Nitrogen uptake by Hylocomium splendens during snowmelt in a boreal forest

Abstract

In most boreal regions snow composes a large portion of the annual precipitation. Although many boreal forest floor bryophytes depend largely on precipitation for their nitrogen (N) supply, bryophyte uptake of snow N is little explored. We studied chemical forms of plant-accessible N in snowmelt, as well as the temporal dynamics of their release. In conjunction we performed a N uptake experiment using the common boreal bryophyte Hylocomium splendens. The results demonstrated that the snowmelt N pool was dominated by NO3− (86%), followed by NH4+ (11%) and amino acid N (3%), in total providing ca 0.3 kg N·ha−1 to the forest floor vegetation. Hylocomium splendens was able to access both inorganic and organic 15N labelled N forms (NO3−, NH4+, and glycine) applied in situ to the snow covering the moss prior to snowmelt. Across all the N forms H. splendens took up ca 24% of the snow-deposited N. Nitrate uptake exceeded that of glycine, while NH4+ uptake was intermediate, reflecting the ambient distribution of the snowmelt N pool between plant-accessible N forms.