Mire margin to expanse gradient in part relates to nutrients gradient : evidence from successional mire basins, north Finland

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>To study the relationship between mire vegetation and ecological variables we tested the Finnish hypothesis that the mire margin to expanse gradient in vegetation composition relates to a gradient of solutes (main plant nutrients) in the soil that is separate from the mainly pH related poor–rich gradient. Successional mire basins where mire margin to expanse is the prominent gradient were surveyed. An indirect method (Ellenberg indicator values) and direct measurements (phosphorous concentrations, pH) were used to assess the relationship between the mire margin to expanse and nutrients gradients. Vegetation with indicators of Subtype A mire margin vegetation (assumed to reflect surface water flow) correlated best with Ellenberg nitrogen values, whereas Subtype B (assumed to reflect groundwater influence) correlated best with Ellenberg reaction values. Subtype C (supposed to reflect mineral soil influence) did not correlate with these Ellenberg values. The study provides information about the complexity of the vegetational gradients. In general, water flow seems to be related to the poor–rich gradient, but surface water flow is also related to the nutrients gradient. Subtype C (influence of mineral soil) seems to differ from the other two subtypes of the mire margin to expanse gradient and also from the poor–rich gradient. It is prominent on forested sites, where the water table is comparatively deep.</p></div>