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Harvard Forest Symposium Abstract 2011

• Title: The changing diversity and evolution of decomposer fungi in response to soil warming and nitrogen additions
• Primary Author: Serita Frey (University of New Hampshire - Main Campus)
• Additional Authors: Eric Morrison (University of New Hampshire - Main Campus); Anne Pringle (University of Wisconsin - Madison); Samuel Pérez (Harvard University); christopher sthultz (Harvard University Faculty of Arts and Sciences); Linda van Diepen (University of New Hampshire - Main Campus)
• Abstract:

  Fungi are ubiquitous in terrestrial ecosystems and play an important role in biogeochemical cycling because of their function as litter decomposers. Fungi are a highly diverse and non-static group and fungal lineages can evolve in response to climate change. This evolution could redirect fungal function and as a consequence influence nutrient cycling within an ecosystem. Our study focuses on understanding the mechanisms by which fungi persist in a changing climate and explores the potential feedbacks on ecosystem functioning. Our goal is to identify the biodiversity of saprotrophic (decomposer) fungi, understand their evolution (phenotypic plasticity vs. adaptation), and examine the relationship between fungal diversity and litter decay in response to climate change.
  
  
  
  Our study takes place at two of the LTER sites at Harvard forest: the Chronic Nitrogen (N) Addition plots and the Barre Woods Soil Warming Study. The Chronic N Addition Experiment consists of 3 N treatments (ambient, 5 and 15 g N m-2 y-1), and the Soil Warming Study has two treatments (ambient, and +5°C warming). We implemented a litter decomposition study in the fall of 2010 using mesh bags filled with leaf litter. To simulate litter fall as accurately as possible, we used fresh leaf litter collected from the control plots and filled each bag with proportional representation of the dominant tree species. At the Chronic N experiment we also implemented a reciprocal design using oak litter (most dominant tree species) from each treatment. One set of litterbags will be harvested after ~9 months and another set after ~1.5 years. One third of the litter from each bag will be used for analysis of active fungal diversity using molecular techniques. The other 2/3 will be used for measurement of biogeochemical parameters (mass loss, C/N, lignin, enzyme activity) and to culture fungi for tests of phenotypic plasticity vs. adaptation.
  
  
  
  To date we have cultured fungi from sporocarps and fresh litter collected from the Chronic N and Warming plots in 2009 and 2010 to 1) practice culturing techniques, 2) estimate the potential of finding the same fungal species in all treatments, and 3) making an inventory of all the species that were present in the treatments. Using three different media types we were able to culture a total of sixteen different morphological species that were present in at least two or all of the N treatments, and six species in both warming treatments. We have confirmed ten of the morphological species using DNA barcoding of the ITS region, which will be used in preliminary tests to measure phenotypic plasticity vs. adaptation.
  
  
  
  In addition, fresh litter was collected from both the Chronic N and the Soil Warming plots to 1) practice techniques for the isolation and quantification of DNA and RNA pools from the fungal community of litter and 2) determine if fungi living as endophytes in the leaves could act as the first members of the decomposer community. Using techniques modified from those designed for soil we have successfully been able to isolate fungal DNA and RNA from the litter. Next a series of molecular techniques, including cloning and sequencing, will be utilized to identify individual members of the fungal communities in litter.
  
  
  
  To complement our litter fungal diversity analysis, an assessment of soil fungal diversity is being conducted at the Chronic N site using metagenetic techniques. Soil samples were taken in June and November of 2009 at the Chronic N site with one composite sample per plot in June and 3 replicate samples per plot in November. DNA was extracted and fungal phylogenetic marker loci ITS1 and ITS2 were amplified through PCR using primer sets ITS1-5.8s, and ITS4-5.8sr. Amplicons were sequenced using 454 sequencing technology. Data analysis is underway.
  
  
  
  Using these techniques to answer our questions will allow us to bridge the gap in understanding how the interaction between ecosystem function and fungal community dynamics are altered under changing climate conditions.
  
  

• Research Category: Biodiversity Studies
  Physiological Ecology, Population Dynamics, and Species Interactions
  Soil Carbon and Nitrogen Dynamics