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Berkeley ETHSTD 196 - Impacts of Heat on the Spore Bank Community Structure

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Abstract The effect of temperature on the presence and community composition of ectomycorrhizal fungi associated with Pinus jeffreyi seedlings was investigated in this study. We followed the colonization of ectomycorrhizal fungi in 8 month old Pinus jeffSoil Extraction Soils from Teakettle were extracted randomly from eight arbitrarily chosen white fir stands. Stands were selected for ecological and environmental similarity to ensure a more accurate comparison. Plots within the white fir stands were seCollecting of ectomycorrhizas After 8 months of growth, Jeffrey pine seedlings were harvested from the heat bioassays; seedling health and percent coverage by ectomycorrhizae was estimated by random sample of root tips and recorded. Root systems were obsMolecular Techniques & Fungal Identification DNA was extracted individually from one to two root tips as described by Gardes & Bruns (1993). Several tips were extracted together only when part of a single morphologically uniform clump.Impacts of Heat on the Spore Bank Community Structure in Mixed Conifer Forest Soil Using Pinus jeffreyi Seedlings as a Host Species. Megan Canright Abstract The effect of temperature on the presence and community composition of ectomycorrhizal fungi associated with Pinus jeffreyi seedlings was investigated in this study. We followed the colonization of ectomycorrhizal fungi in 8 month old Pinus jeffreyi seedlings whose soil had been subjected to one of four treatments: no heat, 40°C heating, 55°C heating and 70°C heating. Ectomycorrhizas were harvested by hand under dissecting microscope from 8 month old seedlings and subjected to PCR/RFLP analysis of the ITS region of the ribosomal DNA for identification to the species or genus level. Significant difference in species richness was analyzed using Wilcoxon’s rank-sum test. Species diversity was measured using the Shannon-Weaver index and tested for significant difference among treatments using t-tests. Species richness was significantly higher in heated treatments as compared to non-heated treatments, however no significant difference in species richness was found between seedlings heated at different temperatures. Species diversity was also significantly different between heated and non-heated treatments, but was not different across heated treatments. Preliminary results indicate that species composition experiences a shift across treatments. Results may show that dominant species include Rhizopogon subcaerulescens in non heat-treated seedlings, Russula amoenolens in 40°C seedlings, Suillus brevipes in 55°C seedlings and Cenoccocum geophilium and Tomentella sublilicina in 70°C treatments. Thelephoraceae sp. may be seen equally across all treatments. If preliminary results reflect actual results, species seen in heat treatments may be either the most heat-resistant ectomycorrhizae or are stimulated by heat and may play a role in the re-establishment of forest ecosystems directly following fire as other less heat-resistant mycorrhizae rebuild their communities. In short, the overall effect of increased temperature seems to be increased species richness and diversity accompanied by a shift in species composition from basidiomycetes to ascomycetes.Introduction Historically, fire has been a common disturbance in California pine stands, especially before the onset of modern fire prevention techniques (Biswell 1989). Studies of historical and pre-historical forest fire regimes have shown that moderate intensity fires typically afflicted pine stands every 3 to 11 years (Brown et al. 2001). Prescribed fire has been utilized in pine stands as a management technique for over 50 years in an attempt to encourage the success of the pine (Biswell 1989). Fire reduces tree density and prevents succession by more shade-tolerant species such as white fir, and protects against disease, pest infestation and stand replacing wildfire (Choromanska et al. 2001; Fule et al. 1997). Moderate intensity prescribed burning has proven to be a useful management tool in Pinus jeffreyi (Jeffrey pine) stands for the prevention of bark beetle infestation. In addition, Pinus jeffreyi responds well to prescribed fire in terms of overall stand health; stand health and density of P. jeffreyi have been shown to increase with prescribed fire treatments (Roy & Vankat 1999). Mycorrhizae commonly associate symbiotically with various Pineaceae species, including Pinus jeffreyi. Walker and Kane (1997) found that after 6 months, mycorrhizal Jeffrey pine seedlings had greater root dry weight, increased shoot dimensions and overall weight. Mycorrhizal hyphae penetrate soils, branching into fine thread-like extensions called hyphae, which are much finer than root hairs. The hyphae are very absorptive and are more efficient than plant roots in taking up nutrients. Mycorrhizae associate with pine roots, helping the tree to take up minerals, namely nitrogen, and nutrients in exchange for sugars produced by the pine during photosynthesis. The increased nitrogen nutrition due to mycorrhizae allows mycorrhizal plants to grow much more quickly than non-mycorrhizal plants (Varma and Hock 1999). The role of mycorrhizal fungi in the re-establishment of pine forests following fire disturbance is unknown. Some research has been conducted looking at the affect of fire on mycorrhizal numbers and biomass. Stendell et al. (1999) found that one year following prescribed fire, ectomycorrhizal biomass was not significantly reduced in comparison to pre-burn quantities, indicating that mycorrhizae are not adversely affected by fire. Vazquez et al. (1993) found that hyphal length post-fire exceeded pre-burn values. However, little research has attempted to tackle the question of how mycorrhizal species composition is altered in response to fire.The goal of this study is to take the first step towards this understanding by addressing the relationship between mycorrhizal community structure and soil temperature. A mixed conifer ecosystem with a historically naturally occurring fire regime was chosen to conduct this experiment because it can be assumed that organisms in this type of environment will respond to temperature disturbance due to the natural fire regime. Three main questions will be addressed by this study in the forest system: What does the spore bank look like for the soil taken from the site? Does temperature have a significant effect on the species composition of mycorrhizae in this soil? If so,


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Berkeley ETHSTD 196 - Impacts of Heat on the Spore Bank Community Structure

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