Title: Growth Differences Among Widely Separated Geographic Access

Title: Growth differences among widely separated geographic accessions of fourwing saltbush (Atriplex canescens) in the Great Basin desert, New Mexico, USA.

KEVIN FITZSIMMONS

CYNTHIA LOVELY

EDWARD GLENN

Department of Soil, Water and Environmental Science

University of Arizona

Tucson, USA

Acknowledgments: Supported by funding from the Electric Power Research Institute and Arizona Public Services. We thank the USDA Shrub Laboratory, Provo, Utah and the USDA Plant Materials Center, Tucson, Arizona, for providing some of the seed accessions and Dr.'s D. McArthur, S. Meyer and S. Sanderson for information on the taxonomy of the accessions. Carl Woolfolk and Howard Bradley of Arizona Public Services provided generous site support without which we could not have completed the study.

Address correspondence:

Kevin Fitzsimmons, Environmental Research Laboratory

2601 E. Airport Drive, Tucson, Arizona 85706, USA

Running Title: Growth differences of A. canescens accessions

Abstract

As part of a revegetation project, sixteen accessions representing five varieties of Atriplex canescens (Pursh) Nutt., were grown in a common garden experiment in northwestern New Mexico, USA. The accessions were collected from Sonora, Mexico to Idaho, USA and from near sea level to 2800 m elevation. Plants were grown for 16 months on native soil irrigated with saline water (4800 - 9400 mg L-1) collected from a seepage intercept system surrounding the ash disposal ponds at a coal-fired power plant, at 1660 m elevation. All but var. grandidentatum from Mexico had high survival but there was a four-fold variation in the amount of net growth among accessions. The northern accessions had 50% greater net growth than the southern accessions. Revegetation projects that utilize A. canescens need to match the seed source to the local site conditions. Saline water recovered from the leach fraction below power plant ash ponds can be used to establish stands of A. canescens for revegetation projects.

Keywords: Salinity, halophyte, Chenopodiaceae, revegetation, irrigation with ash pond seepage water

Introduction

In many arid environments, high-quality water is not available to support the establishment of plants for revegetation projects. On the other hand, mines and power plants often generate waste water streams that represent a disposal problem due to high dissolved solids content. We conducted a two year trial to determine if saline leachate collected from intercept lines from a series of unlined ash ponds in an arid environment could be used to establish test planting of the desert shrub, fourwing saltbush, Atriplex canescens (Pursh.) Nutt. If successful, the leachate could be used to establish vegetation that subsequently could intercept saline water migrating away from the ash piles in the shallow soil (C. Woolfolk, Arizona Public Services, personal communication).

Atriplex canescens is the most widespread saltbush in North America. It is a valuable forage shrub and has been used in arid zone restoration projects around the world, including Asia (Aro et al., 1989), the Mid East (El-Din, 1993; Tarrad et al., 1991), North Africa (Le Houerou, 1994) and Europe (Equita, 1992). It is an extremely plastic species, containing at least 6 varieties as well as numerous ecotypes within varieties differing in ploidy level and morphology (Sanderson and Stutz, 1994), sexual expression (McArthur et al., 1992), salt tolerance (Glenn et al., 1996), water use efficiency (Senock et al., 1991), nitrogen metabolism (Sisson and Throneberry, 1986) and growth performance (Petersen et al., 1987).

Unfortunately, revegetation projects rarely attempt to match a particular cultivar or variety to site requirements. Seed companies generally supply A. canescens as a generic product, sometimes using established cultivars but more often supplying wild seed collected from unspecified locations. Hence, germplasm that is poorly adapted to local site conditions might be used in many projects. Therefore a second purpose of our study was to determine if there are significant differences in growth or survival of A. canescens accessions grown in a common garden environment.

Materials and Methods

The plot was located at Arizona Public Services' Four Corners Power Plant in Farmington, New Mexico, at 1660 m elevation and was near the middle of the latitude range of the species (Figure 1). The 16 accessions of A. canescens used in the test planting are listed in Table 1. The accessions represented five varieties collected throughout the latitude range of the species, from near sea level to 2,800 m elevation. Seeds from the local population of A. canescens were not available at the beginning of the trial and were not included in the experiment. Taxonomic designations were based on descriptions in Sanderson and Stutz (1994) and D. McArthur (USDA Shrub Laboratory, Provo, Utah, personal communication). Seedlings were started in a greenhouse in January, 1994 and transplanted to the field in July, 1994 when they were 20-40 cm in height (n = 9-13 per accession). The test plot had previously been cleared of native vegetation. The clay-loam soil had been salt-affected by leachate from an adjacent ash pond. Plants were randomly assigned within an irrigated ridge and furrow plot (16 m x 12 m) with 1 m between plants. Plants were planted on the top of the furrows and the plot was irrigated every 14 days over two growing seasons (July-November, 1994, March-October, 1995) with saline water (total dissolved solids ranging from 4800 - 9400 mg

L-1, avg. 7020 mg L-1 S.E.= 752) (Table 2). Total irrigation volume was 1.3 m3 water m-2. The saline leachate was pumped from the intercept lines which collected seepage from around two of Arizona Public Services’ nearby ash disposal ponds.

