on the Clear Lake Ridge Preserve

MAPPING AND MONITORING SULFUR CINQUEFOIL (POTENTILLA RECTA) ON THE CLEAR LAKE RIDGE PRESERVE, 2009-2011 Heidi J Schmalz and Robert V Taylor

ABSTRACT Systematic monitoring of the invasive weed sulfur cinquefoil (Potentilla recta) was carried out in 2011 on the Clear Lake Ridge Preserve to provide a measure of plant abundance. Frequency and density data were collected at 116 survey sites across a total surveyed area of 308 ha. A 100 x 100 m grid was used to determine the area occupied by the weed, which was 71 ha. Multi-year analysis of data for the years 2009-2011 revealed a total infestation area of 159 ha, of which 27 were added in 2011. Of the total infestation area, 93 ha were surveyed in every year. Across this 93 ha area, sulfur cinquefoil had an average frequency of 10% ± 6% (90% CI). Density measures were uninformative because of small sample sizes. Further surveying is required for more precise measures of frequency and density and for evaluation of population trends over time.

INTRODUCTION In 2011 we continued to map and monitor sulfur cinquefoil (Potentilla recta) on the Clear Lake Ridge (CLR) Preserve. Monitoring and mapping on CLR began in 2009 to provide accurate information on the extent and abundance of sulfur cinquefoil. 2011 marked the third year in which field observers monitored all known infestations of sulfur cinquefoil on the upland prairie of CLR. This report summarizes monitoring data collected from 2009-2011.

METHODS SURVEY AREA The 1,410 ha Clear Lake Ridge Preserve is located in Wallowa County in northeast Oregon. The preserve consists of rolling, plateau uplands, shallow-soiled ridge tops, and canyons. Elevations range from 853 m where the bottom of Devil’s Gulch meets Little Sheep Creek, to 1597 m south of Downy Lake. The preserve consists of five discontinuous parcels and contains a portion of two shallow, ephemeral, closed lakes – Downy Lake and Clear Lake. The majority of the upland areas

CLR sulfur cinquefoil monitoring report

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have shallow to moderately-deep soils and are dominated by bunchgrass species, predominantly Idaho fescue (Festuca idahoensis) and bluebunch wheatgrass (Pseudoroegneria spicata). Canyons have a variety of shrubland vegetation mixed with grassland vegetation. Along streams (i.e. in Devil’s Gulch) cottonwoods (Populus trichocarpa) and other riparian vegetation dominate. Some north-facing slopes support coniferous forests.

STUDY DESIGN The 2011 surveys followed an established protocol for mapping and monitoring noxious weed on the Zumwalt Prairie Preserve (Taylor and Jansen 2008). In each survey year, the initial survey area (A_s)1 was determined via Geographic Information System (GIS) using all occurrence data from previous years. This area, the most liberal estimate of the area occupied by Spalding's catchfly, was intersected with a permanent grid of 100 x 100 m (1 ha) cells. Next, we created a set of survey sites (S_s) within A_s, at a density of one survey site per grid cell. A random number generator was used to create a random offset from the grid centroid which was applied systematically to all grid cells within A_s. Finally, additional inventory points were generated in the grid cells surrounding the known area of occurrence. Abundance data were not collected at inventory points; rather, locations of any plants found were recorded as waypoints. Since some survey locations were remote and required cross-country travel on foot, additional survey area was generated by including the area traversed by observers. During monitoring, each field observer created a survey tracklog using a handheld global positioning system (Garmin GPS 76sx). Then GIS was used to intersect the survey tracklogs with the 100 x 100 m grid. The output 1 ha cells were merged with the initial survey area to create the total A_s for a given year.

DATA COLLECTION Survey sites were visited on August 15th and 16th 2011, at a time when the foliage of sulfur cinquefoil is bright green and when many plants are in flower and easily detected. Prior to sampling, field observers were trained using calibration plots to ensure that their plant counts were within an acceptable range (±10%) from the mean count across all observers. Observers navigated to survey sites using a GPS and established a temporary 5 m-radius (78.54 m2) circular plot. Within the plot the presence/absence of sulfur cinquefoil was noted and all plants counted. Plants encountered outside of survey sites were recorded as incidental waypoints with the GPS.

DATA ANALYSIS Data were analyzed using ArcMap. The area of occurrence (A_o) for a single year was determined by intersecting all survey sites where sulfur cinquefoil was found, combined with all incidental findings, with the 100 x 100 m grid. Using incidentals to define part of the A_o meant that some grid cells within A_o did not contain survey sites. Frequency (FREQ_o) was calculated by dividing the number of sites where Spalding's catchfly was found within the 5 m radius plot (S_p) by the total number of survey sites within the area of occurrence (S_o). Density was calculated as the plants per m2 averaged across all S_o.

