摘要
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 < 10 cm. The Scholander apparatus and freezing point osmometry were used in order to measure the leaf water potential (Ψw) 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 < 10 cm DBH were identified in 625 m2. 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.
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 < 10 cm. The Scholander apparatus and freezing point osmometry were used in order to measure the leaf water potential (Ψw) 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 < 10 cm DBH were identified in 625 m2. 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.
基金
support by the Open Access Publication Funds of the Gottingen University
