Document: DAN-3-35-6

A single-tree approach to age-related decline in stand growth.

BINKLEY, D.* ¹, M.G.RYAN ² and H.BARNARD ¹

Colorado State University, Ft. Collins CO 80523 USA ¹
USDA Forest Service Rocky Mountain Research Station, Ft. Collins CO 80523 USA ²

Abstract:
The growth of forest stands typically declines after reaching a peak near the time of canopy closure. Our previous work looked for a stand-level explanation for this pattern. In this presentation, we present results of single-tree patterns in resource use and production. Twenty-five Eucalyptus trees in a 10 by 10 m, monoculture plot were examined for stem growth, water use, light interception, and canopy nitrogen content. Dominant trees generally used resources more efficiently. For example, stand growth per unit leaf area was almost twice as high in dominant trees (0.5 kg wood/m² leaf area) than in suppressed trees (0.3 kg wood/m² leaf area). If all trees produced as much wood per unit leaf area as the better half of the trees, then stand growth would be 24% higher for the same total stand leaf area. If all trees used N as efficiently as the better half of the trees, growth would be 15% higher for the same quantity of N in the total canopy. This deconstruction of the stand-level growth supported the idea that differentiation in tree sizes through stand development leads to stand-level decline as a result of shifts in single-tree resource use, and growth per unit of resource used.

Keywords: forest growth, resource use, light, nitrogen, water

This abstract is being presented at: 9:45 AM in session:
Oral Session #1: Plant Carbon Allocation.