NITROGEN AND PHOSPHORUS RESORPTION IN SOME SYMPATRIC PLANT SPECIES IN THE NORTH OF TURKEY

Abstract

In the North of Turkey, foliar nutrient concentrations during summer and autumn and foliar resorption efficiency (RE) and proficiency (RP) were investigated in some sympatric deciduous plant species occurring on soils with low phosphorus availability. NRE and PRE were found to be within the ranges reported by other studies for the same studied species. The highest mass and area-based N and P concentrations were found in A. hyrcanum subsp. sphaerocaryum. The highest mass and area-based NRE were also found in A. hyrcanum subsp. sphaerocaryum, while the highest mass and area-based PRE were found in S.umbellata var. umbellata. However, the opposite trend was found when MLCF correction was used for both species. The most N and P proficient species was C. mahaleb because the lowest N and P concentrations were found in its senesced leaves. However, the most N-proficient species was S. umbellata var. umbellata regarding mass-based NRP. N/P ratios of green leaves of the studied species ranged from 22.95 to 35.25 in the study area and this indicated that P limitation may occur at a local level. It has been found that N/P ratios were increased during senescence in all species. Plant N and P status was not strictly controlled by N and P concentrations of green and senesced leaves in the studied species; all of these show complete resorption according to threshold values. Our results implied that PRE has a much important role in conservation of P as compared to NRE conservation of N. In the study area, compared to other species, A. hyrcanum subsp. sphaerocaryum with the highest both mass- and area-based PRE and C. mahaleb which is the most P-proficient species, have competitive advantages for an effective use of P in P-poor soils.