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

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.

Diametric Structure of One Fragment of One Deciduous Seasonal Forest in Brazilian Savanna Eco Museum

A 10 ha deciduous seasonal forest fragment (15°45'54''S and 49°04'03''W) found in the bioregion of the Savanna Eco Museum localized in the state of Goiás, Brazil was studied. For the phytosociological survey, 10 sample plots of 20 × 20 m were systematically located. All living trees of 5 cm DBH and above were measured with the plot boundaries. There were 742 individuals belonging to 83 species and 38 families. The richest families in terms of the number of species were Leguminosae, Rubiaceae, Myrtaceae, Apocynaceae and Chrisobalanaceae, which contributed 48% of the total species. The species with the highest importance value indices (IVI) were Tapira quianensis (Aubl.), Protium heptaphyllum (Aubl.) March., Callisthene mayor (Mart.), Amaioua guianensis (Aubl.) and Anadenanthera macrocarpa (Benth.) Brenan. The Shannon diversity index was 3.80 nats/individuals and the Pielou equality index was 0.86 for the total population. 549 sampled trees had DBH values lower than 30 cm. This indicates that this forest has a high potential for natural succession. Two DBH distributions were observed: the typical reverse “J”, described frequently in the literature, and a nearly Gaussian distribution.

Eutrophication Process of Soil nearby a Sanitary Landfill and Its Influence on Brazilian Savanna Vegetation

This work aimed to demonstrate if exists a relation between eutrophic processes of soil (N, P, K, pH, and organic matter) with phytosociology mosaic of native tree species in Brazilian adjacent sanitary landfill areas of the savanna. One of the study area is located in Brasilia, Federal District, and the other one in Goiania, State of Goiás, 210 km far each other. The methodology consisted in techniques, procedures and specific software applied to this kind of data. There were used plots and subplots for each area and for the vegetation and soil survey. Statistical significance showed that there exists a relationship between eutrophic processes of soil with phytosociology mosaic of native savanna tree species.

Resilience and response:Unveiling the impacts of extreme droughts on forests through integrated dendrochronological and remote sensing analyses

Extreme droughts are anticipated to have detrimental impacts on forest ecosystems,especially in water-limited regions,due to the influence of climate change.However,considerable uncertainty remains regarding the patterns in species-specific responses to extreme droughts.Here,we conducted a study integrating dendrochronology and remote sensing methods to investigate the mosaic-distributed maple-oak(native)natural forests and poplar plantations(introduced)in the Horqin Sandy Land,Northeast China.We assessed the impacts of extreme droughts on tree performances by measuring interannual variations in radial growth and vegetation index.The results showed that precipitation and self-calibrated palmer drought severity index(scPDSI)are the major factors influencing tree-ring width index(RWI)and normalized difference vegetation index(NDVI).The severe droughts between 2000 and 2004 resulted in reduced RWI in the three studied tree species as well as led to NDVI reductions in both the maple-oak natural forests and the poplar plantations.The RWI reached the nadir during the2000-2004 severe droughts and remained at low levels two years after the severe drought,creating a legacy effect.In contrast to the lack of significant correlation between RWI and scPDSI,NDVI exhibited a significant positive correlation with scPDSI indicating the greater sensitivity of canopy performance to droughts than radial growth.Furthermore,interspecific differences in RWI and NDVI responses were observed,with the fast-growing poplar species experiencing a more significant RWI decrease and more negative NDVI anomaly during severe droughts than native species,highlighting the species-specific trade-offs between drought resilience and growth rate.This study emphasizes the importance of combining tree-level radial growth with landscape-scale canopy remote sensing to understand forest resilience and response.Our study improves our understanding of forest responses to extreme drought and highlights species differences in climate responses,offering crucial insights for optimizing species selection in sustainable afforestation and forest management in water-limited regions under the influence of climate change.