CHARACTERIZING AND MAPPING SOIL CLIMATE

IN THE

NORTHERN PLAINS REGION

W.J. Waltman, H.R. Sinclair, and S.W. Waltman

USDA Natural Resources Conservation Service

Northern Plains Regional Office and National Soil Survey Center

Lincoln, NE



Background

The landscapes of the Northern Plains reflect a complex history of geomorphic and climatic events, which have also significantly affected soil and ecosystem development. The interaction of soils, climate, vegetation/animals, topography, human impacts, and time produces considerable natural and agricultural resource diversity that results in a complex pattern of soil landscapes and conservation strategies.

The Northern Plains region consists of roughly 420 million acres distributed across 57 Major Land Resource Areas. A good indicator of regional land resource diversity is expressed in the soil resource base. The Northern Plains landscape is collectively represented by more than 4427 soil series and 48,165 soil map units . Soil moisture regimes range from aridic to udic and soil temperature regimes extend from thermic to pergelic. In addition, the topography ranges from elevations of 4500 m above sea level (14,433 ft) on Mt. Elbert, Colorado, to 213 m (< 800 ft) in Kansas. Seventy percent of the region has elevations below 1500 m (4,920 feet) and only 4 percent of the land area occurs above 2743 m (9,000 ft). However, due to the broad topographic range and its accompanying orographic effects, precipitation ranges from 142 mm (< 6 in) in the Bighorn Basin of Wyoming to 1110 mm (44 in) in southeastern Kansas. Given this range of climatic environments and their inherent variability, conservation management of both natural and agricultural ecosystems across these landscapes is a difficult challenge.

In both concepts of the Land Resource Regions and Major Land Resource Areas (Soil Survey Staff, 1981), the boundaries and characteristics have been be viewed as rather static in time and space. Similarly, soil moisture and temperature regimes have been traditionally mapped as static delineations. Although Marbut (1935) and Jenny (1941) clearly recognized the importance of climate in soil formation, the ability to map soil climate characteristics and articulate its variability or behavior has been lacking in the soil survey process.

The challenge for the Natural Resources Conservation Service (NRCS) was to derive new indicators for soil climate changes, capture and articulate aspects of the soil climate variability, develop a methodology to better represent soil climate characteristics, which can be integrated to create agro-climatic regions across the Northern Plains region.

The objectives for our research and their application were: 1) to develop an index of inherent soil quality suitable for mapping soil productivity and agro-climatic regions, 2) to design relatively simple indices to represent changes in soil moisture and temper-ature regimes, and 3) to terrain model soil-climate parameters and their shifts from existing geospatial databases.

Soil Ratings for Plant Growth

For soil constraints or qualities, the "Soil Ratings for Plant Growth" (SRPG) was used to group about 25 soil properties into a soil productivity or inherent soil quality index cal-culated for components of STATSGO map units. The SRPG calculations followed the "Storie Index Soil Rating" (Storie and Weir, 1958; Storie, 1978), which was based on soil characteristics that govern the land's potential utilization and productive capacity. The Storie Index was originally adapted to semiarid and arid regions and included profile characteristics that influenced effective rooting depth and the quality of the root zone, subsurface properties (permeability, available water-holding capacity, drainage class, soluble salts), and landscape properties such as slope, microrelief, and the degree of erosion (Miller and Donahue, 1990). However, in the SRPG, Sinclair and Terpstra (1995) also considered soil climate regimes as an additional factor in calculating the index, which is a particularly significant parameter, given the wide range in soil climate across the Northern Plains region. The SRPG tables for STATSGO were developed by the Iowa State University Statistical Laboratory (Sinclair and Terpstra, 1995).

The SRPG wascombined with the USGS Land Use and Land Cover (LUDA) to identify croplands with similar agronomic behavior or soil productivity (Figure 1). SRPG values ranging from 0 to 30 were considered unsustainable for agronomic crop production (Storie, 1978; Miller and Donahue, 1990), but these soil ratings still represent productive range ecosystems. SRPG values from 31 to 50 generally grouped soils with marginal suitability for agronomic production. The most highly productive soil areas have ratings greater than 70. The SRPG classes grouped on the basis of 10 units (i.e. 1 to 10, 11 to 20) seemed to provide reasonable subdivisions of MLRAs and a basis for soil productivity regions. From the SRPG calculations, soil management groups began to emerge, which could relate to areas where particular conservation tillage practices are adaptable. The primary underlying assumption of the SRPG reflects the concept that soils with the greatest "effective rooting depth" and root zone available water-holding capacity are the most productive. The SRPG sub-calculations of effective rooting depth and root zone available water-holding capacity are needed for modeling soil moisture regimes, but also have value for identifying soil landscapes with limited soil water retention characteristics.

