Aim of the study: The major objective of this study was to estimate the biomass increment and carbon (C) storage of the main ecosystem components in an age-sequence of three Acacia mangium plantation stands.Area of study: Chang Riec Historical - Cultural Forest, Southeastern region, Vietnam.Material and methods: In order to assess the biomass of different tree components, 36 trees with diameter at breast height ranging from 13.38 to 22.87 cm were harvested from the different aged stands. Biomasses of understory (shrubs and herbs), and litter were also determined. Carbon storage in the trees and understory biomass, litter, and mineral soil (0-50 cm) were determined by analyzing the C content of each compartment.Main results: The biomass in trees, understory vegetation, litter, and ecosystem increased with stand age. Soil C represented 61.99% of the total, aboveground tree biomass C made up 26.73%, belowground tree biomass C accounted for 7.01%, and litter comprised 2.96%, whereas only a small amount (1.30%) was associated with understory vegetation. The average C content of total tree (47.97%) was higher than those of understory and litter. Soil organic C stock in the top 50 cm depth in 4-, 7- and 11-year-old stands of A. mangium were 86.86, 126.88 and 140.94 Mg. C ha-1 respectively. Soil C concentration decreased continually with increasing soil depth. Total C storage of three planted forests ranged from 131.36 to 255.86 Mg. C ha-1, of which 56.09 - 67.61% of C storage was in the soil and 26.88 - 40.40% in the trees.Research highlights: These results suggest that A. mangium is a promising afforestation tree species with fast growing, high biomass accumulation and high C sequestration potential.Keywords: Acacia mangium plantations; Biomass; Ecosystem carbon storage; Age-sequence; Vietnam.

The present study assessed the trees species diversity and the benefits that arise from their presence in five selected recreation centers in the urban area of Ibadan: Agodi Gardens, Ibadan Recreation Club, National Museum of Unity, Ibadan Golf Club and Ibadan Polo Club. The selected areas were purposively chosen due to the presence of tree species in the urban landscape. Both primary and secondary data were used for the study. Agodi Garden had in total 537 individuals, 46 tree species within 25 families. Ibadan Recreation Club had the total number of 148 trees, whereas 32 species within 22 families were represented. National Museum of Unity had a total number of 770 trees, classified in 23 species within 17 families. Ibadan Polo Club had a total number of 97 trees, 20 species and 15 families were represented. Ibadan Golf Club had a total number of 915 trees, 31 species and 9 families. Fabaceae family had the highest occurrence in Ibadan Recreation Club, National Museum of Unity, Ibadan Golf Club and Ibadan Polo Club, while Verbenaceae was more represented in Agodi Gardens. The study has shown the high occurrence of invasive species in tropical environment based on their regeneration potential. Data collected on total number of tree species, frequency of occurrence and families were subjected to descriptive analysis. A semi-structured questionnaire was used to obtain information. These centers serve as ex-situ urban centers/parks that still maintain and conserve various tree species and are important resources for social, economic and educational use. Biodiversity indices were also analyzed and it can be concluded that the type of organization and the main activity of the centers strongly influence the species diversity. The trend of Shannon-Wiener diversity index (H') showed that Ibadan Polo Club was the most diverse. Despite the higher number of individual trees encountered in NMUI, the H' value was very low, indicating the dominance of a few tree species within the area. From EH values obtained in the study, it can be concluded that trees species are most evenly distributed in IPC, followed by IRC, AG, IGC and lastly by NUMI.