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Updated July 2, 2019
  • Region Layers
  • Climate Layers
  • Soil Layers

    Layers are available in several Calflora applications that use Google Maps, including Observation Hotline. The map applications can show one background layer at a time. However, County Lines and Streams can be turned on at the same time as a background layer. See also the Introduction to Calflora Map Applications, which explains how the map cursor works.

    Background Layers
    Background layers are divided into three groups: Region, Climate, and Soil. Click on a group name -- for instance Region -- to see all of the layers within that group. Then click on the name of a layer -- for instance Protected Areas (CPAD) -- and the colored polygons of that layer will be superimposed on top of the Google Map. Note that not all layers are available at all zoom levels.

    The four checkboxes at the bottom control the appearance of colored polygons in the selected background layer. If the appearance of the polygons is too subtle, you can emphasize the outline of each polygon, or ask for darker background colors for each polygon.

    Here is an example of the Climate / Precipitation layer with darker background colors and a thick white outline (click to see it "live").

    Click on Streams to see rivers and creeks on the map. If you are zoomed way out, you will only see the longest rivers. As you zoom in, the shorter streams appear.

    When you check Stream names, a stream icon will appear at the end of each creek or river. When you click on the icon, you see the name of the creek or river, and the name of the stream that the creek or river flows into.

    For instance, in Monterey County, the icon for the creek called Arroyo Seco appears at the end of the Arroyo Seco, where it flows into the Salinas River. When you click on the icon an info window pops up describing the junction:
    Arroyo Seco / Salinas River
    The course of the stream itself -- the Arroyo Seco -- is highlighted in blue. The course of the downstream creek or river -- the Salinas River -- is highlighted in green.

    Uncheck Stream names to clear the map of all stream icons and all stream course highlighting.

    If you move to a different location on the map or change zoom level, and would like to see stream name icons at the new location, press the refresh button .


    May 27, 2019 version of the California Department of Fish and Wildlife California Streams dataset.

    National Hydrography Dataset (NHD) high resolution NHDFlowline features for California were originally dissolved on common GNIS_ID or StreamLevel attributes and routed from mouth to headwater in meters. The results are measured polyline features representing entire streams.

    The named streams from the California Streams dataset are shown in Calflora map applications. If a named stream flows into an unnamed stream, that unnamed stream is also shown, with a label like "uns123". Many of these unnamed streams are canals or other engineered hydrologic features.

    California Protected Areas Database

    Version 2018a (December, 2018) from Greeninfo Network

    The California Protected Areas Database (CPAD) is a GIS inventory of all protected park and open space lands in California. The database contains lands held in fee ownership by public agencies and non-profits.

    The units level of this database is shown in Calflora map applications. Click in an area to see its name.

    For areas with restricted access or no access to the public, the warning is included after the name. For instance

    San Francisco Watershed Lands - restricted access
      No Access
      Restricted Access
      Park or Open Space area; Public Access
      Federal Land (other than National Parks); Public Access

    From CalWater 2.2.

    Calflora map applications can show the four levels of this dataset listed on the right. Which level is shown depends on how far in the map is zoomed in.

    Level Example
    Planning Watershed 3309.811105 Little Burnett Creek
    Super Planning Watershed 3309.8111 McLaughlin Canyon
    Hydrologic Area 3309.8 Paso Robles
    Hydrologic Unit 3309. Salinas

    Zip Codes
    From United States Census Bureau TIGER/Line Shapefiles

    Major Land Resource Areas (NRCS)

      04B Coastal Redwood Belt
      05 Siskiyou - Trinity Area
      14 Central California Coastal Valleys
      15 Central California Coastal Range
      16 California Delta
      17 Sacramento and San Joaquin Valleys
      18 Sierra Nevada Foothills
      19 Southern California Coastal Plain
      20 Southern California Mountains
      21 Klamath and Shasta Valleys and Basins
      22A Sierra Nevada Mountains
      22B Southern Cascade Mountains
      23 Malheur High Plateau
      26 Carson Basin and Mountains
      29 Southern Nevada Basin and Range
      30 Mojave Desert
      31 Lower Colorado Desert

