Studies on angiosperm diversity and bio-monitoring with resource mapping in Nelliyampathy hills of southern Western Ghats, Kerala, India

Abstract

The present study focuses on the angiosperm diversity of Nelliyampathy hills which lie on the south-western side of the Palghat Gap. The hill tracts flank an area of 206 sq.km. Even though many novel taxa had been identified and reported from the study area, a holistic study of angiosperm diversity is lacking. In this context, an attempt was hereby made to account the diversity of angiosperms, their habitat diversity, biomonitoring and resource mapping of Nelliyampathy hills. The extensive exploration resulted in the documentation of 1529 taxa under 142 families. Poaceae are the largest family followed by Fabaceae and Rubiaceae. Cyperus is the most speciose genera followed by Crotalaria, Ipomoea and Impatiens. Herbaceous taxa predominate the vegetation followed by tree members. Among the forest types, Evergreen forests form the prominent vegetation followed by deciduous forests and grasslands. This was reflected in the elemental composition also, where the evergreen elements account the highest in the study area followed by grassland elements and Moist Deciduous elements. The median altitude accounts for the highest diversity where the altitudinal zone of 900-1200 m forms the most diverse zone followed by the 600-900 m zone. The study could record 66 IUCN red listed taxa and 308 threatened species. About 25% of the collected taxa were found to be endemic to various geographical regions of the country. Apart from Indo-Pacific affinity, taxa are showing highest affinity towards African and South American kingdoms and least towards Australian. Due to the high wind velocity in Palghat Gap region, the concentration of anemochorous taxa is too high in the study area. Special adaptations like parasitism, semi-parasitism, saprophytism, carnivory, epiphytism and climbing habits could be observed among the vegetation. The frequency of chasmophytic taxa is also high since 36% of the collected taxa are showing chasmophytic nature. Adaptations like extensive root system, rosette or cushion-like habit, scapigerous nature, herbaceous habit, therophytic life- form, succulence, pubescence, subterranean perennating organs, semi-parasitism and carnivory were observed among these chasmophytes. About 25% of the collected taxa shows medicinal property and among them, herbaceous taxa are predominantly used in medicinal ailments. Phanerophytes is the predominant life-form in Nelliyampathy followed by therophytes. Seven novel taxa could be identified viz., Glycosmis nelliyampathiensis, Tripogon sp.nov., Ischaemum sp.nov., Eugenia sp.nov., Microstegium sp.nov., Fimbristylis sp.nov. and Peucedanum sp.nov. Reinstatement of Pachystoma hirsuta (Joseph & Vajravelu) C. S. Kumar 3& Manilal from P. pubescens Blume and Rhynchoglossum scabrum Dalzell from Rhynchoglossum notonianum (Wall.) B.L.Burtt. were proposed. Collection of Crotalaria priestleyoides Benth. ex Baker is a recollection after a century from Kerala part of southern Western Ghats. Out of the collected taxa, five hundred and eighty-eight taxa were found to be additions to the Flora of Palghat district (Vajravelu, 1990). Among them, 122 were having an extended distribution to Palakkad district. Forty-three monotypic genera were recorded from Nelliyampathy. Taxonomic singularity at genus level is 0.65 and at family level it is 0.42. Analysis of vegetation across Palghat Gap using PAST software reveals a difference in the species distribution between northern and southern sides of Palghat Gap. One hundred and nineteen taxa with ethnobotanical significance could be recorded from the two tribal colonies of the study area. Forest cover change analysis between two decades revealed that there is an increase in Evergreen Forest cover, deciduous forest cover and grasslands while the forest plantation areas and barren lands have decreased. Evergreen forests predominate the upper altitudinal zones while deciduous forests predominate the lower altitudinal zones. But NDVI analysis of forest cover in two different decades shows a marked deterioration in the health of the vegetation in Nelliyampathy. Slope-wise zonation depicts that the majority of the study area falls under gentle slope areas and steep slope areas. Majority of the land-slide affected areas mapped are either in the Ghat road or at the monoculture plantation areas. Uprooting of larger trees, opening up of canopy, diminishing of ground flora, heating up of forest floor and phenological shift are the major post-flood habitat modifications observed in Nelliyampathy. Seventy two alien invasive elements and 88 degraded forest elements were recorded which shows the degrading nature of the forest tracts of Nelliyampathy. Apart from the natural causes like natural calamities, forest fire and invasive species, there is too much of anthropogenic stresses in Nelliyampathy which includes plantations, tourism, plant introduction, agricultural practices, grazing, selective felling and encroachment to forest land, urbanization, habitat fragmentation by constructions, road construction in interior forests, plastic dumping and pesticide application in tea and cardamom etc. This in turn, calls for the need of proper conservation strategies in Nelliyampathy to maintain its natural vegetation.