The limiting roles of nitrogen and moisture on Sphagnum angustifolium growth over a depth to water table gradient

Abstract

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. ResultsWithin 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.

Field‐Based Estimation of Net Primary Productivity and Its Above‐ and Belowground Partitioning in Global Grasslands

“…Grassland formation explained the second largest variation for ANPP, BNPP, and TNPP (Figure 4). The possible key mechanisms underlying these patterns could be as follows: (a) soil is the direct medium for plant root growth; thus, soil environmental conditions will inevitably exert significant impacts on root growth and biomass allocation (Bardgett et al., 2014; Graham & Vitt, 2016); (b) there is confirmed evidence that topography can affect plant growth by modifying water, heat and their distributions (Chen et al., 2013; Xie et al., 2018); and (c) grassland formation was the primary determinant of root turnover in grasslands as found in a previous study (J. Wang et al., 2019). Overall, our results underscore an urgent need to incorporate multidimensional driving factors into the estimation of grassland productivity.…”

“…Grassland formation explained the second largest variation for ANPP, BNPP, and TNPP (Figure 4). The possible key mechanisms underlying these patterns could be as follows: (a) soil is the direct medium for plant root growth; thus, soil environmental conditions will inevitably exert significant impacts on root growth and biomass allocation (Bardgett et al, 2014;Graham & Vitt, 2016); (b) there is confirmed evidence that topography can affect plant a Top 10 countries in terms of grassland area. The area of each grassland formation or region is derived from distribution mapping of global grasslands (Dixon et al, 2014).…”

Geotropic curvatures of Sphagnum: environmental features of their genesis and trial application for estimation shoot length increment

“…Actual load may be considerably higher than estimated because of additional mire water storage in basal snow layers, which is quite common in microrelief depressions (Eurola, 1975). Thus, known from the literature concepts "permanent bends of the main stem" (Rochefort et al, 1990), "innate seasonal markers" (Jauchiainen et al, 1997); "kinks" (Camill et al, 2001), "snow weighted crooks" (Vitt, 2007), "growth markers created by snowpack conditions" (Turetsky et al, 2008) and "innate snow-bend markers" (Graham & Vitt, 2016) are consistent with nival geotropic curvatures.…”

Weather Factors in Different Growing Periods Determine Inter-Annual Change in Growth of Four Sphagnum Species: Evidence from an Eight-Year Study

“…Numerous studies have shown how Sphagnum length increment changes between years (e.g. Moore 1989, Graham and Vitt 2016. In our 8-year study, large inter-year variation of LI of a lawn-hollow species (S. fallax) and species with a wide ecological niche (S. angustifolium, S. magellanicum) was linked to weather uctuations.…”