Foliar N and P Dynamics of Heracleum Platytaenium (Apiaceae) in Relation to Edaphic Characteristics Along an Elevation Gradient in Northern Turkey

Abstract

Heracleum platytaenium (Apiaceae) is an endemic species in the Central Black Sea region, in the north of Turkey. Its foliar N and P dynamics and absolute and proportional N and P resorptions along an elevation gradient were investigated. The foliar N and P concentrations varied along the elevation gradient and during the growing season in basal leaves. N and P concentrations of stem leaves did not change significantly during the growing season, although significant changes were observed along the topographic gradient. N and P concentrations of basal leaves declined during May and June, and increased through July. Absolute and proportional resorptions were usually higher in slope positions in both basal and stem leaves, except for N resorption in stem leaves. N and P resorptions were more effective in the slopes between the upper and lower parts of the gradient. Absolute and proportional N and P resorptions in basal and stem leaves were significantly correlated with foliar N and P concentrations. Soil fertility varied significantly along the elevation gradient, but no consistent pattern was found between soil fertility and resorption. Foliar resorption was significantly correlated with soil moisture, and nutrient resorption probably reflected topographic differences in soil moisture rather than in soil fertility. Root/shoot ratio was comparatively low at the beginning of the growing season and increased towards the end of the growing season.