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Departamento de Investigaciones Científicas y Tecnológicas


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UNIVERSIDAD DE SONORA

Departamento de Investigaciones Científicas y Tecnológicas


In collaboration with

ARIZONA STATE UNIVERSITY


RIPARIAN VEGETATION AND WATER QUALITY ON THE SAN PEDRO RIVER, SONORA, MEXICO”


FINAL TECHNICAL REPORT


Principal Investigator

Gilberto Solis-Garza


Collaborators

Agustín Gomez-Alvarez

Rigoberto López-Estudillo

Arturo Villalba-Atondo

Lorena Bringas-Alvarado

Ana María Pérez-Villalba


Funded by:

TRANSBORDER WATERSHED RESEARCH PROGRAM”

The Southwest Center for Environmental Research and Policy (SCERP)


March 2000

^ TABLE OF CONTENTS


Page


LIST OF TABLES iii


LIST OF FIGURES v


ABSTRACTS vi


INTRODUCTION 1


OBJECTIVES 1

Specific objectives 2


METHODS 3

Study area 3

Research Approach 4

Floristic Composition and Species Abundance of Herbaceous 4

and Woody Riparian Vegetation

Water Quality 7

Water Quantity 9


RESULTS 10


Floristic Composition and Species Composition and Stand Structure 10

of Woody and Shrubby Riparian Vegetation

Floristic Composition 10

Stand Structure of Woody and Shrubby Riparian Vegetation ^ 15

Relative Density 15

Basal area 18

Frequency 18

Mean Height 23


Vegetation Composition and Structure Vegetation Conclusion 26


Water Quality 27

Quality Assurance/Quality Control (QA/QC) 27

Clean Sampling Equipment 27

Calibration and Frequency Field Equipment Procedures 27

Field parameter 27

Analytical Parameters 27

Quality Control Samples 27

Equipment blanks 27

Field Blanks 28

Travel blanks 28

Indicative of Data Quality 28

Precision 28

Accuracy 28

Cation/Anion Balance 28


Physical, Chemical and Heavy Metals Parameters 29

Physical Parameters 29

Chemical Parameters 29

Dissolved Oxygen 29

Chlorides 29

Sulphates 38

Total Dissolved Solids 38

Nitrate 38

Nitrite 38

Heavy Metals Parameter 38


Water Quality Conclusion 41


Water Quantity 42


RECOMMENDATIONS 45


Vegetation Composition and Vegetation Structure Recommendations 45

Water Quality Recommendations 46

Water Quantity Recommendations 47

ACKNOWLEDGMENTS 48


BIBLIOGRAPHY 49

APPENDIX 51

^ LIST OF TABLES Page

  1. Geographic locations of the floristic and vegetation sampling transects 4

  2. Geographic locations of the water quality sampling sites 7

  3. List of species vouchered in the eight transects on the San Pedro River 11

  4. Summary of plants by classification and the largest families and genera 16

  5. Plant species of the San Pedro River, Sonora: Life form,

distribution, grade of Frequency (F), and wetland indicators classes (I)+ 20

  1. Composition, stand structure and importance value of tree species

on the San Pedro River, Sonora, Mexico. 24

  1. Composition, stand structure and importance value of shrub species

on the San Pedro River, Sonora, Mexico. 25

  1. Results of the first surface water and ground water quality (Physical

and Chemical Parameters) sampling on the San Pedro River, Sonora,

Mexico, during February 18 and 19, 1999. 30

  1. Results of the second surface water and ground water quality

(Physical and Chemical Parameters) sampling on the San Pedro River,

Sonora, Mexico, during April 30 and May 1, 1999. 31

  1. Results of the third surface water and ground water quality

(Physical and Chemical Parameters) sampling on the San Pedro River,

Sonora, Mexico, during August 18 and 19, 1999. 32

  1. Results of the fourth surface water and ground water quality

(Physical and Chemical Parameters) sampling on the San Pedro River,

Sonora, Mexico, during November 10, 11 and 12, 1999. 33

  1. Results of the first surface water and ground water quality

(Heavy Metals) sampling on the San Pedro River, Sonora, Mexico,

during February 18 and 19, 1999. 34

  1. Results of the second surface water and ground water quality

(Heavy Metals) sampling on the San Pedro River, Sonora, Mexico,

during April 30 and May 1, 1999. 35

  1. Results of the third surface water and ground water quality

(Heavy Metals) sampling on the San Pedro River, Sonora, Mexico,

during August 18 and 19, 1999. 36

