The Threat of Increasingly Intense Boreal Fires on Picea glauca Regeneration ? Jack Cossman (BIOL0420) Introduction: Problem, Hypotheses, and Significance Now nearly consensually accepted worldwide by both the scientific and public communities, global climate change is becoming an increasingly urgent reality. Predictions about shifting weather patterns plus hypotheses on failing biodiversity equal eventual haywire in ecosystem dynamics. Although collectively we, as humans, tend to distance ourselves from the natural world, it is our obligation to project what we have not already permanently damaged. If not for reasons of sustainable resource extraction, then for purely aesthetic and moral reasons, we should actively seek solutions for sustainability. Understanding how the biomes and key ecosystems will be impacted by climate change is key to understanding the fate of the planet and of mankind. The International Panel on Climate Change predicts several ecosystems of the world most likely to be particularly affected by climate change, one of which is the boreal forest or taiga due to its sensitivity to warming (IPCC 2007). In northwestern and west-central Canada, winter and spring warming of at least 3º C has been measured so far. Under general circulation models analyzed by Stocks et al. (1998), areas experiencing high to extreme fire danger are certain to increase dramatically in Canada and Siberia. Thus, the threat of threat of permanent ecosystem damage could spread through the taiga of both North America and Asia. The taiga is a biome of coniferous forests in the northern latitudes in North America, Europe, and Asia. It provides a plethora of natural resources for humans, especially lumber. The North American taiga is dominated especially by the white spruce Picea glauca, which, according to Peters et al. (2005), utilizes a masting strategy in sync with forest fire years for optimal reproduction and regeneration. The species will release a large crop of seeds every several years, and their success depends on forest fires to clear away canopy, exposing sunlight, and to recycle nutrients into the forest soil. Peters et al. primarily investigated whether the temporal delay between mast and fire years influenced how well a seed cohort could reestablish a new generation of Picea. Succinctly, they found that more regeneration occurs after mast-year fires than after non-mast-year fires because when fire and mast years coincide, more seed is available when the seedbeds are most receptive. Also, they found that an initial mast cohort persists as the dominant cohort over time after mast-year fires, but that the initial cohort is less important if there is a time lag between the fire and the next masting. However, Peters et al. did not consider the intensity of fire as a factor affecting Picea regeneration. If the taiga becomes more arid, forest fire intensity is likely to increase, perhaps above the limits that Picea seeds can tolerate. Thus, if Picea cannot regenerate, the taiga biome?s successional floral composition will change. A change would impact the natural ecosystem and both the human economy and collective conscience. In fact, Bergeron & Dansereau (1993) determined in the boreal forest of Quebec that dominance of deciduous and coniferous trees transitions in a >200 year fire cycle. Extrapolation leads to the suggestion that more fires more frequently could permanently disrupt the floral cycle. Moreover, pollen, plant macrofossils, and sediment charcoal from the North Cascades, as researched by Cwynar (1987), reveal prehistorically dramatic shifts in tree species dominance corresponding to broader climatic variability. For example, the abundance of Pseudotsuga, Alnus rubra, and Pteridium between 11,030 and 6,830 BP corresponds with increased influxes of charcoal in the sediment, indicating a closed forest zone with a relatively high fire frequency and a variety of post-fire successional communities in which fire-adapted species predominated over fire-sensitive species such as Tsuga heterophlla. Similar changes are within modern possibility. Understanding how Picea regeneration may be affected will help to pinpoint changes in the taiga?s broader ecosystem and to identify protection methods for sustainability. Hypotheses As the taiga regions become more arid, we hypothesize that the intensity of fires will increase, jeopardizing the regeneration of Picea seeds. We further hypothesize that if Picea regeneration declines, ecosystem functioning will be negatively affected as Picea is the most dominant floral component of the taiga. Our hypotheses are based on the assumptions that Picea holds a prominent position in the taiga ecosystem, as it is one of the most prevalent tree species. Additionally, for experimental purposes, we assume