Identifying Climate Suitability for Oregon White Oak

Transcription

1 Introduction Identifying Climate Suitability for Oregon White Oak Lucas Rabins, Ben Larson, & Anders Dowell December 2016 As the earth s climate changes over the next century, many species adapted to specific climates will find themselves under increasing stress as their suitable habitat shifts beneath them. This can be especially harmful to sessile organisms such as plants that are unable to move as their ranges shift. Many of the ranges these plants inhabit can be defined in terms of a specific climate envelopes defined as the set of climatic variables that make up a species habitable range. Our analysis examines a potential climate envelope for Oregon White Oak (Quercus Garryana). Oregon white Oak, commonly known as Oregon White Oak, is one of the Pacific Coast s few native deciduous trees. Using the recent climate data as well as climate change model predictions for the region, combined with Geographic Information Systems (GIS), we attempt to identify the climate envelope for Oregon White Oak. We use this to determine current and future areas with suitable climates of the species. The documented range for Oregon White Oak is along the west coast of the United States and stretches from southern British Columbia, Canada, to central California in the United States. Our findings suggest the current territory occupied by Oregon White Oak will become significantly less hospitable to the species towards the end of the century. However, large amounts of territory in neighboring mountain ranges enter a suitable climate envelope for the tree species, suggesting hope for conservation of Oregon White Oak. Data Data for this analysis included the current range of Oregon White Oak available from the United States Geological Survey (USGS), as well as historical climate data ( ) and future climate scenario data ( ) Obtained from Andreas Hamman s personal website. Climate data was generated with the ClimateWNA v4.62 software package, available at based on methodology described by Hamann et al. (2013). The data for the current range of Oregon White Oak was available in the form of a single vector multipolygon shapefile, outlining the range of Oregon White Oak as compiled by Elbert Little of the US Department of Agriculture, Forest Service, and others in This shapefile was created in the NAD 1927 geographic coordinate system (USGS). Current and future projected climate data was available in the form of a series of raster datasets each outlining either a single current or future climate variable. For our analysis this included current and future mean annual precipitation (MAP), mean annual temperature (MAT), mean temperature of the warmest month (MWMT), mean temperature of the coldest month (MTCM), and extreme minimum temperature (EMT) over a 30-year period using a total of 10 raster datasets. We selected Mean annual temperature and mean annual precipitation as general suitability guidelines. We selected mean temperature of the warmest and oldest month as well as extreme minimum temperature due to the fact

2 that extreme temperatures, particularly low temperature, during the year can cause damage or even mortality to young Garry oak trees, limiting its dispersion (Gucker). All current and future temperature variables were originally created in units of degrees Celsius X 10, while precipitation was created millimeters. In order to correct the temperature variable units to Degrees Celsius, we simply used the raster calculator to divide all cell values of the temperature datasets by 10. Future climate data sets were generated using the A1B moderate emissions scenario and represent projected data from All raster datasets were created in the WGS 1984 Geographic coordinate system with a cell size of one hectare (1 km 2 ). Before any analysis was done, we projected the current and future raster climate data sets as well as the current Oregon White Oak range vector dataset into a custom variation of the USA Contiguous Lambert Conformal Conic projected coordinate system with a central meridian of degrees using a bilinear resampling technique for the raster datasets. Methods To estimate the future range of Oregon White Oak, we first needed to build a climate envelope for the current range of Oregon White Oak by analyzing the current climate conditions in which Oregon White Oak is found. This involved running the zonal statistics as table tool for each current climate variable using the current range of Oregon White Oak as the vector zone field and the current raster datasets as the input raster. (Model 1) Model 1. Zonal Statistics as Table used for generating the mean and Standard Deviation for each of the current Climate variables. Statistics for each Climate Raster was calculated in the current range of Oregon White Oak. This model (Model 1) was run on each of the 5 current climate variables, generating a series of tables which included mean and standard deviation for each of the current climate variables inside of the current Oregon White Oak range. These tables were then compiled and exported to excel where we

3 calculated the upper and lower range of our current climate envelope by adding and subtracting 1.5 standard deviations from the mean (Table 1). Variable Mean Std. 1.5 Std. Mean std. Mean std. EMT ( C ) MAT ( C ) MWMT ( C ) MCMT ( C ) MAP (mm) Table 1. Statistics for each of the current climate variables within the Current Oregon White Oak Range. Mean 1.5 Standard Deviation and Mean +1.5 Standard Deviations represent the lower and upper ranges of each climate variable for our climate envelope. By using 1.5 standard deviations above and below the mean as the ranges of our climate envelope, we effectively eliminate any areas within the current Oregon White Oak range that are have a highly irregular climate, such as mountaintops, where Oregon White Oak is unlikely to grow. In order to map the current climate suitability range of Oregon White Oak according to our climate envelope, we used the raster calculator to select only the area that was within our climate envelope the current and future climate raster datasets. (Model 2) This generated a binary raster with a value of 1 representing all areas in which that specific climate variable was suitable for Oregon White Oak and a value of 0 representing unsuitable areas. We then used these outputs in raster calculator to generated a new raster with a value of one for each cell that had a value of one for all of the current climate variables, and a value of 0 for everywhere else, giving us the range where each climate variable was satisfied (Model 2. Expression2). This process was then repeated using the future climate data.

