Clark, Curtis, and Nancy A. Charest. 1992. Comparison of annual and perennial Eschscholzia californica (Papaveraceae) at the Antelope Valley California Poppy Reserve. Crossosoma 18(2):19-26.

Comparison of Annual and Perennial Eschscholzia californica (Papaveraceae) at the Antelope Valley California Poppy Reserve

Curtis Clark and Nancy A. Charest

Biological Sciences
California State Polytechnic University
Pomona CA 91768

Many visitors to the Antelope Valley California Poppy Reserve (west of Lancaster in Los Angeles Co.) are aware that the poppies just outside the Reserve on the slopes across the road from Fairmont Store (the Fairmont site) are larger than the poppies in the Reserve, and often flower for a longer period. It has also been apparent to botanists who have studied the plants that those of the Reserve grow as annuals, dying completely after seeds are shed, whereas those of the Fairmont site are perennial, resprouting each year from a persistent crown of stem tissue at soil level or slightly below.

There has been much disagreement about the relative extent of annual and perennial forms of California Poppy. Cook (1962) found clear-cut differences between the two; he characterized annuals as having short, slender taproots and a mean stamen number per flower of 22 or fewer, and perennials as having a much thicker, longer taproot and a mean stamen number of more than 22 per flower. Clark (unpublished) showed that the stamen number was not always a consistent indicator (some long-lived perennials of the Big Sur Coast having a mean stamen number of 16, for example), and, more important, that many poppies that behaved as annuals in the natural environment were not only capable of perennating in cultivation, but also occasionally in the natural environment in favorable microsites. At the conclusion of these initial studies, Clark was convinced that all California poppies were capable of perennating under proper conditions, and that there existed a continuum in nature from those plants that routinely devoted a large amount of resources to surviving another season, to those that held back only the slightest amount against the improbable occurrence of favorable conditions, devoting the rest to producing seeds.

Further studies suggested, however, that there might indeed be obligately annual populations of California Poppy in the extreme desert parts of its range. The one population Clark had studied in the Antelope Valley, farther west than the Reserve, was perennial and had a high mean stamen number. The population studied by Cook (1962) was north of this, and was also perennial. It is clear that the plants at the Fairmont site are actively perennial, since they resprout from the base among the dead stalks of previous years' growth. Although it remains to be demonstrated conclusively that the Reserve poppies are obligate annuals, their growth in nature is in sharp contrast to those of the Fairmont site. The purpose of this study was to compare the poppies and the soils of the two sites.

Materials and Methods

Flowering Phenology of Eschscholzia

On 17 April 1983, and again on 22 May, we gathered data on flowering phenology both in the Reserve in the area of maximum display (east of the Visitors Center, south of the main range of hills, and just north of the south boundary) and at the Fairmont site (the hillslope southeast of and across the road from the Fairmont Store). For nine samples from the Reserve and four from the Fairmont site, each consisting of 10 to 30 plants, we recorded height of plant, average width of plant, number of buds, flowers, and fruits, number of stamens in one representative flower, and distance to nearest neighbor (the latter item was never used). Statistical analysis was performed with the MINITAB statistical package.

Soil Analysis

Soil was collected from the region of maximum display in the Reserve, from the region upslope from the display across the 1981 firebreak, and from the Fairmont site, on 22 May 1983, and again on 23 October. All soil samples were air-dried and then fine-sifted (less than 2 mm) before analyses were carried out.

Analyses of the collections of 22 May:

Available Potassium--hot nitric acid extraction (method S:13.1, CFA-SIC, 1980). Three replicates/sample.

Saturation Percentage (method S:2.0, CFA-SIC, 1980).

Soil pH--determined from saturated soil paste (method S:3.0, CFA-SIC, 1980).

Electrical Conductivity--from saturation extract (method S:5.0, CFA-SIC, 1980).

Phosphorus--Olsen sodium bicarbonate extraction method for neutral to basic soils (method S:12.0, CFA-SIC, 1980). Three replicates/sample.

Soluble Calcium and Magnesium--from saturation extract (method S:7.0, CFA-SIC, 1980). Two replicates/sample.

Analyses of the collections of 23 October:

Soil Texture Class--determined by the Bouyoucos method (Kilmer & Alexander, 1949).

Organic Matter--dichromate reduction (method S:18.0, CFA-SIC, 1980). Three replicates/sample.

Available Zinc--DTPA extraction (method s:14.0, CFA-SIC, 1980). Three replicates/sample.

Total Nitrogen--Kjeldahl analysis (Jackson, 1958).

