ObjectiveThe temporal and spatial variations and its formation mechanism on soil bulk density were analyzed in a cold temperate coniferous forest under different intensity fire to understand the dynamic temporal and spatial law of soil bulk density after fire interference and to provide reference for post-fire forest improvement and ecological restoration.

MethodAn autumn experimental fire was conducted in the boreal Ledum palustre-Rhododendron dauricum-Larix gmelinii forests in Daxing'an Mountains of northeastern China. Before and after the fire, the temporal and spatial variations of soil bulk density were examined continuously by latticed co-coupled sampling method.

ResultThe results showed that: (1) At each time node, soil bulk density of severe burning area was 5%-10% higher than that of mild or moderate burning area after the fire. (2) In time series, soil bulk density variation pattern was depended on fire intensity, i.e., soil bulk density of mild burning area decreased immediately and then increased, that of moderate burning area was not changed immediately and then increased continually, that of severe burning area or of all the monitoring site was risen continually. (3) Significant positive correlation was between spatial pattern of soil bulk density (or soil bulk density change) and fire intensity, correlation appeared immediately after the fire, and correlation coefficient was ascended after snowmelt season and rainy season/growing season.

ConclusionAt the initial stages of post-fire recovery, the original change direction of soil bulk density in Larix gmelini forest was different because of fire intensity differences and then all increased after rainy season/growing season, which increased significantly in moderate burning area and severe burning area.