Changes in foliar nitrogen resorption of Phyllostachys edulis with culm development

Abstract

Leaf nitrogen resorption is very important to Phyllostachys edulis development because the withdrawn nitrogen can help newly emerging and growing culms. However, few studies have focused on the ontogenetic changes in leaf nitrogen resorption of P. edulis. Here, we examined the variability in mature leaf nitrogen concentrations (Nm), nitrogen resorption efficiency (NRE) and proficiency (NRP or Ns) and leaf-level nitrogen use efficiency (NUE) of the current-, 3rd- and 5th-year culms in P. edulis stands under extensive management. Analyses of variance and correlation indicated that patterns of Nm, NRP, NRE and NUE were markedly affected by culm age and leaf nitrogen status. Nm, Ns and NRE were significant higher in younger (current-year) culms with 1-year lifespan leaves, while NUE was markedly higher in older (3rd- or 5th-year) culms with 2-year lifespan leaves. Significant linear correlations between Nm and NRP, NRE and NUE, Nm and NUE, Ns and NRE were found for each culm age, and Nm was significantly positively correlated to NRE for all culms pooled. Higher proficiency in older culms led to higher NUE and lower NRE, these relationships can be modulated by Nm, which in turn, is restrained by leaf N availability and acquisition. Our results revealed that at the intraspecific level, P. edulis can adjust its leaf NRE, NRP, and leaf-level NUE in concert with culm development. Understanding nitrogen resorption characteristics and NUE of P. edulis can help decision-makers design appropriate deforestation strategies and achieve precise N fertilization for sustainable bamboo forest management.