Responses of Native Tree Species to Soil Water Stress in a Tropical Forest on Limestone, Vietnam

Le Van Binh,Ralph Mitlöhner,Nguyen Van Thinh,Vo Dai Hai,Reinhard Köpp

doi:10.4236/ojf.2015.57063

Abstract

Forests over limestone in the tropics have received little attention and limestone forests in Vietnam have been overlooked to an even greater extent in terms of tree physiology. In Ba Be National Park, Vietnam, soil water availability in limestone forests seems to be the most limiting factor in the dry season. Therefore, in order to enhance the preliminary knowledge of choosing native tree species for enrichment planting in the restoration zone, characteristics of the 20 native tree species to soil water stress were investigated in a limestone forest. One-ha plot each consisting of twenty-five 20 m × 20 m plots was established in undisturbed forests. All trees ≥ 10 cm DBH were measured in 20 m × 20 m plots, while twenty-five 5 m × 5 m subplots were established in order to sample the regeneration of tree species with a DBH w) and leaf osmotic potential (Ψπ) of the 20 native tree species, respectively in this study. 61 species belonging to 34 families of all trees with a DBH ≥ 10 cm were recorded in one ha, while 31 species representing 18 families of trees 2. The 20 species’ leaf water and osmotic potential values revealed significant differences among species. The maximum leaf water potential was not affected by any anticipated sources of variation, while the minimum water potential, however, showed significant variation to soil water stress. The results in the study area emphasized the importance of water factors in influencing tree species distribution; it could be concluded that native species with wide water potential ranges would be better able to withstand water changes and might be thus good candidates for reforestation (enrichment planting) in limestone areas.

Highlights

Tropical limestone forests and karsts often contain high plant diversity combined with a large degree of endemism (Vermeulen & Whitten, 1999, Clements et al, 2006)
Tree abundance of this study was in keeping with other studies carried out in limestone forests all over the world such as 644 individuals ha−1 (DBH 10 ≥ cm) were counted in such forests in Gunung Mulu National Park, Malaysia (Proctor et al, 1983)
Our findings demonstrated similar patterns of population structure as were observed for the regeneration of a dominant family in the limestone forest of three sites in Xuan Son, Cuc Phuong, and Pu Mat national parks in North Vietnam (Toai, 2012)

Summary

Introduction

Tropical limestone forests and karsts often contain high plant diversity combined with a large degree of endemism (Vermeulen & Whitten, 1999, Clements et al, 2006). The studied forest grows on a limestone substrate estimated to be about 1,150,000 ha (FIPI, 1995) where botanical scientists have discovered many animal species and rare plants (Dung, 2001). Limestone karst ecosystems in Vietnam are important reservoirs for biodiversity but are currently experiencing forest degradation due to land use changes and increasing pressure from the extractive and tourism industries (Furey et al, 2010). In contrast with other natural systems, karst ecosystems cannot be reestablished once damaged (Tuyet, 2001) and recent studies have indicated that their biodiversity goes largely unknown in the face of ongoing forest degradation

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Results

Conclusion