Survival and growth (measured by the increase in length of the main plant axis) were evaluated bi-monthly; data collected on surviving plants after 16 months of growth were used to compare accessions. Elongation of the main plant axis generally corresponded to increased plant height but in some cases the main stem became prostrate after transplant, in which case the length of the main stem along the ground was measured.

Results

The plot received 346 mm of precipitation during the 16-month trial in addition to the 1.30 m used for irrigation. During the winter months there were 120 days with temperatures below freezing with an extreme low of -80 C (Table 3). As might be expected the plants from the southern range and lower elevation exhibited less growth and lower survival. Variety grandidentatum from Puerto Penasco, Mexico, had only 62% survival and variety linearis demonstrated the least growth of all accessions(Table 4). Net growth of live plants at 16 months ranged from 0.1 to 0.6 m of length increase among accessions, corresponding to 54-210% increase in the length of the original plant axis. ANOVA showed that accessions differed significantly in net growth (F = 2.83, d.f. = 15, 160, P<0.001). Means were separated using Duncan's Multiple Range test at P<0.05 and they divided into six overlapping groups (Table 4). The top-performing accession was var. occidentalis from Littlefield, Arizona, at the same latitude but lower elevation than the test site, whereas the poorest-performing accessions were the varieties from the southern end of the range at Puerto Penasco, Mexico.

Means of growth measurements were significantly correlated with the latitude of the collection site (r = 0.52, P<0.05) but not with the elevation of the collection site (r = 0.36, P>0.05), even though latitude and elevations were significantly correlated with each other (r = 0.73, P<0.01). When accessions were divided into those occurring to the south of the test site (n = 6) and those occurring to the north (n = 10), the northern accessions had significantly (P<0.05) greater net growth than the southern accessions (means = 442 and 310 mm, respectively) by the Student’s t-test. On the other hand, when the accessions were divided into those occurring at lower elevation than the test site (n = 12) and those occurring at high elevation (n = 4), there was no significant difference (P>0.05) between means (373 and 399 mm, respectively). The soil analysis of test and control plots demonstrated that there were differences in pH and conductivity. There was no apparent accumulation of heavy metals in the soil (Table 5).

Discussion and Conclusions

The growth and survival of the various accessions of A. canescens demonstrated that the saline leachate recovered from the ash ponds could be used to establish halophyte shrubs. We conclude that different accessions of A. canescens differ markedly in growth performance and other traits in a common garden setting. At a mid-range site, the northern accessions performed 50% better than the southern accessions and var. occidentalis from Littlefield, Arizona, at a similar elevation and latitude performed best. No single accession or variety can be recommended as a general-purpose seed source for revegetation projects. Rather, seeds collected from plants growing in a similar climatic and edaphic setting near the site might be expected to give the best results. Some restoration projects specify that only native plants can be used for revegetation. The different varieties and ecotypes of A. canescens are stabilized by ploidy differences (Sanderson and Stutz, 1994) and should be regarded as genetically distinct, and not interchangeable for the purpose of revegetation. Only local seed should be used when native germplasm is required. International projects should carefully consider whether introduction of this potentially invasive species is desirable. If introduction is deemed desirable, the seed source and variety should be carefully chosen based on local site conditions. Many thousands of hectares of desert and semidesert in North Africa and the Middle East have already been planted with this species (Le Houerou, 1994), in most cases with no prescreening of accessions to ensure a match with local conditions. This practice could introduce suboptimal genotypes of A. canescens over wide new areas of the arid zones. In addition to the 4-fold variation in net growth among accessions, the plants also differed in salt tolerance and tendency to accumulate Na and K (Glenn et al., 1996), which affects their forage value. We also noticed morphological and growth habit variations among varieties similar to those already described (Sanderson and Stutz, 1994).