The Newhall Simulation Model

The Newhall Simulation Model (NSM) has long been used by the USDA Natural Resources Conservation Service to estimate soil moisture regimes as defined in Soil Taxonomy (Soil Survey Staff, 1975, 1993; Newhall and Berdanier, 1992). Van Wambeke et al. (1992) modified the original model and introduced new subdivisions of soil moisture regimes and variable soil moisture storage. Van Wambeke (1981, 1982, and 1985) applied the model to map soil moisture regimes across Africa, South America, and Asia. The NSM was designed to run on monthly normals for precipitation and temperature; generally 30 year normals were most reasonable and appropriate to derive estimations of soil moisture and temperature regimes, as well as biological windows.

Soil Moisture Regimes

Soil moisture regime refers to the presence or absence of soil water held at a tension of <15 bars (or between field capacity and permanent wilting point) in specific horizons during key periods of the year (Soil Survey Staff, 1975). Soil moisture regime is an important soil property because of its impact on cropping systems, tillage/conservation practices, as well as natural plant communities. Tables 1 and 2 summarize the soil moisture regime changes over time for the Mead Agronomy Laboratory (Mead, NE) and the Akron 1 N (CO) weather stations. The interannual variability of soil moisture regimes can be useful indicators of soil climate shifts at local or large map scales.

From the soil moisture regime calculations, the "Pedocal/Pedalfer" boundary (Marbut, 1935; Jenny, 1941) can be terrain modeled to illustrate changes in soil forming pro-cesses. The Pedocal/Pedalfer Boundary is a theoretical threshold where precipitation equals potential evapotranspiration, and defines the boundary between soils in a leaching versus base accumulating (CaCO3) environment (Figure 2).

Table 1. Soil Climate Characteristics of Mead Agronomy Laboratory, Nebraska.

YEAR PREC PET AMD MSD Dry Days M/D Days BIO5 Soil Moisture Regime  
  (mm) (mm) (mm) (mm) (days) (days) (days)    
1969 576 678 -102 -164 0 83 124 Wet Tempustic  
1970 653 705 -52 -175 0 18 186 Typic Udic  
1971 603 696 -93 -283 45 63 107 Typic Xeric  
1972 823 678 145 -220 0 57 155 Dry Tempudic  
1973 907 709 -198 -222 0 25 204 Typic Udic  
1974 530 701 -171 -238 28 103 96 Wet Tempustic  
1975 495 706 -211 -274 80 41 86 Typic Xeric  
1976 497 693 -196 -262 43 66 98 Typic Tempustic  
1977 787 752 35 -175 0 38 191 Dry Tempudic  
1978 721 697 24 -190 0 24 183 Typic Udic  
1979 672 711 -39 -222 22 78 117 Wet Tempustic  
1980 500 756 -256 -159 48 92 83 Typic Tempustic  
1981 686 744 -58 -123 0 22 213 Typic Udic  
1982 1011 700 311 -2 0 0 214 Typic Udic  
1983 745 718 27 -206 9 100 104 Wet Tempustic  
1984 869 692 177 -208 37 34 138 Dry Tempudic  
1985 617 695 -78 -161 0 12 206 Typic Udic  
1986 968 724 244 -83 0 0 226 Typic Udic  
1987 772 738 34 -69 0 4 231 Typic Udic  
1988 523 753 -230 -269 48 152 29 Typic Tempustic  
1989 506 704 -198 -180 49 166 0 Typic Tempustic  
1990 642 711 -69 -113 0 81 150 Wet Tempustic  
1991 873 732 141 -57 0 17 196 Typic Udic  
1992 669 677 -8 -87 0 0 239 Typic Udic  
1993 1071 646 425 230 0 0 199 Typic Udic  
1994 674 695 -21 -13 0 0 228 Typic Udic  
1995 562 678 -116 -348 35 85 85 Typic Tempustic  

Last Updated on 98/04/03
By Dennis Ojima


PREC = Precipitation PET = Potential Evapotranspiration AMD = Annual Moisture Deficit MSD = Mean Summer Deficit Dry Days = Days the Soil Moisture Control Section is Dry M/D Days = Days the Soil Moisture Control Section is Partly Moist and Dry BIO5 = Biological Window at 5 oC

Table 2. Soil Climate Characteristics of Akron 1 N, Colorado.

