The Fate of Five Rare Tree Species after Logging in a Tropical Limestone Forest (Xuan Son National Park, northern Vietnam)

The Long Ngo,Dirk Hölscher

doi:10.1177/194008291400700211

The Long Ngo, Dirk Hölscher

Open Access

https://doi.org/10.1177/194008291400700211

Copy DOI

Abstract

Rare tropical tree species are endangered due to the disappearance of old-growth forests. Although some undisturbed old-growth 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.

Highlights

With the loss of tropical old-growth forest, many tree species, and rare ones, have become endangered
The tree≥5 densities of E. tonkinense (40%), C. tabularis (40%), M. suavis (44%) and G. fagraeoides (55%) were much lower in the logged forest than in the un-logged forest, whereas P. chinensis showed no difference (Fig. 3)
Diameters and heights were clearly lower in the logged than un-logged forest, while only slightly lower median tree sizes were observed for P. chinensis and M. suavis in the logged forest (Table 3)

Summary

Introduction

With the loss of tropical old-growth forest, many tree species, and rare ones, have become endangered. Habitat specialization and regeneration characteristics are considered to be of great importance to conservation [2]. Whether rare tree species persist and regenerate in formerly logged forests is often unclear. Site conditions play an important role for regeneration, and among those habitats considered problematic, limestone karst is a prominent example. Limestone areas are usually difficult to access due to their rugged topography and steep slopes, logging and forest disturbances are still widespread [24,25]. We asked: 1) whether the rare tree species still exist as adults in the logged forest; 2) whether they regenerate; and 3) if so, which ecological factors control the regeneration. We hope this study will improve understanding of the ecology of the studied tree species, and help extend fully protected zones into areas that formerly experienced logging

Methods

Results

Conclusion