However deep peat and shallow water table towards the fen prevented root contact with mineral soil, imposing phosphorus limitations to plants growing in the poor, acidic peat, causing productivity decline by ∼75–80%, and tree biomass decline from ∼6900 to 2100 g C m −2 in themodel vs. Model results suggest that root contact with mineral soil through shallow peat overa deep water table at the upper ecotone sustained phosphorus uptake and plants did not experience phosphorus limitations. Model output was compared with field-derived tree carbonstocks, leaf area indexes, and moss net primary productivities at upper, middle, and lower undisturbed ecotone positions. This zone extended froman upland black spruce forest down to a poor forested fen over an organic–mineral soil gradient withpeat depth increasing from 60 cm to 160 cm. The ecosys model was applied to test these hypotheses in a boreal transition zone in central Saskatchewan, Canada. These phosphorus limitations, together with O 2 limitations to root growth, cause sharp decline of productivity down to the fen. We hypothesize that in boreal transition zones to poor fens, phosphorus limitations to plant growth are imposed by low pH, rising water table and increasing depth to mineral soil in the waterlogged peat. This decline is associated with water table rise and increasing peat depthfrom upper to lower topographic positions.
Ecological Modelling 291:96-108.Īvailability: Order paper copy (free), PDF (request by e-mail)įorest productivity declines along the transition zones (ecotone) occupying the elevational gradient fromupland boreal forest to peatlands. The transition zones (ecotone) between boreal forests and peatlands: ecological controls on ecosystem productivity along a transition zone between upland black spruce forest and a poor forested fen in central Saskatchewan.