Abstract
A high density of sambar deer inhabiting Horton Plains National Park (HPNP), Sri Lanka, has been observed to cause bark damage to woody vegetation. However, the extent to which this contributes to forest dieback in HPNP remains uncertain. Bark damage by sambar was assessed using eighty 100 × 5 m randomly established transects across three forest types (dense forest, open forest, and dieback forest) within the park. The severity of bark damage was categorized as ring-barked (100%), three-quarters (75%), half-ring (50%), and one-quarter (25%).
A total of 53 woody species were identified, of which 41 species had at least 10 individuals showing bark damage. Further analyses focused on these 41 species. Neolitsea fuscata recorded the highest relative density (10.52%), whereas Psychotria nigra var. nigra and Syzygium fergusoni had the lowest. Actinodaphne ambigua and Polyspora gardneri showed no bark damage, while other species exhibited between 1% and >53% damage within their populations. The highest frequency of bark damage was observed in Litsea longifolia and Psychotria nigra var. nigra, despite their low relative densities (0.18% and 0.14%, respectively). This suggests that sambar selectively feed on the bark of certain tree species.
For most species, the proportion of unhealthy, bark-damaged individuals exceeded that of unhealthy, undamaged individuals. The prevalence of unhealthy woody species increased with greater bark damage, with species such as Litsea longifolia and Psychotria nigra var. nigra being particularly vulnerable. Bark damage was strongly associated with declining tree health, indicating that it contributes significantly to forest dieback in HPNP.
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