2. LITERATURE REVIEW
Schimper’s (1903) work on tropical forest has been considered as one of the pillars of modern ecology. The Tropical Rain Forest by Richards (1952) is an acknowledged classic that generated considerable amount of interest. It is based on the studies carried out in Guyana, Borneo and Nigeria. Corner’s, ‘The Life of Plants’ (1964) considers tropical rain forest as the matrix of terrestrial vegetation type. The first important work on India’s vegetation is by Champion (1936) and revised by Champion and Seth (1968).
Early botanical studies in Uttara Kannada district, towards the south of which is situated Kathalekan, the focus of this study, were purely floristic. The systematic and detailed inventories of flowering plants of the erstwhile Bombay Presidency prepared by Cooke (1901-08) and Talbot (1909) are still some of the best reference materials for the flora of this district. Since the time of Cooke and Talbot, more than 1700 species of flowering plants have been reported from the district. (Daniels, 1989). Arora (1961) for the first time explored the Uttara Kannada forests as a part of his studies on the floristic ecology of Western Ghats. Pioneering work by Chandran (1993, 1997) on kans of Western Ghats constitute the basis for this work.
The studies on sacred groves in India gained impetus with the pioneering works of Gadgil and Vartak (1975, 1976) in the Western Ghats, especially from Maharashtra state. Gadgil and Berkes (1991) attributed the traditional practice by most human societies of rendering complete protection to certain biological communities by setting aside of refugia (sacred groves, for instance) to a variety of regulatory measures which have been an integral part of utilization of biological resources. Such regulatory measures also included quantitative quotas as to how much material is harvested restriction of harvests to certain season or life history stages, restriction on harvesting techniques employed etc.
Sacred groves belong to the traditional practice of protecting, patches of vegetation, mostly of the primeval kind, on religious grounds subtended by cultural practices. They have been identified all over the world and in all shades of cultures. In India, the groves have been reported from the forest ranges in the hills, arid regions like the deserts and along agricultural plains as well (Ramakrishnan et al. 1998). Whereas larger groves are considered mini-biosphere reserves, the smaller ones are also of biological value as they harbour some old and magnificent specimens of trees and climbers (Gadgil and Vartak 1975).
The genesis of sacred groves in the Western Ghats may go back to hunting gathering societies which attributed sacred values to patches of forests within their territories as they did to several other topographic or landscape features like mountain peaks, rocks, caves, springs and rivers. But the practice of setting aside patches of forests as sacred groves would have strengthened with the spread of agriculture, involving widespread slashing and burning of forests. The groves, in addition to their role as the abodes of gods, would have also protected a range of landscape elements with their characteristic biodiversity. (Chandran et, al 1998).
Study of a kan forest is the focus of this work. In fact kans were known as special patches of forests from all over the central Western Ghats, especially of Shimoga and Uttara Kannada districts. The kans were known to the local inhabitants as forests preserved primarily on religious grounds. But most British records never acknowledged the role of local communities in preservation of the kans. Chandran and Gadgil (1993), and Chandran (1997), explained various socio-religious, historical, economic, and ecological aspects of the kan forests. They were important pieces of pre-colonial forest conservation in the Western Ghats. Myriad relics of such groves exist even today all over the Western Ghats. These sacred forests in pre colonial landscape, served many functions like conservation of biodiversity and watershed, moderation of climate and enhancement of landscape heterogeneity which promoted varied wildlife. The people had also much reliance on subsistence hunting. The village sacred groves ranged in size from few ha to few hundred ha each.
The practice of keeping aside sacred forests by the early farmers would have provided the necessary seeds for the re-establishment of the evergreen forests that have been during the slash and burn cultivation process, rampant until the late 19th century in the Western Ghats. Although the evergreen forests tend to re-establish on its lost grounds, in the absence of fire and other anthropogenic factors, it is likely that some of the elements of climax evergreen forest did not stage their come back, may be due to some apparently irreversible soil changes brought about burning (Chandran, 1993).