  1. Results of the fourth surface water and ground water quality

(Heavy Metals)sampling on the San Pedro River, Sonora, Mexico, during

November 10, 11 and 12, 1999. 37

  1. Mexican water quality standards. Criterios Ecologicos de Calidad de Agua. 40

  2. Stream Discharge in five sampling stations on the San Pedro

River, Sonora, Mexico. 43

^ LIST OF FIGURES Page

  1. Location of vegetation sampling stations on the San Pedro River,

Sonora, Mexico. 5

  1. Location of water quality sampling stations on the San Pedro River,

Sonora, Mexico. 8

  1. Relative tree density by diameter size classes. 19

  2. Stream discharge in five sampling stations on the San Pedro River,

Sonora, Mexico. 43

  1. Monthly average temperature, precipitation, and evaporation, period

1962-1999 in Naco, Sonora.


ABSTRACTS


Tree species diversity found in the San Pedro River floodplain was low. Populus fremontii and Salix gooddingii were the dominant species. Tree density ranged form 0.12 to 15.49 stems/1,000 m2 an the total basal area of the community was 2.61m2/1,000 m2, Populus fremontii contributed with 73.9%. The 82.5% of the total trees diametric size class was from > .5 dm to 2 dm. Cottonwood was the only tree specie represented in the 11 size classes. Seedling reproduction (<.5 dm) was scarce along of the river with a density that range from 0 to 0.27 individuals/1,000 m2

The understory was composed by 12 shrub species along the San Pedro River. Mesquite and seepwillow were the dominant species. Shrub density ranged form 0.24 to 53.66 stems/1,000 m2. and the total basal area of the understory was 0.12 m2/1,000 m2. Mesquite and seepwillow obtained the highest density.

Along the San Pedro River, many species have a narrow range for depth to groundwater. For example, juveniles of the pioneer species tree Populus fremontii and Salix gooddingii, grew only where groundwater had from 0 to 2 m depth (Stromberg et al., 1996). In the other hand, Prosopis velutina grew from 5 to 8 m depth. Then, it is possible to suggest that the shallow and groundwater decline over the last years in the San Pedro River, could produce a displaced of the riparian vegetation by mesquite and saltcedar present today in the floodplain terraces.

The results obtained in this study in surface water and ground water samples indicated that total dissolved solids, sulphates, nitrates; nitrites and heavy metal including: copper, iron, and manganese values were the parameters that exceeds in the sampling stations 1 (Arroyo Cananea Vieja) and 2 (El Barrilito) the recommended maximum contaminant levels in the Mexican Drinking Water Standards (S.E.D.U.E., 1989) in the San Pedro River. These highly elevated levels were found in the first two study sites near Cananea Mine.

INTRODUCTION


The riparian habitats of the northwest of Mexico and southwest of the United States form a minor proportion of the general landscape, but they have attracted a great deal of attention due to economic, ecological and social importance.


In the past and today, they have been the primary sites for agriculture, ranching, urbanization, mining, among others uses. The riparian habitats provide useful products including: water, forage, protection to wildlife, erosion control, and increase in water quality and quantity. However, the ability of a given site to provide these products is dependent on the vegetation present (Arizona Riparian Council. 1995).


The San Pedro River watershed, highly valued for its biological diversity, is an international river basin and aquifer complex. It is important to determine the influence of residential use, industries, mining, agriculture and ranching, on the quality and quantity of the aquifer and the response of the riparian habitats to water availability and quality. These riparian habitats support the largest remaining Southwest broadleaf riparian forest, often considered as the most threatened forest type. These forest also form an important corridor of Neotropical migratory birds


Despite their importance, limited information is available concerning qualitative and quantitative characteristics of riparian communities in northwest Mexico.


