Background and aims
Boreal peatlands are projected to face numerous stressors in the future, including changes in precipitation and nitrogen cycle perturbations. Nitrogen is currently believed to be the limiting factor to peatlands of western Canada, including to Sphagnum, however new insights suggest the possibility of multiple limiting factors.
Methods
Growth, nitrogen assimilation, and annual retention of Sphagnum angustifolium, a species with a broad niche, were observed across a depth to water table gradient for three years to further understand the partitioning of key limiting factors.
Results
Within each year differences of linear growth were responsible for variations in net primary production (NPP), yet yearly differences of NPP were attributed to annual differences in bulk density. Sphagnum angustifolium on the wet end of the depth to water gradient is characterized as nitrogen limited with high growth and low N concentrations, compared to less growth and high N concentrations at the water limiting dry end. Of the nitrogen that is annually assimilated by S. angustifolium, approximately 1.3 g N m-2 is lost from biomass one year subsequent to assimilation, demonstrating the rapid turnover of this nutrient.
Conclusion
The depth to water table gradient is strongly related to many S. angustifolium growth parameters and is a pivotal mechanism in delineating limiting factors within a single complex peatland ecosystem.