CLIMATE OF THE ZUMWALT PRAIRIE OF NORTHEASTERN OREGON FROM 19 TO PRESENT 24 MAY Prepared by J. D. Hansen 1, R.V. Taylor 2, and H. Schmalz 1 Ecologist, Turtle Mt. Environmental Consulting, 652 US Hwy 97, Toppenish, WA 98948 USA (jimbobtoo@aol.com). 2 Northeast Oregon Regional Ecologist, The Nature Conservancy, 96 S River St, Enterprise, OR 97828 USA (rtaylor@tnc.org). INTRODUCTION The Zumwalt Prairie Preserve (ZPP) was established by The Nature Conservancy of Oregon in to protect a unique grassland-ecosystem in northeastern Oregon. Earlier, we (Hansen et al., 9) reported on its recent climate, including observations on temperature and precipitation using data from the Zumwalt Weather Station (ZumWxStn) which was established at its location on the ZPP in 5. In this report, we have re-analyzed data from the ZumWxStn using data from and 11. A more complete understanding of the climate of the Zumwalt Prairie relies on decades of observation, something that the ZumWxStn cannot yet provide. Thus, in this report we have gathered data from other nearby weather stations some of which have been operating since 19. Although the sites are not geographical identical, they do give a long-term perspective of the climate in that region. Concordance between these stations and the ZumWxStn allow us to confidently assess, retrospectively, periods in the past century when temperature and/or precipitation was substantially higher or lower than normal. This, in turn, provides us with essential information needed for understanding the past and managing for the future.
MATERIALS AND METHODS Weather Collection: Sites and Details Weather data at Zumwalt were from a station (ZumWxStn) located at 45.577745 N and 116.971754 W, 29 km (18 mi) NE Enterprise, Oregon (Fig. 1), and is at an elevation of 1336.59 m (4385.14 ft). Meteorological collection methods are described in our previous report (Hansen et al., 9). Here, yearly data are from 6 to 11 as well as daily summaries per month during that period. Monthly precipitations were obtained for those years, too. To provide both a temporal and geographical perspective, weather data were obtained from NOAA for three nearby sites (Fig. 2): the city of Wallowa (elev.: 2,948 ft); the USDA-Forest Service Station in Enterprise (FS) (elev.: 3,811 ft); and a cattle ranch miles north-northeast of Enterprise (NNE) (elev.: 3,267). Unlike the flatter topography of the other sites, NNE is in the foothills of the Blue Mts Mean yearly temperatures are given for: FS from 1932 to 1978 continuously; NNE from 197 to 3 continuously; and Wallowa from 19 to (with missing data for years 1941, 1945, 1946, 195 to 1955, 1967, 1996 to 1998, 3, and 6). Mean monthly minimum and maximum temperatures per year are the same as the above yearly temperatures for: FS except 1942, 1973, 1974, and 1977; NNE except with maximum mean also missing for 1973; Wallowa including all the missing years. Monthly precipitation was measured for: FS from 1933 to 1981 consecutively; NNE from 1971 to 4 consecutively; and Wallowa from 1931 to 1949, 1954 to 1996, and 1999 to. All temperature data were in F and all precipitation measures were in inches. Data Management Summary statistics were determined for: overall, minimum, and maximum temperatures; overall, minimum, and maximum daily temperatures per month; monthly and yearly precipitations during a water year ; and monthly and yearly temperatures and precipitations. Means, standard deviations (SD), and linear correlations and regressions, including Coefficients of Determination ( r 2 ), were calculated using statistical programs on Microsoft Office Excel (Microsoft Corporation, Redmond, WA). The number of replicates was designated by n. Growing Degree Days (GDD) was calculated first by using the equation, GDD = ((T max + T min )/2) 5 F, where the average maximum temperatures (T max ) is 86 F or less and the average minimum temperature (T min ) is 5 F or greater. Frost-free Days (FFD) were determined by the number of days per month where the minimum temperatures were above 32 F. Precipitation data were arranged by water year starting with measurements in October and ending with September. Water years are ecologically preferable over calendars because they indicate when moisture will be available for plants at the start of the growing season. Year was designated by the one with the most months (e.g., Oct. 1972 to Sept. 1973 was water year 1973 ). RESULTS AND DISCUSSION 2