Studies of Sonoran riparian areas are scarce. A survey of the literature revealed that no vegetative work has been previously done in San Pedro River stream. Elsewhere in Sonora, Gentry et. al. (1942) discusses riparian vegetation along the Rio Mayo, White (1948) surveyed the region of the Rio Bavispe, Solis et. al. (1993) surveyed the Rio de los Ajos, and Solis et. al. (1998) surveyed the Santa Cruz River. Brady et al. (1985) described the structural characteristics on the San Pedro River near to Winkelman, AZ and Stromberg et al. (1996) studied the effects of groundwater decline on riparian vegetation in the San Pedro National Riparian Conservation Area in Arizona.


In relation to surface and groundwater water quality, Gomez-Alvarez et al. (1996) and Villalba-Atondo et al. (1998) did studies on the San Pedro River in Sonora.


OBJECTIVES


The general objectives of this paper were three:


a) To determine floristic composition and abundance composition on the San Pedro River, Sonora.


b) To determine water quality on the San Pedro River in Sonora and


c) To determine stream discharge (m3/sec), in the San Pedro, River, Sonora.

Specific objectives:


a) To determine floristic composition and abundance composition of woody and herbaceous riparian vegetation from Ejido Morelos to Rancho Los Corrales, Sonora, Mexico and:


b) To determine surface and groundwater water quality from the Cananea city to Rancho Los Corrales at San Pedro River, Sonora, Mexico.


c) To determine stream discharge (m3/sec) from El Barrilito to Rancho Los Corrales at San Pedro River, Sonora, Mexico.

METHODS


^ Study area


The San Pedro River originates in the desert grasslands, near Cananea, city, Sonora, Mexico. It flows in a northerly direction to its confluence with the Gila River, southeast of Phoenix, Arizona. The total length of its course is 250 kilometers of which 65.6 kilometers are in Sonora.


The river drains a watershed of 1,800 km2 in Mexico representing the 15.6 % of the total basin. The flows from Mexico represent 61% of the flow in the San Pedro River at the Charleston Gage.


The basin is located in north-central Sonoran between the coordinates 30º 52´ and 31º 20¨ North latitude and 110º 06¨ and 110º 31¨ West longitude. The study area is located between the coordinates 30º 58´ and 31º 19´ North latitude and 110º 18¨ and 110º 08¨ West longitude. The basin is delimited for the Sierra de los Ajos on the eastern side, San Jose to the north side, Sierras La Mariquita/Elenita on the western edge, Huachuca mountains near to the national border and Cananea city in the southern limit.


In the San Pedro basin the landscape is gently undulating with low relief, and the vegetation is characterized by a ^ Chihuahuan semidesert grassland, a typical mesquite grassland community and a riparian vegetation community. The physiognomy of the Chihuahuan semidesert grassland is as follow: in the lower limit of the semidesert grassland is at 1200 - 1400 m elevation, forming a mosaic landscape with desertscrub, in the middle limit of the semidesert grassland plateau or “mesa” at 1300 - 1700 m offers some landscape diversity due to the vegetation distribution and in the upper limit, with evergreen woodland, is at 1600 - 1900 m elevation.


The riparian communities are mainly groves of cottonwood, goodding willow, seepwillow, burrobrush and sacaton, and are considered as one of the finest remaining desert riparian ecosystems. Fremont cottonwood-Goodding willow forest occur along floodplains of large, low gradient (<0.005  0.002 m/m (Szaro 1989) in wide perennial stream and in unconstrained valley.


The climate of the watershed is arid to semi-arid. The mean annual temperature is from 12 to 18ºC, and the mean annual precipitation is 44 cm/year, 65 % of which falls during July to September. The mean potential evaporation rate is almost 2200 mm/year.


In most portions of the river, surface flows occur during the two rainy seasons. The highest annual flows occur during the summer, from July to September and the winter surface flows from December to January. In the northern part of the river the surface flows is perennial with enough water to support several species of fish.


