Human eutrophication drives biogeographic saltmarsh productivity patterns in China

Saltmarshes are important natural carbon sinks with a large capacity to absorb exogenous nutrient inputs. The effects of nutrients on biogeographic productivity patterns, however, have been poorly explored in saltmarshes. We conducted field surveys to examine how complex environments affect productivity of two common saltmarsh plants, invasive Spartina alterniflora and native Phragmites australis, along an 18,000-km latitudinal gradient on the Chinese coastline. We harvested peak aboveground biomass as a proxy for productivity, and measured leaf functional traits (e.g., leaf area, specific leaf area [SLA], leaf nitrogen [N] and phosphorus [P]), soil nutrients (dissolved inorganic N (DIN) and available P (AP)), and salinity. We compiled data on mean annual temperature (MAT) and exogenous nutrients (both N and P). Then, we examined how these abiotic factors affect saltmarsh productivity using both linear mixed effect models and structural equation modelling. Using a trait-based approach, ...