelly sandy clay loam occupies km 2 (12.40 %), of the total surface area, where as clay loam and gravelly clay covers km 2 (8.83 %) and 17.5 km 2 (3.87%) of the surface area respectively. High proportion of clayey and clay loam soil is found around the reservoirs. 55

13 KHADAKWASALA IRRIGATION PROJECT DIVISION SOIL TEXTURE MAP 56 Source Soil survey department, Pune Fig 3.9

14 KHADAKWASALA IRRIGATION PROJECT DIVISION SOIL DEPTH MAP 57 Source : Soil survey department, Pune (Depth in cm) Fig 3.10

15 Fig Area under soil texture classes Soil depth Depth of the soils varies greatly in the study area from very shallow to very deep. Altitudinal variation, slope and soil depth shows positive relationship in terms of soil depth. Around km 2 (57.41 %) of the total surface area has shallow to very shallow depth, followed by km 2 (22.61 %) as moderately deep and 4.30% as very deep. Area under deep soil is only 1.09 km 2 (0.24 %) and very shallow soil depth covers km 2 (3.82 %) of the total surface area. Fig Area under soil depth 58

16 Basaltic ridges in the study area show very thin soil cover. In the plains the soil covers and soil depth is quite consistent and thick. Heavy rains in the valley induce soil erosion, especially in parts of where vegetation has been removed from the slopes. (Fig 3.10 & 3.12) 3.3 Forest types in the study area It is of great importance that area should have 33% of its geographical area under forest because of the significant role forests play in the global carbon cycle, in global climatic trends, and in providing species habitat (woodwell et al. 1984). The forest Survey of India (FSI) is a premier national forest resources survey organization in India. It is functioning from June 1, 1981 and its headquarters at Dehradun. FSI is working under the Union Ministry of Environment and Forests. According to the latest report of the FSI 2011, out of the km 2 of the geographical area, Pune district has 1,732 km 2 area under forests cover. It is 11.07% to the total geographical area of the district. Whereas according to a statistical outline, current salient forest statistics 2011 Pune circle and Pune district has 2311 km 2 and 2080 km 2 area respectively under forest. The plants in the forest area can be divided into Trees, shrubs, climbers and herbs. According to the revised classification of Indian forests types given by Champion and Seth following forest types exist in the study area Western sub-tropical hill forests (3A/C2) This type of forests mainly occurs in the heavy rainfall tract in the west, occupying the higher elevations from 650 to 1350 meters of the Sahyadri. Where interference of cattle and man is minimum a true evergreen nature particularly in Devrais (or sacred groves) is observed. In the present study area villages like Dhamanohol, Bhoini, Admal, Tav, Dapsare, Gondekhal, Gholapghar etc are have Devrais. Although the area under these devrais is very low but these areas still maintained good vegetation status. Terminalia tomentosa (Ain), Hardwickia binata (Anjan), Mangifera indica (Amba), Terminalia belerica (Beheda), Schyziggium cuminii (Jambhol), Lasiosophon eriocephslus (Rametha), Carvia callosa (Karvi) etc are the common plants found in this type Southern moist mixed deciduous forests (3B/C2) This type of forests occurs in a narrow belt along the lower slopes of Sahydri range mainly in Bahuli, Agllambe, Katvadi, Donje, and around the Sinhgad fort. In 59