    4ETa Zones
    4ETa Zones indicating evaopotranspiration (NRCS California)

      b18 - 21inches
      c15 - 18inches
      d12 - 15inches
      e9 - 12inches
      f6 - 9inches
      g3 - 6inches
      h0 - 3inches

    EPA Ecoregions
    Calflora maps display both Level III Ecoregions and Level IV Ecoregions.

    Level III Ecoregions

    1. Coast Range
    78. Klamath Mountains/California High North Coast
    4. Cascades
    9. Eastern Cascades Slopes and Foothills
    80. Northern Basin and Range
    6. Central California Foothilss and Coastal Mountains
    7. Central California Valley
    5. Sierra Nevada
    13. Central Basin and Range
    8. Southern California Mountains
    14. Mojave Basin and Range
    85. Southern California Coast
    81. Sonoran Basin and Range

    Jepson Flora Project Geographic Subdivisions
    Please see Jepson eFlora: Geographic subdivisions.
    Polygons are © 1993 - 2019 Regents of the University of California.

    Jepson Regions

    Northwestern California
    Cascade Ranges
    Modoc Plateau
    Central Western California
    Great Valley
    Sierra Nevada
    East of Sierra Nevada
    Southwestern California
    Mojave Desert
    Sonoran Desert
    Each climate and soil layer described here is presented as a abstract factor contributing to the characterization of a location. The choice of which factors to show as layers on Calflora maps is informed by USDA PLANTS Conservation Plant Characteristics (particularly Growth Characteristics), but within the pragmatic bounds of what data is available. The goal is to be able to use these factors as predictors of where various plants are likely to grow.

    as prepared by the Prism Climate Group at Oregon State University, and available from the USDA Geospatial Data Gateway.

    PRISM data is typically available as a raster, where a cell is 30 arc seconds (~ 800 m) on a side.

    CITATION: U.S. Department of Agriculture, Natural Resources Conservation Service, National Geospatial Management Center

    Average Annual Precipitation
    Annual average precipitation during the period 1971 - 2000.

    For predicting where a plant may grow, it is important to know the minimum annual precipitation it requires (and for certain plants, the maximum annual precipitation it will tolerate).

    Units: inches per year

    157 inches
    133 inches
    107 inches
    81 inches
    61 inches
    37 inches
    17 inches
    3 inches

    As presented in Calflora map applications, the colors indicating climate layers are continuous. Colors associated with selected values of Annual Precipitation are shown here.

    Wet Season
    The number of wet months, as derived from monthly average precipitation (1981 - 2010) cell data. For a particular month, an 800 m cell is considered wet if it receives at least 1.3 inches of precipitation.

    As a characterization of location, this is similar to annual precipitation, but indicates the duration of a season during which rain is likely.

    Units: number of months


    July High Temperature
    based on average minimum monthly data during the period 1981-2010.

    Units: degrees Fahrenheit


    December Low Temperature
    based on average minimum monthly data during the period 1981-2010.

    Units: degrees Fahrenheit


    Accumulated Temperature
    based on average mean temperature and average minimum temperature monthly data during the period 1981-2010. This is a measure of accumulated heat during those months during which the minimum temperature is greater than 43 ° F (6 ° C). It is related to the concept of degree-days, but unlike degree-days calculated for a particular year, this number is based on average mean temperature. It is roughly equivalent to an annual sum of degree-days during the growing season.

    In the context of these climate factors, accumulated temperature can help determine which places are too hot for a plant. It is particularly useful for differentiating very hot places (Death Valley) from moderately hot places (Fresno).

