Silene occidentalis ssp. longistipitata
Deadhorse Mechanical Thinning Treatment Effects
Monitoring Report – Preliminary Results, 3 years after treatment
October 2, 2012
Colin Dillingham and Kirsten Bovee
I.
Introduction
The Nature Conservancy (W-1, 1996) currently lists Silene occidentalis ssp. longistipitata (long-stiped campion) as a G4T1 plant indicating that the taxon is imperiled worldwide. The G-rank reflects the condition of the entire species (secure), whereas the
T-rank reflects the global situation of just the subspecies. The Nature Conservancy (W-1,
1996) gives the taxon as S1.2 in California, indicating that it is critically imperiled and the occurrences are threatened. The California Native Plant Society (W-4) lists the species as 1B.2, which indicates that it is rare, threatened, or endangered in California and 20-80% of occurrences are threatened.
It is not clear which environmental factors limit the distribution or abundance of the longstiped campion (Dillingham and Sanger 2007), but it may be lack of disturbance regime.
There may be too little light reaching the forest floor outside of forest openings currently occupied by long-stiped campion.
Monitoring at Silene occidentalis ssp longistipitata locations indicate that there is large natural variability in the number of plants present each year. A review of annual monitoring plant census at populations on the Lassen National Forest indicate that occurrences can have annual population fluctuations of 50% and return to previous population levels without any vegetation treatment (i.e. South Fork Antelope Creek Site,
Dillingham and Sanger 2007). Therefore, we can expect that some populations will increase or decrease by 50% because of natural variation and not as a response to treatment. With statistical analysis, we may be able to determine that a population has changed by a smaller amount when comparing controls to treatment areas. However, small changes in the population are not considered significant in terms of management.
II.
Methods
We are primarily concerned with maintaining self-sustaining populations at each site.
Both positive and negative effects from proposed management activities are possible.
At the Deadhorse site, mechanical thinning operations were completed in the fall of 2009
(retain 100 trees per acre greater than 6 inches diameter at breast height). One hypothesis was that the new disturbance could provide a suitable seedbed for the species and the opening of the canopy could provide more light to the forest floor for population expansion. An alternate hypothesis was that the timber harvest and prescribed burning operations may also cause direct impacts to individual plants, displace or remove existing duff and eliminate seeds from the seed bank.
The mean post-treatment population (at least 3 years of data) shall be at least equal to the minimum total number of long-stiped campion plants found during pretreatment

conditions. A decrease of up to 50% of the pre-treatment population level, although not considered desirable, would be considered within the range of natural variability for any individual year. It is the longer term population means that we are trying to maintain.
The populations should be maintained at this level through 2015 (5 years after implementation of the thinning project).
Table 1. Monitoring Areas Included in this Monitoring Report
Site Name
Lassen NF
Occurrence Number Treatment Type
Deadhorse Falls
Monterey Point
“Smitty Camp”
13 Mechanical Thin
Control (for
Deadhorse) 8
A complete census of the adult plants within the macroplots was conducted in July of each year. Seedlings were not censused. Although data exists for subplots within the macroplots, no analysis at this small scale has been attempted. It appears that the thinning treatment was applied relatively evenly across the macroplot and no data stratification appeared necessary. All data presented is for adult plants within the entire macroplot. Although we present our data as a census, we recognize that some plants may be missed. We estimate that the percent of adult plants missed is very small, likely less than 5%.
To capture the effects of proposed treatments, photo points were established and the following measurements were recorded in the four corners of each subplot:

duff depth (cm)
 canopy cover (using densitometer or “moosehorn”)
 shrub height in meters
A.
Monitoring location
The Deadhorse and Smitty Camp long-stiped campion monitoring macroplots are located in Tehama County. Previous versions of the monitoring protocol indicated that the Scott’s John Creek occurrence in Butte County would be used as the control plot. Upon further investigation, it was determined that the habitat (red fir), elevation difference and lack of juxtaposition made the Scott’s John Creek less desirable as a control for comparison to the Deadhorse site. The Smitty Camp control at Monterey
Point was much more similar in habitat, adjacency, plot size, population size and elevation and is considered to be a superior control plot. Specific locations are available in the HFQLG rare plant monitoring database.
B.
Intended data analysis approach
The potential population changes will be compared against the pre-treatment and control population estimates. Under the assumption that the control population mean does not have a greater than 25% change from the mean during the same sampling period, the population responses would be considered to be caused by management activities, unless other evidence suggests otherwise. In the event that the control area