Temperature The mean yearly temperatures were consistent during the observation period, with no increasing or decreasing trends (Fig. 3.) When yearly temperatures were combined for each site, the mean and standard deviations were: FS, 43.6 ± 1.2 F (n = 47); NNE, 45.3 ± 1.4 F (n = 34); ZumWxStn, 42.1 ±.8 F (n = 6); and Wallowa, 45.8 ± 1.4 F (n = 66). Overall, NNE and Wallowa were the warmest locations, even though they are in topographically different landscapes. Temperatures for FS and ZumWxStn were similar, but 28 years separated site measurements. Linear correlations and regressions of mean yearly temperatures were calculated for all paired sites, except between ZumWxStn and FS or NNE. The best fit among all comparisons was between ZumWxStn and Wallowa with a r 2 =.926 (y =.94x + 7.9), but this could be a function of the small number of pairings. Still, the slope was close to 1., which indicates that the sites were similar in temperature patterns. The intercept suggests that Wallowa is 8 F warmer than ZumWxStn. The next best fit was between Wallowa and NNE: y =.94x + 3.3, r 2 =.842. Again, the slope is near 1., denoting similarities of weather over time (ca. three decades) between the sites. The correlation between Wallowa and FS was the poorest, r 2 =.6, which was surprising considering both are close and in the Wallowa River Valley. The mean yearly minimum and maximum temperatures (Fig. 4) were similar among the sites except that ZumWxStn had the lowest maximum temperatures. The means ± SD of the minimum temperatures were: FS, 28.8 ± 1.3 F; NNE, 29.9 ± 1.2 F; ZumWxStn, 29.5 ±.8 F; Waallowa, 31.6 ± 1.6 F; and the maximum temperatures were: FS, 58.2 ± 1.9 F NNE, 6.5 ± 1.9 F; ZumWxStn, 53.4 ± 1.1 F; and Wallowa, 6.1 ± 1.8 F. A warm period was observed in the early 19s, but this did not continue for any of the sites. No linear correlations ere done between paired sites. Mean daily temperatures for ZumWxStn (Fig. 5 to 7) show similar monthly patterns, with July being the hottest month and December the coldest. The mean daily temperature per month per year ranged from 41.2 to 43. F; the mean minimum daily temperature per month per year was from 28.7 to.4 F; and the mean maximum daily temperature per month per year was from 52.2 to 54.9 F. The hottest year was 7. At ZumWxStn, the year with the most cumulative growing degree days per month was 7 (Fig. 8). Typically, such a pattern would have resulted in earlier emergence of insects with higher seasonal populations than with other years. For example, Osmia tersula Cockerell (Hymenoptera: Megachilidae), a solitary bee, requires > 25 GGD (base 5 F) for total population emergence in the Rocky Mountain meadows of central Colorado. At Zumwalt, total abundance of pollinating bee morphospecies was three times as much in 7 than in 8 (Kimoto, ). 3
The total number of frost free days per month at ZumWxStn were generally consistent over the years, with January having some unusually warm days (Fig. 9). May frosts were common and freezing weather returned in September. Precipitation The wettest site averaged over the water years was NNE (Fig. ), which also had the greatest precipitation for a single year (28.8 inches in WY 1997). Although precipitation varied by water year, the standard deviations among the sites were similar (FS = 2.9, NNE = 3.6, ZumWxStn = 2.5; Wallowa = 3.3). These precipitation patterns are typical of temperate steppe or cool grasslands (Forman & Godron 1986). Because of incomplete data sets, water years could only be compared between Wallowa and FS or NNE. Although correlated, neither r 2 was particularly strong (Wallowa vs FS, r 2 =.535; Wallowa vs NNE, r 2 =.661. Wallowa tended to be wetter than the other two sites, but rainfall was different among the location over the same time period. When cumulated mean monthly precipitations of a water year were calculated, two patterns became evident, one for FS and ZumWxStn and the other for Wallowa and NNE (Fig. 11). Indeed, the correlation is very tight between FS and ZumWxStn (y = 1.59x -.6. r 2 =.913). It is unfortunate that these measurements did not overlap in chronologically, which may have provided a reliable predictor for ZumWxStn in earlier years. The fit was not as good between Wallowa and NNE (y =.9x, r 2 =.693). The fits for the remaining paired site comparisons were poor (r 2 <.34 for all). General annual climate patterns were defined by combining monthly means and standard deviations of precipitation and temperature over a calendar year. The width and breadth of each ellipsoid is twice the standard deviation on the x- and y-axes, with the mean in the center (Fig. 12). ZumWxStn showed the greatest variation, perhaps because of the small number of years observed. The pattern between Wallowa and NNE was very similar. Another method of illustrating a weather pattern is by using a climograph where the monthly means of precipitation and temperature are compared in chronological order, starting with January (Smith 1977). ZumWxStn has the greatest monthly variation in precipitation, particularly in the spring, yet is similar to FS (Fig. 13). The climographs for Wallowa and NNE are similar, showing the close relationships evident in previous comparisons. However, when climographs of individual years are compared at ZumWxStn, the results are inconsistent, even within several years (Fig. 14). Note the difference between 7 and. This suggests that each year is unique, and more annual measurements are needed to accurately describe climate there. 4
SUMMARY Because The Zumwalt Prairie Preserve is a recent TNC site, it lacks historical meteorological information. To estimate previous climate and to anticipate future changes, we must use past measurements from nearby stations. Data from all sites indicate stable climates with no discernable trends in increasing or decreasing temperatures. Although Zumwalt shows considerable metrological variability, the site it most resembles is the FS at Enterprise. Unfortunately, there is no overlapping in annual measurements between these sites. The Wallowa station has the longest continuous record and has been consistent in temperatures and precipitation overtime. Thus, this site should be the basis for a regional climatic model. A reliable climatic profile is evident between Wallowa and NNE. Although topographically different, their climate patterns are very similar. If these patterns are typical of northeastern Oregon, we now can speculate that the environment at Zumwalt is colder, and more variable then proximate areas. LITERATURE CITED Forman, R. T. T., and M. Godron. 1986. Landscape ecology. John Wiley & Sons, New York. 6 pp. Forrest, J. R. K., and J. D. Thomson. 11. An examination of synchrony between insect emergence and flowering in Rocky Mountain meadows. Ecol, Monogr. 81: 469-491. Hansen, J.D., R.V. Taylor, and V.S. Jansen,. Zumwalt weather and climate annual report (6-9). The Nature Conservancy. Available from http://conserveonline.org/workspaces/zumwaltprairieworkspace/documents/z umwalt-weather-and-climate-annual-report-6/@@view.html Kimoto, C.. Effect of livestock grazing on native bees in a Pacific Northwest bunchgrass prairie. M. S. Thesis, Oregon St. Univ., Wildlife Science. 153 pp. Smith, R. L. 1977. Elements of ecology and field biology. Harper & Row, New York. 497 pp. 5
FIGURES Fig. 1. The Zumwalt Weather Station (ZumWxStn) located on the Zumwalt Prairie Preserve, 29 km (18 mi) NE Enterprise, Oregon. 6
Fig. 2. Location of the Zumwalt Weather Station on the Zumwalt Prairie Preserve, 29 km (18 mi) NE Enterprise, Oregon. 7
Temperature ( F) Mean Yearly Temperature 7 65 6 55 FS NNE ZumWxStn Wallowa 5 45 4 35 25 1925 1935 1945 1955 1965 1975 1985 1995 5 15 Year Fig. 3. Overall mean yearly temperatures ( F) for four sites in Northeastern Oregon. 8
Temperature ( F) Mean Yearly Temperature 7 65 6 55 FS NNE ZumWxStn Wallowa 5 45 4 35 25 1925 1935 1945 1955 1965 1975 1985 1995 5 15 Year Fig. 4. Mean yearly minimum and maximum temperatures ( F) for four sites in Northeastern Oregon. 9
Temperature ( F) 9 8 7 Mean Daily Temperature/Month 6 7 8 9 11 6 5 4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Fig. 5. The mean daily temperature ( F) per month at the Zumwalt Prairie Preserve, 18 mi NE Enterprise, Oregon.
