Discussion

Research works from different parts of the world, especially from the humid tropics, indicate that culturally protected fragments are repositories of rare and endemic species which have declined from rest of the local landscape due to anthropogenic pressures (Mgumia and Oba 2003; Bossart et al. 2006; Sukumaran and Raj 2007; Chandran et al. 2008). Similarly, Indian context adequately illustrates the presence of endemic and rare or threatened plants from sacred groves throughout the country (Khan 2008; Chandrashekhara 2011). But the future of such relic species in the small sacred groves, often isolated fragments of forests, has been rarely investigated. Past studies on Siddapur sacred groves (Chandran and Gadgil 1998; Nagendra 2001; Gokhlae 2004), have primarily focussed on the distribution of these groves in relation to other landscape elements, their vegetation status and socio-cultural aspects. Our study, in the same landscape specifically emphasized on the role of these groves in sheltering the endemic trees and their status of regeneration, a critical aspect closely linked to the future survival of such species in small vegetation patches.

Landuse dynamics
Our study on landuse dynamics corroborates overall landuse change pattern in the Western Ghats as well as in tropical Asia. There is a general trend of deforestation due to establishment of commercial plantation as well as agricultural intensification (Lawrence 2007; Giriraj et al. 2008; Joseph et al. 2009; Reddy et al. 2013). Although recent findings emphasize on industry driven forest conversion the deforestation drivers vary according to regional scenario as well as spatial scale (Verburg et al. 2000; Veldkamp et al. 2001; Rudel et al. 2009; DeFries et al. 2010). The limited extent of the study area offers the opportunity to study the locally active drivers for deforestation which have practical importance for developing mitigation measures. Fragmentation, one of the major consequences of deforestation often associated with increment of forest patch number and reduction of patch sizes which has been evident in many studies conducted throughout the world (Roy and Tomar 2000; Fahrig 2003; Ewers and Didham 2006). The same trend can be observed in our focal area where expansion of agriculture appears to be major driver of deforestation during the study time period and as a result of this cumulative grove area (0.36%) has also been reduced in comparison to its earlier spatial extent (6%) (Chandran and Gadgil 1998).  Conservation of woody endemics in sacred groves

We observed that, groves cumulatively support a number of endemic tree species populations despite their small size. The diverse species assemblage including endemics in the groves certainly contributes to maintain the functional diversity of the ecosystem in the otherwise nearly homogeneous landscape of the study area as evidenced elsewhere (Mayfield et al.2005; Cadotte et al.2011). In comparison to the 100% tree diversity captured in sacred grove survey (merely 0.36% of the study area), 55-70% of tree diversity was captured from non-grove forest patch. The three largest groves (Mat25, Ara39 and Kal49) jointly contribute 65% of the woody species diversity in the study landscape.

Among the 19 reported Western Ghats endemics, Ixora brachiata, Holigarna arnottiana, Hydnocarpus pentandra have widespread distribution in the Western Ghats (from 80 N lat to almost 200 N) and are comparatively more tolerant to anthropogenic disturbances (Pascal and Ramesh 1997). Even their distribution   is better in groves, including very disturbed ones than in the non-grove forests which harbour just few individuals of these tolerant endemics. On the other hand, absence of suitable microenvironment (in terms of moisture, temperature, canopy cover etc.) restricts the distribution of sensitive endemics like Vateria indica, Syzygium travancoricum, Calophyllum apetalum, Diospyros assimillis, Knema attenuata, which are known to be associated with only good evergreen forests (Pascal and Ramesh 1997; Sasidharan 1997; Nair et al. 2007; Chandran et al. 2008). Of these, V. indica and S. travancoricum enlisted as endangered and critically endangered respectively in the Red List of IUCN (IUCN 2013) are restricted to seven and three groves respectively with their regeneration stocks.

The endemics in general show highly skewed distribution towards relatively bigger groves in the area, however exclusion of three largest groves yields non-significant relationship among the others (Spearman’s r = 0.233, P > 0.05). This finding reiterates the results from the earlier studies in Western Ghats and other areas where species composition, diversity and evenness index have not shown strong relationship with grove / fragment area indicating importance of the quality of the fragments rather than its spatial extent (Ganeshiah et al.1997; Gkaraveli et al.2001; Sambuichi et al. 2012).

