2020 ESA Annual Meeting (August 3 - 6)

OOS 73 Abstract - Mangrove root production responses to reforestation in south Vietnam

Marie Arnaud1,2, Paul J. Morris1, Andrew J. Baird1, Thuong Huyen Dang3 and Tai Tue Nguyen4, (1)University of Leeds, (2)University of Birmingham, Birmingham, United Kingdom, (3)Ho Chí Minh City University of Technology (HCMUT), (4)Vietnam National University University of Science
Background/Question/Methods

Globally, one-third of mangroves have been lost since 1950. Duke et al. (2007) predicted that, by the end of the 21st century, the world will be without mangroves if no actions are taken to prevent their loss or replant them. In response, restoration projects have rapidly emerged with the aim of re-establishing mangrove ecosystem services, such as carbon storage. While those projects have mostly monitored the aboveground carbon stock, up to 90 % of the mangrove carbon is in the soil, and a large portion may originate from fine root production. We investigated how fine root production changed following reforestation using the recently-developed EnRoot minirhizotron. We used a chronosequence of mangroves in the Mekong Delta, reforested in 1978, 1986 and 1991. This mangrove area is the second-largest reforested mangrove in the world. The mangroves there were almost completely destroyed during the US-Vietnamese war, and then replanted with mangrove propagules (Rhizophora).

Results/Conclusions

We found that fine root production decreased monotonically with increasing time since reforestation. While this pattern has been observed in the aboveground biomass, it had been an unknown for belowground carbon. The highest fine root production was at the youngest site (28 years old), which had almost twice the fine root production of the 33 year old mangrove, and seven times that of the 41 year old mangrove. This age-related decrease of fine root production is in accordance with the development trajectory of natural mangroves, in which the aboveground production declines gradually after stand maturity until senescence at about 70 years. Previous studies have shown that mangrove age does not affect the soil organic matter decay. Therefore, our findings may explain and suggest the direction of soil carbon accumulation after mangrove reforestation.