Effect of Altruistic Surrogacy of Treefall on Herbaceous Flora Colonisation in Subalpine Forest of Khangchendzonga Biosphere Reserve, Eastern Himalaya, Sikkim, India

The present study represents the herb species' colonisation on the fallen trees in the subalpine forests in the Khangchendzonga National Park (KNP) West Sikkim, Eastern Himalayas. Around 5 per cent of the forest floor was taken up by fallen logs in various stages of decomposition. The study indicated that there must be no less than 13.50 trees with a diameter of at least 50 cm per 0.25 ha for successful colonization. Seedlings of herbaceous species differed in their probabilities of colonising under fallen logs, pits, and mounds but colonization of most species was substratum-specific. Several species generally colonised on pits, mounds, and logs. Pit colonisation by seedlings appeared to be larger in numbers than on logs and mounds. Most colonisation appeared to be local, from plants within 1 m of the log or pit. Summer species appeared to be superior colonisers and then spring-ephemeral species. Overall, plants with wind-dispersed seeds predominated in the colonisation of pits, and logs. The finding indicates that inclusion of other colonisation sites such as pits, mounds, and tree stumps would further favour the altruistic surrogacy of available colonisation areas. The existence of seasonal herbaceous species may be an indicator of the survival mechanisms of plant species to cope with changing climatic conditions and provide insights into how the species interact with their environment.