Impact of postfire management on forest regeneration in a managed hemiboreal forest, Estonia

Fire is a significant agent for the development of boreal and hemiboreal forests, altering soil and light conditions, affecting seedbanks, and removing seed trees. Burned areas should be managed with care, as inappropriate techniques prolong the regeneration period and reduce the diversity and resilience of stands to disturbances. To study the effects of fire and postfire management on the successional changes in regeneration abundance, species composition and tree height sample plots were established in sandy pine forests in northwestern Estonia on areas burned 2 or 22 years ago. Five types of sample plots were established: (i) areas without fire damage, (ii) burned uncleared areas, (iii) burned forest areas cleared after forest fire, (iv) burned uncleared areas with live trees, and (v) burned uncleared areas with dead trees. Three main tree species common to hemiboreal forests were analyzed: Betula spp., Pinus sylvestris L., and Populus tremula L. Results showed that clearing burned areas after wildfire significantly reduced the abundance of regeneration compared with burned uncleared areas but favored height growth of P. sylvestris in later development. To regenerate and maintain mixed stands after wildfire, retaining some residual trees can facilitate regeneration compared with complete clearing, although a dense stand with live trees or a large amount of deadwood can hinder regeneration.

Wildfire and Postfire Restoration Action Effects on Microclimate and Seedling Pine Tree Survivorship

Through modification of structural characteristics, ecological processes such as fire can affect microhabitat parameters, which in turn can influence community composition dynamics. The prevalence of high-severity forest fires is increasing in the southern and western United States, creating the necessity to better understand effects of high-severity fire, and subsequent postfire management actions, on forest ecosystems. In this study we used a recent high-severity wildfire in the Lost Pines ecoregion of Texas to assess effects of the wildfire and postfire clearcutting on six microclimate parameters: air temperature, absolute humidity, mean wind speed, maximum wind speed, soil temperature, and soil moisture. We also assessed differences between burned areas and burned and subsequently clearcut areas for short-term survivorship of loblolly pine Pinus taeda seedling trees. We found that during the summer months approximately 2 y after the wildfire, mean and maximum wind speed differed between unburned and burned areas, as well as burned and burned and subsequently clearcut areas. Our results indicated air temperature, absolute humidity, soil temperature, and soil moisture did not differ between unburned and burned areas, or burned and burned and subsequently clearcut areas, during the study period. We found that short-term survivorship of loblolly pine seedling trees was influenced primarily by soil type, but was also lower in clearcut habitat compared with habitat containing dead standing trees. Ultimately, however, the outcome of the reforestation initiative will likely depend primarily on whether or not the trees can survive drought conditions in the future, and this study indicates there is flexibility in postfire management options prior to reseeding. Further, concerns about negative wildfire effects on microclimate parameters important to the endangered Houston toad Bufo (Anaxyrus) houstonensis were not supported in this study.

Assessing the cumulative effects of postfire management on forest landscape dynamics in northeastern China

We used the LANDIS model to study the long-term cumulative effects of postfire 10-year management (harvest and reforestation) on species abundance, age structure, and spatial pattern in the Tuqiang Forest Bureau on the northern slopes of the Great Hing'an Mountains after a catastrophic fire in 1987. Two simulation scenarios were constructed: the actual postfire management scenario and the natural regeneration scenario that assumed no postfire management activities occurred after the 1987 fire. Both scenarios were run with 10 replicated simulations per scenario over a 300-year period. Our results indicated that postfire management had a significant influence on species abundance, age structure, and spatial pattern. Postfire management effectively increased the abundance of coniferous trees (larch (Larix gmelinii) and Mongolian Scotch pine (Pinus sylvestris var. mongolica)), increased the abundance of white birch in the short-term simulation stage, and decreased the abundance of white birch (Betula platyphylla) in the long run. The aggregation level of white birch responded similarly to postfire management — increasing initially, and then decreasing over time. However, compared with the natural regeneration scenario, postfire management resulted in more fragmented larch and Mongolian Scotch pine, which could last for about 100–150 years because of timber harvesting in the first 10 years postfire. In addition, the age structure of larch forests under the postfire management scenario changed dramatically during the 300 simulation years: the abundance of mature and old-growth age classes of larch forests decreased dramatically in the first 10 years, but then increased and exceeded that under the natural regeneration scenario after about 100 simulation years. Therefore, although postfire management had a positive cumulative effect (less fragmented and more larch abundance) on forest recovery at the long-term successional stage, postfire management, especially timber harvesting within the first 10 years after the 1987 fire, posed negative effects (more fragmented and less mature forests) at short- and mid-term successional stages (about 100 years).