Herbaceous Riparian Ecotonal Species along the Dzücha River, Kohima, Nagaland and Their Ethnomedicinal Uses

The ecotonal community contains several organisms from each of the overlapping communities. Such characteristics are restricted to the ecotone (Odum, 1971). The word “riparian” has not been defined as a single entity but in close association with various suffixes such as riparian area, riparian zone, riparian reserve, riparian system, riparian ecosystem, riparian corridor and riparian ecotone. Verry et al., (2004) state that the meanings of all the suffixes are more or less similar. Among the suffixes used, the riparian zone and riparian buffer zone are the most common ones. Other than these suffixes, the word “riparian zone” has also been synonymously used as stream corridor, river corridor, riparian forests, riparian buffer zones, riparian zones, etc. (Zaimes et al., 2010). The riparian ecotone acts as a filter for the river. Pinay et al., (2018) terms it “skin for the river”. The water draining downwards via the riparian ecotone undergoes a natural filtration process which absorb sediments, pollutants, etc. The vegetation and microbial fauna in the riparian ecotone aid in the filtration process (Silvan et al., 2002; Palviainen et al., 2004). Therefore, riparian vegetation is crucial in maintaining the river environment, including river water temperature and organic-inorganic inputs. Such vegetation affects the intensity of light reaching the river water; the dense canopy lowers the river water, while the open canopy raises the river water (Garner et al., 2017).
       
Vegetation analysis is an important aspect of ecology that enables us to understand the structure and function of a community. This analysis provides key information regarding diversity, structure, resource utilization and turnover rate of a species (Mandal and Joshi, 2014). Plants within the same community have a mutual relationship between themselves and the environment (Mishra et al., 1997). Nagaland, a state in the northeast corner of North East India, is rich in biodiversity. However, various anthropogenic factors are reported to be affecting riparian vegetation globally (Richardson et al., 2007; Njue et al., 2016). The increased rate of agriculture and invasive species has caused a decrease in species diversity (Vivero et al., 2006; Meragiaw et al., 2016). Owing to the rich flora in the region, the tribal people utilize various parts of the plant as a traditional herbal drug (Jamir et al., 1999). Therefore, there is a need to document the rich, unwritten indigenous tribal knowledge (Hussain et al., 2018). Keeping in view the need to document the diverse riparian vegetation present in the state and its varied utilization by the indigenous inhabitant of Nagaland, the present work has been carried out.
 

Study site
 
Dzücha River is a tributary river that flows along the Dzü River. The river is located adjacent to Kohima district, Nagaland, North East India (Fig 1). Dzücha River is located at 25°39'39'N latitude and 94°08'11"E longitude with an elevation of 1100.023 m above sea level. The water body is utilized by the indigenous inhabitant for irrigation, fishing activities, recreational sites and other domestic uses. The study site also possesses many wild herbaceous plants which are widely utilized by the indigenous inhabitants as herbal drugs for various ailments.


 
Vegetation analysis
 
The vegetation analysis was conducted by the line transect quadrat method (Fig 2A and 2B). For the study of vegetation along the river, a total of 20 plots were laid, with each plot measuring 5 mx5 m. A total of 10 plots on the right side and 10 plots on the left side of the river were recorded. Within each plot 3 quadrats of size, 1 m x\1 m were laid randomly. A photograph of each of the herb species observed at the study site was taken. The observed herb species occurring within the quadrats were identified with the help of literature (Prain, 1903; Bennet 1987; Kanjilal et al., 1940). Herbarium specimens were deposited in the Department of Botany, Nagaland University.



Data analysis
 
The vegetation data collected from the study site were analyzed for relative frequency, relative density, relative abundance and Important Value Index (IVI) following the standard formulas given by Curtis and Mcintosh (1950), Mishra (1968) and Mueller-Ellenberg (1974). The data were calculated using the following formulae:
 
 





 

The basal area for the herb species was calculated by measuring the diameter of the emerging stem on the ground level using Caliper.
Basal area of a particular species = πr²
 
Important value index (IVI)
 
The IVI (Curtis, 1959) of each species was calculated by summing the Relative Frequency (RF), Relative Density (RD) and Relative Dominance (RD)


 
 The shannon-wiener diversity index
 
(H¢) was calculated from the IVI values (Shannon and Wiener, 1963):


 
Where
s = Number of species.
pi = Proportion of individuals or abundance of the ithspecies expressed as a proportion of total cover.
ln = Log base n.
Margalef’s index was calculated by using the formula given by Margalef (1968).
                                             K= logS/logN
Where
S = The number of species
N = The total number of individuals in the sample.
Pielou evenness (E) is measured as suggested by Pielou (1966).
                                             E = I_SH /log2(Rs)
Where
Rs = Specific richness
Simpson’s dominance was calculated by using the formula given by Simpson (1949).
Simpson’s dominance = 
             
 
Ethnobotanical methodology
 
Oral interviews were conducted with the ingenious inhabitants and local healers from Kohima Village, Nagaland, North East India. The plant samples and their photos collected from the study sites were then presented to local healers. Different parts of the plant used for treating ailments, based on ethnobotanical information, were recorded based on their response.
 
