Premium
How surface fire in Siberian Scots pine forests affects soil organic carbon in the forest floor: Stocks, molecular structure, and conversion to black carbon (charcoal)
Author(s) -
Czimczik Claudia I.,
Preston Caroline M.,
Schmidt Michael W. I.,
Schulze ErnstDetlef
Publication year - 2003
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2002gb001956
Subject(s) - scots pine , forest floor , environmental chemistry , environmental science , taiga , soil carbon , total organic carbon , carbon fibers , charcoal , chemistry , forestry , soil water , soil science , botany , organic chemistry , materials science , biology , composite number , composite material , pinus <genus> , geography
In boreal forests, fire is a frequent disturbance and converts soil organic carbon (OC) to more degradation‐resistant aromatic carbon, i.e., black carbon (BC) which might act as a long‐term atmospheric‐carbon sink. Little is known on the effects of fires on boreal soil OC stocks and molecular composition. We studied how a surface fire affected the composition of the forest floor of Siberian Scots pine forests by comparing the bulk elemental composition, molecular structure ( 13 C‐MAS NMR), and the aromatic carbon fraction (BC and potentially interfering constituents like tannins) of unburned and burned forest floor. Fire reduced the mass of the forest floor by 60%, stocks of inorganic elements (Si, Al, Fe, K, Ca, Na, Mg, Mn) by 30–50%, and of OC, nitrogen, and sulfur by 40–50%. In contrast to typical findings from temperate forests, unburned OC consisted mainly of (di‐)O‐alkyl (polysaccharides) and few aromatic structures, probably due to dominant input of lichen biomass. Fire converted OC into alkyl and aromatic structures, the latter consisting of heterocyclic macromolecules and small clusters of condensed carbon. The small cluster size explained the small BC concentrations determined using a degradative molecular marker method. Fire increased BC stocks (16 g kg −1 OC) by 40% which translates into a net‐conversion rate of 0.7% (0.35% of net primary production) unburned OC to BC. Here, however, BC was not a major fraction of soil OC pool in unburned or burned forest floor, either due to rapid in situ degradation or relocation.