Propagule sources, disturbance characteristics and the inital establishment of riparian vegetation after debris flows Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/sb397b86w

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Debris flows are a major cause of disturbance to riparian vegetation. Both observational and experimental studies were used to examine the initial recovery of riparian vegetation after debris flows on headwater streams in the western Cascades of Oregon. My goal was to determine the roles of seedlings and vegetative sprouts, propagule sources, and disturbance characteristics in early succession. I sampled three debris flows at the end of the first growing season after disturbance. Vegetative regrowth dominated early succession, providing 74% of the total cover. Early successional patterns reflected the type (scour and deposit) and intensity of disturbance. Vegetative regrowth (13.7% cover, 28 shoots/m²) and total cover (14.8%) were highest on low intensity scour. Seedling establishment was highest on fine and gravel deposits (2.1%-3.0% cover, 38-46 seedlings/m²). The observational results also showed that revegetation of debris flows by sources other than dispersed seed is important. These additional sources are the residual propagule bank and the disturbance-transported propagule bank. I hypothesized that the differences in total cover, seedling establishment, and vegetative regrowth resulted from differences in how scour and deposition affected propagule availability. I used this hypothesis to develop predictions of the effects of increasing intensity of scour and deposition on these three vegetation attributes and constructed experimental debris flow treatments to test the predictions. Six treatments provided three depths of deposition (5, 10 and 19 cm), two depths of scour (2.5 and 5 cm) and a control (no substrate modification). As in the observational study, the experimental results were recorded at the end of the first growing season after disturbance. The potential contributions of all three propagule sources to revegetation were also assessed. Total cover and vegetative regrowth decreased with increasing intensity of both types of disturbance, but seedling establishment did not differ with disturbance type or intensity. The predictions for total cover, vegetative regrowth, and seedling establishment on deposits were consistent with the experimental results, but the predictions for seedling establishment on scour were not. Most individuals establishing on the experimental site in the first growing season came from seeds and vegetative propagules in the transported and residual propagule banks (4731 and 8538 propagules/m² respectively). Dispersed seed contributed 31 seeds/m². Fifteen species, comprising 59.2% of the overall cover, showed significant responses to the experimental treatments. These species responded individualistically to the disturbances and their responses could not be explained solely on the basis of propagule availability. The high cover of six species (for example Madia gracilis and Epilobium paniculatum) on deposits clearly resulted from differences in propagule availability between the residual and transported propagule banks. But the responses of most other species (for example Oxalis oreaana and trilliifolia. Petasites frigidus and Galium triflorum) were determined by propagule availability, propagule removal by scour, physiological tolerances to disturbance and morphological characteristics. This thesis demonstrates that both seedlings and vegetative sprouts are important in early debris flow succession, that debris flow revegetation can occur from three propagule sources and that one mechanism through which early successional patterns develop is through differences in how scour and deposition affect propagule availability. This thesis also demonstrates that understanding early succession requires a consideration not only of disturbance characteristics and propagule availability, but of individualistic species responses to disturbance.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 24-bit Color) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Submitted by Katy Davis (kdscannerosu@gmail.com) on 2013-05-24T20:18:38Z No. of bitstreams: 1 GecyJeanneL1989.pdf: 1225926 bytes, checksum: ee94c1071cfe06742cdba7415e769cb5 (MD5)
  • description.provenance : Made available in DSpace on 2013-07-16T18:38:23Z (GMT). No. of bitstreams: 1 GecyJeanneL1989.pdf: 1225926 bytes, checksum: ee94c1071cfe06742cdba7415e769cb5 (MD5) Previous issue date: 1988-07-14
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-05-29T19:09:04Z (GMT) No. of bitstreams: 1 GecyJeanneL1989.pdf: 1225926 bytes, checksum: ee94c1071cfe06742cdba7415e769cb5 (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-07-16T18:38:23Z (GMT) No. of bitstreams: 1 GecyJeanneL1989.pdf: 1225926 bytes, checksum: ee94c1071cfe06742cdba7415e769cb5 (MD5)

Relationships

In Administrative Set:
Last modified: 08/10/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items