The effect of heterogeneous soil bulk density on root growth of field-grown mangrove species

Background and aimsMangroves harbour large organic carbon (C) reservoirs in their soils that are important in the global C cycle. The below-ground biomass of mangrove trees is a major contributor to these organic C stocks. Root system development tends to be highly plastic in response to environmental conditions such as soil bulk density (BD). Hence, this study aimed to assess the role of soil BD on mangrove root growth.MethodsRoot in-growth bags filled with root-free soil ranging in BD from 0.2 to 1.2gcm(-3) were buried in the soil of three mangrove species.ResultsRoot image analysis indicated that BD had a significant positive effect on root length and root biomass suggesting trees increase biomass allocation to roots and enhance root elongation, possibly to increase the acquisition of water and nutrients in dense soils. However, the responses to variation in BD were species-specific which was attributed to differences in species growth rates and the background soil conditions.ConclusionSoil BD affects mangrove root growth with dense patches likely to have increased root growth and organic C sequestration potential compared to less dense soil patches.