Rocky Mountain Research Station Publications
RMRS Online Publication - Journal
Articles, External Publications, and Special Reports
Contribution of actinorhizal shrubs to
site fertility in a northern California mixed pine forest
Busse, Matt D.; Jurgensen, Martin F.; Page-Dumroese, Deborah S.; Powers, Robert F. 2007. Contribution of actinorhizal shrubs to site fertility in a northern California mixed pine forest. Forest Ecology and Management. 244: 68-75.
Bitterbrush (Purshia tridentata) and mahala mat (Ceanothus prostratus) are common N-fixing shrubs in interior forests of the western United States, yet their contribution to ecosystem N pools is poorly characterized. We compared N fixation and soil N accretion by these shrubs in old-growth ponderosa pine (Pinus ponderosa) -- Jeffrey pine (Pinus jeffreyi) stands versus stands that had been harvested 50 years earlier. No differences (Alpha = 0.10) in cover, biomass, or percent N derived from fixation by bitterbrush or mahala mat were found between harvested and uncut stands. Approximately 46% of bitterbrush N was derived from symbiotic N fixation as measured by the 15N natural abundance method. No accurate measure of percent N derived from fixation was attained for mahala mat using this technique due to the absence of a well-matched reference plant. Estimates of total N fixation rates in both stand types were 0.2 kg ha-1 year-1 for bitterbrush and 0.3 kg ha-1 year-1 or less for mahala mat. No appreciable soil N accretion resulted due to the presence of bitterbrush or mahala mat in either stand type. Nitrogen addition by these shrubs, although small, accounts for 1060% of annual N input in these dry forest ecosystems.
Keywords: symbiotic nitrogen fixation, bitterbrush, mahala mat, Purshia tridentata, Ceanothus prostratus, natural 15N abundance, old-growth, timber harvesting
About PDFs: For best results, do not open the PDF in your Web browser. Right-click on the PDF link to download the PDF file directly to your computer. Click here for more PDF help.
Download Article
http://www.fs.fed.us/rm/pubs_other/rmrs_2007_busse_m001.pdf
PDF File Size: 265 K
Title: RMRS Other
Publications: Contribution of actinorhizal shrubs to site fertility
in a northern California mixed pine forest
Electronic Publish Date: July 6, 2007
Last Update: July
6, 2007