Assam, one of the sister states of Northeast India is regarded as biogeographical gateway for much of India’s biological resources. Nestling between the eastern Himalayan foot hills and the Patkai and Barail ranges of hills, the state covering an area of about 78,523 sq. km. is one of the largest north eastern states of India. Though largely plain, the Barail range is mountainous. Both sides of this range are the Brahmaputra and Barak valleys. The occurrence of heterogenic physiography coupled with varied climatic conditions on and around the state has made the vegetation luxuriant and diverse that support unique flora and fauna.

The mighty river Brahmaputra traverse the state from east to west covering a distance of about 1300 km thereby separating the sub-himalayan region of Assam from the southern parts and forms the gorgeous Brahmaputra valley with an elevation of about 122m at Sadiya the eastern most and 30m at Dhubri the western most part of the valley. Brahmaputra valley being the largest plain in the northeast region and has a great significance not only for agriculture and industry of the region but also for its rich vegetation and wildlives preserved in the various protected areas. The forest types are mostly tropical which harbours a rich pool of biodiversity.

The rich flora of the area has been the centre of attraction for several botanists since early 18th century to till date. Flora of Assam by Kanjilal et al perhaps was the beginning of botanical studies by Indian Botanists. Although the state has been well explored floristically, yet there are areas with ample scope of floristic study particularly in the protected areas and also the river bank vegetation. Riparian i.e. river bank vegetation at a particular location and time results from interactions between the physical conditions created by geomorphic and hydrologic processes in the stream channel and responses by the plants. The present report is being prepared with an aim to work out the vegetation types and flora along the course of the river Brahmaputra river, documentation agro biodiversity, invasive species diversity, grassland habitats, plants of economic and other uses and also the screening of the rare, threatened, endangered as well as the endemic taxa in the valley. In general the vegetation of Assam is primarily tropical type that covers large areas and embraces evergreen, semi evergreen, deciduous forests and grass lands. Stretches of riparian forest along the bank of rivers are also very prominent. The variations in forest types and their vegetation composition in Assam occur mainly due to the varied physiographic, edaphic conditions and range of climate. As there are not much altitudinal variations in the plains particularly in the Brahmaputra valley, it has little significance in determining the forest types of the valley. From all the available sources and personal observation, the vegetation and forest type along the Brahmaputra river in Assam may be considered as tropical moist evergreen, tropical semi evergreen, moist deciduous forest, Grass land and savannah, wetlands and swamps, riparian forest and degraded lands.

The flora of the state of Assam is rich both in terms of diversity and luxuriance. Starting from the 18th century to till date, plenty of studies have been made leading to the addition of the data on the floristics of the state. As per conventional estimates the state flora comprise of 3017 species (Baishya 1999). Chowdhury (2005) gave an account of the 4273 species of comprising infra-specific taxa comprising of 1448 genera distributed in 272 families of vascular plants of Assam. These include fern allies, ferns gymnosperms and angiosperms. More recently Barooah and Ahmed (2014) compiled a detailed checklist of Angiosperms and Gymnosperms of the state by listing 3854 taxa (including infra-specific taxa) under 1394 genera and 236 families. Out of which, 2752 taxa are dicotyledons, 1080 taxa are monocotyledons and 22 taxa are gymnosperms. The flora of Assam represents 18% of the Indian flora. However, the figures are provisional as still many areas are unexplored and underexplored. Comparision of the floristic composition of the two valleys of the state shows that the Brahmaputra valley is richer than the Barak valley as over 90% of the total flora of the state have been reported from Brahmaputra valley. The difference in the floral compositions of the two valleys are readily apparent with the localised elements not found any were else in the state. The luxuriant vegetation and flora of the Brahmaputra valley creates the treasure house of multidimensional biotypes in the area with occurrences of a number of endemic plants and some important primitive angiosperms. It is also blessed with very high degree of taxonomically and ecologically valued floral species. The richness of the composition is reflected with more than 250 species of Orchids, 33 species of Bamboo, 12 species of Canes and number of plants with medicinal properties. The forest cover of the state represents 35.28% area of the state with 17.68% of geographical area in Reserve Forest and 5% of geographical area under protected area net work (Anonymous, 2011).Although, the comprehensive account of the endemic taxa of the state Assam is yet to be worked out, the Botanical Survey of India listed 102 species of angiosperms belonging to 75 genera as endemic taxa for the political boundary of Assam, of which majority i.e. 91 species belonging to 68 genera are found in the Brahmapurta valley. Several groups of flowering plants viz. Orchids, Legumes, Cucurbits, etc. exhibit remarkable species diversity in the valley along with the genus Dendrobium, Elaeocarpus, Piper, Garcinia, Calamus, Dipterocarpus, etc. Families viz. Poaceae, Orchidaceae, Fabaceae, Asteraceae, Araceae, Cucurbitaceae, Lauraceae, Arecaceae, Zingiberaceae, etc. contribute to the rich gene pool of the valley.