that intensity of fire damage correlates with length of burning time. Methods To assess how varying levels of fire intensity affect Picea glauca germination, regeneration, and succession, we will hold a multiple-plot experiment, similar to those in Peters et al., in an artificial taiga environment. To eliminate as best as possible the confounding variable of genetic variation, all seeds will be from the same hardy mature Picea. Seeds will be stored at the average summer temperature of the part of the taiga in which the parent resides. Additionally, soil characteristic of the taiga will be of consistent quality. The same number of seeds will go into each plot. Fire intensity will be measured by degree of scorching in a plot with typical taiga undergrowth and Picea seeds in the soil. We will control fires to burn for a given length of time; the length of burning time will correspond to level of scorching. Fires will be set using tinder and matches. Control plots will be burned commensurate with the current average summer intensity, and seeds will be allowed to germinate naturally. Growth and regeneration of the seeds will be measured for several months after burning. Conditions will be kept constant for all plots, controlling for variables such as amount of artificial sunlight, soil and air temperature, and precipitation. Since the taiga is expected to become arid in the future, artificial temperatures and precipitation levels will mimic drought conditions. Data will consist of time until germination, rate of seedling growth, duration of survival, and overall seedling hardiness. Although other unpredictable factors such as herbivory and nuances of immediate environments will affect actual seedling regeneration, such factors will be ignored as only arid/drought conditions are under study. Interpretation of Results The null hypothesis for this study is that increasingly arid conditions in the taiga will not negatively influence Picea glauca (white spruce) regeneration. Thus, the alternate hypothesis is that Picea prevalence in the taiga will dwindle significantly as the biome?s climate changes. With the data, we will analyze growth and retention trends as intensity of scorching increases. To reach the conclusion that more intense fires could jeopardize Picea?s life cycle, we must observe diminished growth, low survival, or failure to germinate. Long-term studies may be necessary in case the seedlings require prolonged time to germinate and establish themselves. The implications of establishing the limit of Picea seeds? resistance to permanent damage from fire are important for predicting how the flora, and thus ecosystems, of the taiga will change. Strategies of preventing intense forest damage may be developed in light of the threat they pose on the biome. Although we may be able to predict the effects Picea will experience, we cannot be infallibly certain of the overall impacts on ecosystem dynamics. Wildfires, nevertheless, are not only essential for Picea regeneration, but also, especially in Alaska according to Viereck (1973), for animal species (e.g., moose) that rely on successional plant communities and for cycling nutrients in permafrost. If fires grow too intense, plant succession may fail. This consequently endangers the dependent wildlife. If wildfires are suppressed, similar consequences may result as plant succession fails to happen while the living flora contends with the arid conditions. Recognizing that Picea is a predominant tree species of the taiga, we may venture to assume that its diminishing presence will greatly affect the current ecosystem dynamics and, indeed, human activity. By understanding how and where Picea will be most endangered by arid conditions, we may be able to develop preservation strategies. Finally, Picea glauca may serve as a model for analyzing how other plants that use masting reproduction will be affected by global climate change. Bibliography Bergeron, Yves & Danserau, Pierre-Rene. ?Predicting the composition of Canadian southern boreal forests in different fire cycles.? Journal of Vegetation Science, Vol. 4, 1993. Pages 827-832. Cwynar, Les C. ?Fire and the forest history of the North Cascade Range.? Ecology, Vol. 68, Issue 4, 1987. Pages 791-802. Intergovernmental Panel on Climate Change. Fourth Assessment Report. 2007. . Peters, Vernon S. et al. ?The interaction between masting and fire is key to white spruce regeneration.? Ecology, Vol. 86, Issue 7, 2005. Pages 1744-1750. Stocks, B.J. et al. ?Climate change and forest fire potential in Russian and Canadian boreal forests.? Climatic Change, Vol. 38, 1998. Pages 1-13. Viereck, Leslie A. ?Wildfire in the taiga of Alaska.? Quaternary Research, Vol. 3, Issue 3, October 1973. Pages 465-495.
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