Concomitant with a climatic change towards more aridity, during the fourth millennium BP, widespread vegetational changes were expected to have taken place in the Indian sub-continent. To support such climatic change related changes in vegetation Caratini et.al (1991) brought in palynological data from a marine core closer to Karwar in Uttara Kannada. The pollen data showed substantial increase in pollen of savanna plants against those of forest plants. The find was used to buttress the argument that the fourth millennium BP climatic change had not spared even the humid forest belt of lower altitude portions of Western Ghats. However, a look into composition of kan forests of Uttara Kannada, particularly the Kathalekan and Karikan showed that these are today major refugia for hygrophilous species like Dipterocarpus.The pollen of which was present in the Karwar marine core far north in the offshore of Uttara Kannada. The very presence of Dipterocarpus, Vateria indica, Myristica spp. etc. all very sensitive species, specially in the kans are taken as evidence by Chandran (1997) for agricultural clearances and not climatic change as the cause for vegetational mid fourth millennium BP changes.
Rajendraprasad (1995) compared the floristic diversity of climax evergreen forests and sacred groves of Kerala and reported that the Shannon-Weiner’s diversity index value varied from 2.6 to 3.6 for climax forests and it was 2.8 to 3.6 for the sacred forest. Within the sacred forest, the diversity value varied and was positively related to the disturbances. In the disturbed groves of Uttara Kannada, Shannon-Wiener’s index value varied from 3.2 to 3.6. The floristic difference between highland and coastal groves was maximum and the highland and midland showed maximum similarity (Devar,2008).
Balasubrahmanya and Induchoodan (1996) estimated 761 important sacred groves in Kerala with floristic wealth of over 722 species belonging to 474 genera and 217 families. This study revealed that the biodiversity potential of sacred forest was found to be very high when compared to well protected evergreen formations of South India. They estimated the area of groves in Kerala to be 90 sq.km.
Nayar (1996) considers ‘Devavanams’ or ‘Kavu’ meaning sacred groves as some of the last refugia for our endemic flora and fauna. Plants and animals are worshipped along with gods and goddess in sacred groves. Mohanan and Nair (1981) had collected a new species of Kunstleria which is essentially a Malayan genus from one of the sacred groves of Kerala, and described the new species as Kunstleria keralensis. Syzygium travancoricum Gamble, was collected by Bourdillon in 1894 from Kerala and it was not located for about seven decades. Nair and Mohanan (1981) had relocated the species in the sacred groves of Kodumon and Aickad in Kollam district of Kerala in 1981 and Pandurangan had located 15 to 20 trees in Guddrikka (Nayar, 1996).
Boriah (2001) conducted a comparative study with respect to species composition of regenerating species among the reserved forests and sacred groves and revealed that the species richness was highest for the reserve forest (160) followed by disturbed sacred groves (156) and conserved sacred groves (146), the last showing a slight decrease in the species number. This study indicates that some disturbances can increase diversity.
The studies of Bourgeon (1989) and Pascal et al (1988), on the edaphic features of the Western Ghats forests show that in some cases, edaphic compensation, especially better moisture holding capacity of soils enables the maintenance of evergreen formations even when the rainfall is somewhat lower. The ‘kan’ forests of the Karnataka plateau, of particularly Sorab-Sagar region in Shimoga were taken up for illustration.
Sacred groves act as microwater shed in local areas. The sacred groves are always associated with a fresh water ecosystem used to trap and collect the rain water for the local water supply. If they are destroyed or disrupted the water cycle would be interrupted. The heavy canopy and undergrowth along with the litter of the sacred groves is helpful in reducing the impact of rain drops on the soil. This humus rich soil facilitates rapid infiltration of rain water during rainy season as a result of improved hydrological properties of the soil (Pushpangadan et al., 1998)
Kathalekan of Siddapur taluk was obviously a kan or a sacred forest of the pre-Brahmin people. Despite the logging damage it suffered ever since the Second World War, primarily due to the extraction of valuable timbers of species like Dipterocarpus indicus, Calophyllum tomentosum and some other industrial timbers it still harbors great amount of endemism in the ground layer (Gadgil and Chandran, 1989).
