Floodplain vegetation communities are mosaics of succession stages caused by erosion/redeposition as river channels migrate throughout their floodplains. Typically, plants colonizing alluvial deposits are severely N-limited, but N accumulates during succession, and this process determines long term fertility. The Kol River (Kamchatka, RU), received large annual N-subsidies from salmon and we sought to determine how salmon-N contributed to fertility during succession.
We constructed a vegetation chronosequence model and made N-fertility measurements within replicate succession stages before, during and after salmon runs. Natural abundance of 15N was used as a tracer of salmon-N.
We found that new alluvial deposits were N-poor, containing <200 kg-N ha-1 (to 10cm). However, soil-N increased more than 10X within 30 years and soils were N-rich henceforth. Net N-mineralization on young alluvial bars only provided a small fraction of the colonizing forest’s N requirement, whereas soils in older forests provided abundant N. Negative correlation between foliar C:N and soil N during the first 20 years of succession indicated that the youngest succession stages were N-limited.
The salmon run commenced in midsummer and caused river water N to increase 3X. Subsequent late season flooding deposited an average of 25 kg-N ha -1 as salmon carcasses onto young alluvial bars during 2006, but deposition rates were 10 to 30X higher on other years. The N-pulse created by decomposing salmon on young alluvial bars was brief because subsequent flooding flushed these coarse soils, but colonizing willows assimilated N rapidly during this time and high foliar δ15N (3 to 5‰) confirmed that salmon were a major N-source in early succession. Foliar δ 15N was abnormally high throughout the floodplain (1 to 5‰) indicating that older forests recycled salmon-N that accumulated during early succession.
All plant species that occurred during the first several centuries of succession had N-rich foliage (mean C:N 12 to 22). We conclude that salmon fertilized otherwise N-poor early succession annually, and built ecosystem N-pools during early succession, thereby allowing nitrophilic plant species to proliferate.
|Commitee:||DeLuca, Thomas, Eby, Lisa, Hauer, F. Richard, Lorang, Mark|
|School:||University of Montana|
|Department:||Organismal Biology & Ecology|
|School Location:||United States -- Montana|
|Source:||DAI-B 69/04, Dissertation Abstracts International|
|Keywords:||Floodplain, Nitrogen fertility, Pacific salmon, Primary succession, Riparian, Spawning, Vegetation|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
supplemental files is subject to the ProQuest Terms and Conditions of use.