The primary goal of the project was achieved by demonstrating that A. canescens could be established using saline leachate. The plants maintained growth and high survival up to May, 1997, a year after the irrigation had been discontinued (C. Woolfolk, personal communication). Although soil salts were higher in irrigated as compared to unirrigated samples, no heavy metals were detected at level of concern in the leachate water or soils. The 1.30 m of water applied to establish the plants is low compared to the long term potential of plants to intercept water over a typical life span of 10 years or more.

References

Aro, S., M. Sultani, M. Asghar, and J. Keatinge. 1989. Introduction of fourwing saltbush (Atriplex canescens) into degraded rangelands in upland Baluchistan, pp. 1501-1502, in Proceedings of the XVI International Grassland Congress. Association Francaise pour la Production Fourragere, Centre National de Recherch Agronomique, Versailles, France.

El-Din, S. 1993. Effect of grazing season on the productivity parameters of five range shrubs. Arabian Gulf Journal of Scientific Research 11: 209-219.

Enguita, I. 1992. On the introduction of forage shrubs into the dryland areas of Aragon. ITEA Produccion de Animals 88: 129-132.

Glenn, E., R. Pfister, J. Brown, T. Thompson, and J. O'Leary. 1996. Na and K accumulation and salt tolerance of Atriplex canescens (Chenopodiaceae) genotypes. American Journal ofBotany 83: 997-1005.

Le Houerou, H. 1994. Forage halophytes and salt-tolerant fodder crops in the Mediterranean Basin, pp. 123-137, in V. Squires and A. Ayoub, eds., Halophytes as a Resource for Livestock and for Rehabilitation of Degraded Lands. Kluwer Academic Publishers, Dordrecht, Netherlands.

McArthur, E., D. Freeman, L. Luckinbill, S. Sanderson, and G. Noller. 1992. Are trioecy and sexual lability in Atriplex canescens genetically based?: evidence from clonal studies. Evolution 46: 1708-1721.

Petersen, J., D. Ueckert, R. Potter, and J. Huston. 1987. Ecotype variation in selected fourwing saltbush populations in western Texas. Journal of Range Management 40: 361-366.

Sanderson, S. and H. Stutz. 1994. High chromosome numbers in Mohavean and Sonoran desert Atriplex canescens (Chenopodiaceae). American Journal of Botany 81: 1045-1053.

Senock, S., J. Barrow, R. Gibbens, and C. Herbel. 1991. Ecophysiology of the polyploid shrub Atriplex canescens (Chenopodiaceae) growing in situ in the northern Chihuahuan desert. Journal of Arid Environments 21: 45-57.

Sisson, W., and G. Throneberry. 1986. Seasonal nitrate reductase activity in three genotypes of Atriplex canescens in the northern Chihuahuan desert. Journal of Ecology 74: 579-589.

Tarrad, A., A. Younis, M. Nasr, T. Kasseh, A. Bishay, and H. Dregne. 1991. Evaluation of drought and salinity resistance of some Atriplex species in the northwestern Egyptian coast, pp. 367-376. In: A. Bishay, ed., Desert Development Part 1: Desert Agriculture, Ecology and Biology. Harwood Academic Publishers, Chur, Switzerland.

Table 1. Varieties, points of origin, elevation above sea level and seed source of A. canescens accessions used in the study.
Accession number latitude/longitude /
Variety
(ploidy) /
Origin a Elevation
(m)
1 / 31.20E N
113.35E W / grandidentatumb
(20x) / Puerto Penasco, Sonora, Mexico / 5
2 / “ / linearisb
(2x) / Puerto Penasco / 1
3 / 32.52E N
111.46E W / linearisb
(4x) / Casa Grande, AZ / 600
4 / 32.15E N
110.57E W / angustifoliab
(2x) / Tucson Airport, AZ / 700
5 / 40.00E N
112.00E W / gigantac
(2x) / Jericho Dunes, UT / 1700
6 / 40.25E N
110.50E W / occidentalisc
(4x) / Starvation Res., UT / 1800
7 / 38.50E N
111.00E W / occidentalisc
(4x) / Caineville, UT / 1600
8 / 37.08E N
113.40E W / occidentalisc
(4x) / Santa Clara, UT / 900
9 / 37.50E N
113.00E W / occidentalisc
(4x) / Snow Canyon, UT / 1600
10 / 38.50E N
112.50E W / occidentalisc
(4x) / Beaver Canyon, UT / 2800
11 / 36.52E N
113.55E W / occidentalisc
(4x) / Littlefield, AZ / 800
12 / 38.18E N
111.25E W / occidentalisc
(4x) / Torrey, UT / 2300
13 / 36.40E N
114.36E W / occidentalisc
(4x) / Glendale, NV / 800
14 / 42.58E N
117.04E W / occidentalisc
(4x) / Jordan Valley, ID / 1500
15 / 31.50E N
111.00E W / occidentalisd cv. Santa Rita (4x) / Greaterville, AZ / 1200
16 / 32.29E N
111.12E W / occidentalisd cv. Marana (6x) / Marana, AZ / 600