also changes, a more rigorous statistical evaluation would be coordinated between
Lassen NF botanists Kirsten Bovee and Allison Sanger, and SPI monitoring coordinator Cajun James and USDA Forest Service Herger-Feinstein Quincy Library
Group monitoring coordinator Colin Dillingham.
III.
Preliminary results
The thinning treatment reduced the canopy from a pretreatment mean of 66 percent canopy closure down to 48 percent post-treatment (Figure 1). There were minor posttreatment changes to duff depth, shrub cover, or shrub height. The population at the
Deadhorse site increased by 70% between 2009 and 2010 in the immediate year after the treatment was completed (Figure 1). In 2012 the plant count was 225% of the greatest pre-treatment value (Figure 1). The 2012 census results exceeded the range of natural variability (50%) as defined in the monitoring protocol. There was no association between annual rainfall and annual plant counts.
Though preliminary results indicate that the thinning treatment did not have a negative effect to the long-stiped campion population at the Deadhorse site, and may in fact have had a positive effect, data from the control site highlight indicates that natural interannual variability may exceed 50%, the value specified in the monitoring protocol. While the treatment population increased between 2009 and 2010 by 70%, the control population at
Smitty Camp increased by 110% during the same period. And between 2010 and 2012, the control population decreased by 55%, back to 2009 levels (Figure 2). It is therefore quite possible that additional environmental variables not quantified in this monitoring protocol contribute to the large increase in long-stiped campion in the treatment plot.

300
250
200
150
100
50
Plants
%   Canopy
Duff   Depth   mm
Rainfall   (inches)
0
2007 2008 2009 2010 2012
Fall 2009 thinning treatment (Deadhorse)
Figure 1. Preliminary Results of Deadhorse Site Plant and Environmental Data. The
Deadhorse site was treated in the fall of 2009, after the 2009 pretreatment data was collected.
300
250
200
150
100
50
Deadhorse   (Treatment)
Smitty   Camp   (Control)
0
2007 2008 2009 2010 2012
Fall 2009 thinning treatment (Deadhorse)
Figure 2. Preliminary Results of Deadhorse site plant data as compared to the control at Smitty Camp. No data was collected at the control plot in 2007 or 2008. The
Deadhorse site was treated in the fall of 2009, after the 2009 pretreatment data was collected.

Figure 3. Photo point at Deadhorse treatment site established to show effects of treatment at this site. The photo on the left taken during 2009 prior to treatment can be compared against the post-treatment photo on the right taken in 2010. The thinning of the forest canopy is evident as is the increased light reaching the forest floor.
IV.
Preliminary Management Implications
The long-stiped campion monitoring protocol (Dillingham et al. 2007) recommends that at least 3 years of post-treatment data be collected prior to making final management recommendations. Nevertheless, it is appropriate to recognize the current trend and make preliminary management implications now that data has been collected and analyzed from one-year and three-year-post-treatment monitoring visits. Management implications are drawn from the monitoring protocol (Dillingham and Sanger 2007).
One-year post-treatment monitoring at the Deadhorse site determined that the flowering population that year (104 plants) was between the lower count (61 plants in 2009) and upper count (118 plants in 2007) of pre-treatment population counts. Three-year posttreatment monitoring found a flowering population of 265 plants, a value that was more than double the highest pre-treatment population count. At the control site (Smitty
Camp), the 2012 flowering plant population was the lowest of any of the three years this population was monitored. The control population has fluctuated at levels that exceed the predicted range of natural interannual variation (50%), which suggests additional unidentified environmental factors that contribute to interannual variability in these populations. Additional monitoring parameters should be developed to explore other variables that contribute to these population fluctuations. Deer browse may be one such factor. At both the Deadhorse and Smitty Camp sites, between 30% and 40% of plants censused had their flowering stems browed by wildlife.
Based upon one-year and three-year post-treatment monitoring results, we will make the preliminary conclusion that the thinning treatment did not have a negative effect on the population at the Deadhorse site. In 2012, it was observed that the densest patches of long-stiped campion occurred on skid trails and ground disturbed by thinning operations.
This suggests that the direct effects of thinning operations did not have a negative effect on the population, and that the thinning operations may have had a beneficial indirect effect by creating new habitat where ground was disturbed. If additional post-treatment

monitoring at the Deadhorse site shows a continued trend of increased plant numbers relative to pre-treatment levels, forest thinning would be permitted in other long-stiped campion occurrence locations. A five-year post-treatment monitoring visit is planned for
2014.
V.
Literature Cited
Dillingham, Colin P. and Allison Sanger. 2007. Conservation Assessment and Strategy for Long-stiped Campion Silene occidentalis Watson ssp.
longistipitata . Report available from Lassen National Forest. 35 pp.
Dillingham, Colin P. 2007. Silene occidentalis ssp. longistipitata Monitoring Protocol
Version 1.2, revised Nov 2, 2010. Report available from Herger-Feinstein Quincy
Library Group Implementation Team, Plumas and Lassen National Forest. 6 pp.