Impact Of Anthropogenic Activities: A View on The Vegetational Changes of Nambul River Riparian Zone, Manipur, India

ISBN: 978-93-7143-285-6 83 Chapter - 5 Impact Of Anthropogenic Activities: A View on The Vegetational Changes of Nambul River Riparian Zone, Manipur, India Dr. Sorokhaibam Ibechaobi Devi Imphal College, Imphal Email Id: [email protected] ABSTRACT: The anthropogenic activities are accelerating its negative impacts on the ecosystems either land or water. The impacts were exaggerated in sensitive zones and delicately balanced systems. The Nambul River Riparian zone (Latitude 93045'6.48"E-93057'56.88"E and Longitude 24037'59.28"N24058'15.6"N) is one of the delicately balance ecosystem incorporated with various anthropogenic activities. Its catchment with an approximate area of 223 sq. km (approx.)support a vast array of vegetation dominated by Poaceae, Asteraceae, Cyperaceous, Amaranthaceae, Polygonacea, etc. families. These vegetations are frequently exposed to various natural and anthropogenic disturbances. Kitchen gardening, cattle grazing, waste dumping, crematoria practices, construction of retaining wall along the river bank, maintaining playgrounds along the river bank, small commercial constructions, settlements, flooding during monsoon period, inundation, etc. are major disturbances to the natural vegetation of Nambul River riparian zone. These activities Impact Of Anthropogenic Activities: A View on The 84 drastically affect the vegetative composition, diversity and its productivity. The Nambul River riparian vegetation showed low diversity and low productivity on an attempt to assess the impacts of disturbances at the upstream, central and downstream regions of the Nambul Catchment vegetation. Keywords: Riparian vegetation, Nambul river, Anthropogenic activities, Diversity, Productivity INTRODUCTION Riparian ecosystems are delicately balanced and extremely fragile in nature. It is the transitional areas between aquatic ecosystems and the adjacent upland terrestrial ecosystems (Gregory et, al., 1991). The word “riparian” comes from Latin word “ripa” meaning river bank, (Kandolf et al., 1996). The streams and their riparian areas form an inseparable unit for a healthy riverine landscape which is also a part of the structure and functioning of riparian plant communities that support numerous functions including bank stabilization, habitat for various aquatic lives, reducing erosion losses of soil and nutrients, support to diversified riparian vegetation, temperature regulation of river water, etc. Most often the riparian vegetation experiences various disturbances both natural and anthropogenic. These ecosystems are one of the most vulnerable ecosystems of the world due to anthropogenic activities in the form of habitat transformation, vegetation clearing for agriculture and developmental activity, urbanization, damming, grazing, mining and invasive species, etc. (Saumya, et al., 2022). Anthropogenic pressures are Sorokhaibam Ibechaobi Devi 85 increasingly constraining the health of riparian ecosystems by exposing their remnant vegetation to edge effects (Moses et al, 2025). Frequent flooding during monsoon period, marginal encroachment for various establishments, waste dumping sites, grazing ground for cattle, etc. are few disturbances imposed on these ecosystems. These impart severe changes in the riparian plants like decline in vegetative propagation, disturbances in diversity, reduction of productivity, etc. Anthropogenic transformation lead to the decreased in species diversity, decreased biological productivity and degradation of biocenoses (Sokolova, 2021).Riparian plants are embedded within one of the most vulnerable and threatened ecosystems in the world today (Tockner and Stanford, 2002). Population growth, urbanisation, changing socio-economic characteristics of the population, and administrative regulations and laws are the most effective factors that have led to the degradation of natural vegetation cover (Adel & Moatamed, 2021). The Nambul river which is flowing through the heart of Imphal City is one of the major tributaries of Manipur River system discharging into the Loktak lake and is also a major water supply of the Imphal valley. It belongs to perennial types of stream and flows continuously throughout the year. Its Riparian Zone is a fragile ecosystem but supports a wide array of diverse vegetation and it also experiences various stresses including wide spreads of kitchen gardening both at the upstream and downstream regions disturbing the natural vegetation, grazing by domestic cattles, domestic uses like washing and bathing,waste dumping ground, crematoria Impact Of Anthropogenic Activities: A View on The 86 practices, building public urinals and latrines along the river banks,maintenance of playgrounds, small constructions of commercial sites, contruction of retaining wall along the river bank to prevent flood during monsoon period at Imphal city, soil erosion, etc. The riparian zone in general act as the filtering zone from the surrounding catchments so likewise the Nambul River and its riparian vegetation can also act in controlling soil erosion from the river banks. Hence, an attempt had been made to study the impact of anthropogenic disturbances over the vegetation of Nambul River riparian zone. STUDY SITES The present study was conducted along the course of Nambul River riparian zone (Latitude 93045'6.48"E93057'56.88"E and Longitude 24037'59.28"N-24058'15.6"N) having its catchment area of 223 Sq.km (approx). The region is endowed with moderate temperate, rainfall (sub-tropical monsoon) and relative humidity. Along the river riparian course experimental studies were performed at three sites one at upstream (Site 1), the other at Imphal city as middle (Site 2) and the last at downstream (Site 3). The natural vegetation of the Nambul River riparian zone was replaced by species of kitchen gardening mostly at the human habituated areas and hence, the regeneration of the naturally available species was affected. Among the three selected study sites, the upstream site was least disturbed whereas the study site at the heart of Imphal City was the most threatened site from human activities, and the downstream site also posed threats from various land uses. Sorokhaibam Ibechaobi Devi 87 From the remote sensing data installed in 1998, the river catchments were grouped into: 1. Agricultural zone (95.43 Sq.km approx.) 