Fishtail Mesa: a Vegetation Resurvey of Relict Area in Grand Canyon National Park, Arizona

Western North American Naturalist

Volume 61 Number 2 Article 4

4-23-2001

Fishtail Mesa: a vegetation resurvey of relict area in Grand Canyon National Park, Arizona

Peter G. Rowlands Division of Resources Management, Organ Pipe Cactus National Monument, Ajo, Arizona

Nancy J. Brian Science Center, Grand Canyon National Park, Grand Canyon, Arizona

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Recommended Citation Rowlands, Peter G. and Brian, Nancy J. (2001) "Fishtail Mesa: a vegetation resurvey of relict area in Grand Canyon National Park, Arizona," Western North American Naturalist: Vol. 61 : No. 2 , Article 4. Available at: https://scholarsarchive.byu.edu/wnan/vol61/iss2/4

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FISHTAIL MESA: A VEGETATION RESURVEY OF A RELICT AREA IN GRAND CANYON NATIONAL PARK, ARIZONA

Peter G. Rowlands1 and Nancy J. Brian2

ABSTRACT.—Relict sites are geographically isolated areas that are undisturbed by direct and indirect human influ- ences. These sites facilitate long-term ecological monitoring by providing a reference for gauging impacts occurring elsewhere. Knowledge gained through comparing vegetation change on matched relict and proximal disturbed areas can help partition the causes of change into natural and human-produced components. Fishtail Mesa in Grand Canyon National Park is a 439-ha relict site that is inaccessible to domestic livestock. Human visitation is infrequent and irregular, and fires have never been suppressed or managed. In 1958, U.S. Forest Service range scientists conducted a survey of Fishtail Mesa to gather reference data on vegetation, wildlife, and soils. Vegetation sampling was conducted using a method called the “elb.” We returned to Fishtail Mesa in May 1996 to perform a general vegetation and floristic survey, assess the extent of vegetation change after 38 years, and evaluate the suitability of the site as a location for long-term surveillance of ecological change. Fishtail Mesa’s vegetation consists primarily of a Pinus edulis (pinyon) and Juniperus osteosperma (Utah juniper) woodland with an Artemisia tridentata (sagebrush) understory, or tree-type (310.9 ha), and an Artemisia and Poa fendleriana (mutton grass) steppe, or shrub-type (127.5 ha). Since 1958 vegetation changes in both shrub- and tree-types have been limited to only a few species. In the shrub-type we detected slight increases from 1958 to 1996 in both Pinus and Juniperus, and reexamination of 1958 photo sites confirmed that Pinus and Juniperus are reoccupying the shrub-type. Artemisia cover declined from 1958 to 1996, whereas Poa increased from near trace amounts in 1958 to moderate cover in 1996. In the tree-type, Poa has increased from 1958 to 1996, while Artemisia, Juniperus, and Pinus showed no apparent change. Other species such as Ephedra torreyana (Torrey joint-fir), Opuntia polyacantha (prickly pear), and Gutierrezia sarothrae (snakeweed) have decreased. Vegetation analysis aided by TWINSPAN revealed that the shrub-type is defined more on the basis of absence of Pinus and Juniperus rather than any special association of differential species with a high preference for this type. We interpret the “invasion” of the shrub-type by Pinus and Juniperus as a “reoccupation.” Indirect ordination using DECORANA inferred 2 environmental gradients, a moisture gradient and perhaps a substrate texture gradient, that appeared to influence vegetation distribution on Fishtail Mesa. Fishtail Mesa is a valuable relict area for studying the effects of livestock grazing and prescribed fire. It should be designated a Federal Research Natural Area based on its vegetation communities, size, and protection afforded by its location in Grand Canyon National Park.

Key words: relict area, Grand Canyon, Pinyon-Juniper Woodland, Sagebrush Steppe, TWINSPAN, DECORANA.

Vegetation and soils of Fishtail Mesa, a relict narrow canyons impassable to livestock and area in Grand Canyon National Park, Arizona, motor vehicles. These relict areas, validated as were originally studied in May 1958 (Jameson to their undisturbed state by exhaustive inven- et al. 1962). The purpose of the original re- tory and research, can be considered practi- search was to document Fishtail Mesa as a ref- cally pristine reference sites where ecological erence relict area and collect baseline data on processes and components are unmanaged. vegetation, soils, and wildlife. The U.S. Forest Specifically, relict refers to communities that Service hoped that ecological studies of Fish- have either (1) persisted through severe tail Mesa would help to interpret the effects of warming and drying of the interior West’s cli- livestock grazing on similar, grazed areas on mate over the past few thousand years (Betan- Forest Service lands located on the nearby court 1990), or (2) been uninfluenced by settle- North Rim. Southwestern national parks often ment activities, chiefly domestic livestock graz- contain many similarly isolated areas that are ing. In this paper we stress the 2nd criterion. relatively unaltered by human activity. On the Relict areas are scientifically interesting because Colorado Plateau, comparatively small places of their isolated faunas and verifiable lack of with pristine or relict communities abound on herbivory or human interference (Turner 1982, buttes, mesas, boulder-strewn slopes, or in Johnson 1983, Van Pelt et al. 1991).

1Division of Resources Management, Organ Pipe Cactus National Monument, Route 1, Box 100, Ajo, AZ 85321. 2Science Center, Grand Canyon National Park, Box 129, Grand Canyon, AZ 86023. Corresponding author.

