Methane Contributions of Different Components of Kandelia candel–Soil System under Nitrogen Supplementation

Abstract

Kandelia candel is the most widely distributed tree species on the southeast coast of China and is also the main afforestation tree species along the coastal wetland. In recent years, inorganic nitrogen pollution has become increasingly severe, and investigating the effects of nitrogen input on methane emissions in Kandelia candel–soil systems has become significant from a global change perspective. However, the effect of nitrogen input on methane emissions in coastal wetland systems is still uncertain. The field tidal environment is complex and varied, and thus it is difficult to accurately control the amount of nitrogen in the system. Therefore, in order to accurately assess the effects of different concentrations of foreign nitrogen input on methane emission fluxes in a Kandelia candel–soil system, we use indoor tidal simulation experimental devices and design two simulation systems with and without plant planting to explore the difference of methane emission flux in this system under five nitrogen input concentrations: N0 (0 g N·m−2·a−1), N1 (5 g N·m−2·a−1), N2 (10 g N·m−2·a−1), N3 (20 g N·m−2·a−1), and N4 (30 g N·m−2·a−1). The results showed that: (1) The introduction of Kandelia candel promoted methane emissions in coastal wetland ecosystem. Under each nitrogen application concentration, the mean CH4 emission flux in the planting group was 42.98%, 65.59%, 40.87%, 58.93% and 39.23% higher than that in the non-planting group, respectively. (2) Nitrogen input significantly promoted methane emissions in both planted and non-planted environments, and the promoting effect showed as follows: N4 > N3 > N2 > N1 > N0. (3) After the introduction of Kandelia candel, the contribution of Kandelia candel and soil microorganisms to methane emissions was different under different concentrations of nitrogen addition. The contribution rate of Kandelia candel to CH4 emission flux of Kandelia candel–soil system ranged from 10.74% to 60.25%, with an average contribution rate of 37.30%. The changed soil microbes contributed 39.75% to 89.26% to the CH4 emission flux in the Kandelia candel–soil system, with an average contribution rate of 62.60%. Under N3 nitrogen application concentration, the emission flux of plant was the largest, which was significantly higher than that of the soil microbial pathway; at other concentrations, the methane emissions from the soil microbial pathway were greater than that of the plant pathway, and the contribution rate to the plant–soil system reached 60.25%. The results of this study provide an important basis for improving the estimation accuracy of carbon emissions in coastal waters and formulating policies for the restoration and protection of coastal wetlands.

The Influence of Exogenous Nitrogen Input on the Characteristics of Phytolith-Occluded Carbon in the Kandelia obovata Soil System

“…However, due to the unique growth characteristics of mangrove forests, it is unclear whether the large-scale construction of mangrove forests will enhance the organic carbon storage capacity of coastal ecosystems or potentially deteriorate the carbon sequestration capacity of soil. Previous studies by our research group showed that methane emissions increased after the introduction of mangrove plants in coastal bare tidal wetlands; in addition, methane emissions also increased as the nitrogen concentration increased [12], demonstrating that an increase in the exogenous nitrogen concentration will accelerate the decomposition of soil organic matter [13]. This practice could also reduce the extent of stable organic carbon in the soil, ultimately affecting the soil's capacity for carbon sequestration.…”

A comparison of 25 complete chloroplast genomes between sister mangrove species Kandelia obovata and Kandelia candel geographically separated by the South China Sea

“…Based on studies on leaf anatomy, cold-resistance adaptation, chromosome number, and molecular markers from both cp and mitochondria, K. obovata was identified as a new mangrove species differing from K. candel 20 years ago ( Sheue et al., 2003 ), but the genomic information between them remained unknown, which limited our understanding about how their genes evolved and differentiated during the process of plant speciation. This also causes confusion in scientific exchanges, as some scholars still use K. candel for the plant materials of Kandelia collected either from China or Japan ( Geng et al., 2008 ; Enoki et al., 2009 ; Zhang et al., 2012a ; Feng et al., 2022 ).…”