The influence of fire on carbon distribution and net primary production ofboreal Larix gmelinii forests in north-eastern China

The boreal larch forest of Eurasia is a widespread forest ecosystem and pla ys an important role in the carbon budget of boreal forests. However, few c arbon budgets exist for these forests, and the effects of wildfire, the dom inant natural disturbance in this region, on carbon budgets are poorly unde rstood. The objective of this study was to quantify the effects of wildfire on carbon distribution and net primary production (NPP) for three major Da hurian larch (Larix gmelinii Rupr.) forest ecosystems in Tahe, Daxing' anli ng, north-eastern China: Larix gmelinii-Ledum palustre, Larix gmelinii-gras s and Larix gmelinii-Rhododendron dahurica forests. The experimental design included mature forests (unburned), and lightly and heavily burned forests from the 1.3-million-ha 1987 wildfire. We measured carbon distribution and above-ground NPP, and estimated fine root production from literature value s. Total ecosystem carbon content for the mature forests was greatest for Lari x-Ledum forests (251.4 t C ha(-1)) and smallest for Larix-grass forests (12 3.8 t C ha(-1)). Larix-Ledum forests contained the smallest vegetation carb on (13.5%), while Larix-Rhododendron contained the largest vegetation carbo n (63.1%). Fires tended to transfer carbon from vegetation to detritus and soil. Total NPP did not differ significantly between the lightly burned and unburned stands, and averaged 1.58, 1.29 and 1.01 t C ha(-1) year(-1) for Larix-grass, Larix-Rhododendron and Larix-Ledum lightly burned stands, resp ectively. Above-ground net primary production (ANPP) of heavily burned stan ds was 92-95% less than unburned and lightly burned stands. The estimated c arbon loss during the 1987 fire showed substantial variability among forest types and fire severity levels. Depending upon the assumptions made about the fraction of the landscape occupied by the three larch forest types, the 1987 conflagration in north-east China released 2.5 x 10(7)- 4.9 x 10(7) t C to the atmosphere. This study illustrates the need to distinguish betwee n the different larch forests for developing general carbon budgets.