YEAR PREC PET AMD MSD Dry Days M/D Days BIO5 BIO8 Soil Moisture Regime
  (mm) (mm) (mm) (mm) (days) (days) (days) (days)  
1937 276 676 -400 -288 139 71 0 24 Typic Aridic
1938 353 603 -250 -306 112 63 44 80 Weak Aridic
1939 246 688 -442 -302 170 46 0 35 Typic Aridic
1940 413 686 -273 -219 83 132 0 57 Typic Tempustic
1941 545 642 -97 -199 0 37 176 190 Dry Tempudic
1942 529 633 -104 -195 0 87 122 199 Dry Tempudic
1943 314 644 -330 -278 127 83 0 67 Weak Aridic
1944 425 629 -204 -235 78 31 84 109 Typic Xeric
1945 539 617 -78 -53 0 54 172 182 Typic Tempustic
1946 556 644 -88 -109 0 47 167 202 Dry Tempudic
1947 481 632 -151 -154 46 68 84 116 Typic Tempustic
1948 456 650 -194 -125 77 76 47 106 Typic Tempustic
1949 594 642 -48 -48 0 0 224 201 Typic Udic
1950 462 617 -155 -178 44 159 0 59 Typic Tempustic
1951 463 584 -121 -154 56 40 93 104 Typic Tempustic
1952 437 653 -216 -362 98 25 73 94 Typic Xeric
1953 458 647 -189 -138 67 45 81 120 Typic Xeric
1954 275 671 -396 -295 171 45 0 43 Typic Aridic
1955 441 647 -206 -161 86 74 43 101 Typic Tempustic
1956 384 656 -272 -193 93 58 47 57 Typic Xeric
1957 543 620 -77 -136 0 53 133 174 Typic Tempustic
1958 439 641 -202 -185 87 16 93 106 Typic Tempustic
1959 381 640 -259 -284 61 137 0 54 Typic Tempustic
1960 349 660 -311 -295 86 52 73 79 Typic Xeric
1961 424 624 -200 -228 67 85 47 60 Typic Tempustic
1962 452 662 -210 -151 95 71 54 121 Typic Tempustic
1963 415 714 -299 -185 133 92 0 40 Typic Aridic
1964 299 643 -344 -236 121 83 0 44 Typic Aridic
1965 586 633 -47 -75 0 54 164 207 Wet Tempustic
1966 342 652 -310 -170 180 44 0 20 Typic Aridic
1967 511 630 -119 -114 0 119 107 201 Typic Tempustic
1968 299 627 -328 -221 161 50 0 22 Typic Aridic
1969 380 639 -259 -245 74 43 66 99 Typic Tempustic
1970 262 634 -372 -269 150 44 0 20 Typic Aridic
1971 272 630 -358 -315 143 65 0 56 Weak Aridic
1972 367 645 -278 -186 118 100 0 21 Typic Aridic
1973 499 621 -122 -261 7 91 98 118 Typic Tempustic
1974 268 658 -390 -240 160 58 0 28 Typic Aridic
1975 417 621 -204 -250 78 40 80 110 Typic Tempustic
1976 317 641 -324 -263 141 63 0 42 Typic Aridic
1977 348 685 -337 -296 124 14 74 82 Weak Aridic
1978 349 656 -307 -200 153 66 0 37 Typic Aridic
1979 542 629 -87 -109 0 45 163 194 Dry Tempudic
1980 401 662 -261 -171 116 92 0 37 Typic Aridic
1981 459 668 -209 -228 94 28 107 131 Typic Tempustic
1982 446 626 -180 -202 80 16 109 110 Typic Xeric
1983 481 638 -157 -193 51 36 103 129 Typic Tempustic
1984 542 628 -86 -121 0 31 163 170 Dry Tempudic
1985 486 652 -166 -209 58 79 73 115 Typic Tempustic
1986 405 677 -272 -263 124 57 53 102 Typic Tempustic
1987 615 651 -36 -176 0 75 136 199 Wet Tempustic
1988 484 655 -171 -276 71 33 101 125 Typic Xeric
1989 391 654 -263 -96 139 45 40 52 Weak Aridic
1990 536 656 -120 -148 49 41 131 160 Typic Tempustic
1991 326 670 -344 -262 132 79 0 48 Weak Aridic
1992 404 656 -252 -100 105 120 0 47 Typic Tempustic
1993 430 623 -193 -187 64 50 92 102 Typic Xeric
1994 378 698 -320 -241 98 127 0 47 Typic Tempustic
1995 526 632 -106 -233 32 109 81 107 Typic Tempustic
                   
1937-1995 424 646 -222 -204 81 63 64 98 Weak Aridic

Last Updated on 98/04/03
By Dennis Ojima

PREC = Precipitation PET = Potential Evapotranspiration AMD = Annual Moisture Deficit MSD = Mean Summer Deficit Dry Days = Days the Soil Moisture Control Section is Dry M/D Days = Days the Soil Moisture Control Sectio is Partly Moist and Dry BIO5 = Biological Window at 5 oC BIO8 = Biological Window at 8 oC

Biological Windows

The Newhall simulation estimates the cumulative days that the soil moisture control section is moist and greater than 5 oC, as well as the highest number of consecutive days that the moisture control section is both moist in some parts and greater than 8 oC. Both of these estimates are defined as "biological windows" of plant and microbial activity. The concept of biological windows may serve as a useful bioclimatic indicator of inherent soil quality, since it integrates both soil moisture and temperature, as well as the window of time available for root and microbial activity. The biological window calculation would relate to soil processes, such as the mineralization of organic matter, soil carbon storage, herbicide degradation, and nitrification. Tables 1 and 2 also summarize the interannual variability of biological windows for the Mead Agronomy Laboratory and the Akron 1 N weather stations.

