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<br /> <br />003()86 <br /> <br />SECCION IV - GEOHIDROLOGIA <br /> <br />81 <br /> <br />....>.,.;>... ..' <br />;.?Ji".....:L.;:,;'e';...'.. <is, <br />~~~~~...~ <br />:'. ~~~wl""" <br />.\?<).J'.!:, ,...'... ..... <br />:,......>i<:.......\'.. ....,::>~;!; <br />:.XL'.,'.:,::::......,. <br />.>:::.:.>:,,:;,:;,<~ .. <br />.:.....;:....../";:;;.. fVi::!(~;;:;( <br />, '}/);;{,2: <br />:':>'./. .j;,.,-:'" . <br />::.' .. .\.}< ,,,,..: <br />"'f.''',...;, "'.'.' <br />i..:>..'/' :'.......:.:. <br /> <br />>\"L.. ;:>c> ...... .;; <br /> <br /> <br />JfAllI <br /> <br />lb'..; ",.;, i:rI::,:" <br />,::,,/C?;;. /. <br />;i:;'YE};; '.', <br />'<';.<-' <br />:.\ <br />r~~;~~:~~~~ <br /> <br />:";,~\:':! <br /> <br />characteristic-that of their dependence on ground water when growing under <br />natural conditions. In this connection it is important to know that they will <br />grow under artificial conditions also, such as when irrigation water is supplied <br />by man. <br />In the western United States about 80 species of plants have been identified <br />as phreatophytes. No attempt has been made to list the species of phreatophytes <br />for the arid regions of the world, but doubtless such a list would be much larg- <br />er. The ten most widespread phreatophytes of low economic use in the western <br />United States are: <br /> <br />Saltcedar T amarix gallica Willow Salix sp. <br />Batamote Baccharis sp, Arrowweed Pluchea sericea <br />Greasewood Sarcobatus vermi- Mezquite Prosopis sp. <br /> culatus <br />Rabbitbrush Chrysothamnus sp, Alder Alnus ap, <br />Saltagrass Distichlis stricta Cottonwood Populus sp. <br /> <br />Not all phreatophytes are plants of low economic value. Alfalfa, a very <br />common phreatophyte, is an important plant to the stock-raising industry. Owing <br />to its high economic v~ue, it oeurrs largely as a cultivated and iri~ated crop <br /> <br />PHREATOPHYTES AS INDICATOR PLANTS <br /> <br />.... <br />;;,S'-;" Ii <br />..' ,:o' './/{ <br /><..?,::{," ';:"",,,;,.?, '/." <br />;/;.......>, ..... ),;.,.(;,(.<~ <br />'..........,.,.......:..:,: 'C\ <br />.:,<,':..'..,'... J,..;.:.t~~S:~.)..;'<~.'\i;.'.;. ':"":':"'.:\""."./..;,. '::....,,:';;'.,..'.."'. .,.... ""<:~:',.< .... ..,. .....;'...:i.:,;:: ,. ." -"'. '....:>...... '." :.' ;..,..,.<:"....: <.:.,,...}<,. 'ii',' <br />:.,;;<!:,..;: <:,:" ';.",'; "". ,...":'\.::....\.'..;"."'.;;;;r;:{~ .;....;..{;;;:,:;;-.,..'} :<:.,...<..::..;".::> ...,.i',::~<;:;:>::(;:~'::C;.;.::'::;;;.;i.':..;?;..:,' <br />:t:.: ::;,ii::::'~:~;h?:,':\;,'; "'.' ..' ."< :::";:"':~;:;r;,: !:ti,~,;;;,t -:; i ;;C;':' ;' ":;?j";;~'/:';'."'D !<,:/,~~?":::,;:,,?:,>,,,:~";t;\;!. <br />'{i.\;;;:r;:},.(i.,.;,..;...;.....;.; ........... .,t'?,o;'/5y;;>i);:;:"; ';.' /.:::: i" ,"/ ,~;~;] " c'.". XI:...,;,;.>>:::....':;.,;, <br />:,:,<:.;.,....... ", ....,:',<i:>~,ji,... ";'::,;:?' ..'.:..\.:'\:!;.:....:;~,.;:L'>>;)';/; <br /> <br />~,,:~\,,\;;ii~~;~:~~~'~~::'~~~,:~~ii~:":'g~;~;.,,{'~:!,~~,::}, <br /> <br />The occurrence and growth of phreatophytes are controlled largely by three <br />primary factors -climate, depth to the ground water, and quality of the ground <br />water. A considerable amount of information concerning the water supply- and <br />climate of an area may be gained from a knowledge of these factors and their <br />effect on the various species. <br />As to the climatic factor, the element of temperature is the most important <br />control. Some phreatophytes grow only in a warm climate, other's only in a <br />cool climate, and still others have a wide range of tolerance from hot to cool. <br />For example, such plants as saltcedar, mezquite, batamote, and arrowweed are <br />indicative of a warm climate in an area of generally low altitude. In the western. <br />United States these plants occur largely south of the 37th parallel and below <br />an altitude of about 5,000 feet. A cool climate is indicated by greasewood and <br />rabbithrush, which in the United States are found generally north of the 37th <br />parallel, or if south of it above 5,000 feet in altitude. Willow, cottonwood, or <br />saltgrass are not indicative of any particular climatic conditions, for these plants <br />thrive over a large temperature range. <br /> <br /><:' <br /> <br />':,.;.< <br />:','. <br /> <br />2, ,: <br /> <br />';~{ <br /> <br />;> <br /> <br />;,1,.;,,,, <br />