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Corvallis Research Lab
ODFW's Oregon Plan Monitoring Program
 Trends in Habitat Quality 1998-2000

A comparison between survey seasons was completed using cumulative frequency distribution graphs and summary statistics.  We were looking for changes in habitat condition that occurred as a result of landscape level change rather than sampling bias or within season variability.  The comparison of habitat between years was meant to open the discussion of habitat trend detection and assessment.

Habitat Condition and Quality 98-00  

The Oregon Plan’s robust sampling design provides flexibility in statistical analysis.  To determine overall habitat condition and quality for the entire 1998-2000 time period we combined the sites from all years into one dataset.  Summary statistics and quartile calculations showed results that were generally similar to the annual summaries (See 2000 annual report Tables 3-6).   To compare between years we also displayed the data lumped by year in box plots (See 2000 annual report Figure 7). 

A comparison of the 50th percentile mark showed one variable in the overall dataset that did not follow the 2000 results.  Compared to the annual summaries, the percent of fines in riffle units on the North Coast appeared to be lower in the 2000 field season while fines on the South Coast were higher in 2000. 

            Sites in the 1998-2000 dataset were also assessed based on habitat quality and spatial distribution.  The sites were compared to six benchmark criteria developed by the census survey program with the total number of benchmarks exceeded tallied for each site.  We divided the sites based on their location within and outside the distribution of coho. 

Benchmark calculations indicate habitat quality was higher outside the range of coho in the North Coast, Mid South and Umpqua Monitoring Areas.  Both the Mid South and South Coast Monitoring Areas showed little difference in habitat quality based on coho distribution (Table 1).

Table1: Benchmark summary table showing the percent of sites that exceeded at least 3 benchmark criteria.

  Inside the range of coho (%) Outside the range of coho (%)

 Click on icon to link to Adobe .pdf file containing Figure 1. 

 Click on icon to link to Adobe .pdf file containing Figure 2. 

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