    Units: degrees Fahrenheit

    See also
    A comparative study of different temperature accumulation methods for predicting the start of the Quercus pollen season in Cordoba (South West Spain), H. Garcia-Mozo, C. Galan, M. T. Gomez-Casero and E. Dominguez-Vilches, in Grama 39: 194-199, 2000

    Temperature Range
    Calculated as July High Temperature minus December Low Temperature per cell. In climate modelling, temperature range is akin to temperature seasonality.

    In the context of these climate factors, temperature range is useful for differentiating coastal areas from inland areas. Coastal areas typically have a narrower temperature range than inland areas.

    Two Coastal Vacciniums:
    These two plants share much of their geographic range, but parvifolium extends further inland than ovatum. The difference is reflected in the Temperature Range value for each plant. The image below is a screen shot from What Grows Here, showing occurrences of the two plants in Humboldt County with Temperature Range as the background layer.

    Note how the background color reveals temperature range differences between inland mountains (green ~ 48° F) and valleys (orange ~ 66° F).

    Units: degrees Fahrenheit

    Growing Season
    The number of consecutive warm months, as derived from average minimum monthy temperature (1981 - 2010) cell data. For a particular month, an 800 m cell is considered warm if the average minimum temperature is at least 43 ° F (6 ° C).

    Units: number of months

    ≤ 1

    USDA Hardiness Zone
    The map is based on average annual minimum winter temperature, divided into zones by 5 ° F increments. See the USDA Plant Hardiness Zone Map.

    Hardiness Zone differs from December Low Temperature above, in that it reflects the lowest temperature that might ever be experienced at a location.

    Units: degrees Fahrenheit

    5a: -20 to -15
    5b: -15 to -10
    6a: -10 to -5
    6b: -5 to 0
    7a: 0 to 5
    7b: 5 to 10
    8a: 10 to 15
    8b: 15 to 20
    9a: 20 to 25
    9b: 25 to 30
    10a: 30 to 35
    10b: 35 to 40
    11a: 40 to 45

    DISCLAIMER: Shapefiles of the hardiness zones for California were purchased and downloaded from Climate Source in February, 2014. They were subsequently modified (chopped into smaller pieces) for display as a map background layer.
    USDA Agricultural Research Service Terms of Use: Data: Users may obtain enhanced (high resolution) official USDA Plant Hardiness GIS data in shapefile and raster grid formats from Climate Source, Inc. (www.climatesource.com/PHZM/gis_data.html), subject to Climate Source terms of use. The USDA-ARS and OSU logos must be prominently displayed on any maps derived from the GIS datasets. The data may not be altered in any way without an explicit and prominently displayed disclaimer that the map is not the official USDA Plant Hardiness Zone Map, and USDA-ARS and OSU logos must not be displayed in the modified version.
    (See also GIS Data Downloads.)

    Climate Source Inc. Notice: This product contains data from The Climate Source and is used herein by permission. Copyright (c) 2014 The Climate Source, www.climatesource.com. All Rights Reserved.
    (See also License Agreement.)


    from the Soil Survey Geographic (2.2) Database dated October 1, 2018. Updated on Calflora April 17, 2019.
    See also

    SSURGO Table Struture
    California is described by 18,960 mapunit records, each of which corresponds to one or more polygons.

    Within each mapunit there are several soil component records. A component record has a percent (comppct_r) attribute, indicating its relative strength within the map unit.

    A component record may be associated with several chorizon records. Each chorizon record has top depth (hzdept_r) and bottom depth (hzdepb_r) attributes specified in centimeters.

    Click on the Derivation links below for more information about how the value displayed was derived from SSURGO data.

    CITATION: Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic (SSURGO) Database for California. Available online at NRCS Geospatial Data Gateway Accessed 04/10/2019.

    Soil Depth
    Minimum depth to the first restrictive layer of the components of a soil map unit.

    Derivation: For 9,886 mapunit records, minimum depth was available from the brockdepmin (minimum depth to bedrock) attribute in the muaggatt table.