Thirty nine of the 53 studied sacred groves have adult endemic individuals, but juvenile stages (seedling and sapling) have been reported from 31 sacred groves either of same as adults or of different species. Although endemics like Ixora brachiata, Holigarna arnottiana, Flacourtia montana are widely distributed in their adult stage many of the groves are devoid of their juvenile stock due to limited spatial expanse and lack of protection. Therefore, often subjected to grazing and trampling by domestic animals. Due to inadequate juvenile stock, the wider distribution of adult members could be attributed to successful seed dispersal by small mammals and birds from neighbouring areas (Vijay 2006) or it could be explained as “Extinction debt” where lack of juvenile stock is an indicator of slow extinction of the species from the area in future (Lindenmayer et al. 2006). On the contrary, sensitive endemics like Vateria indica, Syzygium travancoricum etc. have better regeneration profile within their limited distribution in the landscape due to some protection provided to their habitats thus maintaining required environmental conditions.

Endemics in forest and other landuse forms –
The non-grove forest patch situated in south-west corner of the study area covering about 265 ha is under severe disturbances as observed through its canopy openness, compact soil and dominance of fire tolerant and heliophytic species. This forest is a continuation of the extended portion of the Western Ghats to eastward site and is surrounded by heavily modified landscape. This secondary partially degraded forest although not too far from the groves (average distance 2.83 km.) doesn’t seem to play much role in conservation of regional endemic plants.

Roadside and the farm areas are mostly represented by single or a few endemic individuals mixed with other local tree species and often lack juvenile populations. However, their chance survival has not received any support from local land and resource use decisions except for Vateria indica. This species have been used widely in afforestation program by the Karnataka Forest Department since 1996 and planted as an avenue tree in many areas because of its faster growth and wide canopy development.

Disturbances over the grove system –
The productive nature of the adjoining landscape have been exerting tremendous pressure on the grove system and causing shrinkage of their spatial extent.  Apart from the spatial extent, CATPCA result (dimension 1 and 2) emphasized on the factors like lack of protection, soil erosion, cattle grazing and proximity to road for deteriorating the system. These factors severely affect ground vegetation by damaging juvenile population stock; so do lopping and debarking to the adult trees (Marcial et al. 2001; Chazdon 2003; Tabarelli et al. 2004). The shrinkage of area greatly affects microclimatic condition which results into increment of generalist and invasive species in expanse of specialist and endemic species (Pardini et al. 2009; Anitha et al. 2010; Tabarelli et al. 2010). Earlier study in Siddapur also pointed out that peoples’ preference to certain tree species because of horticultural usage can change the floristic composition of the grove system, and can even develop single species dominating vegetation (Gokhlae 2004, 2005).

Larger groves are at least under some form of protection (either fencing or social norms) which ensures their structural integrity as well as ecological attributes due to less disturbed interior part. In contrast, the condition changes along the grove border in terms of light, moisture and soil profile (pers obs.). This drastic change in environment restricts the endemics mostly towards the grove interior except few which prefer open canopy and drier condition (e.g. Holigarna arnottiana, Ixora brachiata) (Pascal and Ramesh 1997). There are exceptions however e.g., S. travancoricum, though elsewhere found more in interior swampy forests, in our focal area we found it confined to the grove edges that border rice fields. These edges remain water-logged for most periods of the year perhaps favouring the growth of this sensitive Western Ghats endemic.

Despite some limitations (small study area, absence of suitable replicates etc.), the case study attempted here underscores the importance of small scale forest conservation. This, being of an informal kind, has been operating among traditional agricultural communities of Western Ghats, but escapes attention from conservationists. The existing social protection, though may be insignificant (seldom studied systematically), plays a key role in survival of these woody endemics under changing landuse scenario in Western Ghats. The conservation and management of smaller forest fragments has not deserved much consideration so far, and their continued obliteration can be disastrous for this otherwise acknowledged biodiversity centre.

In order to decimate the increasing conflicts between biodiversity conservation and livelihood improvement, sacred groves could continue to play a central role because of their acceptability and veneration for the deities resident in them. However, the groves are dwindling not merely to cater to the needs for biomass and land but also due to transformations in religious attitudes and worldview of local communities who had protected much larger groves in historical times. The local communities and forest administration need to be convinced about the ecological, cultural and historical significance of sacred groves so as to strike a balance between conservation and utilisation of biodiversity.