Document: KEN-3-63-1

The response of fine roots to nutrient additions in disturbed black spruce ecosystems.

SMITH, C.K.* ¹, A.D.MUNSON ² and M.R.COYEA ²

University of the South, Sewanee, TN, 37383, USA ¹
Universite Laval, Sainte-Foy, Quebec, G1K7P4, CANADA ²

Abstract:
The black spruce ecosystems in central Quebec are highly disturbed by fire and harvesting, yet little is known about soil nutrient dynamics and plant productivity following anthropogenic or natural disturbance in these systems. To evaluate the response of tree and shrub fine roots to additions of three nutrients, we installed a root-ingrowth core experiment in recently burned and harvested stands (< ten years) and in stands that were cut or burned over 50 years ago. The cores were filled with root-free organic material collected from soils under replicated black spruce stands, treated with nutrient solutions (Ca, N, or P), and placed in the top 10 cm of the soil at each of the 12 stands (4 disturbance types by 3 replicates). At each of the stands, 24 cores were installed, and the cores were harvested after 4.5 months in the field (May to October). After their extraction, the concentrations of exchangeable Ca, extractable P, and NH₄⁺ in the treated cores were 40 - 95% higher than in the untreated (control) cores. Preliminary analyses indicate that cores placed in the recently harvested stands (all nutrient treatments) had higher fine root length (220 - 240 cm/cm³) and biomass (602 794 g/m²) compared to the other disturbance types. The calcium treated cores had the highest fine root length in each of the disturbance types, suggesting that Ca may limit productivity in these sites.

Keywords: black spruce, root-ingrowth cores, nitrogen, phosphorus, calcium

This abstract is being presented at: 1:30 PM in session:
Oral Session #12: Roots.