Data from: 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, we also examined how saltmarsh productivity responds
to changing environments across latitude. Exogenous nutrients (both N and
P) compared with temperature and other variables (e.g., DIN, AP, salinity)
were the dominant factors in explaining the biogeographic productivity
patterns of both S. alterniflora and P. australis. Leaf size-related
traits (e.g., leaf area), rather than leaf economic traits (e.g., SLA,
leaf N and P), can be used to indicate the positive effects of exogenous
nutrients on the productivity of these two species. Our results
demonstrated that human eutrophication surpassed temperature as the major
driver of biogeographic saltmarsh productivity pattern, challenging
current models in which biogeographic productivity pattern is primarily
controlled by temperature. Our findings have potential broad implications
for the management of S. alterniflora, which is a global invader, as it
has benefited from coastal eutrophication. Furthermore, exogenous nutrient
availability and leaf size need to be integrated into earth system models
that are used to predict global plant productivity in saltmarshes.