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Studies of fungi at Hubbard Brook


Dead fine roots     
  Contact Info:
  Melany Fisk
Department of Biology
Appalachian State University
572 Rivers St
Boone, NC 28608
phone: (828) 262-6910

Fungal communities that decompose fine roots

This research is funded by a grant from the USDA-NRICGP, and is a collaboration with Dr. Andria Costello at Syracuse University and Dr. Tim Fahey at Cornell University.

FINE ROOT TURNOVER is a large component of northern hardwood forest carbon budgets. However, the biota responsible for the processing and ultimate fate of the large quantities of C and essential nutrients stored in dying roots have not been comprehensively identified. The goal of this research is to improve our understanding of the microbiology and ecology of fine root decomposition in the northern hardwood forest ecosystem at the Hubbard Brook Experimental Forest, (HBEF) NH.

Our objectives are to: 1) identify decomposer fungi found in decaying fine roots and characterize their distribution among fine root categories; 2) examine temporal patterns of fungal taxa inhabiting dead roots; and 3) test effects of rhizosphere disruption on the decomposer community and relative patterns of decay. We are using culturing and molecular genetic approaches to identify decay fungi in fine roots, and are investigating in more detail the colonization and decay of fine roots by different fungi.

We have collected dead fine roots from forest floor and mineral soil horizons, and dead roots from the most abundant size class (0.2 - 0.4mm diameter) and a larger size class (0.6 - 0.8 mm) in sugar maple-dominated northern hardwood forest stands at the HBEF. Each dead root has been split into 3 subsamples: one for culturing, one for fungal DNA extraction, and one for extraction of tree DNA. Identification of tree species for each root will enable us to classify fungi by tree species and by mycorrhizal type (ecto/endo).

In the fall of 2000, clusters of root windows were installed in four sites in sugar maple- dominated northern hardwood forest stands. Root growth has been monitored on acetate sheets since that time.

  Root window in the field  

In July 2002 we initiated an experimental study of root decay by drilling through the windows and killing root networks that were approximately 1 year of age. These networks are being sampled for fungal identification over time, as roots decay. In a second component of the root window study we have experimentally disrupted the rhizosphere by removing 1-year old root networks from behind the root window and then replacing them against the window, in a layer of freshly mixed root-free soil. These roots also are being sampled over time, as decay progresses. The comparison between these approaches (disturbed and non-disturbed roots from root windows) will provide insights into the importance of the rhizosphere fungal community structure in the colonization of root substrates and subsequent decay.

  Root networks  

Basidiomycete fungi in a northern hardwood forest: vertical distribution and response to calcium
The soil environment for decomposer and mycorrhizal fungi changes radically through the surface organic and mineral horizons. We are characterizing the basidiomycete community in Oe, Oa, and mineral soil horizons in a series of plots located within the Mid-elevation litterfall collection site in the watershed west of W6. We are also testing the influence of Ca on the fungal community by comparing Ca-amended and control plots. Plots were established in pairs and one plot of each pair received Ca addition in the form of wollastonite in summer 2000. Soil samples were collected in summer 2002 and currently are being analyzed using molecular genetic approaches. This work is being carried out by Stephanie Juice, an undergraduate at Cornell University.

Basidiomycete fruitbody surveys
We are conducting routine fruitbody surveys in hardwood and spruce-fir zones at the HBEF. These surveys have two goals: 1) long-term monitoring of fruitbody diversity and abundance and 2) development of a reference library of fruitbody material for use in molecular genetic analyses of belowground material.

Fruitbody Species List...

Date Prepared: November 2002