Thursday, May 29, 2008 - 1:45 PM
571

Differences in nitrogen content between native and non-native riparian plants induce changes in ecosystem processes

Mary J. Harner, Division of Biological Sciences, The University of Montana, Missoula, MT 59812, Teresa M. Tibbets, Zoology and Physiology, University of Wyoming, 720 Sweetwater St, Lander, WY 82520, Jennifer Follstad Shah, Biology, Duke University, Box 90338, Durham, NC 27708, Chelsea L. Crenshaw, Department of Biology, Utah State University, Logan, UT 84322, and Robert L. Sinsabaugh, Department of Biology, University of New Mexico, Albuquerque, NM 87131.

Russian olive (<i>Elaeagnus angustifolia</i>), an actinorhizal species native to southern Europe and south-central Asia, is the 4th most abundant tree species along rivers of the western US. Russian olive leaf litter has higher C:N ratios (25:1 molar) than native cottonwoods (110:1 molar). We examined how inputs of N-rich litter from Russian olive affect riparian biogeochemistry along the Rio Grande in New Mexico. We measured production and decomposition of litter, as well as pools and fluxes of soil N, in forests spanning a 160 km reach of river. Russian olive litter contributed less than 4% of the leaf litter across sites, but accounted for approximately 21% of N inputs from leaf litter. On the forest floor, Russian olive litter decayed twice as rapidly as native cottonwood litter and mobilized N during the breakdown period. The quantity of Russian olive litter was correlated strongly with soil inorganic N concentrations, suggesting that Russian olive may increase soil N in this system. Changes in abundance of Russian olive have the potential to alter ecosystem processes, such as forest productivity and N export to rivers, and these effects likely extend to other catchments where the tree has colonized and continues to spread.


Web Page: riparian, vegetation, stoichiometry