Fujian cypress and two other threatened tree species in three conservation zones of a nature reserve in north-western Vietnam

Abstract

Background Fujian cypress (Fokienia hodginsii) is a highly valued but endangered tree species. The Ta Xua Nature Reserve in Vietnam is one of its main conservation centers. This nature reserve consists of a fully protected core zone, a buffer zone in which low intensity forest use is permitted, and a forest restoration zone in which forest regenerates after shifting cultivation. Methods The community and population status of F. hodginsii and two other threatened tree species (Aglaia spectabilis and Quercus platycalyx) were assessed across the three conservation zones. Based on 120 random sample plots of 400 m2, we applied adaptive cluster sampling for trees with a diameter at breast height (DBH) of at least 6 cm. In addition, tree regeneration (DBH < 6 cm) was assessed. Results In the core zone, F. hodginsii, A. spectabilis and Q. platycalyx occurred at moderate densities (4.9, 5.1 and 4.4 trees∙ha−1, respectively). F. hodginsii and A. spectabilis were however much less abundant in the buffer and restoration zones. In contrast, Q. platycalyx had its highest density in the restoration zone. Regeneration of all three target species occurred in the core zone; however, there were only a few regenerating trees of F. hodginsii and A. spectabilis in the buffer and regeneration zones. Regeneration of F. hodginsii and A. spectabilis was mostly in the vicinity of conspecific adult trees. Conclusions F. hodginsii and A. spectabilis were mostly confined to the core zone, and regeneration of these species was rare in the buffer and restoration zones. For these two species, the core zone was the most important refuge, so continued conservation of this zone is important for the preservation of these species. The results of this study in the Ta Xua Nature Reserve do not confirm the classification of Q. platycalyx as ‘vulnerable’ in the Vietnam Red List. Further forest monitoring including repeated population assessments is needed to evaluate the vulnerability of threatened tree species.