Soil classifications and other published data were obtained from Soil Survey of the Antelope Valley Area (U. S. Department of Agriculture, 1970).

Results

Phenology

The mean stamen numbers at the two sites are consistent with Cook's prediction: the Reserve poppies average 19.88 stamens per flower and the Fairmont poppies 23.27. This is a significant difference when all samples from each site are grouped (one-way analysis of variance), although pairs of samples from the Reserve and the Fairmont site can be selected that do not show significant differences (Table 1).

The Fairmont plants are larger, with a mean height of 30.3 cm and width of 26.1 cm, versus 20.7 cm and 13.6 cm for the Reserve; the differences are highly significant (p<0.0005, two-sample t test). They also have a significantly larger number of "floral units" (buds + flowers + fruits) per plant than the Reserve plants, 34.0 per plant versus 12.0 per plant (p<0.0005, Mann-Whitney U test). As might be expected, there are significant correlations between the number of buds, flowers, and fruit and the height and width of the plants, both within the Reserve and Fairmont samples and with the two combined (Table 2).

Table 1. Analysis of stamens per flower

Sample

n

mean

s.d.

Sample

n

mean

s.d.

Reserve 1

10.00

22.10

4.53

Fairmont 1

2.00

17.50

6.36

Reserve 2

15.00

17.80

5.27

Fairmont 2

24.00

25.88

3.04

Reserve 3

14.00

25.86

4.26

Fairmont 3

15.00

20.60

2.56

Reserve 4

17.00

21.35

6.11

Fairmont 4

19.00

22.68

4.01

Reserve 5

14.00

16.64

5.50

all Reserve

125.00

19.88

5.46

Reserve 6

7.00

22.71

3.09

all Fairmont

60.00

23.27

4.07

Reserve 7

18.00

20.72

2.78

       

Reserve 8

11.00

17.55

4.80

       

Reserve 9

19.00

16.53

4.29

       

Table 2. Correlations of height, width, number of buds, and number of flowers (asterisk denotes value significant at p<0.05).

Reserve poppies, n=198

 

Height

Width

Buds

Flowers

Width

.684*

     

Buds

.530*

.715*

   

Flowers

.543*

.689*

.722*

 

Fruits

.581*

.677*

.405*

.784*

Fairmont poppies, n=85

 

Height

Width

Buds

Flowers

Width

.741*

     

Buds

.297*

.532*

   

Flowers

.534*

.754*

.633*

 

Fruits

.674*

.840*

.426*

.828*

All poppies, n=283

 

Height

Width

Buds

Flowers

Width

.756*

     

Buds

.482*

.651*

   

Flowers

.502*

.680*

.635*

 

Fruits

.619*

.752*

.458*

.696*

The Fairmont plants also flower later in the season. Although we did not quantify this in a manner that could be tested for significance, we calculated from the data of 17 April the average ratio of flowers to buds on a single plant, which was 0.553 for Fairmont and 0.745 for the Reserve. Thus, at this point in the season, a greater proportion of the flowers had opened at the Fairmont site than on the Reserve. The difference was very apparent in the field; the Fairmont site was reaching maximum bloom as the reserve began to wane, and later when we collected many dry fruits in the Reserve, very few Fairmont site fruits were yet ripe.

Soils

The soils of both the Reserve and the Fairmont site are derived from granitic rock. The soils are well-drained and easily infiltrated, and with the exception of road cuts and some gully systems outside the Reserve, not easily eroded. The south slope of the Antelope Buttes, a site of poppy displays prior to the 1980 and 1981 fires, is of the Greenfield series, as is the tilled area in the southeast of the Reserve, parts of the western Reserve, and the Fairmont site. The 1983 display was located in Ramona series soil, which is also found south of South Godde Hill. The hills themselves are of the Vista series, shallower soils than the previous two, except for North Godde Hill, which is of the Amargosa series, shallowest of all (U. S. Department of Agriculture, 1970).

The soil analyses (Table 3) were designed to look for differences between the Fairmont site, the display area in the Reserve, and the area just across the 1981 fire line from the display. Among the analyses that were replicated and thus subject to statistical tests, there were no significant differences.

