Carbon allocation and nitrogen acquisition in a developing Populus deltoides plantation.

Area of Science:

• Forest Ecology
• Plant Physiology
• Nutrient Cycling

Background:

• Understanding how nitrogen availability influences tree growth and resource allocation is crucial for forest management and productivity.
• Populus deltoides (eastern cottonwood) is a key species in many ecosystems, making its response to nitrogen fertilization ecologically significant.

Purpose of the Study:

• To investigate if nitrogen-induced carbon allocation in Populus deltoides is driven by developmental controls.
• To determine if specific nitrogen uptake rates increase with nitrogen availability in Populus deltoides.

Main Methods:

• Established Populus deltoides stands with varying nitrogen (N) fertilization levels (0, 50, 100, 200 kg N ha(-1) year(-1)).
• Conducted non-destructive measurements of tree growth and fine-root dynamics over two growing seasons.
• Performed destructive harvests to analyze biomass, carbon (C) and N content, and estimate specific N-uptake rates.

Main Results:

• Shoot growth increased with fertilization, but higher rates (100N, 200N) showed no additional benefit over 50N.
• Root biomass proportion decreased with time and increased N availability.
• Fertilizer-induced changes in C allocation were attributed to accelerated tree development.
• Specific N-uptake rates increased seasonally and were higher in fertilized trees.

Conclusions:

• Accelerated development, not just nutrient availability, explains nitrogen-induced carbon allocation shifts in Populus deltoides.
• Specific nitrogen uptake rates are enhanced by nitrogen fertilization in this species.
• Optimizing nitrogen fertilization may be key for managing Populus deltoides growth and resource allocation.