159 160 WESTERN NORTH AMERICAN NATURALIST [Volume 61

For the land use manager, relict areas are Mesa due to the absence of livestock grazing standards or baselines for gauging impacts and associated land use management practices occurring elsewhere in the parks (Jeffries and coupled with minimal exploitation by native Klopatek 1987, Hermann 1989, Beymer and wildlife. On the other hand, we also hypothe- Klopatek 1992). They help define productive sized that evidence would be found showing potentials of forests and rangelands (Passey et reoccupation of Sagebrush Steppe (or shrub- al. 1982) and are sanctuaries for plant and ani- type) vegetation by Pinus and Juniperus after mal life, some of which are considered endan- exclusion of these trees as part of a natural, or gered or threatened. The National Park Ser- at least near-natural, fire cycle envisioned by vice (NPS) has commissioned 2 relict area sur- Jameson et al. (1962). We also thought that veys, conducted by the Nature Conservancy, Fishtail Mesa, because of its narrow shape and on the Colorado Plateau. The first, by Tuhy island-like situation, would be an ideal place and McMahon (1988), identified 21 relict or to examine the influence of the so-called rim near-relict sites in Glen Canyon National effect on vegetation distribution. According to Recreation Area. The second, by Van Pelt et Halvorson (1972), Grand Canyon produces al. (1991), covered all the remaining Colorado strong, convective air movement resulting in Plateau parks, with the notable exception of hot, dry winds rising from the warmer canyon Grand Canyon National Park. Over 100 addi- bottom. These winds have the immediate effect tional relict sites were identified. of drying and heating upland areas adjacent to Since publication of Jameson et al.’s (1962) the rim. Storms from the prevailing wind research, Fishtail Mesa has been compared direction are forced away from the rim by the with other relict sites (Mason et al. 1967, warm updrafts. This rim effect creates a zone Schmutz et al. 1967, 1976, Mason and West of increased aridity for some distance, up to 1970, Thatcher and Hart 1974, Turner 1982). 400 m or more, away from the rim. Because of But, on the whole, research on Colorado Pla- the long, narrow shape of Fishtail Mesa, almost teau relict areas has been scanty. Besides the parallel to the prevailing winds, a substantial Jameson et al. (1962) report, Johnson (1983) rim effect should be discernible as a vegetation studied island biogeography of isolated buttes gradient from shrub-type along the rim to in Canyonlands National Park and the mam- tree-type within the interior of Fishtail Mesa. mals, reptiles, and insects that were able to colonize through the filter of very steep cliffs. METHODS AND MATERIALS Other than the Mason and West (1970) publication, he cites no relevant relict area research. STUDY AREA.—Fishtail Mesa is an isolated, Only 2 studies of Grand Canyon relict areas semiarid 439-ha mesa located immediately have been published. Jameson et al. (1962) is east of the confluence of Kanab Creek and the the subject of this paper. Later, Beymer and Colorado River in Grand Canyon National Klopatek (1992) published findings on the Park, Arizona (Fig. 1). A narrow ridge separates effects of historical grazing on microphytic the 1867-m-high mesa top from the “main- crusts on the South Rim of Grand Canyon land” of the Kaibab Plateau, located 1.6 km to National Park using Shiva Temple, another the northeast. The National Park Service allows isolated butte, as a comparison site. They lightning-caused fires to burn. It is protected reported that visible crust cover was reduced from domestic livestock grazing by the steep, from 23.3% on ungrazed sites to 5.3% on some 610-m cliffs that encircle it. Its relative isolation previously grazed sites. from native ungulate grazing is compromised The study of Fishtail Mesa provides an un- only by mule deer, which scale the northern usual opportunity to examine some hypothe- edge of the mesa to browse seasonally. ses regarding vegetation change in an unman- Precipitation records for Grand Canyon aged setting. Our principal study objective National Park (Green and Sellers 1964, Sellers was to document vegetation change since 1958 and Hill 1974) indicate that average annual and to evaluate Fishtail Mesa as a relict site rainfall on Fishtail Mesa is probably about 350 for long-term surveillance of ecological change. mm ⋅ yr–1. Forty-five percent occurs during We surmised that there would be little change winter and spring (December through April) in the shrub component of the Pinyon-Juniper and 34% during the summer monsoon season Woodland (or tree-type) vegetation on Fishtail (July through September; Jameson et al. 1962). 2001] RESURVEY OF FISHTAIL MESA 161

Summer thundershowers can be sudden and land) and Artemisia tridentata–Poa fendleriana locally heavy. Precipitation is deficient in all association (Sagebrush Scrub or Sagebrush seasons relative to potential evapotranspira- Steppe) are the primary plant assemblages on tion, and there is little or no surface runoff. Fishtail Mesa (Jameson et al. 1962). We refer The average growing season is 141 days. Aver- to these as the tree-type and shrub-type, age January temperature is –1.7ºC and average respectively. Jameson et al. (1962) reported 2 July temperature is 20.4°C. The area is semi- other minor plant communities: a patch of arid and microthermal (Thornthwaite 1931). Stipa speciosa (desert needlegrass) grassland The mesa has a gently rolling topography in the approximate center of the mesa’s shrub- and varies in elevation from 1769 to 1867 m. type, and a small patch of Gutierrezia Permian-aged Kaibab limestone forms the sur- sarothrae along the rim. These 2 minor com- face (McKee 1938, Hopkins 1990). Thin, small munities are not considered in this paper. A areas of Quaternary deposits are found in the revised 1996 vegetation map (Fig. 1) delin- central portion of the mesa along small, eates 3 plant communities: a Pinyon-Juniper ephemeral drainages and at the bases of slopes. Woodland with sagebrush understory (tree- Aeolian deposits of very minorly reworked type) with 25–60% tree cover (71% of the sands are trapped near vegetation. mesa top), a Big Sagebrush Steppe (shrub- Soils on Fishtail Mesa are shallow and type) with <10–24% tree cover (29%), and a poorly developed. The 5 soil units originally Stipa Grassland (0.1%). described by Jameson et al. (1962) include a Jameson and his colleagues conjectured sandy limestone (ca 47% of the mesa top), nor- that (1) 20% of the original tree-type had been mal limestone (ca 27%), cherty limestone converted to shrub-type by fires, (2) these (17.5%), steep rocky slopes (4%), and alluvium areas made up about 60% of the shrub-type, (4%). We noted a 6th unit of gypsum (0.5%). and (3) there was little reinvasion of the burns Most soils are lithic ustochrepts, while the by pinyon and juniper trees. They did not esti- alluvium is a typic haplustalf. The interested mate the age of the burns due to lack of reli- reader can consult Jameson et al. (1962) for able data, but concluded that fires must have profile descriptions of the soil units. occurred long ago since Juniperus snags with Unlike other relict areas in Grand Canyon, only heartwood remaining were left standing. such as Shiva Temple (Beymer and Klopatek GENERAL STUDY DESIGN.—We resurveyed 1992), microphytic (microbiotic, or cryptogamic) vegetation and soils of Fishtail Mesa 10–15 May crusts are not abundant on Fishtail Mesa. 1996, within a week of its initial survey 38 When observed, crusts were diffuse and did years previously by Jameson et al. (1962). One not form dense, discrete patches. Only traces of the original researchers (Jameson) assisted of such crusts were encountered on the 8 sam- in the fieldwork. Jameson et al. (1962) employed ple sites, not enough to perform any spatial or U.S. Customary units for all their field mea- abundance comparisons with statistical rigor. surements. For the sake of consistency, we Furthermore, since microphytic crusts were duplicated both units and methods. For this never considered in the Jameson et al. (1962) publication all measurements are converted survey, temporal comparisons were also not into SI units to a computed accuracy of at least possible. When encountered, crust cover was 2 decimal points. included with litter. The method they used was an adaptation of Vegetation of Fishtail Mesa could be de- the line intercept (Canfield 1941, Parker and scribed as a southern extension of the Great Savage 1944, Bonham 1989) technique called Basin Desertscrub Formation (Young et al. 1977, an “elb” (Fig. 2), or “elb-strip” (Woodin and Turner 1982). The occurrence of a significant Lindsey 1954). The term elb, short for “elbow,” graminoid component (Bouteloua gracilis [blue refers to the sampling unit whereby 2 orthogo- grama], Hilaria jamesii [galleta], and Stipa spp.) nal, 121.9-m baselines served as line inter- in the sagebrush vegetation type, as on Fish- cepts (LIs). A sequence of 400 Parker loop tail Mesa, leads some authors to classify such (PL; Parker 1951) observations was also made communities as a shrub steppe (Turner 1982), at 0.3-m intervals along the LI. A 6.1 × 121.9- or sagebrush savanna (Clements 1930). At the m belt transect, split into four 30.5-m sections association level, the Pinus edulis–Juniperus and superimposed on the LI, together consti- osteosperma association (Pinyon-Juniper Wood- tuted each elb “arm.” Elb arms were oriented 162 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 1. Fishtail Mesa 1996 vegetation map. at right angles to produce an L-shaped plot shrub-type (elbs 1, 2, 4, 5), but due to time (Fig. 2) and were recorded as left (L) and right constraints, they installed only 3 1/2 in the (R) when observed from the origin. The elb tree-type (elbs 3, 6, 7, 8, the latter consisting sampling design was originally applied to the of only a single arm). For more specific details, study of Fishtail Mesa vegetation to avoid the we refer the reader to Jameson et al. (1962) linear influence of topography whereby a ran- and Woodin and Lindsey (1954), who estab- dom straight line might fall largely within or lished the elb methodology. We were able to parallel to a gully, ridge, slope base, or geolog- relocate most of the previously placed steel ical stratum, thereby obscuring the sampling fence posts and angle irons marking the 30.5- results. A set of long, orthogonal strips was m increments along each of the elbs. Missing supposed to even out the variances in vegeta- markers were relatively easy to reestablish tion response (e.g., cover) to environmental based on the locations of those remaining. factors (Woodin and Lindsey 1954). In 1958, VEGETATION FIELD MEASUREMENTS AND IN- Jameson et al. (1962) established 7 1/2 perma- VENTORY.—In 1958, LI measurement accuracy nent 244-m elbs. They established 4 in the was claimed to be the nearest 0.25 cm. In 2001] RESURVEY OF FISHTAIL MESA 163

