Human eutrophication drives biogeographic salt marsh productivity patterns in China

Area of Science:

• Ecology
• Coastal Ecosystems
• Plant Physiology

Background:

• Salt marshes are crucial carbon sinks, yet nutrient impacts on their productivity patterns remain understudied.
• Understanding these effects is vital for managing coastal ecosystems and invasive species like Spartina alterniflora.

Purpose of the Study:

• To investigate how environmental factors, particularly nutrients, influence the productivity of invasive Spartina alterniflora and native Phragmites australis along China's coastline.
• To explore the role of plant functional traits in mediating salt marsh productivity responses to environmental gradients.

Main Methods:

• Field surveys across an 18,000-km latitudinal gradient measuring biomass, leaf traits, soil nutrients, and salinity.
• Statistical analysis using linear mixed-effect models and structural equation modeling to assess abiotic factor impacts.
• Trait-based analysis to link plant characteristics with productivity across varying environmental conditions.

Main Results:

• Exogenous nutrients (nitrogen and phosphorus) were the primary drivers of biogeographic productivity patterns for both species, surpassing temperature.
• Leaf area, a leaf size-related trait, effectively indicated positive nutrient effects on productivity, more so than leaf economic traits (SLA, leaf N, P).
• Coastal eutrophication significantly influences salt marsh productivity, challenging temperature-centric ecological models.

Conclusions:

• Human-induced eutrophication is a dominant force shaping salt marsh productivity, with implications for invasive species management.
• Integrating exogenous nutrient availability and leaf size into earth system models is crucial for predicting global salt marsh plant productivity.