 

Vegetation analysis
 
A total of 31 species belonging to 15 families were reported (Table 1). The family Asteraceae was dominant, with 12 species. This was followed by Urticaceae, with 3 species. While Polygonaceae, Lamiaceae and Commenlinaceae had 2 species each, respectively. Ageratina riparia (24.1) possessed the highest density, followed by Ageratina adenophora (11.34), Ageratum conyzoides (8.90) and Pneumatopteris penningera (8.82), respectively. The lowest density was recorded in Phaseolus vulgaris (0.22). The distribution analysis of the herb species also displayed that the maximum IVI was recorded for Ageratina riparia (38.45). The co-dominating species were Ageratina adenophora (IVI=22.44), Ageratum conyzoides (IVI =22.35) and Pneumatopteris pennigera (IVI=21.44), respectively. High IVI value of a species indicates its dominance and ecological success, power of regeneration and greater ecological amplitude. A higher value of IVI by any individual species indicates that all the available resources are being utilized by that species (Shameem et al., 2010). The lowest IVI value was observed in Phaseolus vulgaris (1.74). The lower value of IVI could be due to the damage caused by the high moisture content at the site, which leads to infestations of fungi within the roots. The lower IVI values may also be correlated with anthropogenic pressure (Mandal and Joshi, 2014). Moreover, vegetation types along the environmental gradient are largely affected by altitude, light, topography, temperature and precipitation, as these factors determine the composition and distribution of the vegetation (Saolam, 2013). Meanwhile, the lower importance value of species is an index of low grazing pressure by herbivores on the study sites, as vegetation is a reflex of interactions between the plants, animals, soils and climate. Moreover, each species of a community plays a specific role and there is a definite quantitative relationship between abundant and rare species (Bhandari et al., 1999). Bhatti et al. (2014) in Yusmarg forest also report that the higher value of IVI indicates that all the available resources are being utilized by that species and leftovers are being trapped by other species as the competitors and associates.


 
Diversity indices
 
The various diversity indices recorded at the sampling station (Table 2) are as follows: Species diversity (Shannon-Wiener Index) = 2.775, Species richness (Margalef’s Index) = 4.163, Species evenness (Pielou’s Evenness) = 0.808 and Species dominance (Simpson’s Index) = 0.101. The higher values of Shannon-wiener’s diversity Index may indicate the high diversity of species present on the site. It also observed that the low diversity and consequently greater concentration of dominance in vegetation could be due to the lower rate of evolution and diversification of communities in the environment (Connel and Orias, 1964). More species in a community are ecologically important since diversity increases as the community become more stable.


 
Ethnobotanical uses
 
The use of ethnomedicinal plants for various ailments has been recorded extensively (El-Seedi et al., 2013). From the herbaceous species recorded, 11 herb species were utilized by the indigenous inhabitants (Table 3). Traditional knowledge of medicinal plants is critical as they enable for development of novel drugs (Fabricant and Farnsworth, 2001). Similar studies on the ethnobotany of riparian vegetation by Mohanan et al., (2020) report the presence of about 106 medicinal plants belonging to 48 families in the study. One of the biggest threats to such medicinal plants is both over harvesting and destruction of habitats (Cunningham, 1992). The distribution of medicinal plants in the riparian zone is greatly affected by anthropogenic activities. As urbanization rapidly spreads and modern medicines are implemented, the indigenous tribal knowledge which has not yet been documented is being lost. Therefore conservation strategies of the knowledge and sustainable utilization of the plant species are vital. This can be achieved by selecting the endangered important ethnomedicinal plants and understanding their management by the indigenous inhabitants (Woldeab et al., 2018).


 
 

The present study concludes that 31 species belonging to 15 families are reported from the riparian zone of the Dzücha river. Eleven herb species were reportedly utilized by the indigenous inhabitants. The warm and humid condition in the area has created an ideal environment for the genus Ageratina. Further, the diverse vegetation in the area hosts a variety of plants possessing traditional ethnobotanical medicinal values. Anthropogenic activities which negatively impact the important vegetation should also be monitored. Inventory of the bio resources of the region may further shed light on the high biodiversity of the region and its sustainable utilization by the stakeholders.
 

The Head, Department of Botany, Nagaland University is duly acknowledged for providing access to laboratory facilities.
 

The authors declare no conflict of interest.