tailieunhanh - Báo cáo lâm nghiệp: " Biomass and composition of understory vegetation and the forest floor carbon stock across Siberian larch and mountain birch chronosequences in Iceland"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: " Biomass and composition of understory vegetation and the forest floor carbon stock across Siberian larch and mountain birch chronosequences in Iceland" | Ann. For. Sci. 62 2005 881-888 INRA EDP Sciences 2005 DOI forest 2005079 881 Original article Biomass and composition of understory vegetation and the forest floor carbon stock across Siberian larch and mountain birch chronosequences in Iceland Bjarni D. SIGURDSSONa Borgthor MAGNUSSONb Asrun ELMARSDOTTIRb Brynhildur BJARNADOTTIRa c a Icelandic Forest Research Mogilsa 116 Reykjavik Iceland b Icelandic Institute of Natural History Reykjavik Iceland c Department of Physical Geography and Ecosystem Analysis Lund University Sweden Received 20 August 2004 accepted 27 May 2005 Abstract - Changes in understory biomass forest floor carbon C stock and vegetation composition were studied in six age-classes of Siberian larch Larix sibirica and two age-classes of native birch Betula pubescens in Iceland. The ground vegetation was less in the larch during the thicket stage and in the old-growth birch compared to a treeless pasture. Understory biomass was strongly related to canopy gap fraction across forest stands P but not to soil pH or soil C N ratio. Increased mass of dead wood and alterations in vegetation composition increased the forest floor C-stock of older forests. The forest floor had reached as high C-stock as the pasture s ground vegetation in ca. 50 years in the managed larch plantations and in ca. hundred years in the unmanaged birch forest. This study clearly shows the importance of which time-step is used when changes in forest floor C-stocks are computed for afforestation areas. Betula pubescens carbon sequestration woody debris Larix sibirica understory Résumé - Biomasse et composition de la vegetation de sous-bois et stock de carbone du sol dans une chronoséquence de mélèze de Sibérie et de bouleau pubescent en Islande. Nous avons étudié en Islande les modifications de biomasse de composition floristique et de stock de carbone en sous bois dans des peuplements de mélèze de Sibérie correspondant à 6 classes d âge et dans des peuplements de bouleau