diameter loop placed at specified intervals along a permanent transect. At least 100 points should be sampled. In this study we observed 400 PLs at 0.3-m intervals along each elb arm baseline. We noted both basal and foliage cover hits for trees and shrubs and basal cover hits for forbs and grasses. If no vegetation was encountered within the loop, the presence of bare ground, litter, soil crusts, or exposed rock was noted. Data from the 6.1 × 121.9-m belt transects were used to measure density, abundance, and frequency of tree species. In 1958 only live trees >0.9 m in height were recorded and measured. In 1996 we measured trees of all heights and ages, including snags. Tree seedling diameters were measured at ground level. Due to the low branching characteristic Fig. 2. Diagram of the left and right arms of an elb of Pinus and Juniperus, poles, mature trees, showing elb transect with central baseline line intercept, and snags were measured at 0.3 m above the belt transect, angle irons, and elb marker posts. ground (hereafter referred to as basal diameter or BD), as opposed to breast height (≈ 1.5 m). 1996 we set LI measurement accuracy to a We recorded the position of all trees with more realistic 1.25 cm. When plant cover was respect to elb arm baselines using Cartesian x- less than this, we recorded it as a “trace,” and y-coordinates. We also recorded canopy equal to a nominal value of 0.03 cm. We mea- diameter and tree height. Canopy cover was sured understory vegetation cover along the 2 estimated as the area of a circle; when the LIs forming the baseline of the elb arms. We canopy was not circular, canopy cover was refer to cover in 2 different ways within this estimated as the area of an ellipse. Trees with paper. Absolute cover of a species is the cover most of the base located inside the strip of a species (total length of its vegetative parts perimeter were counted, while those outside intercepted by the LI or PL hits) with respect were omitted. to size of the sample (length of the LI or num- We compared differences in absolute cover values for the study years 1958 and 1996 using ber of PLs observed). Absolute cover derived ∆ from LIs is “linear” cover. Statistical compar- percent change ( %): isons were always made using linear cover or, (Vp–Vf) in the case of PLs, the number of hits. Relative ∆% = ______× 100 (1) cover of any plant species is the cover of that [ Vf ] species relative to the total cover of all species encountered. Multiplying absolute cover and where Vp is the present value of a variable and relative cover values by 100 yields absolute Vf is the former value of the same variable. percent cover (AC) and relative percent cover Cover values for 1958 (Jameson et al. 1962) (RC), respectively. We used RC for TWIN- were presented as AC for each species accord- SPAN and DECORANA computations. ing to shrub- and tree-type and not for indi- To conform to the original Jameson et al. vidual elbs or elb arms. Original 1958 LI val- (1962) study, we also made PL observations ues (ft ⋅ LI–1) for each species had to be back- (Parker 1951, Driscoll 1958, Parker and Harris calculated from AC because we discovered 1959). These observations provided indepen- that field data sheets had been lost. Percent dent estimates of plant cover for comparison cover was converted to a decimal, multiplied with LI data. The PL method is basically a fre- by 3200 ft total elb length for the shrub-type quency technique to enable rapid estimation (2800 for the tree-type), and then divided by 8 of plant cover and community composition. for the shrub-type (7 for the tree-type). Even One records “hits” on plants, or portions so, resulting values are actually overall means thereof, occurring within a 1.9-cm- (0.75-in-) of cover as ft ⋅ LI–1 for each species according 164 WESTERN NORTH AMERICAN NATURALIST [Volume 61 to vegetation type. Values from 1958 for indi- To increase the number of samples, we ana- vidual elb arms could not be recalculated. lyzed the 1996 data according to separate elb Similarly, 1958 PL percent cover estimates arms. That is, the right and left arms of each also had to be back-calculated from data con- elb were considered to be independent sam- tained in Jameson et al. (1962). Where appro- pling units. We believe this decision is a rea- priate, values were converted to metric. sonable one because of the great length of TREE CORES.—We collected samples from each elb arm and the right-angle orientation of 4–6 living Pinus trees located outside the elbs the elbs to one another. Thus, the shrub-type to ascertain tree age. Height and basal diame- was represented by 8 sampling units and the ter measurements were also recorded, and tree-type by 7. The decision affected only the then cores or cross-sectional slabs were taken 1996 data that we collected. Temporal com- at 0.3 m above the ground. Pinyon cores were parisons are based on the recalculated 1958 glued to wooden mounts, sanded, and pol- data, as described above (Jameson et al. 1962). ished until rings were visible (Stokes and Smi- QUANTITATIVE VEGETATION ANALYSIS.—We ley 1968). Rings were counted using a 10–30X employed the Shannon diversity index, H፱ zoom microscope. In cases where the core (Kent and Coker 1992), which was calculated missed the pith, we estimated missing rings from plant species’ RC using the 1958 and using a pith locator. False rings were identified 1996 LI observations. Computation of species’ using anatomical criteria (Stokes and Smiley RC values in 1996 was done according to indi- 1968). Tree ages should be considered esti- vidual tree- and shrub-type elb arms. The mates since no cross-dating and analysis for Shannon index is defined as: missing rings was done, and there is general disagreement among researchers on how well s ፱ ring counts represent growth (Despain 1989). H = – ∑ pi ln pi (3) If some error can be tolerated, Despain (1989) i =1 has demonstrated that ring counting can estimate 10-year diameter growth rates. Conse- where H፱ is the Shannon index, s is the num- quently, we estimate that an error of as much ber of species, and ln is the natural logarithm. th as 5% could have been introduced into our The term pi is the relative abundance of the i Pinus age estimates based on ring counts. The species expressed as: date of 1850 was chosen as the presettlement date for tree-ring analyses. Juniperus were not ____Ai pi = (4) cored, as this long-lived tree is subject to ∑A highly irregular diametric growth and generally does not yield easily countable tree-rings. where Ai is the abundance (cover, biomass, Age-size relations of the trees were estab- density, etc.) of the ith species and ∑A is the lished by fitting basal diameters and tree-ring total abundance of all species in the sample. counts to the Chapman-Richards equation We chose H፱ because it is normally distributed (Clutter et al. 1983, Tausch and Tueller 1990). and more sensitive to rare species than other The Chapman-Richards model is derived from such indices (Magurran 1988). Also, according basic biological considerations and has proven to Kent and Coker (1992), H፱ is often preferred to be very flexible in modeling growth of both because species abundances are standardized individuals and populations (Clutter et al. to proportions. Species richness estimates were 1983). In this paper the equation takes the 3- made using the “jackknife” statistical method parameter form: with 95% confidence limits from replicate samples (Heltshe and Forrester 1983). diameter = A(1 – e–BAge)C (2) To better understand the relationships between the two codominant tree species, Pinus and was fitted using the Levenburg-Marquardt and Juniperus, and the 2 major vegetation nonlinear fitting algorithm. Three constants, types on Fishtail Mesa, we believed it neces- A, B, and C, are the parameters of the Chap- sary to conduct both a vegetation classification man-Richards equation. These parameters are and ordination. Species and elb arm (stand) estimated by nonlinear regression and deter- vegetation data were classified using 2-way mine the exact shape of the generated curve. indicator species analysis, or TWINSPAN (Hill 2001] RESURVEY OF FISHTAIL MESA 165

