Tuesday, 8 November 2005
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This presentation is part of: DOC, SOM, and CO2

Pre- and Post-Harvest Stores of Carbon and Nitrogen in a Highly-Productive Forest Site Subjected to Increasing Biomass Removals in Coastal Washington.

Adrian Ares, Thomas Terry, Robert Harrison, Kathryn Piatek, Constance Harrington, Rick Leon, Rod Meade, Richard Miller, Harry Anderson, Barry Flaming, Christopher Licata, Kyle Petersen, and Brian Strahm.

Biomass removals during harvesting or site preparation cause major changes in C and nutrient stores and potentially affect long-term site productivity. We assessed C and N stores in a highly productive coastal Washington site before and after imposing biomass removal treatments to a 46-year old Douglas-fir/western hemlock stand. Treatments included removal of commercial bole (B0), bole only up to 5-cm top diameter (BO5), total tree (TT), and total tree plus all legacy woody debris (TT+). The stand contained similar amounts of C above the mineral soil (294 Mg ha-1) as within the mineral soil to 80-cm depth including roots (297 Mg ha-1). Carbon stores above the mineral soil by size were live trees (194 Mg ha-1), forest floor (27 Mg ha-1), coarse woody debris (11 Mg ha-1), dead trees/snags (7 Mg ha-1), and understory vegetation (0.1 Mg ha-1). Carbon in the mineral soil amounted to 249 Mg ha-1 while roots added 49 Mg ha-1. Total N in mineral soil and roots was more than ten-fold greater (13.6 Mg ha-1) than the N store above the mineral soil (1.3 Mg ha-1). After harvest, C stores above the mineral soil decreased to 130 Mg ha-1 in BO, 121 Mg ha-1 in BO5, 64 Mg ha-1 in TT and 51 Mg ha-1 in TT+. Post-harvest forest floor C averaged 24 Mg ha-1 in TT and TT+, against 45 Mg-1ha in BO and BO5, and 27 Mg ha-1 in the pre-harvest stand. Total N above the mineral soil averaged 779 Mg ha-1 in BO and BO5, and decreased to 414 and 347 Mg ha-1 in TT and TT+, respectively, while soil N remained mostly unchanged. Proportion of C stores above and within the mineral soil was markedly altered by removals while total N was only reduced by 6% in the most intensive treatment.

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