Temperature ( F) Mean Daily Minimum Temperature 9 8 7 6 5 6 7 8 9 11 4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Fig. 6. The mean daily minimum temperature ( F) per month at the Zumwalt Prairie Preserve, 18 mi NE Enterprise, Oregon. 11
Temperature ( C) Mean Daily Maximum Temperature/Month 9 8 7 6 5 4 6 7 8 9 11 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Fig. 7. The mean daily maximum temperature per month for the Zumwalt Prairie Preserve, 18 mi NE Enterprise, Oregon. 12
GDD F Cumulative GDD F 25 6 7 8 9 11 15 5 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Fig. 8. Cumulative growing degree days (GDD) per month based on F for years between 6 and 11 at the Zumwalt Prairie Preserve, 18 mi NE Enterprise, Oregon. 13
Total Days FFD 35 25 6 7 8 9 11 15 5 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Fig. 9. Total frost free days per month between 6 and 11 at the Zumwalt Prairie Preserve, 18 mi NE Enterprise, Oregon. 14
Inches Yearly Sum 35 FS NNE ZumWxStn Wallowa 25 15 5 1931 1941 1951 1961 1971 1981 1991 1 11 Water Year Fig.. Total precipitation (in inches) of a water year (Oct. Sept.), designated by the year with the most months, at four sites in Northeastern Oregon. Solid lines are the means for all water years at that site. 15
Inches Cumulative Mean Monthly Precipitation 25 15 FS NNE ZumWxStn Wallowa 5 OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month Fig. 11. Cumulative mean monthly precipitation (in inches) during a water year (Oct. Sept.), designated by the year with the most months, at four sites in Northeastern Oregon. Time period for: FS is 1933 to 1981; NNE is 1971 to 4; Zumwalt is 6-511; and Wallowa is 1931 to, excluding years 195 to 1953, 1997, and 1998. 16
Temp. ( F) Monthly Means ± SD 7 6 5 4 FS NNE ZumWxStn Wallowa.5 1 1.5 2 2.5 Precip. (in) Fig. 12. Monthly means and standard deviations of precipitation and temperature over a calendar year for four sites in Northeastern Oregon. 17
Temp. ( F) Temp. ( F) Temp. ( F) Temp. ( F) FS NNE 7. 7. 6. 6. 5. 5. 4. 4... 1 12.. 1 12.....5 1. 1.5 2. 2.5 3. Precip. (in)...5 1. 1.5 2. 2.5 3. Precip. (in) 7. ZumWxStn 7. Wallowa 6. 6. 5. 5. 4. 4... 1 12.. 1 12.....5 1. 1.5 2. 2.5 3. Precip. (in)...5 1. 1.5 2. 2.5 3. Precip. (in) Fig. 13. Climographs showing mean monthly precipitation and temperature in chronological order (1 = January, 12 = December) for four sites in Northeastern Oregon. 18
6 7 7 7 6 6 5 5 4 4..5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5...5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5. 7 8 7 9 6 6 5 5 4 4..5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5...5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5. 7 6 5 4 7 6 5 4 11..5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5...5 1. 1.5 2. 2.5 3. 3.5 4. 4.5 5. Fig. 14. Annual climographs at Zumwalt (6-11) from monthly mean precipitation and temperatures. 19