1979a, Kent and Coker 1992). The method is over time. Vegetation maps were prepared based on progressive, iterative refinement of a using ortho-rectified 1978 color aerial photog- single-axis reciprocal averaging ordination (i.e., raphy, with a scale of 1:12,000. Accuracy in correspondence analysis). Eventually, these scale was ±10 m. Data from 1996 post- progressive ordinations lead to the delineation processed Global Positioning System (±3 m) of one or more differential species according coordinate data collected from the mesa per- to their scores (+ or –) on the single ordina- imeter and elbs were used in the map prepa- tion axis, or positive and negative differential ration. All maps produced by this study comply species. The concept of differential species is with national map accuracy standards estab- based on presence and absence, but Hill (1979a) lished by the United States Geological Survey. introduced the concept of pseudospecies as a All 1996 plant voucher specimens have been way of adapting abundance data to a qualita- deposited in the Grand Canyon National Park tive equivalent which can then be used in the herbarium. construction of a classification dichotomy (Kent and Coker 1992). In this study relative RESULTS percent vegetation cover data were used to define 9 pseudospecies based on an octal scale FIRE.—We noted, as did Jameson et al. conversion: 0–0.5% = 1, 0.5–1% = 2, 1–2% = (1962), patches of standing Juniperus snags 3, 2–4% = 4, 4–8% = 5, 8–16% = 6, 16–32% with only heartwood showing. Similar to = 7, 32–64% = 8, and >64–100% = 9 pseudo- Jameson et al. (1962), we assumed that these species. snags were from Juniperus that died 80 to 100 The same vegetation data were also used to years ago. We also observed standing snags on obtain an indirect ordination by means of several transects. The Juniperus:Pinus ratio detrended correspondence analysis (DECO- was 19:1. This is to be expected since Pinus RANA or DCA), an eigenvector-based ordina- trunks, unlike the more resistant Juniperus, rot tion procedure related to reciprocal averaging quickly at the root collar and subsequently and based upon an occurrence of a set of species topple. We observed no direct evidence of any in a set of samples (i.e., elbs; Hill 1979b). Effi- recent burns such as charred tree trunks, cacy of the DCA was assessed by relating eco- burned and dead shrubs, or charcoal. No fire logical distances for n*(n–1)/2 = 105 samples scars were observed on any of the 40+ Pinus (i.e., elb arm) pairs calculated for the original increment cores collected for population age- species by samples matrix with the similarly size assessment. calculated distances derived from the final 2- SPECIES RICHNESS AND DIVERSITY.—The dimensional stand ordination. The distance shrub-type exhibited greater species richness, metric employed was the Czekanowski coeffi- with 31 species, as opposed to the tree-type cient or “percent similarity.” In our study we with 26 species. A weighted calculation of employed 15 elb arm samples; thus, 105 simi- species richness, allowing for one less elb arm, larity coefficients are possible. Since no quan- gave a crude estimate for the tree-type of 30. titative observations on physical factors such Application of the jackknife statistical tech- as soil structure, moisture and chemistry, or nique to the Fishtail Mesa data produced a microclimatology were made, DCA results from 1st-order, jackknifed species richness estimate this study are intended as an adjunct to for the shrub-type of 42 ± 6 plant species, TWINSPAN. The Multivariate Statistical Pack- whereas the estimate for the tree-type was 36 age (MVSP V.3.01) developed by Kovach (1998) ± 9 species. Because there is considerable over- was used to perform DCA, whereas PC-ORD lap in the 2 species richness estimates, we (McCune and Mefford 1999) was used to gen- believe species richness to be essentially the erate the TWINSPAN 2-way ordered table. same for both vegetation types. However, REPHOTOGRAPHY, MAPS, AND OTHER DOCU- there was a significant difference in mean MENTATION.—Black-and-white scenic and land- species diversity, as measured by H፱, between scape photographs were taken to replicate the shrub-type (H፱ = 0.760, n = 8) and tree- ፱ photographs taken in 1958. Existing aerial type (H = 1.448, n = 7) (t[13;α=0.05] = 6.174; photography of Fishtail Mesa taken in 1940 P =3.4E-05). This is probably the result of and again in 1944 was also examined to deter- dominance by sagebrush in the shrub-type. A mine if changes in vegetation could be observed 38-year comparison of community composition, 166 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 3. Rank-abundance curves for Fishtail Mesa shrub- and tree-types: 1958 vs. 1996. as rank abundance, for the shrub- and tree- In the shrub-type, Artemisia was by far the types is shown in Figure 3. Species diversity principal cover dominant (19–20% AC), fol- (H፱) of the shrub-type was 0.62 in 1958 and lowed by Poa, Ephedra, and Pinus. Results 0.90 in 1996. Similarly, H፱ of the tree-type was from PL and LI observations showed that bare 1.59 in 1958 and 1.73 in 1996. We cannot ground, including litter, accounted for 73–76% claim any degree of significance. of the samples in the shrub-type. Litter consti- SPECIES COMPOSITION.—The current species tuted 6% and exposed rock 0.1% of 3200 PL composition of Fishtail Mesa’s vegetation is observations taken within the shrub-type. In summarized in Table 1 and includes results the tree-type, cover dominance of Artemisia, from both LI and PL observations. Only the 8 Pinus, and Juniperus was almost equal (9–10% most abundant species throughout Fishtail AC). Bouteloua, Yucca, Ephedra, and Shepher- Mesa are included. All other species contributed dia rotundifolia (roundleaf buffalo berry) were <1% cover each. Both methods yielded simi- the prevalent secondary species. Each of the lar values, although in general, especially where remaining species comprising the tree-type the more uncommon species are concerned, contributed only minor amounts of cover the PL method was much less efficient. The (<0.3% AC) to the vegetation composition of elb arm LIs in the shrub-type encountered 31 the tree-type. Results from PL and LI observa- plant species, but only 15 were encountered tions showed that bare ground, including litter, using the PLs. Likewise, LIs associated with accounted for 62–64% of the samples in the the 7 tree-type elb arms encountered 26 tree type. Litter constituted 4% and exposed species as opposed to 15 by the PLs. rock <0.1% of 2800 PL observation taken Artemisia is currently the primary plant within the tree-type. species (15–16% AC) on Fishtail Mesa, fol- Changes in plant cover during the 38-year lowed by Pinus and Juniperus with a com- period of record (1958–1996), based on LI ob- bined AC of 9–10%. Poa had the 4th highest servations and PL samples, of selected domi- overall cover, followed by Bouteloua gracilis, nant plant species and total vegetation cover Yucca baccata (banana yucca), and Ephedra are shown in Tables 2 and 3. In the shrub-type torreyana. Combined vegetation cover esti- the intercepted cover (in m ⋅ elb arm–1) of Poa mated from all 8 elbs was 30–31% AC. Results increased dramatically, with percent change from PL and LI observations showed that bare (∆%) varying between 5675% and 8263%, de- ground, including litter, accounted for 69-70% pending on the Vp parameter (mean, upper, or of the samples throughout Fishtail Mesa. Lit- lower confidence limit of 1996 cover) used to ter constituted 5% and exposed rock <0.1% of calculate it. Likewise, Ephedra exhibited a 6000 PL observations taken throughout Fish- definite but less dramatic increase in cover. tail Mesa. Pinus and Juniperus were not recorded in 1958, 2001] RESURVEY OF FISHTAIL MESA 167 based on % ∆ = 7 elb arms) n e (4 and 3.5 elbs, respectively) overall tion cover. These calculations were based on the tion cover. 6.62 –5.34 10.24 25.83 5.516.29 –33.62 –56.83 10.07 –5.69 53.77 45.45 5.36 –44.58 –0.25 44.09 0.43 –98.13 –57.94 –17.76 1.20 1760.00 2960.00 4160.00 95% confidence 1996 confidence ± ± ± ± ± ± meson et al. (1962), but confidence interval calcula- ± e another. One elb in the tree-type contains only one e another. ence limits, also. Individual line intercept data associ- (PL) observations. ) and based on line intercept measurements, in the shrub-type and tree-type on Fishtail % Relative % Absolute % Relative % Absolute % ∆ based on Year % ∆ = 8 elb arms) ( Tree-type n 1996 lower 1996 upper 1996 lower 1996 upper Mean intercepted plant cover in linear meters per elb arm and percent change between 1958 1996 Shrub-type ( 3.14 45.03 54.26 64.24 42.47 46.82 0.24 — — — 12.30 11.60 0.99 — — — 12.61 13.88 2.98 –29.98 –19.76 –11.3 12.09 12.06 0.27 6.10 32.93 66.7 1.07 0.45 1.04 5675.00 6975.00 8262.50 0.10 3.06 95% confidence 1996 confidence 1996 ± ± ± ± ± ± ± 1996 Year Relative % Absolute % cover within the cover within the cover within the cover within the 8.62.82.71.5 8.20.7 1.1 2.2 1.3 0.6 2.6 0.8 0.8 0.4 2.6 0.2 0.4 0.7 0.4 10.8 0.2 0.1 0.0 10.4 2.1 0.0 0.1 0.0 2.1 2.6 0.0 <0.1 0.0 2.3 <0.1 0.5 0.0 0.0 0.6 6.9 4.9 0.0 4.8 6.4 1.9 1.0 1.2 4.1 0.7 2.5 1.8 1.0 1.7 2.4 0.7 0.4 0.4 1.5 0.3 0.4 LI PL LI PL LI PL LI PL LI PL LI PL 49.815.315.1 50.7 17.6 14.6 14.9 4.6 4.5 16.2 5.6 4.7 79.5 1.7 81.8 0.4 1.5 0.6 19.2 21.4 0.4 0.1 27.2 0.4 0.2 25.7 25.6 26.2 30.6 9.9 25.9 9.8 9.3 9.5 11.6 9.8 ______0.82 1.09 0.08 5.66 29.19 23.42 Absent 0.23 Absent 0.90 ______2. Plant cover differences between 1958 and 1996, shown as percent change ( 1. Summary of current dominant perennial plant species, according to cover, on Fishtail Mesa within the shrub-type and tree-typ on Fishtail 1. Summary of current dominant perennial plant species, according to cover, Plant species cover mesa-wide cover mesa-wide shrub-type shrub-type tree-type tree-type ABLE ABLE T T Juniperus osteosperma Combined cover/elb arm 33.95 52.37 Pinus edulis Artemisia tridentata Plant species 1958 confidence limit limits mean limits 1958 confidence limit limits mean limits Ephedra torreyana (7.5 elbs). Values are expressed as both absolute cover and relative percent cover based on line intercept (LI) and Parker loop as both absolute cover and relative percent based on line intercept (LI) Parker are expressed (7.5 elbs). Values Pinus edulis Juniperus osteosperma fendleriana Poa Bouteloua gracilis baccata Yucca Ephedra torreyana Shepherdia rotundifolia Bare ground (incl. litter) 70.2 69.1 75.8 73.3 63.7 62.1 Artemisia tridentata fendleriana Poa Mesa. Both vegetation types are represented by 4 sample sites (elbs) containing two 120-m line intercepts at right angles to on changes in cover were calculated for selected dominant plant species and total vegeta arm and one 120-m line intercept. Percent mean of the intercepted plant cover per elb arm (in units meters arm) and, for 1996 data, upper and lower confid from Ja The 1958 values shown were back-calculated in the text. ated with each elb arm were not available for 1958 as explained tions could not be made. 168 WESTERN NORTH AMERICAN NATURALIST [Volume 61 based on % ∆ = 7 elb arms) n ot available for 1958 as explained in the text. The in the text. ot available for 1958 as explained 21.5 –9.7 5.3 20.2 17.718.921.5 –47.0 –37.1 –58.9 –3.0 6.2 –9.2 41.0 49.2 40.4 4.70.9 66.7 –92.9 223.3 –28.6 380.0 35.7 95% 1996 lower 1996 upper lated for selected dominant plant species and total ± ± ± ± ± ± ± samples at 0.3-m intervals along each elb arm baseline. based on Year % ∆ = 8 elb arms) ( Tree-type n 1996 lower 1996 upper 1996 ), based on the Parker loop method, between 1958 and 1996 in the shrub-type and tree-type on Fishtail Mesa. Four sample Mesa. Four loop method, between 1958 and 1996 in the shrub-type and tree-type on Fishtail ), based on the Parker % ∆ Shrub-type ( 11.8 –24.0 –14.6 –5.1 144.0 151.6 3.21.0 — — — — — — 43.7 43.3 46.4 39.3 10.7 –28.9 –19.0 –9.1 40.2 39.0 0.9 –64.3 –4.2 –33.3 1.4 1.0 6.8 43.3 270.0 496.7 3.0 9.7 95% confidence 1996 confidence confidence 1996 confidence confidence ± ± ± ± ± ± ± Plant cover as estimated by mean number of Parker loop hits per elb arm and percent change between 1958 1996 Plant cover as estimated by mean number of Parker 1996 Year 2.4 2.3 3.0 11.1 107.9 87.4 AbsentAbsent 1.6 0.6 ______3. Plant cover differences (percent change = ABLE T Plant species 1958 confidence limit limits mean limits 1958 limit limits mean limits Pinus edulis Juniperus osteosperma Combined hits/elb arm 125.0 106.8 sites (elbs) represent both vegetation types. Each elb contains 2 sequences, at right angles to one another, of 400 Parker loop of 400 Parker sites (elbs) represent both vegetation types. Each elb contains 2 sequences, at right angles to one another, One elb in the tree-type contained only one arm and therefore only one sequence of Parker loop samples. Percent change is calcu loop samples. Percent One elb in the tree-type contained only one arm and therefore sequence of Parker loop data associated with each elb arm were n loop hits per elb arm. Parker vegetation cover based on the mean number of Parker from Jameson et al. (1962), but confidence interval calculations could not be made. 1958 values shown were back-calculated Ephedra torreyana Artemisia tridentata Poa fendleriana Poa 2001] RESURVEY OF FISHTAIL MESA 169 whereas in 1996 intercepted cover of Pinus However, Pinus and Juniperus were not com- was observed on a single elb arm LI (elb 4R) pletely faithful to the tree-type. Pinus was pre- and Juniperus was observed in 2 (4L and 5R). sent in at least one shrub-type elb arm LI in Artemisia exhibited an overall decrease; ∆% moderate abundance (13% AC, 12% RC). Juni- varied between approximately –30% and –11%. perus was present in 2 shrub-type elb arm LIs Mean combined plant cover per LI increased (0.1% AC, 0.4% RC). Poa was absent from approximately 45% to 64% (Table 2). In the both arms of one tree-type elb arm LI and also tree-type, intercepted cover of Poa increased occurred in one shrub-type elb arm LI. Other- sizably by 1760% to 4160%. The cover of wise, it was faithful to the tree-type. Ephedra appears to have decreased in the DECORANA ORDINATION.—The first 2 tree-type by 98% to –18%. Determination of axes produced by DCA (Figs. 4, 5) accounted changes in the abundance of the other plant for 70.3% of the variation within the original species listed under the tree-type, as well as species-samples matrix. Although this is not as mean total plant cover per LI, is problematical important as it would be in a principal compo- as the statistics show (Table 2). nent analysis (Kent and Coker 1992), it does Values of ∆% derived from PL sampling indicate a successful ordination in the first 2 (Table 3) were largely comparable, with respect dimensions. Only 4.5% more variation was to general patterns, to corresponding values accounted for by the addition of a 3rd axis. derived from the LI sampling (Table 2). There The efficacy of the ordination in representing were 2 exceptions from the shrub-type. the original species by samples matrix in only Ephedra apparently decreased in cover over 2 dimensions is corroborated by R2 values the 38-year time interval and mean combined resulting from comparisons of ecological dis- plant cover per LI increased. PL-based results tance between the original data matrix and from the tree-type are generally conformable ordination distances (Table 5). The cumulative with those derived from LIs even though spe- R2 increases from 0.870, when only the 1st cific values differ. PL observations also con- ordination axis is considered, to 0.970, when firmed the encroachment of Pinus and Junipe- both ordination axes are used to calculate rus on the shrub-type elbs. ordination distances. Note the close corre- TWINSPAN RESULTS.—We found that sev- spondence between the species order (bottom eral of the more commonly observed species, to top) in the TWINSPAN 2-way ordered though important overall, were not useful as table (Table 4) and the species scores (left to differential or association-defining species. right) along DCA axis 1 in the species ordina- These ubiquits included Poa, Opuntia, Artem- tion (Fig. 4). The stand ordination (Fig. 5) isia, and Ephedra. The first 2 species were revealed 5 major elb arm groups that corre- present in most elb arm LI samples for both sponded nicely with their arrangement in the tree- and shrub-types. Opuntia was absent TWINSPAN 2-way ordered table. only from 2 elb arm LIs, and Ephedra was WOODLAND TREE DEMOGRAPHICS.—In 1996 present in all elb arm LI samples except one Pinus density in the shrub-type was 17 ± 15 (Table 4). These common and, in the case of trees ⋅ ha–1, whereas Juniperus density was 17 Artemisia, dominant species did not define the ± 19. Total estimated tree density within the shrub-type vegetation on Fishtail Mesa since shrub-type was 34 ± 31 trees ⋅ ha–1. However, they also formed the understory of the Pinyon- these estimates are based on only a few sam- Juniper Woodland. In general, Poa, Artemisia, pled trees, 10 each of Pinus and Juniperus. and Ephedra tended to increase in relative The density of Pinus and Juniperus in the tree- importance from the tree-type to the shrub- type (n = 7 elb arms) was 471 ± 196 and 250 ± type and were therefore classified by TWIN- 113 trees ⋅ ha–1, respectively. Total estimated SPAN with the shrub-type species group after tree density within the tree-type was 720 ± the 1st (primary) TWINSPAN division. Opun- 306 trees ⋅ ha–1. tia showed no apparent trend in abundance It is difficult to compare estimates of tree values but had relatively high importance in density observed in 1958 and 1996. The 1958 tree-type (Table 4). Therefore, it was classified data were reported by 186-m2 (2000-ft2) sec- into the tree-type species group. tions within 2 soil types, a limestone and Differential species for the tree-type included sandy limestone upland (elbs 1, 2, 3, 5, 6, 7) and primarily Pinus, Juniperus, and Poa (Table 4). cherty ridges (elb 8). Apparently, the alluvial 170 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 4. Two-way ordered table produced by TWINSPAN in PC-ORD. The 2 heavy solid lines mark primary stand dotted line marks a quaternary division. Tree-type samples are in the upper left with dark gray shading, while shrub-

