New Study Uncovers Key Links Between Vegetation Types and Soil Carbon in Yellow River Delta Wetlands.

A recent study conducted by a team of researchers from the Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), has highlighted notable differences in soil organic carbon (SOC) levels across various vegetation types in the Yellow River Delta. The investigation, led by Professor Han Guangxuan, emphasizes the critical role of wetland ecosystems in carbon storage, water purification, climate regulation, and biodiversity support.

The research, carried out at the Yellow River Delta Field Observation and Research Station, involved multiple experimental approaches. These included manipulating the genetic diversity of Phragmites australis, adjusting groundwater levels, simulating changes in precipitation, and analyzing SOC dynamics under different plant communities.

In a common garden experiment, the scientists examined how variations in the genotypic richness of P. australis influenced multiple ecosystem functions (EFs). Results showed that increased genotypic diversity negatively impacted soil bacterial richness and was associated with a decline in overall ecosystem multifunctionality—an outcome likely due to intensified competition among genotypes.

Interestingly, the effects of genotypic richness varied depending on the performance thresholds for ecosystem functions. At lower thresholds (20%, 40%, and 60%), higher genetic diversity led to more function indicators achieving peak values. However, at the highest threshold (80%), increased genotypic richness caused a drop in the number of functions reaching maximum performance, suggesting that elevated genetic variation could reduce overall ecosystem efficiency at higher functional demands.

Complementing this work, a three-year field study (2020–2022) using a precipitation manipulation platform assessed the impact of changing rainfall patterns on carbon exchange and plant types. The wetlands consistently acted as a carbon sink (net ecosystem CO₂ exchange, or NEE, remained below zero). Periods of increased precipitation favored the growth of perennials like P. australis and Imperata cylindrica, enhancing biomass and NEE. In contrast, reduced rainfall led to elevated soil salinity, allowing salt-tolerant annuals such as Suaeda salsa and Tripolium pannonicum to dominate. These annuals, with lower biomass, contributed to reduced primary productivity and weakened carbon uptake.

In another set of experiments, changes in groundwater depth significantly influenced plant community structure and biomass distribution. Shallower groundwater led to higher soil salinity and nutrient concentrations, triggering a shift in dominance from P. australis to S. salsa. Plants also allocated more biomass aboveground to compete for light and space, which was associated with decreased biodiversity.

Finally, a comparative analysis across four vegetation zones revealed stark differences in SOC levels. Mudflats dominated by S. salsa exhibited the highest SOC, while areas covered by P. australis had the lowest. Variation in SOC within the top one meter of soil was linked to soil water content, which indirectly shaped SOC levels by influencing vegetation type. Statistical modeling, including Mantel analysis and Structural Equation Modeling (SEM), confirmed soil moisture as a key mediator in SOC dynamics.

These findings provide valuable insights into the complex interactions between vegetation, hydrology, and carbon storage in coastal wetlands, informing strategies for ecosystem management and climate resilience.

Source:https://phys.org/news/2025-05-weather-extremes-lens-regional.html

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