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<br />RIO GRANDE COUNTY AREA, COLORADO
<br />groups ml the basis of uniformih' in kind, arrangement,
<br />and degree of expression of pedogenic horizons, mois-
<br />ture, and temperature and in base status. 1?ach great
<br />group is identified by a word of three or four syllables;
<br />a prclix is added to the name of the suborder. An exam-
<br />ple is Ila;~larluoll (Flnpl, meeting minimum horizon
<br />differentiation, plus ayrznf[, the suborder n1' Dlollisols
<br />that ha."c:ul agate moishn'e regime).
<br />Snncrnur~. Each great group is divided into three
<br />hinds of subgroups. The central (typic) concept of the
<br />great o~rnups (nut necessarily the most extensive sub-
<br />group); Ule intergrades, or transitional forms to other
<br />m-der.c, suborders, or great groups; and extragrade
<br />subgroups, which have some properties represenfatice
<br />of the great groups, but do not indicate tr;ulsitimis to
<br />anv other knun'n kind of soil. Each subgroup is identi-
<br />fied by the name of the great group preceded by one
<br />m' more adjectives, 1'he ari,jective Typic is used far the
<br />subgrmlp that is thought to typify the great group.
<br />An example is Typic Ilaplaquoll.
<br />P'naul.Y. Sail families are established within a sub-
<br />group that hate similar physical aunt chemical proper-
<br />ties aunt nearly the same responses to management.
<br />Among the properties considered in horizons of major
<br />biological activity below plow depth, are particle-size
<br />dish'ibutinn, mineralogy, temperature, thic4rncss of the
<br />soil pcnehable by roots, consistence, moisture, slope,
<br />and permanent cracks. A family name is the subgroup
<br />name preceded by a series of adjectives. The adjectives
<br />are the class names for particle-size distribution, min-
<br />eralogy, and temperatw'e, for example, that are used
<br />as family differentiae (see table 9). An example is
<br />TypIC ]iaplaquolls clayey Deer sandy or sandy-skeletal,
<br />montmm'illonitic, frigid.
<br />SERIES. The series cmisists of a group of lolls that
<br />formed in a particul:u• kind of p:u•ent material and,
<br />except for texture of the surface layer, have horizons
<br />similar in di(ferentiatingcharacteristics.tttd in arrange-
<br />ment in the profile. Among these ch;nncteristic~ are
<br />color, texture, structure, reaction, consistence, aunt min-
<br />eralogical and chemical composition. The series name
<br />83
<br />can be a place name in an area vv'h re the soil veal first
<br />defined. An example is the Acasco s Ties.
<br />Soil Temperatur
<br />All soils of the Rio Grande Coun y Area have frigid
<br />or cryic soil temperature regimes. They- have a mean
<br />annual temperature of less than 97° F. and a difference
<br />of 9° or more between the mean su mer and the mean
<br />wintet• temperatures. Cryic soils lso have a colrlet•
<br />summer temperature than frigid oils. The limit de-
<br />pends on whether or not the soil saturated during
<br />the summer and whether or not it has an w'ganic
<br />surface layer.
<br />Table 10 lists average soil temp natures of six soil
<br />series in bfarch through November or the period 1967
<br />to 1971. The soils were frozen during the winter months.
<br />The temperature of the frozen so 1 was 25° to 30°.
<br />These measured temperatures were used as a guide in
<br />estimating temperatures of similar s its.
<br />Genera[ Nature of tlce Area
<br />The San Luis Valley )vas Spanis territory that be-
<br />came part of Mexico, and subseq ently part of the
<br />United States during the Mexican War. During the
<br />early 1860'x, small Spanish settle ents were estab-
<br />]ished along the Rio Grande, wes of Monte Vista.
<br />Stockmen from the East also settled along the river to
<br />utilize the grass that grew well on t veet bottom land.
<br />A few ranches in the vicinity of Del orte became sup-
<br />ply points for mining camps to th µ'est in the San
<br />Juan Momltains. In the 1870'x, ranch s were established
<br />along Rock Creek south of nlonte Vi ta.
<br />Settlement increased sharply aft r the Civil War.
<br />Del Norte, founded in 1871, was the county seat when
<br />Rio Grande County w'as farmed in 879. The town of
<br />Monte Vista was founded in 1881 hen the railroad
<br />was extended west of Alamosa. The population of the
<br />county was at its peak about the ti of World War I.
<br />It has declined slowly since then. he population in
<br />1970 was 10,994.
<br />'rAi3Lls ]0.-Sot! lrmpernhrres of six sorbs
<br />iTemperaturc measured at a drplh of 20 inrhe~ about the lath of the month during the period 1967 71. Dnta prese~led ore xveragesl
<br /> Soil
<br />?,f onth - ---
<br /> --- --- - -- - - - -- -
<br /> Eulchrr Jndrm Luhon MishaA Monte Seitz
<br />1.tarch______ ____ _______ :10 3~f 35 33 3G 30
<br />.April . _.._.. _..
<br />_... :3 fi 4:1 45 36 43 3^
<br />[.tay___.. __ .. _._ 42 ail 53 45 50 3d
<br />June_________ __ _____ __ ;,1 ;~ri 59 53 53 39
<br />Jub'___. ____.._ ._ ... 5fi G'_ GS 59 G5 47
<br />August. _..._ .. .._ SS 63 G5 60 66 49
<br />Srptrmbrr_____ ._ _, .53 54 60 .5g 61 47
<br />Oct ober.._.... __.__. 46 .i] 51 47 49 42
<br />Nnrembcr ___._ _.. ..__ 37 41 43 40 41 3G
<br />`
<br />.A verage annual. -- 43 --i-- - 4f~-- 4G 43 37
<br />46
<br />Avrrage summer __ i S.i GO i G3 57 63 d5
<br />_..~~.
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