Species diversity and population status of chestnut (<i>Castanopsis</i> spp.) at Soraya Research Station, Leuser Ecosystem

Abstract Soraya Research Station (RS), as part of the Leuser Ecosystem, is a natural habitat of chesnut ( Castanopsis spp). Information on the diversity and population of chestnuts in Soraya RS has never been reported. This study aims to confirm the number of Castanopsis species found and to determine its population status in the Soraya RS forest area. Data collection in this study was carried out using the multiple plots square method of 27 plots sampling placed randomly at the research site. In each measuring plot, nested plots were made. Plot with the size of 20 m × 20 m is to collect data for tree stage, 10 m × 10 m for poles, 5 m × 5 m for saplings, and 2 m × 2 m for seedlings. Data was collected in the form of the number of individuals of each plant species and the diameter of each stem only for the pole and tree growth stage. Data analysis used were relative density, relative frequency, and relative dominance to determine the Importance Value Index (IVI). The chestnut species found in the Soraya RS forest are Castanopsis argentea (Blume) A.DC., Castanopsis costata (Blume) A.DC., and Castanopsis cf. hypophoenicea (von Seemen) Soepadmo. C. argentea was the species that had higher IVI than the other two chestnut species. The population status of the three chestnut species differed in each growth stage. Seeding, sapling, and pole of C. costata and C . cf hypophoenicea were not found in the forest vegetation of Soraya RS, but only the tree growth stage found at the low IVI value in the forest community (ranking 45 of 81 for C. costata and ranking 23 of 81 for C.cf. hypophoenicea ). Meanwhile, C. argentea has seedlings (ranking 27 of 30), saplings (ranking 30 of 30), and trees (ranking 4 of 81). There was also no pole growth stage of C. argentea found in the forest vegetation of Soraya RS, as with the other two chestnut species.