The National Water Commission, a Mexican governmental agency, report a mean annual groundwater pumping extraction of 33.6 million cubic meters from 223 wells and a mean annual groundwater recharge of 16 million cubic meters (INEGI, 1993). The mean annual extraction of the Cananea mine is 12.5 million cubic meters. The main economical activities on the San Pedro basin are: mining, agriculture, and ranching.

^ Research Approach


The research approach involved collecting data on flora, vegetation, and water quality and quantity within the floodplain along the gradient of the stream. A preliminary survey of the area was conducted to select the collection sites. The sites were chosen by visual observation based in the criteria of relative homogeneity of the dominant species. The sites for water quality were chosen in representative locations. along the gradient of the river.


^ Floristic Composition and Species Abundance of Woody and Shrubby Riparian Vegetation


Eight transects distributed approximately 3.5 kilometers apart were selected between Ejido Morelos to Rancho Los Corrales (Map 1 and Table 1).


Transects were aligned perpendicular to the stream. Plots were 5 x 20 m (long axis parallel to the stream) and were located at 10 meter interval (5 m apart) from both edges of the stream at the location of each transect. The number of plots per transect varied according to the width of the riparian zone.


In September, 1999, woody plants were sampled, by species for stem density, basal diameter, height and frequency. All trees, from established seedlings, or saplings, to the largest individuals were recorded in 11 diameter size classes (20 cm above of the ground): >.5 dm, 1-2 dm, 2-3 dm, 3-4 dm, 4-5 dm, 5-6 dm, 6-7 dm, 7-8 dm, 8-9 dm, 9-10 dm, and > 10 dm.. Reproduction, from 0 dm to 0.5 dm, was also recorded. Plants with a diameter of > 0.5 dm were recorded as tree, those with diameter size classes of <0.5 dm as seedlings. Also, all shrubs were recorded in 11 diameter size classes. The size classes are the same as trees by expressed in cm.


Trees heights were recorded according to one of six height classes: < 1 m, 1-2 m, 2-5 m, 5-10 m, 10-20 m, and >20 m.


The trees, shrubs herbaceous and grasses were sampled and collected for floristic composition and frequency in February, April, June and September of 1999 in the same transects for abundance. Each segment was visited four times. Species lists do provide an indication of species diversity and a starting reference for future studies.


Table 1. Geographic location of the floristic and vegetation sampling transects


Site Number Site Name Latitude Longitude

1 Los Corrales 31º 19´ 26.4” N 110º 08¨ 48” W

2 El Álamo 31º 18´31” N 110º 08¨48” W

3 Barbacoa 31º 17¨57.9¨” N 110º 09¨41.1” W

4 El Nogal 31º 17¨04.9” N 110º 09¨54.1”W

5 El Pedregón 31º 16¨42.5 ”N 110º 10¨20.3” W

6 La Coja 31º¨15¨25.1” N 110º 10¨48.1” W

7 San Pedro Palominas 31º 14¨34.7” N 110º 11¨18.5” W

8 Ejido Morelos 31º 12¨37.1” N 110º11`38.2” W




Fig 1. Location of vegetation sampling stations on the San Pedro River, Sonora, México.


A voucher for all the species encountered at each transect were collected (trees, herbaceous annuals and perennials, grasses and vines). Epiphytic, vines, and cacti species were considered as shrubs in the life form. The identification of the vouchers was conducted in the Universidad de Sonora (USON) in the Departamento de Investigaciones Cientificas y Tecnologicas herbarium.


The voucher were deposited in the herbarium USON of the University of Sonora in Hermosillo, Sonora. The nomenclature (species name and synonyms) and identifications were accomplished through the use of Lehr (1978), and Kearney and Pebbles (1961).

^ Water Quality


Water quality were sampled quarterly at ten study sites, located in representative locations, 6 for surface water and 4 for groundwater positioned along the San Pedro River from Cananea city to Rancho Los Corrales near to the Mexico - USA border (Map 2 and Table 2).


