Enhancement of Soil Organic Carbon by Acacia Mangium Afforestation in Southeastern Region, Vietnam

Abstract

The knowledge about dynamics of soil organic carbon (SOC) accumulation and its controls are critical in understanding of the C cycling in forest ecosystems. Acacia mangium Willd. is one of the most important fast-growing afforestation tree species in Vietnam, providing significant ecological, economic, environmental, and social benefits. The existing studies offered information limited on the distribution and regulation of SOC in the A. mangium plantations. The primary purpose of this study was to explore the variation trend of SOC and its driving factors in an age-sequence of three A. mangium plantation stands in Changriec Historical -Cultural Forest, Southeastern region, Vietnam. The study was conducted to estimate SOC content and storage, and soil physicochemical characteristics of three different-aged (4-, 7-, 11-year-old stands) A. mangium plantations. The SOC content increased significantly from young to older stand, and its maximum concentration occurred in the topsoil layer and decreased continually with increasing soil depth. The SOC stocks increased significantly with the stand age. The SOC stocks showed obvious surface aggregation, with more than 60% of SOC distributed in the soil of 0-30 cm depth. The soil total nitrogen content and soil texture (i.e., soil silt content) were identified as the major factors controlling the SOC distribution. The other parameters (i.e., plant biomass, soil pH, bulk density, available nitrogen, total phosphorus, available phosphorus, total potassium, and available potassium) also significantly influenced the distribution of SOC. These findings suggest that afforestation with A. mangium can facilitate SOC accumulation, improve soil nutrient regimes, and

Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam

“…These results agree with those from earlier studies (Zhao et al 2014;Liu et al 2016;Cuong et al 2023). These findings may be explained by a significantly greater plant litterfall production and fine-root turnover in older plantations and a larger amount of root exudates entering the soil (Cuong et al 2023). Plant biomass parameters (involving understory plant biomass and litter biomass) are positively correlated with soil nutrient concentrations (Table 1), illustrating the accumulation of soil nutrient contents with increasing plant biomass, which is due to the important regulation of plant biomass on soil nutrient concentrations.…”

“…The findings from this study indicated that soil nutrient concentrations (SC, SN, and SP) increased significantly with increasing age in Acacia hybrid plantation. These results agree with those from earlier studies (Zhao et al 2014;Liu et al 2016;Cuong et al 2023). These findings may be explained by a significantly greater plant litterfall production and fine-root turnover in older plantations and a larger amount of root exudates entering the soil (Cuong et al 2023).…”

“…Our study data established that SC, SN, and SP decreased considerably with increasing soil depth in all plantations and were present predominantly in the surface layer (0-20 cm). These findings are similar to those from previous reports (Fan et al 2015;Yin et al 2021;Cuong et al 2023). This observation could be attributed to the rich distribution of plant aboveground litter and underground roots in the upper soil layer (0-20 cm).…”

“…However, there are still controversies regarding the effects of forest age on soil nutrient contents (e.g., decrease gradually with age increment (Lee et al 2015;Wu et al 2015); first increase and then decrease (He et al 2022), or show no significant variation with forest age (Yang et al 2018a). One possible description for this divergence is that, besides forest age, numerous other parameters influence soil nutrients, such as the difference in species planted, soil characteristics, previous land use, climate, and management practices (Cuong et al 2023).…”

“…The SC concentration was determined using the H2SO4-K2Cr2O7 oxidation procedure (Nelson and Sommers 1982). SN and SP were estimated by referring to our recently published study (Cuong et al 2022). The SN concentration was derived using the Kjeldahl procedure after digestion with a mixture of C7H6O3 and H2SO4.…”