The fate of five rare tree species after logging in a tropical limestone forest (Xuan Son National Park, northern Vietnam)

Abstract

Rare tropical tree species are endangered due to the disappearance of old-growth forests. Although some undisturbed oldgrowth and formerly logged forests are protected today, the extent to which rare tree species persist and regenerate in such logged forests is often unclear. In a forested area over limestone in northern Vietnam, we studied the fate of five rare tree species after decades of logging and subsequent nine years of full protection, in comparison with an un-logged forest. Three of the studied species are largely restricted to limestone hills (Excentrodendron tonkinense, Chukrasia tabularis and Garcinia fagraeoides), while two of the species have a wider distribution (Parashorea chinensis and Melientha suavis). The bigger trees of the study species had lower densities and/or differences in the diameter distributions between the two forest types, indicating that these species had formerly been cut. The regeneration stem density of the study species was much lower (46% in M. suavis to 80% in P. chinensis) in the logged than un-logged forest. In the un-logged forest, we found clear relationships between ecological factors and regeneration density in four of the five study species; e.g., the regeneration of E. tonkinense increased with increasing rock-outcrop cover (r = 0.6, p < 0.01). Such relationships were almost absent in the logged forest. The widely distributed generalist species Cleidion javanicum dominated in the tree regeneration of the logged forest. Our results suggest that the studied rare tree species still existed as adults after logging and there was regeneration but at low densities. We assume that the potential for recovery remains, which further justifies the full protection of this and other restoration areas. © The Long Ngo and Dirk Hölscher.