______Sampling units on Fishtail Mesa ______Tree-type elbs Elb Elb Elb Elb Elb Elb Elb Plant species 8 6L 6R 7L 7R 3L 3R Shepherdia rotundifolia – 4––– 44 Lesquerella gordonii – –––– 1– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Arceuthobium divaricatum – –1–– –– Cowania mexicana – 411– –– Echinocactus triglochidiatus – 1––– –– Phoradendron juniperinum –24–––– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Yucca baccata 7 544– –– – Juniperus osteosperma 6 7887 56 Pinus edulis 4 6888 88 ------Coryphantha vivipara 1 –––– –– Fallugia paradoxa 4 –––– –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Bouteloua gracilis 7 2211 –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Castilleja chromosa – –––– 1– Opuntia polyacantha 1 3111 33 ______- Phlox longifolia – –1–– –– Astragalus calycosus – 11–1 11 Poa fendleriana 5 5566 44 Artemisia tridentata 7 7756 88 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Euphorbia fendleri – –––– –– Penstemon sp. – –––– –– Achnatherum hymenoides – –––– –– Sphaeralcea grossulariaefolia – –––– –– Lomatium nevadense – –––– –– ------Leucelene ericoides – –1–– –– Astragalus pinonis – –111 –1 Hymenoxys richardsonii – –1–– –– Ephedra torreyana 4 112– 41 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Kraschenninkovia lanata – –––– –– ...... Eriogonum corymbosum – –––1 –– ------Erigeron concinnus – –––– –– Arabis perennans – –––– –– Coleogyne ramosissima – –––– –– Stipa speciosa – –––– –– Astragalus newberryi – –––– –– Atriplex canescens – –––– –– Stipa comata – –––– –– Gutierrezia sarothrae – –––– –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Chrysothamnus greenei – –1–– –– Streptanthus arizonicus – –––– –1 Sitanion hystrix – 1––– –1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Stands division level 0 0000 00 0 1111 11 0000 11 – - 2001] RESURVEY OF FISHTAIL MESA 171 and species divisions. Heavy dashed lines mark secondary divisions. Dashed lines mark tertiary divisions and the fine type samples are in the lower right with light gray shading.