1

See Appendix for explanations of all abbreviations


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To compare abundance across years, a subset of data from the years 2009-2011 was utilized. Since survey areas were slightly different each year, only the area that was surveyed in all years was used to select data for these analyses. In addition, the data were restricted to those grid cells in which the plant was found in at least one year. This final selection of grid cells was called the multi-year survey-occurrence area (A_sox). Mean frequency and density were calculated and 90% confidence intervals generated by year for the set of data that was derived from A_sox (a modified Wilson Score formula was used for frequency confidence intervals). Confidence intervals are the range of plausible values for the mean estimated in each year (i.e. we can be 90% confident that the CI for a given mean contains the actual population mean). These are provided for visual comparison of means across years and for interpreting precision (narrower confidence intervals imply more precise mean estimates). Means from two years are likely to be different if their confidence intervals do not overlap or overlap only slightly. However, such interpretation is for general guidance only, and is not a replacement for statistical tests of differences between years.

RESULTS SINGLE-YEAR-2011 The area surveyed (A_s) in 2011 was the largest of the three years, at 308 ha and 116 survey sites (Table 1). Sulfur cinquefoil was found within 71 ha (A_o). Forty survey sites were within A_o, but sulfur cinquefoil was present within only 11 of the 5 m radius survey sites, resulting in a frequency of 28% ± 11% (90% CI).

MULTI-YEAR The combined area of occurrence over three years (A_ox) was 159 ha, while the area that was surveyed in every year (A_sx) was 140 ha. The resulting multi-year survey occurrence area (A_sox) was 93 ha (Table 2; Figure 1). Previous years’ analysis showed that the A_ox for 2009 and 2010 was 132 ha. Therefore, the 2011 survey effort added 27 ha to the previously-known area of occurrence. Average frequency across A_sox was 10%, with no significant differences between years (Table 2; Figure 2A). Average density was 0.013 ± 0.014 (90% CI) plants per m2. Density estimates with so few data points (N = 51 in 2009 and N = 56 in 2010) result in large confidence intervals—in 2009 and 2010, the confidence intervals crossed zero, indicating that our data were too variable to provide a measure of density. In 2011, N = 83, and the confidence interval was barely above zero (Figure 2B). The population estimate based on 2011 density is 31 – 24,373 (90% CI) individual plants within A_sox. Part of the difficulty in making density estimates based on our data is that there are a lot of zero values in the dataset. Our sample size is also quite small. There was no chemical treatment of sulfur cinquefoil in 2010. For information on treatment in 2009, please see the 2010 monitoring report (Jansen and Taylor 2010).

SUMMARY AND CONCLUSIONS


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Mapping sulfur cinquefoil on CLR in 2011 showed that the known area of occurrence is still increasing, with 27 ha added to the previously known infestation area of 132 ha. Since monitoring began in 2009, and sample sizes have been small, our data are not yet informative for trends in frequency or density. Sample size for estimating abundance has increased over the three years, and if this continues, trend analysis will become feasible. Another alternative for increasing sample size is to place more than one survey site in each 1 ha grid cell. This approach would be feasible for CLR because of its small size. Sulfur cinquefoil has been treated chemically only once in the span of years relevant to this report (in 2009). Treatment did occur in 2011, in the fall after monitoring, and the effects would be most easily assessed by monitoring again in 2012.

REFERENCES Jansen, V. S., and R. V. Taylor. 2010. Mapping and Monitoring Sulfur Cinquefoil (Potentilla recta) on the Clear Lake Ridge Preserve, 2009-2010. The Nature Conservancy, Northeast Oregon Field Office, Enterprise, OR. Available online at: http://conserveonline.org/workspaces/ZumwaltPrairieWorkspace/documents/mapping-andmonitoring-sulfur-cinquefoil/@@view.html Taylor, R. V., V. Jansen. 2008. Mapping and Monitoring the Abundance of Noxious Weeds on the Prairie Uplands of the Zumwalt Prairie Preserve with Analysis of Short-term Trends. The Nature Conservancy, Northeast Oregon Field Office, Enterprise, OR.


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TABLES Table 1: Single-year statistics for sulfur cinquefoil monitoring on Clear Lake Ridge. Abbreviations are A_s—area surveyed; A_o—area occupied; S_s—sites surveyed; S_o—survey sites in the area occupied; S_p—survey sites where the plant was found; FREQ_o—frequency within the area occupied. Area surveyed and area occupied are based on analysis using a 100 x 100 m grid. Ranges of values (indicated by the ‘±’ symbol) are 90% confidence intervals. Year

A_s (ha)

A_o (ha)

S_s

S_o

S_p

FREQ _o (%)

Density (Plants per m2)

Pop. Estimate2 (90% CI)

2009

288

71

92

36

7

19 ±11

0.029 ±0.036

0,000 - 102,714

2010

261

95

61

33

6

18 ±11

0.021 ±0.024

0,000 - 71,550

2011

308

71

116

40

11

28 ±11

0.024 ±0.018

8,646 - 67,309

Table 2: Multi-year statistics for monitoring of sulfur cinquefoil. Years included for analysis were 2008-2011. Abbreviations are A_sx—area surveyed in all years (intersect); A_ox—all areas occupied in any year (union); A_sox—multi-year survey-occurrence area (intersection of A_ox and A_sx); S_sox—sites surveyed within A_sox; S_pox—survey sites where the plant was found;

