An Assessment of Plant Diversity in the Sacred Grove Sites of Nilgiri Biosphere Reserve

SACRED GROVES IN THE NILGIRI LANDSCAPE

In the Western Ghats of India where habitat degradation and forest fragmentation have had a long history, sacred

groves are patches of natural forest that have been protected by the religious beliefs of indigenous people for over

1000 years (Sinha 1995; Ramakrishnan 1996; Chandran & Hughes 1997; Chandrashekara & Sankar 1998; Colding &

Folke 2001). In places like Karnataka’s Coorg district and most of Maharashtra, sacred groves are isolated from

natural forests and are important residual patches of semi-natural forest in a landscape that is otherwise

intensively cultivated (Nair et al. 1997). There is a long history of management by local people as a source of non-

timber forest products (NTFP) (Daniels, Chandran & Gadgil 1993), but there are strict restrictions and regulations

of harvesting timber or conversion to other landuse types, since protection of these forest patches is a cultural

legacy. , it is believed that most have never been subject to intensive timber harvesting nor cleared for other forms

of land use (Chandran 1997).

The Alu Kurumbas of the Nilgiri Biosphere Reserve are an indigenous group that have Devasolai or traditional

worship sites as pockets within dense forests. On the slopes of Coonoor and Kotagiri mountains, a recent study

mapped over 23 worship sites of the Kurumba community. What is notable in this region is that sacred groves are

nested within larger patches of continuous forests and although there are plantation estates and modified forests

around them, there is contiguity with the natural forest type and its vegetation. Therefore, unlike in other sacred

grove sites in the Western Ghats, the Nilgiri sacred groves appear less fragmented and are rather intact.

Conserving biodiversity is especially crucial in countries where people’s livelihoods are directly dependent on

natural resources such as forests, fisheries and wildlife. Often, there is a lack of baseline biodiversity information

necessary for better conservation and long-term sustainability of natural resources and human communities.

Where information is available, it is often restricted to select species or habitats and is insufficient to derive

strategies for management and conservation.

A strategy to slow the loss of biodiversity and to enhance its contribution to development must integrate three

essential elements: conservation of biodiversity, sustainable use of its components and the equitable sharing of

benefits. This would need on priority to assess the biodiversity surviving in a given area. Species inventories will

remain perhaps the largest part of such assessments and are of value in the selection of protected and threatened

areas and of ecologically and economically sensitive areas.

A preliminary plant biodiversity study was carried out in the sacred groves of the Coonoor slopes, aimed at

assessing the overall vegetation composition and recruitment status of dominant tree and liana species in each of

them. The surveys were led by indigenous people who had a strong hold of ethnobotany and at the end of the

study, the findings were discussed in a village meeting.

STUDY SITES

Four sacred groves were selected for the study. They were located in evergreen to semi-evergreen forests of the

Coonoor slopes, varying in vegetation composition. Kavalcombai (E76.84695,N11.31880; 1020 m) was the largest

grove extending 9.5 acres, Sengalcombai (E76.8161, N11.287674; 1100 m) covered an area of over 6 acres,

Erikkumalai combai (E76.835645,N11.304660; 980 m), less than 4 acres, and Dodatti (E76.84665,N11.35281; 1700

m) – 1.2 acres.

APPROACH AND STUDY DESIGN

A mapping of the sacred grove boundaries was carried out in the beginning of the project. A plant diversity study

was initiated in January 2012 which composed of an inventory of trees and lianas, and an assessment of

recruitment.

An intensive field survey was carried out in each site. Plots of sizes 20 x 20 m were laid along the edge/ boundary

of the grove and trees and lianas with girth size above 20cm dbh were recorded. . On two diagonal edges of the 20

x 20 m plot, 5x5 m plots were laid for recording saplings that would fit into the recruitment class. The number of

plots laid was proportional to the size of the sacred grove; in Kavalcombai (11 acres), we laid 9 plots, in

Sengalcombai (6 acres), we laid 5 plots, in Erikkumalacombai (4 acres), we laid 4 plots and in Dodatti (1.4 acres),

we laid 2 plots

In addition, transects were laid inside the groves and an inventory list of all observed plants was made. We

considered the species found in the inventory as expected to be seen in the grove and included them in the

diversity analyses.

