Multivariate analysis of elements from the microhabitats of selected plateaus in the Western Ghats, Maharashtra, India

The Western Ghats represents a small part of the Deccan Traps continental flood basalt province that erupted about 65 million years ago. It is an area of outstanding scenic beauty and has attracted the attention of geologists, naturalists and geomorphologists for over a century. One of the unique habitats in the Western Ghats are the rocky plateaus. Previous studies have covered plant species composition, geological and geomorphological status of the rocky plateaus. An analytical study of microhabitats and associated therophytes of four rocky plateau sites was conducted. The study sites were Durgawadi Plateau, Naneghat Plateau which are basalt outcrops and Zenda plateau and Amba Plateau, which are laterite outcrops on the escarpment of the northern Western Ghats. The results revealed a correlation between basalt and lateritic rock outcrops as well as ephemeral plant elements. All four outcrops are similar in their nutrient status but the microhabitats of these plateaus are extremely different from each other.


INTRODUCTION
The Sahyadri Range is one of the spectacular geographic features of the Indian subcontinent. Documenting the plant species was necessary to understand the nature of vegetation (Sambhaji 2015). A compilation with commentary of landmark papers by the Geological Society of India's (Gunnell & Radhakrishna 2001) findings till date gives us an idea about its uniqueness. One of the distinctive aspects of the geomorphology of the Sahyadri Range is the presence and preservation of two "paleosurfaces" indicated by laterite (Fox 1923;Widdowson & Cox 1996;Widdowson 1997). Cliffs, isolated hills, and platforms of rocks formed due to landscape level activities of weathering are the types of outcrops seen commonly in India, whereas "rock outcrops" is the term recognized by IUCN as a category of habitats wherein some portions of freely exposed bedrock project above the soil level due to natural reasons (Porembski & Watve 2005). According to Porembski (2007) well-known rocky outcrops in the world are inselbergs, barrens, cedar glades, cliffs, serpentine, ultramafic, limestone, and gypsum outcrops. He also suggested that each of these are known to harbor highly specialized vegetation rich in microhabitat-specific and endemic plants. Rock outcrop habitats are generally of small extent within a region and present particular habitat limitations, e.g., greater exposure to sun and scarcity of soil. The microenvironment at the rock surface ranges from very hot and arid in dry season to water logged in the wet season. Hence edaphically controlled herbaceous plant communities are characteristic of rock outcrops. Rock outcrops are very well known throughout the world for their uniqueness, but are less studied habitats. Most studies are from African, American and Australian outcrops (Porembski et al. 1994Burke 2005a,b;Jacobi et al. 2007) describing the habitat types and associated vegetation composition. In India, relatively very few reports exist about vegetation on these special habitats (Porembski & Watve 2005;Watve 2008Watve , 2013Lekhak & Yadav 2012;Bhattarai et al. 2012).
The rock outcrops in the Western Ghats of Maharashtra are of two types based on the rock formation and soil type developed from it: (i) Lateriticlateritic rock cover is well preserved over the parent basalt rock and soil rich in iron, and (ii) Basaltic-having black hard rock and soil. Durgawadi and Naneghat plateaus from the northwestern corner of Pune District are entirely basaltic but have some lateritic soil due to weathering. They have a diversity of micro-habitats and are rich in flora and fauna. Trees or shrubs are less in number, but herbaceous angiosperms, algae, mosses, ferns and lichens are generally abundant in these habitats. Many of the endemic ephemerals, herbaceous angiosperms, pteridophytes and lichens, however, are restricted to these special habitats (Watve 2008). Species composition patterns and outcrop communities are influenced by multiple environmental factors like soil type, elevation, aspect of that rock outcrop and microenvironments (Watve 2013). Moreover, transect studies of plateaus in northern Western Ghats region conducted by Watve (2008Watve ( & 2013 discuss the vegetation composition and pattern of some microhabitats on the plateaus. A comprehensive botanical study of two rock outcrops, Durgawadi Plateau (DP) and Naneghat Plateau (NP), on the escarpment of northern Western Ghats revealed a very high plant diversity within the sites and between the sites (Rahangdale & Rahangdale 2014). Herbaceous vegetation of high-level lateritic plateaus of southwestern Maharashtra have been studied by Lekhak & Yadav (2012). These studies have revealed the importance of microhabitats as this plateau vegetation has unique microhabitats that support distinct plant communities depending primarily on soil, depth of the soil and moisture availability. None of these studies describe the interrelationship between nutrient status and plant communities. Hence, the present study was carried out to find out the correlation between nutrient status of selected microhabitats and associated plant communities with the following objectives.
1. Identification and RS & GIS based mapping of microhabitats at plateau ecosystem 2. Sampling and analysis of trace and major elements of rock as well as soil from microhabitats 3. Identification and selection of ephemerals in plateau ecosystem 4. Sampling and analysis of trace and major elements of selected plant communities 5. Understanding correlation among elements, microhabitats and plant communities as well as plateaus using statistical methods There is a tar road from Junnar to Naneghat (Ghatghar Village). The basalt is exposed as a broad expanse at a low altitude and bounded by sacred groves, reserve forest patches, rice fields and vertical slopes. The outcrop and its surroundings are affected by biotic pressures. Hemadri (1980) and Rahangdale (2009) denoted that Naneghat Plateau area is rich in plant diversity.

METHODS
Maharashtra possesses characteristic habitats called high level plateaus (Watve 2007). Many of them represent lateritic, basaltic as well as sandy characteristics. Of the four plateaus which were found least disturbed, the ones representing basalt and laterite were selected for the said research. All of these are located in the Western Ghats at Pune and Kolhapur regions. These were specifically selected after referencing existing literature and after conducting several field surveys.

