The main aim of this thesis is to establish a modern pollen-vegetation relationship, past vegetation-climate change in a rainfed tank and to assess leaf trait measurements and their application in the functional classification of vegetation in the Eastern Ghats. Modern pollen-vegetation relationship is essential for interpreting the past vegetational, environmental and climatic change obtained from analyzing the tank sediments. The leaf trait measurements form the basis for the functional classification of vegetation in this region. The salient findings of these studies are summarized in this chapter and the conclusions of the study are also presented. Unresolved questions and directions for further research are also discussed.
Modern Pollen-Vegetation Relationship Modern pollen-vegetation relationship has been established from the Eastern Ghats. 26 surface soil samples and 2 spider webs were palynologically analyzed. 91 pollen taxa have been identified. Pollen morphology of 33 species were investigated in the present study. A comprehensive diagnostic pollen key for the identification of pollen grains from lake sediments and surface soil samples has been prepared for the first time from this region.
Past Vegetational, Environmental and Climatic Change Pollen data proved useful in reconstructing the vegetational history of Rusula Cheruvu. Pollen content of 1.5 m deep lake sediment at different depths was investigated. Sediment cores examined in this study goes back to ~700 years B.P. Findings on vegetational, environmental and climatic history of ~700 years B. P. were revealed from an unexplored region of Eastern Ghats of India. During the past ~700 years B.P. significant changes in climate occurred in and around Rusula Cheruvu. It is found that four wet and three dry events occurred in the past. The wet period is corroborated by increased abundance of Cyperaceae (sedge) pollen along with tree pollen taxa. The marked increase in both degradation and forest markers in the recent past indicates that both deforestation and afforestation have gone hand in hand. A total of 72 pollen taxa were identified from this 1.5 m sediment core.
Leaf Trait Measurements and Their Applications This study, for the first time, systematically documents together the life form, phenology and leaf size, quantitatively. Data analysis reveals that leaf parameters showed correlation with climatic factors such as temperature and precipitation and it is a significant contribution to the functional classification of vegetation of the Eastern Ghats. It is suggested that future course of analyses with reference to other climatic parameters such as length of the dry season and evapotranspiration could be undertaken. There are indications that plants show adaptations not only with reference to the amount of precipitation received, but also with reference to the intensity and duration of the precipitation. Estimated parameters can be of use also from the management-conservation point of view. This is an important base line data and frequently field-based information on the leaf phenology is not readily available, particularly so because the study area considered here comprises forests often having semi-evergreen, moist deciduous and even semi-deciduous formations, increasing the ambiguity further. Though not explored here, the proportion of evergreen, leaf-exchanging and deciduous trees in tropical forest is obviously related to climate, particularly to the length and severity of the dry seasons. Leaf-fall and longevity depend on various parameters, both internal and external. Leaf-fall can be connected with climatic factors as well as edaphic factors but some trees are independent of both these factors and can follow sporadic rhythm of timing for leaf shedding (Schimper, 1903). Since leaves play the vital function of providing plants with carbon, there is a strong selection on species to produce leaves that maximize carbon gain over the lifetime of the leaf (Santiago, 2007). These, along with the various parameters to be considered when classifying any vegetation type, are explored at length by Richards et al. (1940) and Richards (1996).
Directions for Future Research Future lines of research can be perceived along the following lines (i) to extend the study to the other parts of South India for a regional synthesis in order to understand the complexity of regional climate. Additional palaeoclimate records distributed in different climate zones of Eastern Ghats would provide a valuable contribution to understanding this pattern, (ii) to study the behaviour of forest and disturbance markers in the past 30-50 years along multiple lines: fine resolution RS studies, Palynological studies and forest department records and (iii) to study the leaf trait measurements on all life forms of the plants of Eastern Ghats and Western Ghats to classify vegetation functionally.
Conclusions Modern pollen-vegetation relationship was established using the standard method. This modern pollen-vegetation relationship is useful for further exploration of past vegetational reconstruction. A ~700 years B.P. vegetational, environmental and climatic history was deduced from analyzing lake sediment from Central Andhra Pradesh of Eastern Ghats, India. Data on base-line leaf area measurements was generated and can form a basic input for the functional classification of vegetation of India. This has application in many areas such as agronomy, ecology, conservation and management of forests. The primary productivity and precipitation-use efficiency can be studied using the PFT composition of the given area (Vermeire et al., 2009). This is one such usefulness in the field of Agronomy. In the field of Ecology, PFT can be used to understand the ecological processes, eg., Succession and competition (Duckworth et al., 2000). Description and classification of vegetation is another important applied aspect of PFT (Webb, 1959; Duckworth et al., 2000). PFTs can be used as the improved tool to predict the vegetation composition and can be used to manage the forests efficiently. Moreover, it can be used as a complementary to species-based approaches to description in plant ecology and biogeography.