Threatened and endemic plants were enlisted from the sampling plots and transects and their presence across the

four groves compared. Unidentified plants have been preserved as herbarium specimens at Keystone.

Species Richness and Diversity Index

In each site, we listed the number of tree and liana species (species richness) cumulatively recorded in the

inventory and the plot sampling method. The data thus collected in each sacred grove were used to derive the

abundance and density of each tree and liana species. Inverse Simpson diversity index values were calculated for

the four sites. A Tukey HSD test was employed for comparison of means of the diversity index values, a test

generally used in conjunction with an ANOVA to find which means are significantly different from one another. All

tests were carried out in free software R2.9.1.

Importance Value Index

One measure of the relative dominance of species in a forest community is called the Importance Value Index (IVI).

Importance values rank species within a site based upon three criteria: 1) how commonly a species occurs across

the entire forest; 2) the total number of individuals of the species; and 3) the total amount of forest area occupied

by the species.

We calculated IVI values of tree and liana species (Curtis and McIntosh method, 1951) for the four groves, from

adding values of relative density, relative frequency and relative dominance. The index gives an overall estimate of

the influence of importance of a plant species in the community.

Recruitment

Seedlings were counted in the 5x5m plots placed within the 20x20m plots and abundance values calculated. We

also asked if there was a correlation between recruitment diversity and tree densities in the different sacred

groves. A Tukey HSD test was employed for comparing the means of the diversity indices in the four sites.

RESULTS AND INTERPRETATION

Species richness and Plant densities

The inventory of higher plants in Sengalcombai, Kavalcoimbai, Erukkumalaicombai and Dodatti documented 28,

63, 51 and 31 species of trees and lianas respectively. The plot sampling method, almost always, recorded fewer

number of species than were encountered in the inventory (Table below).

Species richness

Plot sampling method

Inventory inside

Overall richness (considering overlaps)

Sengalcombai Kavalcombai Erikkumalaicombai Dodatti

28 49 36 12

28 63 51 31

48 69 52 32

Plant density 8.60 45.33 28.75 18.00

The sacred grove at Kavalcombai held the highest plant density, with a species richness of 69 species. Although

Dodatti was lowest in species richness, the plant density in Dodatti was higher than in Sengalcombai where

bamboo dominated the plots and was not included in the density analysis.

Ranking

Dominance was shared by several species at each site, and, with the possible exception of Celtis tetrandra in Dodatti, no one species exerted complete

dominance over any appreciable area.

Tree species Sapindus emarginatus, Mallotus philippensis, Albizia odoratissima, Dalbergia sissoo and the liana Acacia sinuata were dominant in the evergreen

forest of Erikkumalalacombai. Endangered species like Cycas circinalis and endemics like Excoecaria crenulata and Canarium strictum were found in negligible

densities.

Fig 1a. Importance value indices of tree and liana species in Erikkumalacombai.

In Kavalcombai, the largest site, Clausena dentata, Hydnocarpus alpine, Mesua ferrea, Scheichera oleosa and Linociera courtallensis dominated the vegetation

and along with Nothopegia heyneana and Holigarna arnottiana, they composed over half of the total IVI of the site. Endemics Hydnocarpus alpinia and

Holigarna arnottiana were seen in reasonably good densities. We recorded a very high abundance of lianas in this evergreen site, including the endangered

Dalbergia horrida, Hiptage benghalensi and Derris benthamii.

Fig 1b. Importance value indices of tree and liana species in Kavalcombai.

In Sengalcombai, the dominant species were Gmelina arborea, Tectona grandis, Pterocarpus marsupium, Grewia tiliifolia and Anogeissus latifolia. Bamboo was

found predominantly in the upper slopes, and since it was included in the basal area based calculation of IVI, it does not reflect in the IVI graph below.

Fig 1c. Importance value indices of tree and liana species in Sengalcombai.

