© 2004 Heron Publishing—Victoria, Canada
Carbon allocation and nitrogen acquisition in a developing Populus deltoides plantation
Mark D. Coleman (1, 2), Alexander L. Friend (3) and Christel C. Kern (4)
1. USDA Forest Service, Southern Research Station, P.O. Box 700, New Ellenton, SC 29801, USA / 2. Corresponding author (mcoleman01@fs.fed.us) / 3. USDA Forest Service, North Central Research Station, 410 MacInnes Drive, Houghton, MI 49931, USA / 4. USDA Forest Service, North Central Research Station, 1831 Hwy 169 E, Grand Rapids, MN 55744, USA / Received December 15, 2003; accepted April 12, 2004; published online October 1, 2004
Summary
We established Populus deltoides Bartr. stands differing in nitrogen (N) availability and tested if: (1) N-induced carbon (C) allocation could be explained
by developmental allocation controls; and (2) N uptake per unit root mass, i.e., specific N-uptake rate, increased with N
availability. Closely spaced (1 × 1 m) stands were treated with 50, 100 and 200 kg N ha–1 year–1 of time-release balanced fertilizer (50N, 100N and 200N) and compared with unfertilized controls (0N). Measurements were
made during two complete growing seasons from May 1998 through October 1999. Repeated nondestructive measurements were carried
out to determine stem height and diameter, leaf area and fine-root dynamics. In October of both years, above- and belowground
biomass was harvested, including soil cores for fine-root biomass. Leaves were harvested in July 1999. Harvested tissues were
analyzed for C and N content. Nondestructive stem diameter and and fine-root dynamic measurements were combined with destructive
harvest data to estimate whole-tree biomass and N content at the end of the year, and to estimate specific N-uptake rates
during the 1999 growing season. Shoot growth response was greater in fertilized trees than in control trees; however, the
100N and 200N treatments did not enhance growth more than the 50N treatment. Root biomass proportions decreased over time
and with increasing fertilizer treatment. Fertilizer-induced changes in allocation were explained by accelerated development.
Specific N-uptake rates increased during the growing season and were higher for fertilized trees than for control trees.
Keywords:
belowground allocation, carbon sequestration, functional equilibrium, ontogenetic drift, phytoremediation, short rotation
woody crops, specific nutrient uptake.