GIS mapping -tools and techniques
The research area was surveyed extensively to mark the boundaries of the plateaus. Exact latitudes and longitudes were recorded and marked by using Garmin 5 handheld GPS. These lat-longs were then calibrated with Google Earth version 6.2 (http://www.Google.com/ earth/index.html) to get .kmz images as a reference database. For freshly captured images, satellite data was procured from NRSC, Hyderabad. The data was further used to mark each microhabitat at each plateau (Table  1) on ArcGIS … and ERDAS 9.1 platform. Each plateau as well as each microhabitat was GPS marked.
In all, three field study visits were carried out during different seasons: pre-monsoon (March-May), monsoon (June-October), and winter (November-February) to understand the seasonal variations from 2013 to 2017.

Sampling and analysis of soil and rock
Rock and soil sampling was done from the microhabitats marked using GIS; wherever soil was accumulated in microhabitats soil samples were collected from 100cm depth. For habitats like boulders and exposed rock surfaces, the intact rocks were broken and samples were collected. These samples were analyzed using x-ray fluorescence spectrophotometry (XRF). It is a non-destructive analytical technique used to determine the elemental composition of materials. XRF analyzers determine the chemistry of a sample by measuring the fluorescent (or secondary) x-ray emitted from a sample when it is excited by a primary x-ray source. The method is used extensively to analyze trace and major elements of rock as well as soil in a powdered form. Nutrients, Nitrogen by Kjeldahl's method and organic Carbon by Walkley & Black method. The data of XRF analysis is heterogenously distributed over 50 elements around two rock types from four locations distributed over 10-11 microhabitats. Dimensions of which are 2*4*11*50 and types of measurements are percentage and part-permillion.
The statistical analysis was carried out using R v 3.3.3 and ggplot2 v 2.2.0 package

Identification of micro habitats at plateau ecosystem
Plants on the plateaus are adapted to various microhabitats and each of these is unique in its edaphic properties, water availability and species composition (Porembski & Barthlott 2000). According to Jacobi et al. (2007) and Watve & Thakur (2006) the most common habitat types observed on plateaus have been identified by following an established categorization for rock outcrops.

Identification and selection of ephemerals at plateau ecosystem
A comprehensive list of plants has been prepared for each microhabitat classified as per Raunkiaer (1934). Phenology was recorded and all the specimens collected were therophytes. An analysis reveals that nearly 70% of the species associated with plateau ecosystem are therophytes (Porembski 2000). The species found in abundance were collected by direct uprooting method along with all parts including roots to flowers. Care was taken to avoid disturbing species nearby. Identification of species was done using regional flora of Kolhapur and Pune and the literature available. Collected plant specimens were processed at the herbarium using standard techniques. All herbarium specimens were deposited in Agharkar Research Institute, Pune for authentication. This was recorded as a first set of samples. The second set of samples were carefully dried in shade. Soil particles from the roots were carefully removed from the plants, and the sample plants were powdered with mortar and pestle. Further, these set of samples were analyzed by XRF to understand trace  (Shtangeeva & Alber 2009). Interrelationship among elements was also identified. Table 1 shows the details of the samples collected and processed.

RESULTS AND DISCUSSION
The multivariate analysis of variance (MANOVA) was carried out between the selected elements of plants and rocks across four regions (Durgawadi, Naneghat, Amba, and Zenda) for 10 nutrient elements. The p-values were estimated using multivariate Pillai-Bartlett test statistic.
The overall MANOVA, carried out across all the regions, indicated a significant difference in the content of all the nutrient elements between rocks and plants (p-value = 2.2e-16; <0.001) (Fig. 1).
In the case of Durgawadi region, based on the MANOVA it was observed that there was significant difference in the content of nutrient elements between rocks and plants (p-value = 1.795e-12; <0.001). Further investigations revealed that except Zinc, all other elements were significantly contributing towards the differences in nutrients of rocks and plants in the Durgawadi (Fig. 2) plateau.
Similar to Durgawadi, the Naneghat region also showed a significant difference in the content of nutrient elements between rocks and plants (p-value = 4.761e-09; < 0.001). Copper, however, did not contribute significantly towards the differences between rocks and plants in the Naneghat (Fig. 3) region.
When Amba region was analysed using MANOVA it revealed that there was significant difference in the content of nutrient elements between rocks and plants (p-value = 5.667e-10; <0.001). Further investigation revealed that except Zinc, all other elements significantly contributed towards the differences in nutrients of rocks and plants in the Amba region, which is similar to Durgawadi (Fig. 4) In case of Zenda region, based on the MANOVA it was observed that there was significant difference in the content of nutrient elements between rocks and plants (p-value = 1.31e-06; <0.001). Closer inspection showed that the elements Calcium, Manganese, Zinc and Copper did not contribute towards the significant differences in plants and rocks of Zenda region (Fig. 5). It shows that the nutrient profiles of plant and rocks in Zenda region is characteristically different from other regions.

CONCLUSION
The overall results show that nutrients, trace and major elements under study in all four selected plateaus are significantly different. The Zenda Plateau, the least disturbed plateau in all four plateaus, shows characteristically different nutrient and element content. As Calcium, Manganese, Zinc, and Copper do not contribute towards significant differences in plants and rocks of Zenda region. Each of these areas is different and needs to be studied in detail to understand the dynamics of the ecosystem. Except Zinc, similarity was observed in all elements when samples were analyzed from rocks as well as plants at Durgawadi-Basalt and Amba-Lateritic plateaus. For understanding the causes of such similarities more such studies are needed. The environmental exceptionality, high diversity, lack of studies and speedy destruction of these ecosystems pose an abrupt challenge for their conservation. These should not be considered as wastelands as they are ecologically significant and a hold scientifically unknown facts. www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.