______Sampling units on Fishtail Mesa Shrub-type elbs ______Species Elb Elb Elb Elb Elb Elb Elb Elb division 2L 4L 5L 5R 4R 1L 1R 2R level – – – – – – – – 11111 – – – – – – – – 11111 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 11101 – – –1–4 – ––– 11101 – – – – 6 – – – 11101 ------– – – – – – – – 11100 – – – – – – – – 11100 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 3––– – ––– 110 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –––– – 1–– 10 ______2–11 1 34– 10 –1–– – ––– 01 1111 1 1–1 01 6576 5 656 01 9999 9 999 01 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 1 – – – – – 0011 – – – 1 – – – – 0011 1 – 1 – – – – – 0011 1 – – – – – – – 0011 1 – – – – – – – 0011 ------– – – 1 1 – – – 0010 – 1 3 1 4 – – – 0010 –1–1 – –11 0010 2 4 4 3 3 4 4 1 0010 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 2 1 – – – – 2 – 00011 ...... 1 – 1 1 1 2 3 1 000101 ------– – – – – – – 1 000100 – – – – – – – 1 000100 – – – – – – – 3 000100 – – – – – – 2 – 000100 –––– 1 1–1 000100 –––– – 21– 000100 –––– – 51– 000100 –––– 1 5–3 000100 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 4 – 0000 –––– 1 1–3 0000 – 1 – – – 4 1 3 0000 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 1111 1 111 0000 0 111 0000 1 – – 172 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 4. Detrended correspondence analysis—species plot—of the current vegetation on Fishtail Mesa. See Appendix for alpha code index for scientific and common names. soil type (elb 4) was not included in the 1958 mation of tree density within size classes in study. Also, trees <0.9 m high were not sam- the manner of Goff and West (1975), the distri- pled. After eliminating trees <0.9 m from our bution curve was fitted, with significant results, data and employing Jameson et al.’s (1962) to a 4th-degree polynomial as shown in the 2 reporting scheme, we found approximately 5.0 inset graph of Figure 6 (R = 0.96; F[α=0.05,;3,7] Pinus trees in limestone uplands, identical to = 52.5; P = 3.6E-05). The size-density rela- that reported for 1958. Similarly, we found 3.0 tionship for Juniperus was best fitted by a 2nd- Juniperus trees in limestone uplands compared degree polynomial, but the regression was not 2 to 4.2 for 1958. We found 1.0 Pinus trees on significant (R = 0.19; F[α=0.05;3,7] = 2.075; P cherty ridges, compared to 3.2 reported for = 0.196) and quite anomalous in terms of the 1958; there were no Juniperus trees in 1996 “rotated sigmoid-curve” ideal (Fig. 6, inset). compared to 3.1 in 1958. The relationship is actually somewhat bimodal, In 1996 we found substantially more Pinus with a peak at the 1–5 cm and again at the trees in the <1 cm stem diameter class in the 15–20, 20–25, and 25–30 cm classes. Density tree-type than Juniperus in any stem diameter depressions occurred in the 5–10 and 10–15 class (Fig. 6). Establishment of seedling Junipe- cm diameter classes and at the largest diame- rus was sparse to nonexistent. After thorough ter classes, i.e., >30 cm (Fig. 6, inset). This sampling, only 3 Juniperus seedlings were dis- pattern suggests that recruitment to the Jun- covered throughout the elbs in the tree-type iperus population on Fishtail Mesa is low and vegetation, and none were discovered in shrub- perhaps pulselike. type elbs. In general, numbers of both trees in The age-size (basal diameter) relationship, the shrub-type were low for all classes, and for which age was directly determined, was age-size relations could not be ascertained. conducted for 40 Pinus. These data were fitted The size-density distribution curve for Pinus, to the Chapman-Richards function. Both upper calculated from observations gained from all and lower 95% confidence limits are shown to tree-type elb strip plots, exhibits a classic, assess the possible error in the diameter esti- inverse J-shaped distribution curve (Fig. 6). mate. Observations were analyzed both as a This type of curve indicates plants with high complete set (Fig. 7a) and separately for shrub- reproduction, where the probability of death type trees and tree-type trees (Fig. 7b). The decreases exponentially as plants age (Pearl age-size relation as predicted by the Chap- 1928, Begon et al. 1996). After log10 transfor- man-Richards function was significant, but 2001] RESURVEY OF FISHTAIL MESA 173

