**MLRA OFFICE 6 INSTRUCTION NO. 430-387** June 18, 2003

**SUBJECT:** SOI -- GUIDELINES FOR RECOGNIZING FAMILY LEVEL TAXONS

[Purpose:]{.underline} To transmit instructions on the use of family
level taxons in soil survey legends in MLRA Office Region 6.

[Effective Date:]{.underline} This instruction is effective when
received.

[Background:]{.underline} Family level taxons have a definite place in
soil surveys, particularly in lower intensity surveys. It is not always
clear when a family is to be used in lieu of a soil series, and under
what circumstances a family level taxon is valid. This instruction
emphasizes the policies contained in the National Soil Survey Handbook
on this topic, and provides supplementary guidelines that will be used
in MO6. The objective is to maintain consistent correlation of family
level taxons within MO Region 6.

[Filing Instructions:]{.underline} File with previous MLRA Office 6
Instructions. An updated tabulation sheet is enclosed.

J. CAMERON LOERCH

MLRA Office Leader

Attachments: narrative, spreadsheet, tabulation sheet

Distribution:

Regional Soil Scientist, Reg. 2, Forest Service National Soil Survey
Center, Lincoln, NE

MO6 Soil Survey Project Offices MLRA Office 5, Salina, KS

State Soil Scientists, MO 6 MLRA Office 7, Bismarck, ND

MLRA Office 3, Reno, NV MLRA Office 8, Phoenix, AZ

MLRA Office 4, Bozeman, MT

**MLRA OFFICE 6 INSTRUCTION SERIES**

###### TABULATION SHEET

+---------+--------+------------------------------------+-------------+
| *       | #      | #                                  | ##          |
| *INSTRU |  ISSUE |                                    |             |
| CTION** |        | # TITLE                            | ## COMMENTS |
|         | **     |                                    |             |
| **NO.** | DATE** |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-380 | 11-    | Establishment of the MLRA Office 6 |             |
|         | Jul-96 | Instruction series                 |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-381 | 28-    | NSSH Amendment MO6-1 (OSD          | ### To      |
|         | Jun-96 | instructions, template, and        | be reissued |
|         |        | policy)                            |             |
+---------+--------+------------------------------------+-------------+
|         | 15-    | Official Soil Series Descriptions  | *Reissued   |
|         | Dec-97 | (policy, guidelines, and template) | I           |
|         |        |                                    | nstruction* |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-382 | 11-    | Soil Survey Field Review           |             |
|         | Jul-96 | Procedures                         |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-383 | 26-    | Soil Survey Manuscript Procedures  |             |
|         | Sep-97 |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-384 | 22-    | Procedures for Submitting SSURGO   |             |
|         | Dec-98 | Materials                          |             |
|         |        |                                    |             |
|         |        | For Quality Review                 |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-385 | 16-    | Process to Approve Map Units       |             |
|         | Oct-01 |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-386 | 24-    | NASIS Data Entry Guidelines        |             |
|         | Jan-03 |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-387 | 18-    | Guidelines for Using Family Level  |             |
|         | Jun-03 | Taxons                             |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-388 |        |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-389 |        |                                    |             |
+---------+--------+------------------------------------+-------------+
|         |        |                                    |             |
+---------+--------+------------------------------------+-------------+
| 430-390 |        |                                    |             |
+---------+--------+------------------------------------+-------------+

GUIDELINES FOR RECOGNIZING FAMILY LEVEL TAXONS

Lakewood MLRA Office

June 2003

Family level taxons are fairly common in soil surveys within the
Southern Rocky Mountain Soil Survey Region, particularly on National
Forests. The following guidelines are provided to ensure consistent soil
correlation in MO6.

Although family level taxons may satisfy the needs of some lower
intensity surveys, their disadvantages should be recognized. Families do
not promote regional correlation between surveys. The Alpha families
mapped in two adjacent survey areas may be different soils with entirely
different interpretations. Conversely, the soil named Alpha family in
one area may be the same as Beta family in another area.

Because a family is a higher category than a soil series, more precise
statements can be made about series than families. The potential native
vegetation on a series can be expected to be similar for all occurrences
of that series, but this is not necessarily true for a family.
Laboratory data for a series can be extrapolated to unsampled areas with
a greater reliability than could be done for a family. Recognizing soils
at the series level allows for more reliable technology transfer from
known to unknown areas. Interpretations made for a series can also be
more specific and accurate, because series are more narrowly defined.

Because of the greater usefulness and interpretive value of series level
taxons, we will correlate soils to series when possible and where
supported by field documentation. Thus, the variability of the soil
properties will determine which level of taxon will be used.

Family level taxons are used in soil surveys in two situations:

1\. In lower intensity surveys, when the MOU specifies that families are
adequate for the purposes of the survey;

> 2\. In a survey where the MOU specifies mapping at the series level,
> when the natural variability of the soil typically crosses series
> limits to a significant degree, but falls within the limits of a
> family.

Before correlating a soil to a family in surveys where mapping is at the
series level, the procedures for recognizing similar soils should be
correctly applied. Similarly, conventions for recognizing and populating
soil properties that extend beyond the established limits of the taxon
should be correctly applied (Soil Survey Technical Note No. 4, Feb.
2003). Families are intended for situations where the modal soil
properties vary so widely that they cannot be accommodated by these
conventions. In a family, the soil properties that vary beyond
established series limits are properties that significantly affect soil
management and interpretations.

The following are guidelines that will be used in MO6 when correlating a
taxon to a family:

1\. A family level taxon does not necessarily imply a higher order of
mapping. Families may be appropriate in certain situations in order 2
mapping, just as series are appropriate in order 3 mapping. Correlating
to a higher or lower taxonomic level is not equivalent to mapping at
higher or lower intensities. Mixtures of series and families in a single
legend are acceptable.

2\. *Use either taxonomic names or, preferably, a family phase name,
such as Alpha family, as reference terms of the family level.* (NSSH
627.04(b)). If a series name is not available in a certain family, the
taxonomic name is used. Series are not proposed solely for the purpose
of providing a reference term. Also, *a taxonomic name used as a
reference term for a map unit component implies no specific range of
properties beyond that which is described in the map unit description
and database.* (NSSH 627.04(b)). The taxon named Alpha family may not
necessarily have anything in common with the Alpha series, except for
their taxonomic class.

3\. Only one reference term is recognized for each taxonomic family in a
legend. For example, it is incorrect to recognize both "Alpha family"
and "Beta family" if both of these taxons are fine, smectitic, frigid
Typic Argiustolls (both are in the same taxonomic family). The fact that
the taxon named Beta family is very similar to the Beta series is not
relevant; it still falls within the Alpha family and is named as such.
Family level taxons should not be used as if they were equivalent to
very loosely defined series.

4\. Phases of a family may be recognized. They are named using the same
conventions used for phasing a series. The range in characteristics of
an individual phase may be narrow, and within the limits that are
conceptually applied to soil series. In most circumstances these soils
will be correlated to a series.

5\. At the minimum, one taxonomic unit description must be written for
each family level taxon. It should encompass all the recognized phases
of the family. Alternatively, taxonomic unit descriptions may be written
specifically for each individual phase of a family if desired.

6\. For surveys where taxons are recognized mainly at the series level,
families (or higher categories) should not be used to avoid proposing a
new series. In such a survey, families should be reserved for use where
the natural variability of a map unit component extends significantly
beyond series limits. These components should commonly be on landforms
that have inherently variable parent materials, such as floodplains or
very steep escarpments. Map unit documentation should support both the
degree and the frequency of the soil variability.