Journal Article

Aboveground sink strength in forests controls the allocation of carbon below ground and its CO₂-induced enhancement

Finzi, A.C, Palmroth, S, Schlesinger, W.H, Oren, R, Butnor, J.R, Ryan, M.G, McCarthy, H.R, Johnsen, K.H

2006

Overview

The partitioning among carbon (C) pools of the extra C captured under elevated atmospheric CO₂ concentration ([CO₂]) determines the enhancement in C sequestration, yet no clear partitioning rules exist. Here, we used first principles and published data from four free-air CO₂ enrichment (FACE) experiments on forest tree species to conceptualize the total allocation of C to below ground (TBCA) under current [CO₂] and to predict the likely effect of elevated [CO₂]. We show that at a FACE site where leaf area index (L) of Pinus taeda L. was altered through nitrogen fertilization, ice-storm damage, and droughts, changes in L, reflecting the aboveground sink for net primary productivity, were accompanied by opposite changes in TBCA. A similar pattern emerged when data were combined from the four FACE experiments, using leaf area duration (L(D)) to account for differences in growing-season length. Moreover, elevated [CO₂]-induced enhancement of TBCA in the combined data decreased from approximately equal to 50% (700 g C m⁻² y⁻¹) at the lowest L(D) to approximately equal to 30% (200 g C m⁻² y⁻¹) at the highest L(D). The consistency of the trend in TBCA with L and its response to [CO₂] across the sites provides a norm for predictions of ecosystem C cycling, and is particularly useful for models that use L to estimate components of the terrestrial C balance.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Atmosphere - chemistry / Biological Sciences / Carbon / Carbon - metabolism / Carbon dioxide / Carbon Dioxide - analysis / Carbon Dioxide - metabolism / deciduous forests / Drought / Ecology / Ecosystem / elevated atmospheric gases / Environmental science / fertilizer application / Forest canopy / Forest litter / forest plantations / Forest soils / Forests / free air carbon dioxide enrichment / Global environmental change / Growing seasons / Italy / leaf area index / Leaves / Models, Biological / net primary productivity / nitrogen / nitrogen fertilizers / North Carolina / nutrient availability / Photosynthesis - physiology / Pine trees / Pinus - metabolism / Pinus taeda / Plant Leaves - anatomy & histology / Plant Leaves - metabolism / Plant species / primary productivity / Respiration / root growth / roots / Seasons / Soil ecology / Soil respiration / Storm damage / Tennessee / total allocation to carbon below ground / Trees - metabolism / Wisconsin