The samples of water quality were collected during the months of February, May, August and November of 1999. Surface stream water and groundwater were sampled for physical parameters such as: pH, water temperature, suspended solids, dissolved oxygen, and electrical conductivity; for chemical parameters such as; chlorides, sulphates, phosphorus, carbonates, nitrogen as nitrates; nitrogen as nitrites, and ammonia, and for total heavy metal (cadmium, calcium, cobalt, copper, total chromium, iron, potassium, magnese, nickel, manganese, zinc, sodium, and lead). Samples were collected, preserved and analyzed in following APHA and EPA recommendations.


Table 2. Geographic location of the water quality sampling sites


Site Number Site Name Latitude Longitude

1 Arroyo Cananea Vieja (surface water) 30º59´ 57” N 110º17´01” W

2 El Barrilito (surface water ) 31º02´30” N 110º13´33” W

3 La Sauceda (groundwater) 31º12´18” N 110º11´51” W

4 Ejido Morelos (groundwater) 31º13´04” N 110º13´40” W

5 Ejido Morelos (surface water) 31º12¨37” N 110º11`38” W

6 San Pedro Palominas (groundwater) 31º 14¨34” N 110º11¨18” W

7 San Pedro Palominas (surface water) 31º 14¨34” N 110º11¨18” W

8 El Pedregon (surface water) 31º 16¨42 ”N 110º10¨20” W

9 Los Corrales (groundwater) 31º 19´ 58” N 110º 08¨ 59” W

10 Los Corrales (surface water) 31º 19´ 26” N 110º 08¨ 48” W


Samples were performed in the water quality laboratory of the University of Sonora. A quality assurance and quality control plan were developed including: sampling plan, sample preservation; measurement and calibration procedures, field and laboratory quality control checks (replicate, blank samples; etc), analysis, validation and reporting procedures.


^ Water Quantity


Stream discharge were sampled quarterly at six study sites, located in representative locations positioned along the San Pedro River from El Barrilito to Rancho Los Corrales near to the Mexico - USA border (Map 2 and Table 2). The sampling stations were the same used for surface water sampling.


A flotation method of discharge was used to determine the surface water discharge (m3/sec). The method consists of obtaining a cross-sectional area in each station in the one which will be calculated its area (A). This variable is defined with the measurement of the depth each 15 cm on the section. Once obtained the total area, the water speed was measured with the use of a float in a distance of 10 m. (Molloy and Stuble, 1988).


These last variable (distance in m and time in seconds) were necessary for the calculation of the velocity of the water passing through the cross sectional area. Since surface velocity is different through the section, the float exercise is carried out at least in 5 occasions in different such section points. It is made the explanation that the present method does not consider the difference of velocity that could have the flow with respect to the water depth. Once obtained the area variable (m2) (Area) and mean surface velocity (V) (m/sec) is obtained the stream discharge (Q) with the equation: Q = V * A; Q = m/sec * m2; Q = m3/sec) for the calculation of the stream water discharge from the San Pedro River streambank.


RESULTS


^ Floristic Composition and Stand Structure of Woody and Shrubby Riparian Vegetation


Floristic Composition.


The eight sites yielded a flora of 107 species in 82 genera and in 43 families. True to the pattern everywhere on this part of the continent, the families with greatest number of genera and species were: Asteraceae with 11, Poaceae with 10 and Fabaceae with 6 (Table 3). A summary of the groupings and numbers of best represented groups are listed in the Table 4.


The genera best represented were: Astragalus and Senecio with 9 and 4 genus, respectively. According to literature reviewed, Astragalus allochrus and Astragalus praelongus, which were presence in the San Pedro River, are indicators of soils rich in selenium.


Of the total species identified in the eight transects in the San Pedro River, 56 were herbaceous (52.3%), 15 grasses 28 shrubs, and 8 trees. Obligate riparian species were represented by a total of 5 species: ^ Salix gooddingii, Berula erecta, Rorippa nastartium-aquaticum, Polygonum argyocoleon, and Veronica americana.


The highest number of species were identified in the transects 1, 2 and 3 located near to US - Mexican border (Table 5). The mean diversity for these transects was 56 species. The total mean diversity for the 8 transects was 51.2 species. Arizona walnut a tree species considered as threatened in Mexico was present on the San Pedro River in the 75% of the sites sampled.


