HR: 1340h
AN: B33D-1585    [Abstracts]
TI: Can an Alder Disease Influence the Controls of Ecosystem Water Flux?
AU: * Rohrs-Richey, J K
EM: fsjkr1@uaf.edu
AF: Department of Biology and Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, United States
AU: Mulder, C P
EM: ffcpm2@uaf.edu
AF: Department of Biology and Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, United States
AU: Ruess, R W
EM: ffrwr@uaf.edu
AF: Department of Biology and Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, United States
AU: Winton, L M
EM: lori.winton@uaf.edu
AF: USDA Agricultural Research Service, Subarctic Agricultural Research Unit, University of Alaska, Fairbanks, AK 99775, United States
AU: Stanosz, G R
EM: grs@plantpath.wisc.edu
AF: Department of Plant Pathology, University of Wisconsin, Madison, WI 53706, United States
AB: In Alaska, nitrogen-fixing shrubs (Alnus spp.) comprise a large component of the vegetation and are important for water and energy flux in the Alaskan tundra, the Interior boreal forest, and south-central Alaska. Recently there has been high incidence and severity of a canker disease on Alnus which alters small scale controls (e.g., leaves, branches) of water and carbon flux and may have ecosystem scale effects in severely diseased areas. The fungal pathogen, Valsa melanodiscus (anamorph =Cytospora umbrina), kills active xylem and phloem, causes long, girdling cankers on stems, and is frequently associated with stem mortality in the thin leaf alder (Alnus tenuifolia) and green alder (Alnus crispa). We are just beginning to understand how this canker disease affects the physiology of its host and the implications for water loss and carbon fixation. An inoculation experiment at the University of Alaska is currently being conducted on well-watered and water-limited green alders to: 1) monitor the response of the water transport system to infection and canker development; 2) assess the ability of colonized alders to adjust water use efficiency; and 3) measure the effect of canker development on photosynthesis. Only 4 weeks after inoculation, stems (3-5 mm diam.) with incipient cankers had an overall reduction in total daily water loss and up to 50 percent decrease in daily peak water loss. Stems with incipient cankers were also unable to attain the maximum photosynthetic rate of healthy stems, and had lower light saturation points and quantum efficiencies. Further quantification of these relationships is underway. This study, in combination with recent field measurements of sapflow, will allow us to estimate the impact of varying degrees of disease severity on stand-level water flux. Alders are a keystone species and are currently responding to climate change by expanding into the Alaska tundra, increasing abundance in northern Alaska, and migrating into river drainages in the Interior. Thus, this canker disease poses the potential for wide ecophysiological consequences across the state of Alaska.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0476 Plant ecology (1851)
DE: 1813 Eco-hydrology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting