CHAPTER 1 INTRODUCTION CHAPTER 1 Introduction The Western region of India is one of the World’s hottest biodiversity hotspots (M^ittmeier, 1998, 2004). It mainly comprises mountain passes locally called ‘Ghats’ 'I or ‘Bari’ (Mahabale, 1987). The Western Ghats (WG) is also known as ‘Sahyadri Mountains’, a range all along the ‘Western Side’ of India. It consists of flat topped mountains, valleys, ravines, knolls, scre^etc. The region is bounded by the ‘Arabian Sea’ on the west (Bawa et al, 2007; Map 1.2). The Western Ghats of Maharashtra (WGM) lies between 72° 61’ to 74° 40’E and 15° 60’ to 20° 75’ N covering about 52,000 km. area from Daman to Terekhol creek (Gogate and Jagtap, 1997; Bawa, 2007). The WGM varies in altitude from 20m to 2000m above sea level. The North-South stretch of Western Ghats is about 750 km. and average breadth is of 80 km. The range starts near the border of Gujarat and Maharashtra states, south of the river Tapi, and runs approximately 1600 km through the states of Maharashtra, Goa, Karnataka, Tamilnadu and Kerala ending at Kanyakumari covering an area of about 180,000 km^. Maharashtra state is essentially a part of Western India. The state covers a larger part of Indian Peninsula, lying between the latitude 22° 1’ to 16° 4’ N and longimde 72° 6’ to 80° 9’ E. It is about 800 km east- west and 700 km north-south forming an irregular dentate pentagon. It covers an area of 3,07690 sq. km. The state is bounded on the west by the Arabian Sea, making a long coast line of about 720 km on the north-west by Gujarat, on the north by Madhya Pradesh, on the south-east by Andhra Pradesh and on the south by Karnataka and Goa (Map 1.1). The major hill range starting from the north is Sahyadri (Benevolent Mountains), and the southern part of the western India is Sahya Parvatam in Kerala (Mahabale, 1987). The northern portion of the narrow coastal strip between the Western Ghats and Arabian Sea is known as ‘Konkan coast’ or ‘Konkan’; the central portion is called ‘Kanara’ and the southern portion is called ‘Malabar coast’. The foothill region, east of Ghats in Maharashtra state is known as ‘Desh’ which merges into the Deccan plains or plateau towards eastern side of Maharashtra. “Konkan” is to the west side of the Sahyadris, varies between 27-48 kms in breadth and 800 km in length from Goa to Tapi basin. The average height of this region is 6m-9m MSL. Page I 1 ‘Desh" plateau rises by the stages from 335m-366m and 366m-610m at different Map 1.1: Western Ghats of India t ' T N b' J A ANCjHRA Ar.-rsH V i f f - r~\ \ fCXJ Ohat« Srt larta Hot^pol LANKA ?- ■■ S(ii9 fkxKKtenes -I—"' . , i. Ji'- places but the major part of Maharashtra is only 91m-183m high on Desh side. The highest peaks of the Sahyadri lie near its main axis forming water-shade between Desh and Konkan. The altitude drops suddenly to 122m on Konkan side and then almost to the sea level. Two conspicuous features in Sahyadri are the mountain passes- locally called ‘Ghats' or ‘Bari’ and the hill forts built all along the line of Sahyadri. These ghats are often quite narrow and lead from plains at lower altitude to higher mountain plateau and vice-versa (Mishra and Singh, 2001). Very often rivers, brooks, or small streams follow zigzag path by their side and open into a low altitude basin of a river in the valley. Such valleys are well protected by two mountain spurs running parallel and are fed by mountain streams. They are called 'Mavals’ which are Page I 2 Map 1.2: Study area and locations of all the forts under study I ' ; ..... "A Mahimangad more in number in Western Maharashtra. The forts are constructed at such peculiar locations on the spurs. The spurs of the forts provide unique climate and locations for plants to grow. A single fort may form 2-3 Mavals due to spurs. Most of the Mavals are situated on the eastern part of the Western Ghats of Maharashtra (WGM). They are different from the surrounding areas. Their climate and flora are different and resemble like the ‘Sholas’ in the Nilgiris in S. India (Jagtap and Singh, 2000). Forts constitute vegetation pockets of considerable interest being well protected uplands and isolated from the rest of the surrounding areas. Thus, Sahyadri has a great diversity in geomorphological forms, varying from place to place which produce distinct climatic zones separated from each other by mountain barriers and has different vegetation. The WGM region traverses 11 districts which include Thane, Raigad, Ratnagiri, Sindhudurg, Dhule, Nashik, Ahmednagar, Pune, Satara, Sangli and Kolhapur (Singh & Karthikeyan, 2000). Topographically western Maharashtra can be divided in to three parts namely Konkan, Desh Region or Mountain Sahyadri and Deccan Plain