WOOD DECAY FUNGI IN HORNBILL NEST CAVITIES IN KHAO YAI NATIONAL PARK, THAILAND

We investigated the abundance and species diversity of wood decay fungi inside and outside cavities of predominant hornbill nest trees, Dipterocarpus gracilis and Cleistocalyx nervosum and compared with those of Balakata baccata, which is known as non-nest tree for lack of cavity, in a moist evergreen forest of Khao Yai National Park, Thailand. We also examined the abundance of cavities in these tree sampled from wild population. Wood samples were collected twice yearly, once in dry and the other in wet season, from inside and outside the cavities of 10 D. gracilis trees, 10 C. nervosum trees, and 6 B. baccata trees. Additional dead wood of Dipterocarpus and Cleistocalyx was collected in dry season to determine true wood decay fungi. A total of 1,199 fungal isolates were obtained and were classifi ed to 68 species, 52 genera, 33 families, and 4 phyla The number of isolates was signifi cantly higher from inside than outside the cavities and in wet season than in dry season, particularly the isolates from Dipterocarpus indicating wet season provides optimal condition for fungi. Cleistocalyx hosted the highest species richness, i.e. 51 species (75%). Forty species (58.8%) were identifi ed from Dipterocarpus, and as expected the lowest was from Balakata, with only 16 species (23.5%). Eight species (11.8%) were found in common among all trees studied while 10, 20 and 4 species were exclusively isolated from the respective trees. Simpson's and Shannon-Weiner indices were used to determine fungal species diversity. In dry season, Dipterocarpus hosted the highest diversity according to Simpson's index, while Cleistocalyx had the lowest diversity, as demonstrated by both indices, in fungal species. Unexpectedly, wood decay fungi were dominated by soft rot fungi (91.2%) but not white rot (5.9%). The most common soft rot fungi were Trichoderma sp., Gliocladium sp. and Fusarium sp., and the white rot were Coprinus sp. and Sporotrichum sp. The present study suggested that wet season and enclosure condition such as inside the cavity infl uence the abundance and species richness. Other than moisture, additional conditions inside the cavity that may enhance the abundance and species richness of fungi included the volume of substrate (dead wood) and remaining nest debris (fruits, insects, and old feathers of imprisoned female). Further study on nature of sap and chemical compounds produced by Balakata is needed in order to explain the lack of large size cavity in Balakata, despite being a softwood tree. Nest cavities of hornbills were predominantly found in two tree genera/species, Yang sian (Dipterocarpus gracilis) and Wa (Cleistocalyx nervosum). By contrast, Sali nok (Balakata baccata), although it is large in size and common in the study area, no nest cavity was found. In this study, the abundance of cavities in these three tree genera was determined. The numbers of trees with at least one cavity were the lowest for Balakata (4%), 15.5% for Dipterocarpus, and 13.7% for Cleistocalyx. The trends were also similar for the abundance of cavities. The abundance of cavities in these tree genera was somewhat related to susceptibility of the tree to wood decay fungi. The susceptibility (or resistance) and host specifi city may be related to wood structure and/or chemical substance the tree produced, which may inhibit (or enhance) growth rate of fungi and in turn affect decay process. This paper was presented at the 5 th International Hornbill Conference jointly organised by the National Parks Board (Singapore) and the Hornbill Research Foundation (Thailand), in Singapore on 22 nd -25 th March 2009.