A total of 15 non-native species were identified in the San Pedro River floodplain: three were grasses, seven herbaceous, three shrubs and one tree (Table 5). The establishment of these exotic species can to lead to ecosystem changes. The presence of exotic plant species is often a symptom of altered ecosystem processes.


Saltcedar, a species that has displaced native vegetation in large tracts at other riparian areas in the west, could be considered as recently established in the San Pedro River due to a DBH less than one decimeter. It was found in four of the eight samples sites. Another important species found in the eight samples sites was Bermuda grass that compete with native understories of cottonwood-willow forests.


Fremont cottonwood and goodding willow were the most common trees occupying the eight study sites (100% of presence) in the San Pedro River floodplains.


^ Baccharis salicifolia and velvet mesquite were the shrubs species found in the 100% of the sites sampled. Another important shrub species was Hymenoclea monogyra.


Cynodon dactylon, Muhlenbergia rigida and Sporobolus airoides were also present in 100% of the sites sampled.



^ Table 3. List of species vouchered in the eight transects in the San Pedro River. Synonyms appears on

the right in brackets.

 

 










PTERIDOPHYTA







Equisetaceae







Equisetum

laevigatum A. Braun

(^ E. kansanum) J. Schatfner










SPERMATOPHYTA







Gymnospermae







Ephedraceae







Ephedra

trifurca Torr.













ANGIOSPERMS







DICOTYLEDONS
















Amaranthaceae







Amaranthus

albus L.




Amaranthus

palmeri S. Watson













Anarcadiaceae







Rhus

microphylla Engelm.













Asteraceae (Compositae)







Agroseris

heterophylla (Nutt.) Greene




Baccharis

salicifolia (Ruiz & Pavón) Pers.

(^ B. glutinosa) Pers.

Baccharis

sarathroides A. Gray




Chrysothamnus

nauseosus (Pall.) Britt.




Cirsium

neomexicanum A. Gray




Cirsium

arizonicum (A. Gray) Petrak.




Helianthus

annuus L.




Hymenoclea

monogyra Torr. & A. Gray




Isocoma

tenuisecta Greene

(Haplopappus tenuisectus)







(Greene) Blake

Iva

axillaris Pursh.




Senecio

flaccidus Less. var. douglasii (DC.)

(S. douglasii D.C.)




B. L. Turner & T. M. Barkley




Senecio

salignus DC.




*Senecio

vulgaris L.




*Sonchus

asper L.




Xanthium

strumarium L.

(^ X. saccharatum Wallr.)










Bignoniaceae







Chilopsis

linearis (Cav.) Sweet













Boraginaceae







Cryptantha

angustifolia (Torr.) Greene













Brassicaceae (Cruciferae)







*Brassica

campestris L.




Descurainia

pinnata (Wallt.) Britt.




Lepidium

lasiocarpum Nutt.




^ Rorippa nasturtium

-aquaticum (L.) Hayek

Nasurtium officinale R. Br.

Sisymbrium

irio L.













Cactaceae







Echinocereus

fendleri Engelm.




Opuntia

phaecantha Engelm.




Opuntia

spinosior (Engelm.) Toumey

 

(Cont´d)
















Capparaceae







^ Polanisia dodecandra (L.)

ssp. trachysperma (Torr. & A. Gray) Iltis

P. trachysperma (Torr. & A. Gray)










Caprifoliaceae







Sambucus

mexicana Presl.













Chenopodiaceae







Atriplex

canescens (Pursh) Nutt.




*Salsola

tragus L.













Convolvulaceae







*Convolvulus

arvensis L.













Cucurbitaceae







Cucurbita

digitata A. Gray




Cucurbita

foetidissima H.B.K.













Cyperaceae







Cyperus

sp.













Euphorbiaceae







Euphorbia

postrata Ait.













Fabaceae (Leguminosae)







Acacia

neovernicosa Isely

A. vernicosa Standl.

Acacia

farnesiana (L.) Willd.