Fig. 5. Detrended correspondence analysis—elb plot—of the current vegetation on Fishtail Mesa. with moderate scatter around the regression shrub-type. In the tree-type change determi- line. Separate analysis improves the fit to the nation, except for a substantial increase in Chapman-Richard function (Fig. 7). cover of Poa, is problematic, but the cover of REPHOTOGRAPHY.—Panoramic rephotogra- most plants has probably remained stable. phy of the shrub-type shows little change in We found that Poa was a significant sec- standing dead juniper snags and growth of the ondary member of shrub- and tree-types on surrounding shrub vegetation. Only finger- Fishtail Mesa. Its absence on the mainland in sized tips of snag branches have been removed the postsettlement era (Jameson et al. 1962, in the past 38 years. Before-after photographs Schmutz et al. 1967) was probably due to land of elb 5R (Fig. 8) are shown as an example. It management practices. Whereas Poa had 0.06% is clear, however, from the increase in pinyon and 0.07% absolute cover in shrub- and tree- tree density in both the foreground and back- types in 1958 (Jameson et al. 1962), we found ground of the 1996 photographs, compared with 2.6% and 2.5%, respectively, in 1996. The dra- the 1958 photographs, that Pinus trees are matic increase in cover values of Poa between invading or reoccupying this shrub-type site. 1958 and 1996 may be a response of the plant to climatic changes, such as recovery from the DISCUSSION 1950s drought (Neilson 1986), protracted absence of fire, or a combination of such factors. Comparison of 1958 and 1996 data from LI Results of change determination derived observations shows that species cover compo- from PL observations for the 4 major species sition of Fishtail Mesa vegetation types, with a in shrub- and tree-types are likewise difficult few notable exceptions, has not changed appre- to interpret but parallel LI results. Where ciably over the past 38 years. Most observed exceptions occured, such as the contradictory changes in plant cover do not appear to be sig- results for change in combined plant cover nificant (Tables 3, 4) and may even reflect dif- within the shrub-type over the time period of ferences in measurement precision and obser- concern, the PL methodology is probably sus- vation technique of field personnel. Within the pect due to its inherent inefficiency relative to shrub-type, Artemisia has declined, whereas direct cover-measuring techniques such as the Poa has increased. Absolute cover of trees LI (Bonham 1989). (Pinus and Juniperus) increased in the shrub- Since TWINSPAN is based on progressive, type between 1958 and 1996, but only in 2 refined reciprocal averaging, species and stand elbs. Other species like Ephedra, Opuntia, and orderings in the 2-way ordered table (Table 4) Gutierrezia have decreased since 1958. Pinus reflect, to an extent, an ecological gradient. In and Juniperus appear to have increased in the general, the 2-way ordered table classified 174 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 5. Summary statistics for the eigen-analysis component of the Fishtail Mesa DCA. Coefficients of determination (R2) relate ordination distances to the distance metric of the original data matrix. The distance metric employed was percent similarity, otherwise known as Czekanowski’s coefficient (sometimes mistakenly referred to as Sørenson’s coefficient or Jaccard’s coefficient [Kent and Coker 1992]), as defined in the Methods section. Distance comparisons between the original and ordination matrices were based on the n(n–1)/2 possible comparisons for 15 samples.