Table 3. Soil Analyses

Samples of 22 May 1983

Reserve display area 1

Reserve display area 2

Reserve above display

Fairmont

Electrical conductivity (mmho/cm)

0.32

0.40

0.56

0.20

pH

6.70

6.80

6.60

6.80

Saturation percentage

30.00

24.00

20.00

19.00

Available potassium* (ppm)

813.00

713.00

913.00

772.00

Phosphorus* (ppm)

29.80

35.30

25.00

22.30

Calcium + Magnesium* (me/l)

2.20

3.10

4.00

2.10

Samples of 23 October 1983

Reserve display area

 

Reserve above display

Fairmont

Percent sand

75.70

 

75.80

75.50

Percent silt

13.50

 

13.00

15.30

Percent clay

10.80

 

11.20

9.20

Percent organic matter*

2.12

 

1.77

1.34

Available zinc (ppm)

2.60

 

2.80

2.20

Total organic nitrogen(percent)

0.12

 

0.12

0.10

* replicated experiment, no significant difference among samples

Discussion

In addition to their difference in growth habit, the poppies of the two sites are physically dissimilar. The dissimilarities are consistent with those expected between annual and perennial Eschscholzia californica.

It is very unusual for poppies so different to be in such close proximity . Excluding instances where cultivated poppies have escaped and coexist with morphologically different native populations, such occurrences are usually found along the coast, where the plants of the coastal bluffs and dunes differ from those of a few kilometers inland. In these cases, however, the environments in which the different populations grow are very dissimilar.

The environmental differences between the south slopes of the Antelope Buttes in the Reserve and the Fairmont site are not immediately apparent. We have shown that the soils do not differ significantly in physical or chemical attributes. The areas are close enough to one another (about 2.5 km) that they would be expected to have similar climatic regimes. The Fairmont site has more north-facing exposures than the area of the Reserve sampled in this study, but annual poppies can be found on north-facing exposures in the Reserve.

Plants of neither site are especially similar to the poppies growing further to the west in the Antelope Valley. The poppies of the Reserve are similar to the annual poppies of other inland areas in Southern California, and presumably to the annuals that spring up around Lancaster in a good year. As far as we have determined, the poppies growing in recently cultivated fields in the area are of the same type. The Fairmont poppies are most reminiscent of poppies growing around Kernville in Kern County, which have been treated (unnecessarily, in our estimation) as E. procera Greene; the most pronounced similarity is their very thick stems. Nevertheless, the environment at Kernville is very different. The perennial poppies further to the west in the Antelope Valley have somewhat more slender stems than the Fairmont plants, but are similar in other respects.

We conceive of two alternate hypotheses for the presence of dissimilar poppies on the Reserve and the Fairmont site. The first is that either the Fairmont form or the Reserve form, or both, have been introduced as seed by humans, either intentionally as ornamentals, or inadvertently, as an agricultural weed. The second is that the co-occurrence antedates European settlement. The Reserve poppies are of the type that most likely extended across what is now the Mojave Desert during the height of the Wisconsinan glaciation, when the region was a pinyon-juniper woodland (Wells & Berger, 1967). Poppies of the Kernville type must have lived at lower elevation, and the Fairmont poppies may be a remnant of this. As conditions became warmer and drier with the retreat of the glaciers and basin lakes, the annual forms could have retreated up the Antelope Valley, coming in contact with the perennials that had formerly inhabited the region.

We have considered that differing land use may have allowed the persistence of the different poppies on the two sites, and may maintain them still. A possible candidate for this influence is grazing at the Fairmont site, as overall herbaceous cover seems to be less. However, grazing was restricted on the Reserve only in recent decades, and the differences between the poppies at the two sites are possibly much older.

Acknowledgments

We thank Mark Patterson for the soil analyses, Emilia Parra, Mark Patterson, Donald Sanders, and Christina Wedaa for assistance in the field, and the California Department of Parks and Recreation for financial support and access to unpublished records and photographs.

References Cited

CFA-SIC Publication. 1980. Soil testing procedures for California. California Fertilizer Association, Sacramento.

Clark, C., and N. A. Charest. 1992. Vegetation survey of the Antelope Valley California Poppy Reserve. Crossosoma 18(1):15-24.

Cook, S. A. 1962. Genetic system, variation, and adaptation in Eschscholzia californica. Evolution 16:278-299.

Jackson, M. L. 1958. Soil chemical analysis. Prentice-Hall Inc., Inglewood Cliffs, N.J.

Kilmer, V. J., and L. T. Alexander. 1949. Methods of making mechanical analysis of soils. Soil Sci. 68:15-24.

U. S. Department of Agriculture. 1970. Soil Survey, Antelope Valley Area, California.

Wells, P. V. and R. Berger. 1967. Late Pleistocene history of coniferous woodland in the Mohave Desert. Science 155:1640-1647.


This page Copyright © 1992, 1999 by Curtis Clark.