The study by Pomeroy et al (2003) on the four plots in Uttara Kannada such as Kathlekan, Devimane, Malemane, Kodakani in Uttara Kannada showed that the forest of Kathlekan has relatively lower density of trees, around 330 trees/ha. In contrast to the other forests, Kathlekan has a higher percentage of large trees (>50 cm dbh). Road construction followed by selective logging occurred through these plots, though Kathlekan was exposed to these activities earlier than other nearby places). The census in the 1993 and 1997 indicates that the mortality rate of trees in Kathalekan had reached 8% and the mean estimated recruitment rate also increased dramatically to around 4% approximately balancing the mortality. The timber extraction from Kathalekan had caused a decline in forest cover; the low point was during 1977 to 1984, the peak of industrial felling, when tree density was only 70 % of the original density. Prohibition on timber extraction from 1987 obviously promoted forest recovery. By 1993 there has been some pronounced recovery in Kathalekan forests.
Dasappa and Swaminath (2000) described a new critically endangered species viz., Semecarpus kathlekanensis from the kan forest of Kathlekan .The reproductive biological study of the same plant by Vasudeva et al. (2001) reported that the species has primitive breeding system a combination of dioecious and monoecious species.
Devar (2008) in his study on species composition and diversity with respect to various size classes of kan forests in the Sirsi Forest Division of Uttara Kannada showed that among various size classes the small fragments had comparatively higher species composition and diversity than that of large kans and medium sized kans. The species composition of small kan forests showed that though the species distribution is accumulating with increased size of the kans, it does have strong relationship with the increasing species richness. Similar trend was followed with respect to species diversity which indicates that species diversity increases with the size of the kan. The distribution of species also shows a positive relationship with the size of the kan forests suggesting more equitable distribution in the entire area of kan forests.
Among the different species recorded in the kan forests of Sirsi Forest Division, were Actinodaphne hookeri, Artocarpus hirsutus, Cinnamomum macrocarpum, Diospyros cadolleana, Flacourtia montana, Holigarna beddomei, Hopea ponga, Knema attenuata, Macaranga peltata, Mimosops elengi, Olea dioca, Syzigium cumini, S. gardneri, Terminalia paniculata and Vitex altissima. Thesewere more commonly seen across rainfall ranges indicating their broad distribution. (Devar, 2008)
Kathalekan is also home to rare type of swamp forests. Swamp forests were reported from the foothills of the Himalayas (Dakshini, 1960; Somadeva and Srivastava, 1978, Ghildiyal and Srivatava, 1989; Gupta, et.al., 2006) and Kalakkad-Mundathurai (Ganesan, 2002). Krishnamurthy (1960) first reported the Myristica Swamp from the Travancore region of South Western Ghats which was classified under a newly introduced category, ‘Myristica Swamp Forests’ under the sub group 4C by Champion and Seth (1968). These Swamps are well developed in the valleys of Shendurney, Kulathupuzha and Anchal forest ranges in the Southern Western Ghats of Travancore. In Uttara Kannada district of Karnataka studies revealed 51 swamp patches. The swamps were highlighted for their evolutionary and ecological characters. (Chandran, 1993; Chandran et al 1999; Chandran and Mesta, 2001) A swamp associated with a sacred grove in the Satari taluk of Goa was reported by Santhakumaran et al (1995).
Nair, et al. (2007) made an excellent effort towards documenting the biodiversity of the Myristica swamps of southern Kerala. They estimated the total area of MyristicaSwamp in Kerala to be about 1.5 km2 (which hardly make up the 0.004 % of the total land area of the state). The biodiversity inventory revealed that the swamps contained 12 red-listed plants and 28 plants endemic to Western Ghats. It also highlighted the enormous faunal wealth of the Myristica swamps, including various species of nematodes, annelids, molluscs, insects, arachnids, fishes, amphibians, reptiles, birds and mammals.