A. smallii Isely

Astragalus

allochrous A. Gray




Astragalus

didymocarpus Hook & Arn




Astragalus

gilensis Greene




Astragalus

mollissimus Torr. var. bigelovii (A. Gray) Barn.

A. bigelovii A. Gray

Astragalus

nuttallianus D.C




Astragalus

praelongus Sheldon.




Astragalus

sesquiflorus S. Watson




Astragalus

tephrodes A. Gray




Astragalus

wootonii Sheldon.




Lupinus

concinnus Agardh.




*Melilotus

albus Desr.




*Melilotus

indicus L.




Mimosa

aculeaticarpa Ortega var. biuncifera (Benth.) Barneby

Prosopis

velutina Woot.

( P. juliflora (Swartz) DC.







var. velutina (Woot.) Sarg.

Fumariaceae







Corydalis

aurea Willd.













Hydrophyllaceae







Nama

hispidum A. Gray




Phacelia

corrugata A. Nels.













Juglandaceae







Juglans

major (Torr.) Heller.













Labiatae







Hyptis

emoryi Torr.




*Marrubium

vulgare L.

 

(Cont´d)
















Loasaceae







Mentzelia

involucrata S. Watson




Mentzelia

multiflora (Nutt.) A. Gray.




Mentzelia

pumila (Nutt.) Torr. & A. Gray













Malvaceae







*Malva

parviflora L.




Sphaeralcea

angustifolia (Cav.) G.Don













Martyniaceae







Proboscidea

parviflora (Woot.) Woot. & Standl.













Nyctaginaceae







Boerhavia

erecta L.













Oleaceae







Fraxinus

pennsylvanica Marsh ssp.







velutina (Torr.) G. N. Miller




Onagraceae







Oenothera

kunthiana (Spach) Munz.













Papaveraceae







Argemone

ochroleuca Sweet













Plantaginaceae







*Plantago

major L.













Polygonaceae







Polygonum

argyrocoleon Steud.




Rumex

sp.













Ranunculaceae







Ranunculus

uncinatus D. Don Ex G.Don

(^ R. bongardii) Greene










Rhamnaceae







Condalia

warnockii M.C. Johnst.




Zizyphus

obtusifolia (Hook. ex. Torr. & A.Gray) A.Gray.

Condalia lycioides (A. Gray)







Weberb. var. canescens (A. Gray)

Salicaceae







Populus

fremontii S. Watson




Salix

bonplandiana H.B.K.




Salix

gooddingii Ball.













Scrophulariaceae







Veronica

americana (Raf.) Schwein













Solanaceae







Datura

discolor Bernh




Datura

lanosa Barclay ex. Bye




*Nicotiana

glauca Graham.




Solanum

rostratum Dunal.













Tamaricaceae







Tamarix

chinensis Lour

(T. pentandra) Pallas

(Cont´d)
















Ulmaceae







Celtis

reticulata Torr.













Umbelliferae







Berula

erecta (Huns.) Coville













Viscaceae







Phoradendron

tomentosum (DC.) A. Gray.

(P.flavescens (Pursh) Nutt.)










Vitaceae







Vitis

arizonica Engelm.

(V. treleasei Munsan ex Bailey)



















MONOCOTYLEDONS
















Agavaceae







Nolina

microcarpa S. Watson













Juncaceae







Juncus

interior Wieg. var. arizonicus (Wieg) Herm.













Poaceae (Gramineae)







Aristida

adscensionis L.




Aristida

ternipes Cav.




Bouteloua

curtipendula (Michx.)Torrey




Bouteloua

hirsuta Lag.




Bouteloua

rothrockii Vasey.




*Chloris

virgata Swartz




*Cynodon

dactylon (L.) Pers.




Eragrostis

curvula (Schrad.)




Eragrostis

erosa Scribn.




*Eragrostis

lehmanniana Ness.




Heteropogon

contortus (L.) Beauv.




Muhlenbergia

rigida (H.B.K.) Kunth.




Setaria

leucopila (Scribn.& Merr.) K. Schum.




*Sorghum

halepense (L.) Pers.




Sporobolus

airoides (Torr.) Torr var. airoides

 










*Non-native species



















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