Bonanza Creek LTER: Annual Active Layer Depths at Core Floodplain Sites from 1990 to Present in the Bonanza Creek Experimental Forest near Fairbanks, Alaska

Annual thaw depths are measured at the time of maximum thaw at any of the 35 BCEF-LTER sites that have permafrost or intermittent seasonal frost. 1. Wildfire in the black spruce permafrost sites will cause an increase in the active layer thickness and subsidence of the surface layers that may last for up to 25 years. The active layer thickness should return to the pre-fire depths between 25 and 30 years after the fire. 2. Climate warming in interior Alaska may result in an increase in the active layer thickness in black spruce permafrost sites. 3. Fire and climate warming together may result in the elimination of permafrost from some black spruce permafrost sites in interior Alaska. 4. Forest succession on the floodplain of the Tanana River results in a gradual decrease in soil temperature as the organic layer increases with time. The development of a thick feathermoss layer in later stages of succession is especially important in the development of permafrost. Permanent or intermittent permafrost should develop in the older white spruce stages. Black spruce stands on the older terraces should be underlain by permafrost with a shallow active layer. 5. Climate warming will delay the formation of permafrost until the latest stages of forest succession and may eliminate it completely from floodplain stands.

本数据集针对35处存在多年冻土（permafrost）或间歇性季节冻土的BCEF-LTER站点，于各站点的最大解冻期测定年解冻深度。
1. 黑云杉多年冻土区域发生野火后，活动层（active layer）厚度将增加，地表层沉降现象可持续长达25年；火灾发生后25至30年间，活动层厚度将恢复至火灾前水平。
2. 阿拉斯加内陆的气候变暖，可能导致黑云杉多年冻土区域的活动层厚度增加。
3. 野火与气候变暖共同作用，可能会消除阿拉斯加内陆部分黑云杉多年冻土区域的多年冻土。
4. 塔纳纳河河漫滩上的森林演替过程中，随着有机质层随时间增厚，土壤温度逐渐降低。演替后期形成的厚层羽藓群落，对多年冻土的形成尤为关键。在老龄白云杉林分阶段，将形成永久性或间歇性多年冻土；古老阶地上的黑云杉林分地下应存在下伏多年冻土，且活动层较浅。
5. 气候变暖将推迟多年冻土的形成，直至森林演替的最晚阶段，甚至可能完全消除河漫滩林地上的多年冻土。