Ecology of Kandelia obovata (S., L.) Yong: A Fast-Growing Mangrove in Okinawa, Japan

Abstract

Mangroves are the association of woody trees and shrubs in the intertidal zone of tropical and subtropical coasts. Mangroves play a significant role in carbon sequestration, as they store large amount of organic matter in their substrates and roots. This chapter focuses on the ecology of biomass production and carbon trapping potentials in the pioneer mangrove Kandelia obovata in the light of canopy radiation balance, intraspecific competition, allometric relationships, biomass allocation, net primary production and carbon sequestration. K. obovata shows a low light extinction coefficient of leaves (0.43) suggesting a shade-intolerant nature of the species. In the young stage, trees form smaller clumps that hinder each other in growth but do not lead to a significant size class differentiation. However, after ca. two decades, the self-thinning starts and a mutual inhibition of growth and size differentiation is observed. As a stand grows older, the spatial pattern of individuals becomes more regular from a clustered pattern. In the allometric equations for estimating the above-ground phytomass, the parameter D _0.1 ² H (D _0.1, diameter at one-tenth of tree height H) instead of D ² H (D = diameter at 1.3 m height) or D performs better. At the stand age of 10 years, the species is capable of yielding an above-ground biomass of 80.5 Mg ha⁻¹ and belowground biomass of 71.5 Mg ha⁻¹. The above-ground net primary production estimates 29.9–32.1 Mg ha⁻¹ year⁻¹, which is ca. 2.8–3.0 times of annual litter fall. The low leaf longevity (9.3 months) and high growth efficiency (5.35–5.98 Mg ha⁻¹ year⁻¹) make it a highly productive mangrove species. The carbon stock in the above ground (35.1 Mg ha⁻¹) is 1.3 times in the belowground (26.9 Mg ha⁻¹). Soil C stock (57.3 Mg ha⁻¹) is closer to the vegetation C stock (62.0 Mg ha⁻¹), indicating that the mangrove stores a large amount of carbon in the soil. The growth efficiency and carbon trapping mechanism of the mangrove K. obovata make it a highly suitable species in the study region Okinawa Island. New plantations can be raised in the intertidal zones of Okinawa Island using K. obovata, which would in turn contribute towards carbon sequestration and climate change mitigation.