Monitoring forest vegetation in the North Coast and Cascades Network: 2010 annual report

Acker, Steven; Boetsch, John; Bivin, Mognonne; Whiteaker, Lou; Cole, Carla

Late-successional, coniferous forest is critical for ecosystem function and biological conservation in the Pacific Northwest. Such forests are well-represented in the North Coast and Cascades Network (NCCN) of the National Park Service. As part of monitoring of natural resources within the NCCN, we track trends in tree recruitment, growth, and mortality in forests which represent the range of environments in NCCN parks. At project initiation in 2008, we established 35, 1-hectare plots in three parks (Mount Rainier, North Cascades, Olympic), at elevations from near sea-level to almost 1800 m. We selected monitoring locations using the Generalized Randomized-Tesselation Stratified algorithm. We used GIS to conduct initial screening in the office, evaluating suitability factors including safety of access routes and proximity to trails and roads. Points passing the office screening were evaluated in the field for safety of access, forest species composition and age, and other factors. In 2010, we performed site selection for Lewis and Clark National Historical Park. We evaluated 100 points in the office, 42 of which passed. Most rejections were due to non-target vegetation or insufficient distance from roads or trails. We evaluated all 42 points in the field, 11 of which were suitable. Most rejections were due to non-target vegetation. We also conducted a limited number of field evaluations at Mount Rainier, North Cascades, and Olympic National Parks to address gaps from previous work. As a consequence we established one additional plot at Mount Rainier in 2010 and plan to establish one more at Mount Rainier and two at North Cascades in 2011. The newly-established plot was similar in species composition to other plots at Mount Rainier in the same elevation stratum (600-900 m). However, there were fewer total stems and fewer stems of Pseudotsuga menziesii and Abies amabilis than was typical of the other plots. Tsuga heterophylla accounted for a much higher proportion of basal area and Pseudotsuga menziesii a much lower proportion than was typical of the other plots. The newly-established plot was similar to the other plots with respect to numbers and extent of decay of snags. Our second interval for measuring tree mortality was 2009 to 2010. Roughly one-third of the plots had no tree mortality; the overall average rate of tree mortality was 1.1%. The most common condition of trees reported dead in 2010 was standing with no obvious cause of death (50% of cases); the second most common condition was standing and killed by insects (over 20% of cases). The overall average rate of tree mortality was slightly higher than the range expected for older forests in the Pacific Northwest in the absence of severe wind damage. The data collected in 2010 provided the first opportunity to assess change in the annual rate of tree mortality. Mortality rate changed between the 2008-2009 interval and the 2009-2010 interval in over three-quarters of the plots, with slightly more increases than decreases. In all but two plots, the change in mortality rate was between -2.5% and +2.5%. The two exceptions had larger increases in the rate of mortality. One plot had 13 newly-dead trees, including 10 Pseudotsuga menziesii which were killed by bark beetles. In the other plot, only mortality was recorded, but it was of a tree in the sapling size-class. The high mortality rate on this plot in 2011 was a consequence of the small total number of trees on the plot and the relatively small fraction of each plot in which saplings are monitored.

Monitoring forest vegetation in the North Coast and Cascades Network: 2010 annual report

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