a Az:Arizona

ID:Idaho

NV:Nevada

UT:Utah

b Collected by Environmental Research Laboratory

c Provided by USDA Shrub Laboratory, Provo, UT

d Provided by USDA Plant Materials Center, Tucson, AZ

Table 2. Composite analysis of three water samples used to irrigate A. canescens at the Four Corners Power Plant. Not detected: F, As, Ba, Cd, Cr, Hg, and Ag (EPA Methods 300.0, 200.9, 200.7, 245.2).

______

AnalyteMolar percentage in dissolved solids a

______

Cations (100%)

Na+64.1

Mg2+23.3

Ca2+10.8

K+1.6

Others0.2

Anions (100%)

SO42-94.2

Cl-5.7

Others0.1

______

a average total amount 7020 mg L-1.

Table 3. Climatological data from Farmington, New Mexico from

July 1994 to October 1995.a

Month /
Atmospheric to, oC Mean Max. Mean Min. /
Precipitation
(mm) /
Number of days of frost
July 1994 / 34.0 / 15.7 / 5.08 / 0
August / 32.8 / 16.2 / 16.7 / 0
September / 27.3 / 10.2 / 34.8 / 0
October / 18.9 / 3.8 / 30.0 / 3
November / 9.8 / -2.8 / 24.4 / 21
December / 7.6 / -4.6 / 16.3 / 27
January 1995 / 5.7 / -4.4 / 14.5 / 27
February / 14.2 / -1.5 / 3.6 / 16
March / 14.3 / -0.5 / 36.8 / 14
April / 16.2 / 1.5 / 32.5 / 12
May / 21.8 / 6.0 / 22.9 / 0
June / 28.6 / 9.9 / 0.8 / 0
July / 32.6 / 14.5 / 5.8 / 0
August / 32.4 / 16.1 / 47.7 / 0
September / 27.3 / 11.2 / 51.8 / 0
October / 20.8 / 2.8 / 2.54 / 7

a Provided by The National Climatic Data Center

Table 4. Survival, initial length, and length increase of A. canescens accessions grown for 16 months at Four Corners, New Mexico. Accessions are listed in order of decreasing net growth. Means followed by the same letter(s) are not significantly different at P<0.05.

Accession / Survival
% / Initial Length (mm) / Length Increase
(mm + S.D.)
11 / 100 / 289 / 599 (319) a
14 / 100 / 236 / 547 (218) ab
10 / 100 / 262 / 492 (234) abc
8 / 100 / 270 / 488 (211) abc
9 / 100 / 215 / 452 (239) abcd
5 / 100 / 375 / 442 (272) abcd
4 / 92 / 247 / 438 (208) abcd
7 / 100 / 262 / 430 (218) abcd
13 / 100 / 240 / 415 (186) abcde
16 / 100 / 254 / 374 (187) bcde
3 / 92 / 276 / 357 (194) bcde
15 / 100 / 281 / 332 (286) cde
12 / 100 / 200 / 308 (207) cdef
6 / 100 / 226 / 248 (135) def
1 / 62 / 242 / 219 (158) ef
2 / 100 / 252 / 137 (97) f

Table 5. Composite analysis of three soil samples from inside common garden plot of A. canescens and three soil samples from outside the plot at the Four Corners Power Plant at end of trial. Not detected: F, As, Ba, Cd, Cr, Hg, Ag (EPA Methods 300.0, 200.9, 200.7, 245.2).

______

Analyte Test Soil Sample from Control Soil Sample from

inside garden plot outside garden plot

______

pH a8.98.6

E.C. dS m-1 a 9.06.2

K+, mg kg-197188

Ca2+, mg kg-1398447

Na+, mg kg-147164

Cl-, mg kg-1 550320

Pb, mg kg-12020

Se, mg kg-1<1<1

Sand, %32.432.4

Silt, %39.236.2

Clay, %28.431.4

TextureClay loamClay loam

______

a Analysis by 1:1 soil to water extraction

Figure Caption

Figure 1. Origin of Atriplex canescens accessions (listed in Table 1) and the location of the common garden test site in the northwestern New Mexico.