Year

A_sx (ha)

A_ox (ha)

A_sox (ha)

2009 2010

140

159

93

S_sox

S_pox

FREQ _sox (%)

Density (Plants per m2)

Pop. Estimate3 (90% CI)

51

6

12 ±8

0.018

-5,835 - 62,093

56

6

11 ±7

0.013

-2,147 - 41,933

2011 83 7 8 ±8 0.008 0,031 - 24,373 FREQ_sox—frequency within A_sox. All areas are based on analysis using a 100 x 100 m grid.

2 3

Population estimates for single-year measures utilize the A_o for each individual year. Population estimates for multi-year measures utilize the A_sox.


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FIGURES Figure 1: Multi-year survey-occurrence area (A_sox; green area) and survey routes for sulfur cinquefoil on the Clear Lake Ridge Preserve, 2009-2011. A_sox is defined as the area where sulfur cinquefoil was found in any year but was surveyed in all years. Area is based on a 100 x 100 m grid.


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Figure 2: A) Frequency and B) density of sulfur cinquefoil on the Clear Lake Ridge preserve for the years 2009-2011. Error bars are 90% confidence intervals.


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APPENDIX: ABBREVIATIONS Survey area and points Notation Short_Desc A_s Survey area

Unit ha

Description This is the area surveyed within the target plant species (e.g. weed) occurrence area. The area to be surveyed is determined by prior knowledge of the distribution of the plant and the level f survey effort to be expended. A_S is a subset of the entire grid (e.g., ZPPCampCk25m, ZPPPineCk100m, etc.). Collection of systematic survey sites within A_s.

S_s Basic results Notation S_p

Survey sites

points

Short_Desc Sites present

Unit points

Description Sites were target plant species (e.g., weed) is present in the plot (e.g., 5m radius area).

Inc

Incidental observations

points

Collection of incidental observations of the target plant within A_s (used in for defining A_o)

A_o

Occurrence area

ha

This is the area occupied by the plant species. Defined as: SPATIAL JOIN(Grid_Nm, MERGE(S_p, Inc)

Survey sites in occurrence area Statistics - Single year Notation Short_Desc FREQ_s(Yn) Frequency

points

Collection of survey points within A_o

Unit n/a

Description This is the frequency of the target plant species across A_s (inside and outside occurrence area. Defined as: FREQ(S_p, A_s) = S_p / S_s

FREQ_o(Yn)

Frequency

n/a

This is the frequency of the target plant species within A_o. Calculated using the presence/absence data from S_o. Defined as S_p / S_o

SUM_o(Yn) DEN_o(Yn)

Density Density

plants plants / m sq

N_o

Population size

plants

This is the total number of plants counted within the 5m square plots. This is the density of the target plant species within A_o. Calculated using plot counts at survey sites within A_o. First, each plot count is converted to density per square meter (i.e., DEN_SQM). Defined as mean of DEN_SQM across all S_o. DEN_SQM = n_plants_in_5m_radius_plot / 78.54 This is the estimated population size of the target plant species within A_o and is calculated by converting density to a per ha measure and multiplying by the area occupied. Defined as: (DEN_o x 10,000) x A_o

S_o


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Statistics - Multi-year (Y1, Y2) Notation A_sx

Short_Desc Survey area - multiyear

Unit ha

Description This is the combined survey area using data from multiple years (Y1, Y2, …). Defined as: INTERSECT (A_s(Y1), A_s(Y2), ... )

A_ox

Occurrence area multi-year

ha

A_sox

Multi-year SurveyOccurrence Area

ha

S_sox(Y)

Survey sites - multiyear

points

S_pox(Y)

Sites present - multiyear

points

FREQ_sox(Yn)

Frequency

n/a

This is the combined occurrence area for the target species using data from multiple years. A_ox includes all grid cells where the target species was found in at least one of the years under examination. Defined as: UNION (A_o(Y1), A_o(Y2), ...) Area within A_ox that was surveyed in all of the years. A_sox is the area that is used for multi-year comparisons of abundance. Defined as: INTERSECT (A_ox, A_sx). Survey sites for each year are selected separately for analysis. For a given year (Y), S_sox(Y) is defined as all S_s for that year that are within the area of A_sox Subset of S_sox for a given year (Y) where the target species is present within the 5m radius plot. That is, it is all the points in S_p(Y) that fall within A_sox. This is the frequency of the target plant species for a given year (Y) across A_sox. Defined as: S_pox(Y) / S_sox(Y)

DEN_sox(Yn)

Density

plants / m sq


This is the density of the target plant species for a given year (Y) across A_sox. Calculated by averaging the density of the target species as measured at all sites within S_sox(Y).

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