Abstract:

Foliar nutrients, particularly nitrogen (N), phosphorus (P), and potassium (K) are transferred from the senescing leaves to other tissues of the plant for storage. The recovery of these nutrients, termed resorption, significantly affects plant growth in the following year, and is therefore important to plant adaptation to nutrient-poor habitats. Thus, foliar nutrient resorption efficiency can reflect the ability of nutrient conservation, nutrient use efficiency and adaptation to nutrient-poor habitat of trees. In this study, leaf characteristics and nutrient concentrations before and after leaf senescing, and foliar nutrient resorption efficiency in four Pinus sylvestris var. mongolica plantations of varying ages (11, 20, 29, 45 years old, respectively) were studied in Zhanggutai area, which is situated at southeastern Horqin Sandy Lands. The results showed that foliar leaf mass and area of P. sylvestris var. mongolica trees decreased obviously; the foliar nutrient concentrations of P. sylvestris var. mongolica trees before leaf senescing didn't show a tendency with tree ages. The concentrations of N, P, K and Mg in leaf litters of P. sylvestris var. mongolica trees showed an increased tendency with ages, but the Ca concentration tended to decrease with ages. The foliar N, P, K resorption efficiencies of 11-year-old P. sylvestris var. mongolica trees were similar to those of 20-year-old P. sylvestris var. mongolica trees, however, their resorption efficiencies were both significantly ( P<0.05) higher than those of 29- and 45-year-old P. sylvestris var. mongolica trees. The foliar Mg resorption efficiency showed a decreased tendency with tree ages. The foliar Ca concentrations gradually increased during leaf senescing, thus the Ca resorption efficiencies were negative values. The foliar Ca resorption efficiency of 20-year-old P. sylvestris var. mongolica was the highest among the four aged trees, and the foliar Ca resorption efficiencies of 11- and 45-year-old trees were the lowest. On the whole, foliar N, P, K, Mg resorption efficiency of P. sylvestris var. mongolica trees decreased with tree ages, which indicated that the adaptation ability of P. sylvestris var. mongolica trees to nutrient-poor sandy habitat also decreased with ages, and reflected a decline characteristic on nutrient conservation of P. sylvestris var. mongolica trees.

Key words: Pinus sylvestris var. Mongolica, leaf, nutrient concentration, nutrient resorption efficiency, Zhanggutai area