Regular Article J F E S Journal of Forest and Environmental Science pISSN: 2288-9744, eISSN: 2288-9752 Journal of Forest and Environmental Science Vol. 31, No. 3, pp. 164-176, August, 2015 http://dx.doi.org/10.7747/JFES.2015.31.3.164 164 Journal of Forest and Environmental Science http://jofs.or.kr Population Structure and Regeneration Status of Cyathea gigantea (Wallich ex Hook. f.) Holttum, a Tree Fern in Arunachal Pradesh, India Ashish Paul 1, *, Sonal Bhattacharjee 2 , Baharul Islam Choudhury 3 and Mohamed Latif Khan 4 1 Department of Botany, Rajiv Gandhi University, Rono Hills, Doimukh - 791112, Arunachal Pradesh, India 2 Alternative Fuels and Raw Materials, ACC Limited, Coimbatore, Madukkarai - 641105, Tamil Nadu, India 3 Department of Biology, Concordia University, Montreal, Sherbrooke Street West - 7461, Quebec H4B 1R6, Canada 4 Department of Botany, Dr. Hari Singh Gour Central University, Sagar - 470003, Madhya Pradesh, India Abstract Cyathea gigantea is a tree fern distributed throughout humid tropical regions of northeast India and other parts of the country. However, wild populations of this species are largely affected by various natural and anthropogenic activities. Therefore, an attempt was made to study the population structure and regeneration status of C. gigantea in and around greater Itanagar area of Papum Pare district, Arunachal Pradesh. Altogether 45 patches, ranging from 19.63 to 260 m 2 of area, were randomly sampled to study population structure and regeneration status of the species. Population study showed highest number of youngs in the height class of 0.50-0.75 m while, immatures were recorded highest in the height class of 2.0 to 2.5 m. Majority of the matures belonged to 6-9 m height class while it was recorded maximum in the diameter class of 10-15 cm. Average density of C. gigantea was 0.07 individuals ha -1 which varied greatly among different patches with a range of 2 to 14. Significant correlations were found between patch size and density of youngs, immatures, matures and total density. Maximum concentration of youngs was observed in patch size 60-140 m 2 , while for immatures, it was highest in patch size 20-160 m 2 . Similarly, highest concentration of matures was observed in patch size 20-80 m 2 and 80-180 m 2 . Population structure of the total population exhibited inverted pyramid shaped distribution. Population structure consisting of youngs, immatures, matures showed that around 60% patches lack of regenerating individuals which depict very poor natural regeneration of the species. Effective conservation strategies are therefore to be formulated to save C. gigantea from the threat of extinction in near future. Key Words: Arunachal Pradesh, Cyathea gigantea, population, regeneration, tree fern Received: October 8, 2014. Revised: July 7, 2015. Accepted: July 15, 2015. Corresponding author: Ashish Paul Department of Botany, Rajiv Gandhi University, Rono Hills, Doimukh - 791112, Arunachal Pradesh, India Tel: 91-9862035885, Fax: 91-360-2277317, E-mail: ashishpaul1@gmail.com Introduction Ferns are large and ancient group of plants which evolved in Carboniferous period (Dinosaur Stampede 2012). There are around 12,000 species of ferns distributed all over the world and most of the species grow in tropical or sub-tropical forests leaving very few in extremely arid or cold regions (Hassler and Swale 2001). Ferns are key com- ponent of tropical and temperate vegetation and play sig- nificant roles in ecosystem functioning in the both canopy (Hietz 1997) and forest floor (Hill and Silander 2001). Tree ferns represent an important characteristic for rain for- est of tropical and subtropical climate and play an important role in ecology of lands of origin. Some species have im-