The area is also known for several plants of botanical curiosities. Some of the phylogenetically primitive families such as Magnoliaceae, Anonaceae, Schizandraceae, Menispermaceae, Altingiaceae, Lardizabalaceae, etc. grow in the Brahmaputra valley and further eastwards but do not occur in other parts of India. This array of floristic richness has prompted many naturalists to describe Assam as the ‘Biological Gateway’ of northeastern India. Moreover, the flora of the valley has distinct affinity with the nearby Nepal, Bhutan, Indo-Burma, Sino-Himalayan, Malaysian flora and to a lesser extent with peninsular India. Besides, elements of Sino-Himalayan affinity are also found in the flora of the valley. Some plants of African and American origin are also found to be naturalized in the valley. Gymnosperms, in Assam are poorly represented. In Brahmaputra valley they are restricted to Darrang, Dibrugarh, Goalpara, Golaghat, Lakhimpur, Sibsagar and Sonitpur districts.

As many as 5 common species of gymnosperm viz. Cycas pectinata, Podocarpus nerifolia, Gnetum gnemon and G. montanum grow naturally in the valley. Similarly, fern allies and ferns are the important component of biodiversity of the Brahmaputra valley. The species representation of other cryptogamic group of plants like Moss (Musci), Liverworts (Hepaticae), Lichens, etc. are also remarkable in the valley. The rich floristic diversity of Brahmaputra valley has tremendous utilitarian value. Plant resources available in the area starting from their timber yielding value can also be used as medicines, as food, as source of essential oils, gums, for making paper and pulp, dyes, resins, tannins, essential oils, fibres, etc. The Brahmaputra valley produces some of the finest and expensive teas in the world. The valley harbours high prized timber yielding plants and medicinal plants with commercial importance. Proper exploration of these resources will lead to the discovery of novel drugs. The state of Assam particularly Brahmaputra valley is famous for orchid diversity. Besides, several ornamental plants with prospect for floriculture are found in the valley. The state is one of the important areas of northeast region as far as the production of canes and bamboos are concerned. As many as 12 species of canes and 33 species of bamboos are found in the Brahmaputra valley, which are of great importance in developing forest based cottage industries. The cross cultural ethnobotany is also very rich as the area is resided by ethnically diverse communities with wide range of uses of plants of different groups. Over 332 plant species of Assam used as food, drinks, medicine and also in cultural aspect. About 40 species of various wild plants are marketed as food and vegetables in local tribal and village markets of the valley. Use of plants for a variety of purposes is indicators of intimate dependence and relationships of people of the area with the plant resources of their viscinity. The valley has rich biological assets in the form of wild relatives of cultivated plants as they are reservoir of various genes of agronomic and economic importance needed for genetic improvement of crop plants. Like higher plants, the cryptogams are equally important as they are used in various purposes like food, medicine, dye, antibiotic and ornamental, etc. Brahmaputra valley harbours a number of rare and threatened plant taxa. Botanical Survey of India estimated about 700 plants of northeast region fall under various threat categories of which 43 species belong to Assam. Baishya (1999) compiled a list of 60 rare and threatened plant taxa from Assam. Barooah and Ahmed (2014) categorised 871 taxa of angiosperms and gymnosperms of the state under different conservation status. Among these, 167 taxa are recorded to be endemic, 318 taxa are kept under critically endangered, endangered and vulnerable and 386 taxa are identified as rare to the state. Some critically endangered plants of the Brahmaputra valley are region are Livistona jenkinsiana, Swertia chirayita, Smilax glabra, etc. Plants viz. Aquilaria malaccensis, Brucea mollis, Cibotium barometz, Citrus macroptera var. assamensis, Dendrobium nobile, Flickingeria fugax, Garcinia pedunculata, Homalomena aromatica are endangered in the valley and vulnerable species include Elaeocarpus sphaericus, Gynocardia odorata, Hydnocarpus kurzii, Mahonia napaulensis, Oroxylum indicum, Piper peepuloides, Rauvolfia serpentina (IUCN-CAMP, 2003).

