1 / 15

Biotic Disturbance

Biotic Disturbance. White and Pickett (1985) Definition (from White and Jentsch 2001, Italics mine). “[D]isturbance is a relatively discrete event in time that disrupts the ecosystem, community or population structure and changes the resources, substrate availability or physical environment .”

allan
Download Presentation

Biotic Disturbance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Biotic Disturbance

  2. White and Pickett (1985) Definition(from White and Jentsch 2001, Italics mine) “[D]isturbance is a relatively discrete event in time that disrupts the ecosystem, community or population structure and changes the resources, substrate availability or physical environment.” “A disturbance, in this sense, changes the state of structural and physical variables in the ecosystem, although these changes also influence ecosystem functions and processes.”

  3. Azayus and Canuel 2004 • 2 sites on York R. • Similar sediment and OM delivery • POD • High energy • High physical disturbance • LY • Lower energy • Biotic mixing dominates

  4. Box Corer

  5. Kasten Corer

  6. Fig 2 Spikes in TOC = mixing events Greater C/N = less yummy OM (could be terrestrial or more degraded) Positive Eh at POD = more aerobic conditions

  7. Fig 3 Depleted 13C signature = different OM sources or local OM processing Mixing model suggests difference due to local processing

  8. Degradation of recalcitrant compounds significantly greater in POC (physical mixing) than LY (biotic mixing) Degradation of labile compounds similar between sites Difference my be due to increased contact between OM and O2and other electron acceptors in more mixed site OM Degradation Rates1954 - 1964

  9. Conclusions • POD has a more severe sediment disturbance regime based on physical mixing • POD has chemical evidence of more aerobic conditions and more degraded OM • POD and LY are similar in the breakdown rate of labile C • Physical mixing more important for the breakdown of recalcitrant OM

  10. Flecker and Taylor 2004 Biotic disturbance in the form of Bulldozer grazing. Study Site: Rio Las Marias Venezuela

  11. Predictions • Fish disturbance would create resource heterogeneity • Greatest heterogeneity would be at intermediate fish density • Benthic macroinvertebrate diversity would be greatest at highest resource heterogeneity

  12. Fish did influence resource heterogeneity

  13. Fish also affected expected richness but according to predictions

  14. Some Questions • Is the lack of a strong biotic effect due to biotic and physical having same mechanism? • What is the importance of spatial and temporal scale? (see Sun et al. 2002) • Is the big black box between disturbance and OM mineralization a problem? • Is diversity the “correct” response variable for resource heterogeneity? • Are aquatic systems unique with respect to biotic disturbance?

  15. Sun et al. 2002

More Related