17 these regions rainfall is between 150 to 200 cm. Previously teak was occasionally found but now due to the afforestation programmes taken by the forests department it is found predominantly. Terminalia tomentosa (Ain), Mangifera indica (Amba),, Carissa carands (Karwand), Carvia callosa (Karvi) and Lantana Camera (Ghaneri) are also found in few patches Southern dry deciduous forests (5A/C3) The dry deciduous forests type covers the broad central region. Due to the gradual but continual deterioration in the edaphic site factors along with unauthorized hacking of sag and other tress vegetation cover has been mostly annihilated. Tectona grandis (Sag), Aegle marmelo (Bel), Semecarpus anacardium (Biba) Grewia tillaefolia (Dhaman), Acacia catechu (Khiar), Buhinia racemosa (Apta), Bamboo Cassia tora (Tarota) and Andropogon sepiaria (Dongri gavat) are some of the common species found in this zone Southern thorn forests (6A/C1) These types of forests are found in all isolated blanks which are surrounded by villages and subjected to excessive grazing, mainly characterized by dry conditions of eastern region. Sparse stunted growth of Azadirachta indica, (Neem) Acacia arabica (Babul), Zizyphus jujuba (Bor), Vitex negundo (Nirgudi), are common species. Thin sparse growth of grasses during the moist season can be observed. Otherwise most of the area is barren Babul forests (5/E3) This type of forests is now rarely seen in the entire study area. It was previously observed along the banks of the rivers and streams as well as on the barren hill slopes. Many areas of these valuable babul species are now replaced by Prosopis juliflora (Villayati babul), which has invaded into the valuable babul forests. Acacia arabica (Babul), Azadirachta indica, (Neem), Pongamia glabra (Karanj), Prosopis juliflora (Villayati babul), etc are common species found in this zone. Very low area under this forests type in western part of the study area is observed and Terminalia tomentosa (Ain) Terminalia chebula (Hirda) are some of the common trees. Anogeissus latifolia (Dhavda), Teak belongs to the deciduous types where as Acacia arabica (babhul), Zizyphus jujube (Bor) are the scrub forest. 60

18 3.4 Legal estimation of forest cover The area selected for the present research work is one of the micro watersheds in upper Bhima basin. It covers an area of km 2 geographical area including about 83 small villages. Entire area falls under the Pune circle forest division of Pune district. Pune district includes Pune and Junnar division and Bhor subdivision. (Table 3.1) A forest area in the selected research area comes under the Pune division and Bhor subdivision. According to working plan ( ), legally total forest under Pune division and Bhor subdivision was and km 2 respectively, which includes reserved, protected and unclassed forest. Table 3.1 : Taluka wise classification of forest Classification of Forests area District Taluka Reserved Protected Un classed Forest Forest forests Total Pune Mulshi Haveli Velhe Total Source : Forest working plan, Pune ( ) The forests in India are managed under the direct control of the governments of states and union territories, but the central governments have the sole discretion and jurisdictional powers. Three National Forests Policies (1894, 1952 and 1988) have been formulated. These policies have classified Indian forests as Protection forests, national Forests, Village forests and Tree forests. In India forests area are also classified as functional, legal, territorial, and management forests areas. Functional classification includes production and protection of minor forests and grazing lands while legal classification includes four well known forests areas namely reserved forests, Village forests, protected forests and unclassed forests. Reserved forests are exclusively property of government and it is constituted under the section 20 of Indian Forests Act 1927 (IFA). Although these forests areas are completely protected, villagers sometimes granted to collect their basic livelihoods from these areas. Village forests, constituted under section 28 of IFA 1927, are the government s forests which are assigned to village community for a supply of forests produce to a village. Protected forests constituted under section 29 of 61

19 IFA and are subjected to limited degree of protection. On the other hand unclassed forests are excessively grazed, felled, and burnt. Territorial forests area broadly includes Block, Compartment and sub compartment. A block is main territorial division bounded by all sides with numbered pillars. Block is divided into number of compartment (Rao Y.L.P). These forests are used for purpose of administration and record. Sub compartment is small division of a compartment, generally of temporary nature. 3.5 Terrain-soil and vegetation cover relationship With the growing concerns over changes of the living and ecological environment, more and more thrust has been shifted now on understanding terrain soil and vegetation cover complex. Slope of terrain and soil properties together make an impact on types, composition and density of vegetation cover in an area. Slope and soil characteristics are the result of contemporary geomorphic processes. In the study area, it is observed that, physical determinants have pronoumed effect on soil environment and thereby vegetation type and cover. Toposequence soil environment exist in the study area. This has certainly affected biodiversity of the area in general and flora in particular. 62