From the detailed study it is possible to suggest some measures for the conservation of the aqua resources of the Brahmaputra:There should be efforts to create awareness about the importance of aqua faunal diversity and their proper utilisation among the fishing communities.

It is the geographical isolation from rest part of the country, which has helped to protect the biodiversity from large-scale developmental activities in the state. But the situation has changed gradually and the biodiversity of the region is confined to only a few pockets. The rate of forest degradation is also supported by the invasion of weeds causing a serious problem in the state. Various species of native and exotic weeds viz. Ageratum conyzoides, Argemone maxicana, Eupatorium odoratum, Lantana camara, Mimosa rubicaulis, Mikania micrantha, Parthenium hysterophorus, etc. have completely dominated the forested land, degraded forests and the agricultural landscapes of the region posing serious threat to all sorts of healthy growth of plants, forest regeneration and agricultural productivity as well. Natural calamities like earthquake, seasonal flood, etc. as well as soil erosion also lead to the shrinkage of the forest cover.
Of late, the various developmental activities like construction of mega dams, hydroelectric plants, roads, etc. also act as the key factors of forest destruction. Building of mega dam on the mainstream of the Brahmaputra as well as in some of its major tributaries may adversely affect the natural importance of some protected areas of the valley. The capability of the ecosystems to sustain certain types of grasses and other vegetation required for the survival of rhinos, elephants and other herbivores in these critical ecosystems are determined by natural connectivity of the forests with waters of the rivers. Construction of large dams may change the flood cycle and hydrological relationship of some critical ecosystem like Kaziranga national park.

The existence of different habitat types in the park is dependent on the annual sluicing of the landscape by flood water. Moreover, the livelihood of the people living in the catchment areas of the river would also be at stake.Injudicious collection of plants is leading to the depletion of the rich bio-resources of the state. Political and social unrest prevailed in the state for the last couple of decades are also influencing adversely to the rich floristics in general and the Brahmaputra valley in particular. As far as the diversity of cultivated crops is concerned, the replacement of local land races by High Yielding Varieties (HYV) in cultivated fields has caused considerable loss in diversities of crop and economically important plant in the valley. More recently, climate change is another important issue that need to be addressed for Assam, along with the deforestation, degradation, encroachment and associated concerns of logging and habitat fragmentation. Climate change is likely to impose a variety of stress on sustainable livelihood of the poor inhabitants of the state through stresses on functioning of the ecosystem. Environmental problems in the state of Assam have been influenced partly by the increasing population, survival needs of the poor and the economic greed of the commercial interests. It is also aggravated by prevalent economic disparities and unemployment. As far as the forest resources of the Brahmaputra valley is concerned, gap in scientific knowledge, increasing demands, lack of value addition are the main causes for which the vast potential is yet to be tapped properly and in some cases over exploited. Strategies need to be formulated in the context of all the imperatives of biodiversity conservation, livelihood improvements and unsustainable utilization. In the perspective of the state of Assam, proper assessment of the status of various forest ecosystems and resources, their potential in supporting life and livelihood are the foremost requirement. Sustainable management of these resources requires the collection of accurate information and a programme of regular monitoring.

