What happens to soil chemical properties after mangrove plants colonize?

Abstract

Understanding soil chemical properties is necessary to characterize the basic properties of ecosystems. In mangrove ecosystems, soil iron, phosphorus, methane and nitrogen have been well studied under field conditions. However, it is difficult to understand fundamental relationships between mangrove root functions and soil chemical properties, because of the multiple factors present in field data. The aim of this study was to clarify what will happen to soil chemical properties after mangrove plant colonize. To examine the effect of mangrove roots on these soil properties, three representative mangrove species (Avicennia marina, Rhizophora stylosa and Bruguiera gymnorrhiza) were cultivated in a greenhouse and selected soil chemical properties were monitored in comparison with those in unplanted soil.We detected oxidative effects in all three species, including deposition of iron oxide on root surfaces, lowered methane concentrations and increased oxidized inorganic nitrogen concentrations in the soil pore-water, suggesting that radial oxygen loss from mangrove roots had affected these soil chemical properties. Besides the oxidative effects, enhanced Fe 2+ concentrations in the soil pore-water were present in A. marina, and enhanced phosphorus concentrations in the soil pore-water were present in all three species, suggesting that mangrove roots provide Fe-and phosphate-solubilizing substrates. The most remarkable change was in soil nitrogen enrichment. During the experimental period, amounts of nitrogen in the mangrove soils increased four times more than in uncolonized soil. Six months from the start of cultivation, bacterial nitrogen fixation (nitrogenase activity) was significantly higher in soil colonized by mangrove plants than in uncolonized soil, suggesting that mangrove roots stimulated bacterial nitrogen fixation. Among these properties, Phosphate mobilization and soil nitrogen enrichment are likely to be particularly important for the growth of mangrove plants, because phosphate and nitrogen are generally limited in mangrove ecosystems. This self-supporting ability of mangroves observed in this study could be one key to the high productivity of mangrove ecosystems.

Interactive relationship between plant growth and soil chemical properties in a mangrove afforestation stand, Kiribati

“…Most phosphorus in soils is immobilized by adsorbing onto Fe-and/or Al-oxides, calcium compounds, and polymerized organic matter(Raymond et al 2021), and phosphorus in mangrove sediments is noKothamasi et al 2006; El-Tarabily and Youssef 2010), and an increase in PO 4 − in mangrove-rooted soil has been reported in a cultivation experiment(Inoue et al 2011b). Our observation of a positive relationship between estimated mangrove root biomass and PO 4 − concentration in soil pore water supports these ndings.…”

Interactions between topsoil properties and ecophysiological responses of mangroves (Avicenniamarina) along the tidal gradient in an arid region in Qatar

“…Soil pH decreased gradually as the distance from the inland boundary of the mangrove forest increased in the present study. Soil pH reduction due to organic acids may be greater on the seaward side due to high OM (Inoue et al, 2011). A large amount of OM and decreasing alkalinity might induce increasing amounts of nutrient sources (Lacerda et al, 1995) and nutrient availability in soils (Tam and Wong, 1998).…”

“…Increasing nutrient contents in soils could stimulate mangrove growth (Feller et al, 2003) and the structure and composition of mangroves could be influenced by species-specific responses to changes in nutrient contents (Ukpong, 2000). Mangroves also could increase soil nutrients through litter input (Xiong et al, 2018), bacterial nitrogen fixation (Inoue et al, 2011), root exudates (Inoue et al, 2011), and sediment accretion (Kumara et al, 2010).…”

Global mangrove root production, its controls and roles in the blue carbon budget of mangroves

“…Therefore, roots are believed by some to form the main autochthonous input for mangrove carbon burial (Bouillon et al, 2003; Kida & Fujitake, 2020; Kristensen et al, 2008). Mangrove roots may also accelerate the mineralisation of SOM through the release of (1) oxygen (Pi et al, 2009), which changes the redox condition of the soil (Inoue et al, 2011; Kristensen et al, 2008), and (2) exudates that may remobilise old protected carbon as observed in forests (Keiluweit et al, 2015; Phillips et al, 2011). Upscaling of those root processes with their subsequent effects on carbon dynamics is currently limited due to the lack of an updated estimate of global root production, as well as a lack of understanding of the controls and response of root production to global changes (Arnaud et al, 2020; Coldren et al, 2019).…”