An evaluation of the wetland grass flora of Mizoram, India

: Mizoram, a diminutive state in northeastern India forms a major segment of the Indo-Burma biodiversity hotspots. The wetland grasses in the ecosystem are elements adapted in assorted habitat as one of the primary producers. This present assessment is principally focused to augment and evaluate information on the current status of the aquatic and semi-aquatic grasses from the taxonomic and ecological perspectives from this ecoregion. The paper encompasses the present taxonomic account of the wetland grasses with recent citations, protologue, type, basionym, phenology, growth forms, field status, worldwide distribution and specimens examined. The present investigation revealed the occurrence and distribution of 16 genera including 23 species of wetland grasses from this state. This kind of study always sets the ground for launching in-depth ecological projects for working out the present ecological characteristics and status of the wetlands and their restoration and conservation.


INTRODUCTION
Wetlands are frequently referred to as the 'Kidneys of landscape' which are the land-water transitional zone between terrestrial and aquatic systems where the water table is usually at or near the surface or the land. The region usually remains covered by marshy, shallow or muddy water. The RAMSAR convention defined wetlands as 'areas of marsh, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters' (Bridgewater & Kim 2021). Wetlands all over the world are threatened directly due to reclamation for development activities, reduction in function due to pollution, water demand, change in hydrologic regime, overexploitation of wetland resources and also due to underlying causes such as market failure, information failure and intervention failure. In this scenario, fundamental knowledge on location, characteristics, functions, values, threats and assessments of status of wetlands are prerequisite for developing sustainable conservation programme for wetlands. They are amongst the most productive ecosystems on earth and any alterations might lead to changes in their bio-physical, socioeconomic and climatic conditions. Grass-dominated communities cover about 24% of the Earth's vegetation (Judd et al. 2002). They not only provide ecosystem services such as water and climate regulation in support of agriculture, biogeochemical cycling, carbon storage, but also form a habitat for a variety of aquatic macro-invertebrates and herbivores (White et al. 2000). Moreover, they have wide ecological amplitude and are able to adapt in diverse habitats as one of the primary producers, as in wetland ecosystems (Mukherjee 1993). The members can acclimatize to farreaching range of habitations more than sedges and are aptly considered one of the most ecologically successful taxa due to their broad diversification, adaptability and tolerance (Palit et al. 2017).
The graminoids form the fifth largest family of flowering plants (Stevens 2001) but its importance is beyond doubt for it provides to the grasslands which occupy a third of the land's surface (Schantz 1954). They are globally represented by 12,000 species under 780 genera (Christenhusz & Byng 2016) among which India includes 263 genera and 1,291 species (Karthikeyan et al. 1989). There are 18 genera (Sreekumar & Nair 1991) and 350 species (Jain 1986) of grasses which are endemic to India. An exhaustive survey to generate the grass flora of Mizoram amalgamated with literature compilation and herbarium study revealed 64 genera comprising 100 species of grasses. The taxonomic and functional appraisal of the wetland grass flora of this state recorded 16 genera having 23 species which indicates the relevance in ecological management and restoration. This assessment was carried out from 2016 onwards to augment and update information on aquatic and semi-aquatic grass flora from the taxonomic and ecological perspectives. The present commentary includes the current taxonomic status, type, abundance, growth forms, phenology, distribution in India and in the world of the diverse variety of the wetland grass species which are encountered from this geographical area. While studying the grass diversity in Mizoram, special concentration was given to the wetlands because of its intimate aquatic association. Adequate numbers of plant specimens were collected from the wetlands from 2016 onwards, some of which were processed for herbarium preservation at CAL herbarium and the rest were taxonomically worked out. Standard taxonomic methods were applied for description and identification using authentic literature (Bor 1960;Guhabakshi 1984;Baruah & Baruah 2006). The taxonomic account includes current taxonomic citations, protologue, type, basionym, phenology, growth forms, status, field notes, distribution and specimens examined. The genera and species under each genus are arranged alphabetically.

RESULTS AND DISCUSSION
The present survey and investigation revealed the occurrence of 16 genera including 23 species of grasses (Poaceae) from the wetlands of Mizoram.
In the current study, 16 genera having 23 species under family Poaceae (grasses) from the various wetlands of Mizoram were encountered. They were worked out taxonomically, identified and preserved. The study revealed that, the diversity of the wetland grasses observed in the concerned geographical area remained quite dissimilar to other places of India. The assemblage of the grasses in the wetlands significantly altered in accordance with the availability of soil and intensity of light. Moreover, many species exhibited a wide range of tolerance to the variations in the altitude, wind velocity and intensity of submergence. The species also showed longer culms where the height of water was higher than those in the marshy zones. Furthermore, the plant height gradually decreased with the increase in altitude. In addition to the above, the comparative account of the wetland grass species assemblage indicated variations in the richness and the abundance in accordance with the soil and slope pattern. The extent of species range and plant assemblage in close proximity of large water bodies was considerably higher than that of forested wetlands. Thus, the pattern of the assemblage in the wetlands depends on the water regime, soil nutrient content, altitude and use as observed in varied geographical locations.

CONCLUSION
The present study based on 23 wetlands grasses is purely a taxonomic approach with notes on location, type, growth form, phenology, and distribution. Extending the observations to the present context, continuous monitoring of the wetlands should be continued to retrieve the variations in the distribution of the wetland grasses and associated changes in the community structure. These kinds of revisions are always important for the studies of ecological characteristics of the wetlands, their restoration and conservation.