IMPACT OF SAMBAR DEER(Cervus unicoior unicoior) ON THE VEGETATION AT THE HORTON PLAINS NATIONAL PARK

Abstract

A survey was carried out at the Horton Plains National Park to investigate the influenceof sambar deer on grassland and fares' vegetation. The method adopted was, comparisonof the dominant grassland communities and seedlings in the forested areas with andwithout the effect of deer. Three enclosures (20 m x 5 m) were erected in the grasslandand four enclosures (20 In x 15 m) were erected in the forest to serve as controls (nograzing). Similar areas adjoining the plots were marked with pegs as test areas (withgrazing). Field surveys were carried ou. during the years 1997 and 1998. Incidence andextent of bark damage by sambar deer \Y<JS also examined using a scoring method on sixtransects each measuring 250 lJ1. GSN (Grazing Susceptibility Number) was used as anindicator of the the phytosociological behaviour of sambar in the grassland SummedDominance Ratio (SDR)) was used to calculate the GSN. During the months of January,March. July and October 1997, GSN values for dominant species in the grassland vizPennicetum and Chrysopogon were 184,20,23.75, -3.06 and 18.6,8.1, 17.23, 19.0respectively. The minus GSN value of ).06 indicates that during October Pcnnicctumgrass was not damaged by deer which coincided with the flowering period of thatspecies. Grazing presusure values obtained during the periods July-Sep 97, Sep-Nov 97 .Nov-Jan 98, Jan-Mar 98 for Pennicetum and Chrysopogon were 17, 5.6, -17.6, 5.8 andI, I I, -0.5, 0.9 respectively. Here the minus values indicates heavy grazing. During theperiods of less rain and also during peak lactation periods of sambar, the grazingpressure is high (July-September and November-January) compared to positive values ofgrazing pressure which coincides well with the comparatively high rainfall periods Studiesof the forest vegetation revealed that after a period of two years (1997-1999) 88'% ofseedlings survived (N=1499) in the enclosure but only 73% of the seedlings survived(N= 1488) in the open area. Bark damage is distinct on plants like Cinnamomumovalifolium, Neolitsea fucata, Calopiiyllum walkeri, Eurya japonica, Eleocarpussubvillosus, Syzigium revolutum and rJedyotis lawsoniae all of which have high IV)(Importance Value Indices). Trees with average gbh 28 cm and average height 7 m weremore prone to damage by deer. Only S% of a total of 921 trees were dead due to barkdamage.