Effects of tree thinning on carbon sequestration in mangroves

Abstract

Mangrove overgrowth could decrease biodiversity and increase flooding risk. Thinning has been proposed as a managerial action, which would decrease the capacity of mangroves for carbon sequestration. The aim of the present study was to examine the relationship between differences in mangrove tree density and carbon sequestration capacity. Three sampling sites were established in the Fangyuan mangroves of Taiwan, including seaward and landward sites with Avicennia marina and a site with Kandelia obovata, with control (C; no thinning), medium thinning (MT; 50% thinning) and high thinning (HT; only one tree left at the centre) treatments. The HT treatment significantly reduced the areal carbon sequestration rates (66–84%), but the reductions in the MT treatment were much lower (3–30%). Considering the carbon sequestration per tree, the HT treatment resulted in the significantly highest rates (two- to fivefold higher) than those under the MT and C treatments. Medium thinning appears to be the optimal strategy to meet the demand of reducing the loss of carbon sequestration capacity for mangrove management. Together, the data from in the present study and the relevant literature suggest a maximum level of carbon sequestration by managing the density to 30600treesha–1 for K. obovata and 10500treesha–1 for A. marina.

Factors regulating carbon sinks in mangrove ecosystems

“…It appears that the main factor affecting the aboveground NP rate is tree density. Ho, Huang, and Lin () found the aboveground NP rate to increase with increasing tree density to a maximum point and then to decrease with increasing tree density for both A. marina and K. obovata , possibly due to the higher intraspecific competition. Their data suggested the maximum level of aboveground NP at a density of 30,600 trees ha −1 for K. obovata and 10,500 trees ha −1 for A. marina .…”