Low phosphorus availability frequently limits plant growth in diverse, mineral-rich fens. It has been hypothesized that small, shallowly rooted, slow-growing fen plant species (which form a large proportion of fen diversity) may persist under these difficult growth conditions through specialized mechanisms for obtaining phosphorus. We conducted a moss removal experiment at three rich fens to investigate the influence of mosses, which cover the peat surface, on chemical and biological conditions that influence phosphorus availability in fen soils.  

Results/Conclusions

In cumulative monthly measurements at two of the fens, phosphorus supply rate to anion exchange resin membrane (AEM) was consistently greater under intact mosses (0.13-1.2 μg PO₄^3- 10 cm^-2 month^-1) than when mosses were removed (0.09-0.5 μg PO₄^3- 10 cm^-2 month^-1). Greater cumulative phosphorus availability underlying mosses may derive from moss effects on soil microbial activity: both microbial biomass (measured through a substrate-induced respiration assay) and microbial phosphorus (measured through hexanol fumigation and extraction to AEM) were greater for soils underlying mosses than where mosses were removed (p=0.02 and 0.05, respectively). Soil phosphatase (specifically monoesterase) enzyme activity was also greater under mosses (p=0.06), suggesting that mosses may promote release of phosphorus from organic sources via stimulation of microbial activity in shallow soils. Solution ³¹P nuclear magnetic resonance (NMR) spectroscopy confirmed the dominance of organic phosphorus in the system but was unable to determine a consistent change in forms of phosphorus present after two years of applied treatment.