or Plateau. Konkan region covers Raigad, Ratnagiri and Sindhudurg districts which can be further divided in to three parts, namely, 1) Coastal region: consisting of creeks, inlets, river deltas and islands; 2) Alluvial plains: narrow strips of land between coastal region and adjoining hills towards the east; and 3) Low lying hills: originating from the great scarp of Sahyadri hills. The crest of Sahyadri and its ranges towards west, spread in Pune, Nashik, Satara, Sangli and Kolhapur districts. The Sahyadri region consists of great scarp towards west incorporating plateaus and conical hill tops. Average altitude of the crest line is 1400m dotted with lofty mountain peaks like Kalasubai (1646 m; Lakshminarasimhan & Sharma, 1991), Harischandragad (1410 m; Billore & Hemadri, 1972) and Mahabaleshwar (1438 m; Deshpande, 1993 & 1995). Sahyadri mountain range in Maharashtra state is significant because of the construction of many ‘Durg’, nowadays called ‘forts’. The forts are constructed especially on mountain peaks, hilly regions or even in Arbian Sea and near seashore. Most of these forts were constructed before 15* century to rule ‘Mavals’ ana surrounding areas (Anno., 1883; Hunter 1886; Toy, 1965; Radhe Shyam, 1966; Naire and Alexander, 1988; Dubey, 1993; Naravane, 1995, 2003; Dele and Ramchandani, 2000; Kapadia 2003; Sitaramam et al, 2009). Page 1 3 Geology The rock formation in WGM is basaltic - trap capped with laterite which gives rise to red loamy porous acidic soil. The basal trap is made up of basaltic lava (Mahabale, 1987). It has step like appearance due to peculiar mode of weathering of trap rocks. However, small southern portion of Ratnagiri, Sindhudurg and Goa, the territory remains outside the trap region and incorporates detritus laterites. Among these are few pockets of archaic rocks rich in iron and manganese ore. This difference in the geology of South Konkan plays an important role in deciding its vegetation pattern (Vartak, 1983). Soil The soil in WGM is mainly derived from the Deccan Traps, generally from augite or amygdaldial basalt. These soils are black, dark brown or reddish in colour, and hence are called Black Cotton soil or ‘Regur’ soils meaning thereby red soils (Mishra and Singh, 2001). Black Cotton soil has a high percentage of clay and is heavy in texture. It contains adequate mineral nutrients and provides good habitat for plants. In Desh region, two types of soils are observed, namely, light brown soil is in Mavals and deep coloured soil on low gradients occurs in Kolhapur, Satara, Pune and Nashik. In these regions below the black soil, there is generally coarse powdered sedimentary rock which is called ‘Murum’ mixed sometimes with lime or ‘Kankar’ or salt or salinized lime and gypsum (Mahabale, 1987; Mishra and Singh, 2001). Climate The climate of Maharashtra is monsoonal. It is controlled Arabian sea by its cooling effect and by Sahyadri Mountains by its altitude. The year is divided in to 4 main seasons. The winter season is from December to February, summer season from March to May, monsoon season from June to September and post monsoon season from October to November. The main form of precipitation in Maharashtra is the monsoon (Mishra and Singh, 2001). Rainfall The total annual rainfall in WGM varies widely with an average of about 200 cm to 600 cm or even more in the hills along higher elevation. Over 90% of the rainfall is due to Southern-Wes tern Monsoon and is received during the four months from June to September. Only 5% is received in October from North-East retreating monsoon and rest from the sporadic thunder storms during summer. Transition towards eastern plains is marked by a ‘Rain Shadow’ belt of abruptly decreasing rainfall gradient (Reports of Metrological Department 1930-1960). Humidity Over the coast, humidity is generally high. During June to October, it is more than 80% and least during winter afternoon and may drop down up to 60% at most places. Temperature Temperature in WGM varies according to the seasons. In the coastal area, temperature mainly controlled by sea breezes and it ranges from 17°C to 28°C during winter and from 20°C to 35°C during summer. Along the crests of the Ghats, the climate is cooler than the plains. In winter, temperature ranges from 15°C to 20°C and in summer 18°C to 30°C. Along the eastern plains, temperature is moderate during winter and summer. At some places it often exceeds 40°C. Vegetation in Western Maharashtra The floristic pattern of Western Maharashtra differs greatly due to factors like rainfall, temperature, humidity, type of soil and topography. There are six major forest types in Western Maharashtra, namely, Tropical semi-evergreen, Tropical moist deciduous.