    For the other mapunit records, minimum depth was calculated by choosing the deepest non-rock horizon of each component, and then averaging these numbers weighted by the component percent.

    Units: cm

    Soil pH
    pH of the components of a soil map unit.

    From Soil Properties and Qualities:

      "Soil reaction" is a numerical expression of the relative acidity or alkalinity of a soil. ... Soils that have a pH of approximately 6 or 7 generally have the most ready availability of plant nutrients.

    See also this Calflora analysis of
    how many plants tolerate each soil pH

    Derivation: Each component record has one topmost chorizon record (where hzdept_r = 0). pH for the mapunit was calculated by averaging the chorizon ph1to1h2o_r attribute of these topmost horizons, weighted by the component percent.
      Class pH
      Ultra acid 1.8 to 3.4
      Extremely acid 3.5 to 4.4
      Very strongly acid 4.5 to 5.0
      Strongly acid 5.1 to 5.5
      Moderately acid 5.6 to 6.0
      Slightly acid 6.1 to 6.5
      Neutral 6.6 to 7.3
      Slightly alkaline 7.4 to 7.8
      Moderately alkaline 7.9 to 8.4
      Strongly alkaline 8.5 to 9.0
      Very strongly alkaline 9.1 to 11.0

    Soil CaCO3
    The maximum calcium carbonate equivalent in the components of a soil map unit.

    From Soil Properties and Qualities:

      “Calcium carbonate equivalent” is the quantity of carbonate (CO3) in the soil expressed as CaCO3 and as a weight percentage of the less than 2 mm size fraction.
      ... The availability of plant nutrients is influenced by the amount of carbonates in the soil. This is a result of the effect that carbonates have on soil pH and of the direct effect that carbonates have on nutrient availability.
    Derivation: Each component record has one topmost chorizon record (where hzdept_r = 0). CaCO3 for the mapunit was calculated by averaging the chorizon caco3_r attribute of these topmost horizons, weighted by the component percent.

    Units: percent

    Available Water Storage

      Available water storage estimate (AWS) in standard zone 3 (0-30 cm depth), expressed in mm. The volume of plant available water that the soil can store in this zone based on all mapunit components (weighted average). NULL values are presented where data are incomplete or not available.
    Derivation: Copied from the valu1 table aws0_30 attribute.

    Units: mm

    Soil Salinity
    as indicated by electrical conductivity. The maximum conductivity of the components of a soil map unit.

    From Soil Properties and Qualities:

      Electrical conductivity is a measure of the concentration of water-soluble salts in soils. It is used to indicate saline soils. High concentrations of neutral salts, such as sodium chloride and sodium sulfate, may interfere with the absorption of water by plants ... [and] may also interfere with the exchange capacity of nutrient ions...
    Derivation: Each component record has one topmost chorizon record (where hzdept_r = 0). Electrical conductivity for the mapunit was calculated by averaging the chorizon ec_r attribute of these topmost horizons, weighted by the component percent.

    Units: mmhos / cm
      Class Conductivity in mmhos / cm
      Non-saline0 to <2
      Very slightly saline2 to <4
      Slightly saline4 to <8
      Moderately saline8 to <16
      Strongly saline≥16

    Soil Texture
    Texture as used here is based on the texture description of the major component of a soil map unit. A typical categorization of textures is shown below (image from the NRCS Soil Texture Calculator).

    From Soil Properties and Qualities:

      "Particle size” is the effective diameter of a particle as measured by sedimentation, sieving, or micrometric methods. ...
      The broad classes are
      • clay  [<0.002 mm]
      • silt    [0.002 to 0.05 mm]
      • sand [0.05 to 2.0 mm]...
    Derivation: Copied from the chtexturegrp table texdesc attribute, for the topmost horizon in the major (largest percentage) component of the mapunit.



    California Climate Data Archive


    Plant Tolerances:

    Las Pilitas Nursery (native plant ranges and tolerances)