Celtis tetrandra singly dominated the sacred grove at Dodatti, along with Persea macrantha, Macaranga peltata and Actinodaphne lawsonii. Macaranga

peltata, a pioneer, was a clear sign of disturbance and tree fall gaps at the site. This grove also showed frequent Lantana invasion.

Fig1d. Importance value indices of tree and liana species in Dodatti.

Diversity index

Fig 2. Bar chart depicting the mean Inverse Simpson diversity index values of the four sacred grove sites.

The diversity indices of Erikkumalacombai and Kavalcombai featured highest. The Tukey HSD test for multiple comparison of means revealed the most significant difference in the means between Erikkumalaicombai and Dodatti (p=0.1449), and the sites with least difference in their means were Kavalcombai and Erikkumalacombai (p=0.9158).

(Fig 3)

The plant diversity indices (represented on the map as graded tree size) and the recruitment class diversity indices

(represented as graded size of leaf) were overlaid on the forest types map of the Coonoor slioes of the NBR.

Biodiversity information on plants, birds or mammals when explored on GIS domain is valuable in identifying

threatened and ecologically sensitive areas. In addressing conservation around forest-based communities of the

Nilgiri Biospehere Reserve, it might provide pointers to systematic management through long-term community

engagement.

Recruitment

Data from the 5x5 m plots on seedling numbers were pooled in to calculate abundances and diversity indices. To answer “What species in each of these populations are doing well and what species are taking over in the recruitment class?”, we compared the dominant species data from each site with the dominant seedlings data. The patterns of recruitment are described here.

Fig 4a Abundance values of seedlings of trees and lianas in Erikkumalacombai.

In Erikkumalacombai, Cassine glauca, Clausena dentata, Ficus mollis, Sapindus emarginatus and Diospyros montana seedlings were abundant. Sapindus emarginatus is the only species from the dominant species in the grove (refer IVI chart, Fig.1a) that showed a reasonably good recruitment index. Among the dominants in the site – Albizia odoratissima, Dalbergia sissoo, Acacia sinuata and Albizia odoratissima, only seedlings of the liana Acacia sinuata were recorded in the sampling.

Fig 4b. Abundance values of seedlings of trees and lianas in Kavalcombai.

In Kavalcombai, seedlings of Syzygium sp., Excoecaria crenulata, two species of Clausena, Cassine paniculata, Nothopegia heyneana, Clerodendrum viscosum, Hydnocarpus alpina and Mallotus philippensis were abundant. All the dominants in the site – Clausena dentata, Hydnocarpus alpine, Mesua ferrea, Schleichera oleosa and Linociera

courtallensis (refer IVI chart, Fig 1b) reflected well in the recruitment class. Species such as Canarium strictum that are actively harvested from the site showed low recruitment in this assessment. The trees are fairly abundant in the population and their low recruitment may be cause for conservation concern.

Fig 4c. Abundance values of seedlings of trees and lianas in Sengalcombai.

In Sengalcombai, seedlings of Clausena sps., Cycas circinalis, Mallotus philippensis and Sapindus emarginatus were recorded in high abundance. A look at the IVI chart (Fig 1c) shows how none of the dominant species – Gmelina arborea, Pterocarpus marsupium, Grewia tiliifolia and Anogeissus latifolia reflected in the recruitment class, except Tectona grandis. Meanwhile, there was a high regeneration of endemic and endangered species like Cycas circinalis and lianas like Acacia sinuata. It must be noted that there was indiscriminate harvest of Cycas in the population and almost all the trees that were spotted in the transect were lacking fronds. Fruits are apparently not harvested in this region unlike in the western slopes of the NBR. This may be why harvest does not have a negative impact on regeneration.

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Seedling abundance in Sengalcombai

Fig 4d. Abundance values of seedlings of trees and lianas in Dodatti.

The sacred grove in Dodatti displayed seedlings of Clerodendrum viscosum, Clausena sps, Debregeasia longifolia and Ficus mollis in high abundance. Of the dominant species (IVI chart, Fig. 1d) in the population – Celtis pentandra, Persea macrantha, Macaranga peltata, Actinodaphne lawsonii and Poomaram (vern.), only Actinodaphne lawsonii reflected in the recruitment class. This may be suggestive of a shift in dominance in the population, but only long-term monitoring can confirm.