The biological window concept is indirectly expressed in Soil Taxonomy (Soil Survey Staff, 1975; Smith, 1986), but the calculation can be derived through the NSM and terrain modeled to USGS DEMs (Figure 3).

Terrain Modeling

A terrain modeling approach was used together with the NSM (Van Wambeke et al., 1992) results to spatially extend climatic parameters onto the landscape. These climatic parameters included: mean annual precipitation, air temperature, potential evapo-transpiration, annual moisture surplus/deficit, mean summer moisture deficit, moisture index, biological windows, growing-degree days, frost-free period, and soil climate regimes. The transfer of climatic parameters to terrain (1:250000 USGS digital elevation models or DEMs) followed the methology described by Ollinger et al. (1995). Regression equations were derived from a population of 875 weather stations with 1961 to 1990 normals in Northern Plains states. The regression equations were based upon five land-scape parameters: easting (longitude), northing (latitude), elevation, slope, and aspect. From these equations, continuous surfaces of the climatic parameters provided a better fit to the terrain while capturing local orographic effects.

SUMMARY AND CONCLUSIONS

The SRPG or inherent soil quality index, clearly defines soil productivity regions or soil management groups (in a non-political context) within the Northern Plains and should provide global change modelers with reasonable, quantitative values for effective rooting depth and root zone available water-holding capacity across soil landscapes.

Soil moisture and temperature regimes, the Pedocal/Pedalfer Boundary, and biological windows, are useful indicators of soil climate shifts in the Northern Plains.







REFERENCES

Jenny, H. 1941. Factors of Soil Formation. McGraw-Hill, New York. 109p.

Marbut, C.F. 1935. Soils of the United States, Atlas of American Agriculture, Part III,

Washington, D.C.

Miller, R.W. and R.L. Donahue. 1990. Soils: An Introduction to Soils and Plant Growth.

6th edition, Prentice-Hall Inc., Englewood Cliffs, NJ.

Newhall, F., and C.R. Berdanier. 1992. Calculation of soil moisture regimes from the

climatic record. Unpublished manuscript. USDA-SCS, Washington, D.C.

Sinclair, H.R. and H.P. Terpstra. 1995. Soil Ratings for Plant Growth. Iowa State Univ.

Statistical Laboratory, Ames, IA.

Smith, G.D. 1986. The Guy Smith interviews: Rationale and Concepts in Soil Taxonomy.

Soil Management Support Services Monograph No. 11, Department of Agronomy,

Cornell University, Ithaca, NY.

Soil Survey Staff. 1975. Soil Taxonomy. A basic system of soil classification for making

US Gov't Printing Office, Washington, D.C.

Soil Survey Staff. 1994. Keys to Soil Taxonomy. 6th ed. USDA Soil Conservation Service,

Washington, D.C.

Storie, R.E. 1937. An index for rating agricultural value of soils. Bulletin 556, University of

California, Berkeley, CA.

Storie, R.E. and W. W. Weir. 1948. Manual for identifying and classifying California soil

series. University of California, Berkeley, CA.

Storie, R.E. 1978. Storie index soil rating (revised). Special Publication 3203, Division

of Agricultural Science, University of California, Berkeley, CA.

USDA Soil Conservation Service. 1981. Land Resource Regions and Major Land

Resource Areas of the United States. Agric. Handbook No. 296, U.S. Gov't Printing

Office, Washington, D.C.

USDA Soil Conservation Service. 1993. State Soil Geographic Database (STATSGO),

User's Guide. Miscellaneous Publication No. 1492, National Soil Survey Center,

Lincoln, NE.

Van Wambeke, 1981. Calculated soil moisture and temperature regimes of South

America. Soil Management Support Services Technical Monograph No. 2, USDA-

SCS, Washington, D.C.

Van Wambeke, A. 1982. Calculated soil moisture and temperature regimes of Africa.

Soil Management Support Services Technical Monograph No. 3, USDA-SCS,

Washington, D.C.



Van Wambeke, 1985. Calculated soil moisture and temperature regimes of Asia.

Soil Management Support Services Technical Monograph No. 9, USDA-

SCS, Washington, D.C.

Van Wambeke, A., P. Hastings, and M. Tolomeo. 1992. Newhall Simulation Model--

A BASIC Program for the IBM PC (DOS 2.0 or later). Dept. of Agronomy, Cornell

University, Ithaca, NY.