Information on density and distribution of the economically important species within the forest, population structure, productivity, regeneration capacity and ecological impact of harvest are prerequisite for the planning, design of management strategies and running enterprise based on raw materials collected from the forest.Monitoring and maintaining of the complex ecosystem is important aspect of bioresource management. There is also social aspect of resource management as dealing with people, cultures, belief systems, attitudes and behaviour, ethics, aspirations and social values. Finally, exercise of administrative power in another important facet to hold control over users of resources and decision-making.Brahmaputra valley is blessed with very high degree of endemic, taxonomically and ecologically valued plant species. Recent years are witnessing considerable developments and the overwhelming demand for forest based raw materials, especially bamboo, cane and natural health products. Moreover, there is growing market demand globally for these products. However, majority of these species in wild are under severe threat, many are on the verge of extinction due to imprudent resource use and management practices. Therefore it is imperative that multi-dimensional action (social, ecological, economical, institutional) need to be urgently taken for the conservation of these vital resources. Management plan should be in such a way that livelihood improvement and biodiversity conservation are in balanced state in order to reduce the poverty and underdevelopment of the state.There is a need of sustainable management of the important forest resources of the valley that would also contribute to the food security, poverty alleviation, economical development, and sustainable land use, in the wider context of sustainable development. Policy based initiatives are required to protect and conserve the pristine biodiversity of the state. It may be mentioned that the state has lost several hectares of forest cover in recent years. There is large scale unabated encroachment in the reserved forests even in the protected areas by the new settlers, people displaced by floods and ethnic clashes in the state particularly the Brahmaputra valley, immigrants and excessive dependence of thepeople in the rural areas on the forests leading to deforestation. The state has also experienced rapid urbanization, infrastructure development and the agricultural intensification with resulting large scale habitat loss and degradation. Special strategy may be formulated for recovering encroached areas. Incorporation of some incentive mechanisms or benefit sharing mechanisms in the community conserved areas and protection of valuable species outside the forest would be an encouraging steps towards conservation and management of biodiversity. Important carbon stocks in many forests around the world have been maintained and enhanced with the help of the local communities. Payments for ecosystem services may be useful in preserving, acknowledging and rewarding good community forest management practices. More areas should be incorporated under protected area network and the ongoing programme/project of forestry sectors, viz. Joint Forest Management, Project Tiger, Project Elephant, Project Rhino, Eco-development programme, National aforestation programme, etc. should be strengthen. Eco-sensitive zones in the valley should be identified and regulations may be imposed on developmental projects like mega dams, industrial activities, quarrying and mining in such areas. Integration of various other forestry sectors viz. watersheds, wetlands and also grass lands is important for formulating management planes. Special initiatives need to be taken for protection of the areas outside the protected areas or reserve forests with rich flora and fauna. The natural corridors of the wildlife in the valley disrupted due to change in the land use and land cover, industrialization and other developmental activities should be protected and restored. Updation of the database on floristic diversity in terms of species, ecosystems & genetic traits with reference to status, pressures and also in regard to changing climate is another aspect of management of resources. Documentation ethno-cultural interlink is also important to safe guard IPR of the communities. Besides, pest-resistant or drought-tolerant varieties; genotypes of species expected to be adapted to new climate conditions are also to be screened out.The state of Assam try for lobbying at regional, national and international level against the large dams coming up on the Siang, Dibang, Lohit, Subansiri and even in the Brahmaputra river as these may cause disruption in maintaining the annual flood cycle and hydrological relationship of some important wildlife areas of the valley. Special measures to be taken for control of the alien /invasive plant species as several interacting factors contribute to successful invasion of these species. Priority should be given to plantation on the degraded forest and riparian sites. In riparian sites plantation of bamboo and various species of grass can be initiated to check erosion. All the conservation efforts are become futile without research input and these may be formulated looking at the probable impact or consequences of climate change. Therefore comprehensive studies on the various aspects of floristics need to be initiated.Capacity building of the local communities is necessary prerequisites to biodiversity conservation programme. The local communities should be imparted with technical, financial, managerial, marketing and training support so that they will have a new economic incentive to conserve the resource base of their raw material. Government institutions like North East Development Finance Corporation Ltd. (NEDFI), North East Council (NEC) and Department of development of North East Region (DONER) have already started encouraging to tap the vast bio-resource of the northeast region in general and Assam in particular involving both local citizen as well as state governments in a sustainable way to boast the economy and to provide livelihood to the entire population of northeast India. Citizens are provided with technical, financial, managerial, marketing and training support, so that they have a new economic incentive to conserve the resource base. The rich floristic diversity with a large number of endemic plants of state of Assam in general and Brahmaputra valley in particular not only constitutes the ‘green gold’ of the present century but also of the future. These rich genetic resources of the region also hold promises to yield organisms. A rational, scientific and judicious utilization of the bioresources of the region will help us in the long run in improving the welfare of the humanity; at the same time will also facilitate to conserve this pristine glory for the posterity.

 

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