Diversity index

The mean inverse simpson index for diversity was calculated to compare seedling diversities. The Tukey HSD test for multiple comparison of means revealed the most significant difference in the means between Kavalcombai and Sengalcombai (p=0.084), followed by the difference between Erikkumalacombai and Sengalcombai (p=0.3408). The sites with least difference in their means were Kavalcombai and Erikkumalacombai (p=0.965).

Fig. Mean Inverse Simpson diversity index values of individuals in the recruitment class for the four sacred grove sites.

Analysis of recruitment data showed a clear, positive correlation between good recruitment and areas of high tree

density (refer Table 1). In Sengalcombai, for instance, where we recorded the least tree density, the recruitment

diversity index was the lowest.

CONSERVATION IMPLICATIONS

The four sites were comparable in terms of frequency of access, although it was only in Sengalcombai and

Kavalcombai that we found signs of harvest. The edges and the borders of the Dodatti patch were invaded by

Lantana and there were gaps in the canopy where pioneers like Macaranga peltata and Clerodendrum viscosum

thrived.

Unlike sacred groves in some other sacred sites in the Western Ghats, there appears to be no restriction on

harvesting plant resources from these sites. Signs of indiscriminate harvest of Cycas leaves from Sengalcombai

were noted, and so were trees of Canarium strictum in Kavalcombai recently harvested for resin. We had

inconclusive evidence from the study on recruitment on the status of seedlings and juveniles of these species.

There is potential for setting up long term community-based monitoring of recruiting individuals to understand

regeneration patterns.

We held a meeting to discuss the findings with villagers from near Sengalcombai and Erukkumalacombai sacred

groves. In Sengalcombai, not only was there a decline in seedling diversity when compared to adult diversity, there

was also a change in composition of dominant species. While bamboo dominance in this site may be one reason

for this, the village meeting pointed out recent and frequent instances of fire and harvesting of plant parts such as

Cycas, Acacia sinuta and Sapindus emarginatus. These aspects need management attention from the perspective

of the Kurumba community that accesses this sacred forest site. In Erukkumalacombai, no instance of fire was

recorded in recent times, although villagers remember two big fires in the site, one 20 years and the other 40 years

ago. There is also some harvesting of plant products in Erukkumalacombai. There is no threat from grazing in the

two sites.

The process of dialogue has been initiated to look into the current management regime of these sacred groves,

particularly in the context of communities having had to move away from the sacred sites in the past few decades.

The study presents an opportunity to compile the indigenous knowledge base on biodiversity and exploring

avenues for conservation of biodiversity with people’s participation. Restoration planting of species found to be

declining in regeneration and thought to be declining by the community may be taken up through the Keystone

nurseries.

Sacred groves being ancient sites that are reasonably undisturbed, are sites ideal for understanding long term

evolutionary processes and impact of recent anthropogenic influences on the forest structure and composition.

They are also crucial repositories of genetic diversity. A valuable approach for future studies would be to ask what

ecosystem services are offered to communities living close to these sacred sites – for instance, pollinators for

agricultural crops, litter decomposing arthropods and fungi, soil and water retention functions of native

vegetation.

Forests in the Nilgiris have declined in size owing to a range of anthropogenic threats - illegal cutting, forest fire

and encroachment of forest land for estates of tea and plantation to name a few. These threats, particularly,

habitat loss and habitat fragmentation have acted on sacred sites of Kurumba communities in the past and may

have resulted either in loss of certain faunal species and change in composition and dynamics in the various forest

types.

While efforts are underway to reestablish legal rights and cultural links with the sacred groves from which the

indigenous settlements have moved away in recent times, there is need to explore and help build local capacities

to revive these forests. Discussions with the community on dominant forest resources used by them, tree

population sizes and their regenration status are crucial to evolve strategies of protecting and if necessarey,

initiate a species enrichment programme in-situ.