Identifying Mycorrhizas Present in Bigleaf Maple Canopy and Forest Floor Soils in a Coastal Old-Growth Temperate Rainforest in Western Washington

Abstract

The temperate rainforests of Western Washington are known for their old-growth forests and unique ecosystem processes. In these stands of old-growth, it is common for trees to be 200-300 years old. On branches, Epiphytic mats form in the canopy. The bottom layer of these mats starts to decompose over time, forming a layer of organic matter known as ‘canopy soil’. To better understand the role of canopy soil in the overall ecosystem, research needs to focus on canopy soil characteristics and the host tree relationships. The specific aims of this research were to attempt to 1) taxonomically identify mycorrhizal species in adventitious canopy and forest floor roots, and 2) compare the identified species between the canopy and forest floor levels. Twenty-four root samples were taken from four bigleaf maples (Acer macrophyllum Pursh) located in the Olympic National Rainforest in the Queets River Watershed, Washington State. Roots were washed and DNA was extracted for PCR, cloning, and DNA sequencing. The results were processed through the NCBI BLAST Database and EMBI ClustalW website to identify and analyze differences in genetic diversity for roots collected from the canopy and the forest floor. Mycorrhizas were successfully identified from both the canopy and forest floor roots. Due to a lack of vouchered references, some samples were only identified to class, order, or genus, while others were placed in a group entitled ‘unidentified ectomycorrhizal clones’. Three samples were identified to be from the class Leotiomycetes, one was narrowed to the order Helotiales, and another sample was identified as a Cadophora spp. All three groups have species that have been reported as being ectomycorrhizal. Although species weren’t identified past these levels, sequence alignment still allowed analysis of their DNA. There appears to be several different mycorrhizal sequences present in both the canopy and forest floor roots. Further research will be needed using DNA extractions to better understand the coevolution of these species found in canopy soils.