The non-biotic ecological conditions essential for the Myristica swamp have been projected by Varghese, (1992) and Chandran et al. (1999). The swamps need special ecological conditions like flat bottomed or gently slopping valley in between heavily forested hills of evergreen forests, deep soil in the adjoining hills with rock below which will allow water to be stored above the rock layer, slow seepage of water from the side hills in to the valley throughout the year, heavy annual rainfall averaging 3000 mm and temperature ranging from 20-30 o C. Hence these Swamps are highly restricted in distribution.
Myristica Swamp may be considered as an endangered habitat. Rare Western Ghat endemics like Myristica fatua var. magnifica, Gymnacranthera canarica, Semicarpus kathalekanensis and a fragile palm Pinanga dicksonii were notable of the plants associated with the swamps. Although swamps are sources of perennial streams they have faced large scale destruction in the recent past causing in all probability diminishing watershed value of the Western Ghats (Chandran and Mesta, 2001).
According to Whitmore, (1984), in tropical evergreen forests, the level of disturbance as expressed as gap size is very important. A small gap may be filled by one or more ‘fugitive’ species which can result in an increase in species diversity. On the other hand a large gap may be filled by a dense stand of a single pioneer species or a handful of them.
The forests of Uttara Kannada have had a long history of disturbance and transformation by man. As they stand today, woody plant species numbers tend to fall with the declining rainfall gradient in a northeastern direction. The evergreen forests have the highest species richness. Daniels (1989) observed that one hectare of evergreen forest in some of the least disturbed parts of the district contain between 40 and 60 species of trees (≥30 cm GBH)
Pascal, 1988 characterised the species like Terminalia, Lagerstroemia, Artocarpus, Olea dioica and Macaranga peltata as invaders of disturbed evergreen forests. He suggested that these species cannot increase the diversity significantly. They are all characteristic of the northern Sahyadris (of Goa-Maharashtra), a region subjected to greater dry period. Hence their increased number in more south could be indicative of disturbance.
Endemism of the Western Ghats is very high among the evergreen trees than deciduous ones. The significant positive correlations exist between evergreenness and endemism. The cutting and burning of the forest patches for shifting cultivation, widely practiced once, in Uttara Kannada and other parts of the Western Ghats would have naturally lowered the endemism of the forest patches where they operated since the regrowth on abandoned cultivation sites would initially have promoted the growth of deciduous trees (Chandran, 1993). The alterations brought about in the primary forest of the Western Ghats by the early agricultural societies would have lowered the endemism substantially. However on the abandoned ‘kumri’ the foresters often noticed the return of the evergreen forests (Gadgil and Chandran, 1989).
According to World Conservation Monitoring Center (1992), preservation of the tropical forest is vital for conserving biodiversity. Although they cover only 6-7% of the earth surfaces these forests probably contain more than 50% and possibly as much as 90% of all species of plants and animals. Lugo and Brown (1992) indicate the importance of the forest in the carbon dioxide assimilation process. The study reveals, tropical forest including vast areas of degraded forests, also function as sinks of atmospheric carbon.
The kan forests were not given due importance in state-centred conservation circles. That many kansare relics of the original climax forests has been more an overlooked fact. Recently, in some such relic forests of Uttara Kannada were found the presence of critically endangered trees Madhuca bourdillonii (Gamble) Lam. and Syzygium travancoricum Gamble. These trees were at one time thought to be extinct from southern Western Ghats from were they were reported for the first time. Later, however, they were rediscovered in the south. Their presence about 700 km north of their original home in latitude between 14º and 15º N may be considered as an evidence of the persistence of the relic forests with their rare biota (Chandran et al., 2008). The kansare obviously such relic forests, and much need to be done in future for study and conservation of kans. That is why Kathalekan, a notable kan of central Western Ghats has been chosen as the theme for this work.
