Abstract
Aims
Leaf nutrient resorption is sensitive to changes in soil nutrients. However, the effects of N deposition on nutrient resorption efficiency (NuRE) in plant macro-nutrients remain unclear. Poplar (Populus deltoids) is one of the most extensively cultivated hardwood species worldwide. We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition.
Methods
We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar (Populus deltoids) plantations (8- and 12-year-old stands) in a coastal region of eastern China. We measured soil and foliar (green and senesced leaves) concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) for a series of N addition treatments including N0 (0 kg N ha ‒1 yr ‒1), N1 (50 kg N ha ‒1 yr ‒1), N2 (100 kg N ha ‒1 yr ‒1), N3 (150 kg N ha ‒1 yr ‒1), and N4 (300 kg N ha ‒1 yr ‒1).
Important Findings
Consistent for (both) 8- and 12-year-old stands, N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio). NRE-PRE scaling slopes were consistently less than 1.0 under N addition. These results suggest that NRE generally decouples from PRE within each N treatment. Moreover, these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between nutrient resorption efficiency and green leaf nutrient concentrations. Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in a coastal region of eastern China.
Effects of body size and root to shoot ratio on foliar nutrient resorption efficiency in
Amaranthus mangostanus
