Geographical location and climatic condition of the study sites North eastern region of India is comprised of eight states namely; Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim and Tripura. It is one among the Indo-Burma biodiversity hotspots; situated at the confluence of the Indo-Malayan, Indo-Chinese and Indian biogeographical realms, the north east India is unique in providing a profusion of habitats, which features diverse biota with a high level of endemism. These states have predominantly humid sub-tropical climate with hot, humid summer, severe monsoon and mild winter. The North eastern region has distinct climatic variation (Maheswaran, 2012). Arunachal Pradesh Arunachal Pradesh (26º40-29º27 north and 91º35-97º24 east) is the land of the dawnlit mountains. Its three sides are surrounded by the International border Bhutan to the west, China to the north and Myanmar to the east. The weather and the climate of Arunachal Pradesh are quite unique from the rest of India. The climate of Arunachal Pradesh is governed by the Himalayan system and the altitudinal differences. The territory receives wide rainfall from May to early October, June and July being the wettest month. The annual average rainfall varies from less than 1500 mm to more than 4000 mm. Average temperature during the winter months ranges from 15º to 21ºC and 22º to 30ºC during monsoon. Assam Assam (24º09-27º58 north and 89º42-89º01 east) is mainly forest ecosystem covering both the hills and the plains. The sub-tropical to tropical climate of Assam is characterized by high rainfall and high humidity and is divided upto three dominant seasons, viz. winter (November to February), summer (March to May) and monsoon (June to October). Most of the rainfall in the state received under the influence of the south-west 34
35 monsoon between June and October. The Brahmaputra valley represents three broad climatic regions, viz. eastern, western and middle. The mean annual rainfall of eastern, western and middle regions is 245.2 mm, 1982.5 mm and 1527.4 mm respectively. The mean annual temperature is 23.5ºC, 24ºC and 24.5ºC with nine months having 20ºC in eastern, western and middle regions respectively. Manipur Manipur (23º50-25º42 north and 92º59-94º46 east) enjoys a sub-tropical monsoon climate. It belongs to the temperate rainy climate region with dry winter and hot summer. Average warmest temperature ranges between 25ºC and 31ºC. Rainfall is relatively abundant and widespread, varying from a maximum of 2589 mm to 970 mm, at period from December to February continues the cold season, March to May is the hot weather, the monsoon starts from May and lasts up to September and the season of retreat of monsoon is from September to November. Meghalaya Meghalaya (25º02-26º07 north and 89º49-92º50 east) is literally the Adobe of the clouds. The climate of the state as a whole may be described as cold, chilly and frosty in the highest region which is the central plateau, mild and pleasant in the regions, where the central plateau meets the two border areas, but not moist and oppressive towards the border of Bangladesh and Assam. The mean maximum temperature is around 30ºC while the mean minimum temperature is around 12ºC at Shillong. The average rainfall in the state varies from 4000 mm to 11,436 mm and the average relative humidity being 76%. Practically, the whole of the state is covered by the south-western monsoon which normally begins from the month of May and lasting up to the month of October. The Southern border area of Jaintia hills district of the state receives the highest amount of rainfall where the two wettest places
36 in the world are situated viz. Cherrapunjee and Mawsynram. On the whole, the rainfall in the state can be described as heavy in comparison with many other states in the country. Mizoram Mizoram (21º57-24º30 north and 92º15-93º26 east) located in the extreme southern most end of the Purvanchal Himalayan range bounded on the north by Assam and Manipur, on the east and south by Myanmar and on the west by Bangladesh and Tripura. Mizoram enjoys a pleasant climate which is neither very hot nor very cold. The state has a moderate humidity too. In summer, the temperature varies between 20ºC and 29ºC while in winter it varies between 11ºC and 21ºC. In autumn (September to October) except for a few showers, heavy rains cease and the temperature is usually between 25.4ºC and 18.7ºC. In winter (November to February) the temperature is usually between 11.8ºC and 24.7ºC. There is little or no rain during winter. Mizoram gets a substantial amount of rainfall each year. The average rainfall being 2540 mm per annum. Nagaland Nagaland (25º10-27º01 north and 93º17-95º15 east) is located in the extreme of north-east India. Nearly the whole of Nagaland is situated in a hilly terrain. In the north, where Nagaland has a common border with Assam, the hills are lower in altitude and gradually taper down into the Brahmaputra plains. Towards the south and east, the hills are higher in altitude. The altitude varies from 194 m to 3841 m. Because of the altitude, temperature is low. The climate is tropical monsoon type. The annual rainfall varies from 1000 mm in the southwest to 6000 mm in the north. The summer high temperature ranges between 24.4ºC and 32.8ºC.
Tripura Tripura (22º57-24º33 north and 91º10-92º20 east) is surrounded by Bangladesh on three sides except east which is surrounded by Assam and Mizoram. The climate is generally hot and humid with temperature ranging between 10.4ºC to 35ºC. Humidity becomes the maximum in June and minimum in April. Rainy season is from May to October. The normal average rainfall in the state is 2300 mm. Sikkim Sikkim (27º05-28º09 north and 87º59-88º56 east) is one of the smallest and the least populous state in India. It is bounded by the Darjeeling district of West Bengal in the south and a stretch of Tibetan plateau in the north. Sikkim shows great biological diversity. The climate of the state has been roughly divided into the tropical, temperature and alpine zones. For most of the period in a year, the climate is cold and humid as rainfall occurs in each month. The area experienced a heavy rainfall due to its proximity to the Bay of Bengal. Cold winters occur in the month of November to February with minimum temperatures dipping to 4ºC during January- February. Sunshine is quite abundant between the month of March and early May. Sikkim is almost always wet due to the heavy monsoons, with rains at times continuing for days on ends and September to October is autumn. 37
38 North-east India Assam Arunachal Pradesh Sikkim North-east India Nagaland Meghalaya Tripura Mizoram Manipur Fig.3: Study sites for cyanobacterial sample collection in North-east India