4 Expression 2 ("%MTWM_Binary_Suitability%" == 1) & ("%MTCM_Binary_Suitability%" == 1) & ("%MAT_Binary_Suitability%" == 1) & ("%MAP_Binary_Suitability%" == 1) & ("%EMT_Binary_Suitability%" == 1) Expression 1 ("%EMT_Current%" >= ) & ("%EMT_Current%" <= ) Model 2. Calculation of the current and future climate suitability ranges for Oregon White Oak. The inputs and outputs depicted are for generating the current climate suitability range. Raster calculators 1-5 generate the binary suitability rasters for each of the individual climate variables (Expression 1), while raster calculator 6 generates the binary suitability for all the climate variables (Expression 2).

5 Results Figure 1 represents the observed range that the USGS has recorded for Oregon White Oak. This area spans approximately of 127, Km² along the west coast of the United States, with the biggest swaths of White Oak territory in Oregon, Southern Washington, and Northern California. The suitable area for Oregon White Oak based off our current climate envelope discussed above, represents an area of 153,191 Km² or nearly 25,000 Km² more than the USGS s current mapped range for Oregon White Oak. This calculated range is similar to the form and size to the observed area for Oregon White Oak. Our climate envelope found much more area in the sierra Nevada range on eastern California to be suitable for Oregon White Oak than is currently documented. Similar to the observed range, the current climate envelope identifies suitable habitat that follows the western coastline of the United States with a small amount of suitable territory located in southern, coastal British Columbia, Canada. While our identified suitable range for Oregon White Oak is not a perfect fit to the Documented Range data, we find the inconsistencies to be relatively minor. Figure 1: USGS defined Climate envelope for Oregon White Oak Suitability Figure 2: Current Climate envelope based on our analysis Figure 3: Projected climate envelope for 2080 Figure 3 represents our projected suitability for Oregon White Oak in the 2080 s and covers a territory of 117,762 Km². This area is 76.87% the size of the previous area indicating a loss of suitable territory of 23.13%. More troubling, however, is the smaller overlap of territory which remains in suitable climate envelope for both periods of time shown in figure 6. This area is only 27,221 km², or 17.77% of the area of the original climate envelope. This means the vast majority of the territory currently suitable for Oregon White Oak will not be suitable towards the end of the century. Such a reduction in the extent of the climate envelope could potentially cause vast damage to the species over the course of the century. Most suitability is lost along the coasts and central territory of the suitable climate extent. Most of the gains are concentrated in the cooler, higher elevations of mountain ranges stretching up and down inland of the coast.

6 Figure 4: Map of the current suitability envelope based on our analysis

7 Figure 5: Map of the projected changes in area for the year 2080.

8 Figure 6: Map of the projected changes in area for the year 2080.

9 Figure 7: This map details the current, future, and overlap of those two climate envelopes on top of a topographic base map. Orange represents the current envelope, green is the projected envelope for 2080, and blue represents where current and future overlap.

10 Conclusion Our analysis of the Oregon White Oak tree species has predicted rather drastic changes in the area habitable of this tree. Our model predicts a loss of 23.13% - or 35,429 Km² - in total habitat, a loss of 82.23% - or 125,970 km²- of territory within the current climate envelope, and an inland shift in the locations of that habitat. To improve our model, there are many other climatic variables, biotic variables such as slope and aspect, as well as biotic variables that could have been utilized. In particular, there is strong evidence to show that the presence or absence or other species of plants and animals play a large role in determining suitable ranges for Oregon White Oak. Unfortunately, many biotic variables for any given area are also climate dependent and would therefore not remain consistent over the next century, making them not appropriate for use in our model (Costanzo). Additionally, soil characteristics such as ph play a role in Oregon White oak suitability, however gathering consistent and accurate soil data for our entire area of study proved impossible. Finally acquiring higher resolution datasets would also improve the accuracy of our model (Stein). There are many environmental services that White Oak provide as well as wildlife species which rely on the Oregon White Oak for a host of services. These include shade, pollutant capture/filtration, carbon sequestration, food and nesting sites therefore the implications of this reduction in habitat directly threatens the well-being of wildlife interacting with the tree itself. In coastal areas, primarily in the pacific northwest and British Columbia, we can expect expedited erosion due to loss of the Oregon White Oak (Gucker). As the effects of climate change become more and more apparent we will see more and more White Oaks disappearing from the more coastal regions of the west coast and a shift to inland areas becoming more suitable. A loss in Oregon White Oak translates to a loss in habitat for many wildlife species, as well as a loss in a host of ecosystem services in these regions.

11 Sources Cited Costanzo, Brenda, Et al. "Distribution and Description." Restoring British Columbia's Oregon White Oak Ecosystem. Ed. David Clemens Et al. Victoria: Oregon White Oak Ecosystems Recovery Team, Print. Gucker, Corey L Quercus garryana. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [2016, December 7]. Hamann, A. and Wang, T., Spittlehouse, D.L., and Murdock, T.Q A comprehensive, high-resolution database of historical and projected climate surfaces for western North America. Bulletin of the American Meteorological Society 94: Stein, William I. "Oregon White Oak." USDA Forest Service, n.d. Web. 27 Nov United States Geological Survey. "Digital Representations of Tree Species Range Maps from "Atlas of United States Trees" by Elbert L. Little, Jr. (and Other Publications)." Gec.cr.usgs.gov. USGS, 21 Nov Web. 29 Nov