Differences in biomass and silica content in typical plant communities with ecotones in the Min River estuary of southeast China

Unraveling the impact of Spartina alterniflora invasion on greenhouse gas production and emissions in coastal saltmarshes: New insights from dissolved organic matter characteristics and surface-porewater interactions

Saltmarshes along the Chinese coast are threatened by the invasion of Spartina alterniflora (S. alterniflora). This study was carried out in the Andong Shoal, Hangzhou Bay, China, with the aim of comprehending the intricate impacts of S. alterniflora invasion on greenhouse gases (GHG) production and emissions. To address this issue, we thoroughly examined the chemistry of dissolved organic matter (DOM) and the rate of surface water-porewater interaction. Porewater and surface water samples were collected from farm land, S. alterniflora invaded areas, and Scirpus mariqueter (S. mariqueter) dominated areas. The findings indicated that the invasion of S. alterniflora impeded the interaction between surface water and porewater, resulting in reduced porewater exchange rates within its affected region (0.015-0.440 cm d-1), in contrast to areas dominated by S. mariqueter (9.635-18.232 cm d-1). The invasion also increased dissolved organic carbon concentration in porewater and created a stable and closed soil environment that resulted in DOM with smaller molecule sizes and higher humification levels. The presence of high tryptophan-like fluorescent DOM caused an increase in the production of methane and carbon dioxide in S. alterniflora invaded area. However, both limited surface-porewater exchange and significant differences in GHG concentrations between porewater and surface water suggested that the aerenchyma tissues of S. alterniflora may play an important role in transporting GHG from soil to the atmosphere.

Phytolith-Occluded Carbon Sequestration Potential of Oil Palm Plantation in Tamil Nadu

Oil palm (Elaeis guineensis) has proven to be a phytolith-occluded carbon (PhytOC)-rich species that plays a vital role in acting as a carbon sink for reducing atmospheric carbon dioxide (CO₂) concentration. The present research estimated the silicon, phytolith, and PhytOC contents in four (OP4), eight (OP8), and fifteen (OP15)-year-old oil palm plantations. Qualitative analysis using a scanning electron microscope (SEM) revealed the presence of abundant globular echinate phytoliths with varied diameter (8.484-10.18 μm) in fronds, empty fruit bunches, and roots. Furthermore, a wide band (400-490 cm^-1) underlined a higher relative abundance of Si-OH groups in empty fruit bunches, fronds, and roots, which emphasized the amorphous nature of silica. Quantitative analysis revealed that the phytolith (phytolith/dry biomass), PhytOC (PhytOC/phytolith), and PhytOC (PhytOC/dry biomass) contents in all oil palms differed significantly (p < 0.05) and increased with age. The PhytOC stock showed significant variation, with the trend of OP15 > OP8 > OP4. The belowground biomass of OP4 (16.43 g kg^-1) and OP8 (17.13 g kg^-1) had a maximum PhytOC concentration compared to the aboveground biomass, and the belowground proportion varied from 20.62 to 20.65%. The study demonstrated a positive correlation between the phytolith and PhytOC contents of oil palm; thereby, oil palm should be cultivated for enhanced long-term sequestration as a phytolith accumulator.

Dynamics of biogenic silica accumulation and ecological characteristics in single-species communities and ecotones in Min River estuary, China

The role of silicon in plant resistance to biotic and abiotic stresses is clear; however, its role in interspecific interactions is not well understood. Biogenic silica (BSi) accumulation and ecological characteristics in single-species communities (Phragmites australis, Cyperus malaccensis, and Spartina alterniflora) and ecotones (P. australis-C. malaccensis and C. malaccensis-S. alterniflora) of Shanyutan marsh, China, were monitored from January to December in 2016. The BSi content of the three plant species decreased at the end of winter and beginning of spring, and continued to increase after March. In ecotones, the density of P. australis, the lengths of C. malaccensis and S. alterniflora, and the BSi content of C. malaccensis were greater than those in single-species communities. However, in single-species communities, the densities of C. malaccensis and S. alterniflora, the length of P. australis, the biomass and BSi stocks of the three species, and the BSi content of P. australis and S. alterniflora were greater than those in the ecotones. The three species may apply different strategies to compete for resources during interactive growth. Phragmites australis may improve its competitive ability by increasing vegetation density, aboveground biomass, and Si allocation to the leaves and withered body. Spartina alterniflora appears to enhance root biomass accumulation and the Si uptake and allocation capacity of roots. Cyperus malaccensis appears to allocate greater biomass and BSi to aboveground organs, as well as improve the absorption capacity of roots to resist competition pressure from P. australis. Cyperus malaccensis mixed with S. alterniflora increased its belowground biomass and BSi stocks. These results help clarify the mechanisms and processes of Si translocation during mixed plant growth, and increase our understanding of the strategies involved in plant competition.