2. Settlement area (57.88 Sq. km approx.) 3. Degraded land (55.41 Sq km approx.) 4. Marshy land (7.95 Sq.km approx.) 5. Forested area (6.10 Sq.km approx.) METHODOLOGY The paper focuses on the analysis of vegetational life form, species diversity, and biomass productivity from thesampling sites following standard methods. Life form of different species were studied and determined after detailed floristic studies (Gupta and Kachroo, 1978; Raunkier, 1934). Different characters of each species life form, habit and nature of perennating buds were studied in the field. Shannon Index, H’ (Shannon and Impact Of Anthropogenic Activities: A View on The 88 Wiener, 1949) and Simpson Index, λ (1949) were analysed for species diversity. For vegetational productivity, biomass variation and net production was also estimated by short term harvest method (Odum, 1960; Milner and Hughes, 1968). The size of the sampling blocks for biomass was 25cm x 25cm x 30cm. The Net Above Ground Primary Production (ANP) was determined by the sum of positive changes in biomass plus mortality (Singh and Yadava, 1974). Likewise, the Belowground Net Primary Production (BNP) was calculated as the summation of positive increments in belowground biomass and Total Net Primary Production (TNP) is the sum of ANP and BNP. TNP = ANP + BNP RESULTS AND DISCUSSIONS The vegetation Nambul River riparian zone reflected the scene of a herbaceous grassland ecosystem. From the selected study site along the Nambul river riparian zone, the plant species comprised of 25 families 71 genera and 90 species where the dominant families were Poaceae and Asteraceae ( Ibechaobi and Gupta, 2024). Life form characteristics displayed an obvious relationship of the plants to the environmental factors. Figure 3 highlighted that the Life form pattern of the riparian vegetation which was found to be dominated by Therophytes followed by Chamaephytes at all the sites. The predominance of Therophytic composition was indicative of better adaptation of the annuals to the existing environmental factors. Cain (1950) and Pandeya (1964) reported that increase in the percentage of Therophytes were due to Sorokhaibam Ibechaobi Devi 89 overgrazing. Major part of Nambul riparian vegetation was also open to various stresses like grazing, scraping, trampling, etc. and the plant species of Nambul riparian zone showed the predominance of Therophytic composition which revealed the adaptive capability of the annuals and indicated the disturbance of the system from various anthropogenic activities. However, active performance of chaemophytes showed the competitive ability and adaptability of rhizomous species. Th-Therophytes, HCHemicryptophytes, ChChamaephytes, Ph – Phanerophytes G –Geophytes Fig 3: Annual percentage contribution of different life-forms at the 3 study sites of Nambul Riparian Zone Species diversity which indicates the species richness of a region showed its least value for the Nambul River riparian vegetation at the most disturbed site i.e site 2 during the three seasons (Table 1). The results of species diversity of the Impact Of Anthropogenic Activities: A View on The 90 Nambul River riparian vegetation were low. The Shannon’s index of diversity (H’) showed its values ranging from 1.9 to 2.8 whereas the Simpson’s index of co-dominance (λ) resulted an inverse relation to the Shannon’s index(H’) with its value ranging from0.06 to 0.2. The values of table 1 highlighted that human disturbances like settlements along the river bank, waste dumping, cattle grazing, practicing of kitchen gardens, building flood retaining walls at the river bank, etc. hinders the growth of natural vegetation thereby showing low response to species diversity. Cultivation may degrade riparian habitat and floodplains through siltation that modify the fluvial geomorphology of the channel and reducing the complexity and diversity of the plant species (Cosmas, 2016). The existing anthropogenic activities affected the plant population structure and loss of species among plant communities thereby degrading the species diversity of a region (Mwakosya & Cosmas, 2014). Table 1: Diversity indices for Nambul river riparian vegetation at the 3 study sites. INDICES Seasons Site 1 Site 2 Site 5 Shannon’s index (H’) Summer 2.4 2.03 2.5 Rainy 2.8 1.9 2.8 Winter 2.4 2.04 2.8 Index of codominance (λ) Summer 0.13 0.2 0.12 Rainy 0.06 0.2 0.06 Winter 0.1 0.2 0.13 Table 2 : Net primary productivity in gm-2yr-1 at the 3 study sites of Nambul Riparian Ecosystem. Sorokhaibam Ibechaobi Devi 91 Parameters Seasons S I T E S 1 2 3 ANP Annual 1220.11 287.51 587.37 Summer 245.74 124.60 239.53 Rainy 825.63 92.79 264.93 Winter 148.74 70.11 82.91 BNP Annual 104.72 49.87 79.56 Summer 33.37 23.12 13.95 Rainy 37.67 12.63 39.6 Winter 33.68 14.12 26.01 TNP Annual 1324.83 337.38 666.93 Summer 279.11 147.72 253.48 Rainy 863.3 105.42 304.53 Winter 182.42 84.23 108.92 ANP – Above Ground Net Primary Production BNP – Below Ground Net Primary Production TNP – Total Net Primary Production The net primary production is the rate of storage of organic matter in plant tissue in excesses of respiratory utilization during the experimental period (Odum, 1971). Total dry matter production is considered to be a measure of its systems efficiency to fix energy in its entire compartment (Rochow, 1974).The natural ecosystems maintain their high production through particular above and below-ground processes that serve to conserve nutrients, water and soil organic matter (Sanchez, 1990).