<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 />
|