Abstract Detail

Ecological Section

Goslin, Matthew [1].

Modeling the environmental drivers of distribution for a river ecosystem engineer, Carex nudata.

Carex nudata (torrent sedge) occurs in rivers throughout Oregon and northern California and appears to function as an ecosystem engineer capable of altering river morphology where prominent. Established plants are found along the edges of the low flow summer channel and also form emergent islands. C. nudata appears to enhance channel complexity, a key goal of river restoration, and previous studies (Levine 1999) have also found that C. nudata may indirectly facilitate the presence of other species, enhancing species diversity. While the species appears to play a key role in some river ecosystems, relatively little is known about the species’ distribution and the environmental drivers of that distribution. Using archival data from herbariums, GIS spatial analyses and a species distribution model (Maxent) designed for presence-only data, I have constructed a range-wide species distribution model. I have used this initial predictive model to develop a systematic sampling scheme for C. nudata in two river basins, the John Day and Santiam. Systematic sampling will facilitate a more robust model of the environmental drivers of C. nudata distribution.  In addition to the climate variables traditionally used to predict species distribution, the Maxent model incorporated hydrological and fluvial geomorphological variables such as discharge, velocity, slope and stream power derived from the National Hydrographic Dataset Plus (NDHPlus).  The model found that the explanatory power of hydrological variables dwarfed those of climate.  Stream power appears to set upper and lower limits on the distribution of the sedge.  At high stream power, the sedge is likely unable to remain established in the river (too much force), while at low stream power, finer sediment sizes may limit C. nudata establishment. Initial sampling suggests that C. nudata is more abundant in gravel bed and bedrock rivers than in rivers with finer sediment sizes.  However, seed planting experiments in the Middle Fork John Day River did not find significant differences in establishment and survival rates among substrate (sediment) types.  Seed planting experiments did find significant differences in survival among different elevations above the low flow water surface. Both seed planting experiments and initial basin-wide sampling also suggest C. nudata is tolerant of moderate shade but not extreme shade.  The Maxent distribution model is the first step in generating hypotheses and designing field surveys which will contribute to a more robust predictive model that incorporates absence and abundance data rather than just presence.

1 - University of Oregon, Geography, 1251 University of Oregon, Eugene, OR, 97403, USA

Keywords:
Carex
species distribution model
Maxent
riparian
river.

Presentation Type: Oral Paper:Papers for Sections
Session: 47
Location: Clearwater/Grove
Date: Tuesday, July 29th, 2014
Time: 2:00 PM
Number: 47001
Abstract ID:893
Candidate for Awards:Ecological Section Best Graduate Student Paper