Eigen-analysis ______DECORANA axis number statistcs 1234 Eigenvalue 0.496 0.106 0.039 0.019 Percent of total 57.904 12.409 4.540 2.223 Cumulative percent 57.904 70.313 74.854 77.077 Coefficients of determination (R2)—incremental 0.870 0.100 –0.008 — Coefficients of determination (R2)—cumulative 0.870 0.970 0.962 — stands and species according to an inferred there were no distinct species subgroups due moisture gradient, with less xeric-adapted to the influence of the ubiquits. species and plant associations in the upper left We interpret the species sequence along quadrant of Table 4, replaced by more xeric DCA axis 1 as a reflection of a complex moisture species and plant associations in the lower gradient. We attribute this to the previously right quadrant. Stand order from left to right described rim effect. Species typical of the across the top of the table reflects one compo- more xeric shrub-type vegetation (group A, nent of this moisture gradient. Less xeric tree- Fig. 4) were gradually supplanted from left to type vegetation in the mesa interior is re- right along axis 1 by plant species more typical placed by more xeric shrub-type vegetation of the tree-type vegetation (groups C, D, E; along the mesa rim and exposed interior sites. Fig. 4). Ubiquits and occasional species with Elb 4R was unique in that the transect ran little or no faithfulness to either vegetation across a small valley with deep, fine alluvial type were aggregated in group B. fill. Elbs 1L, 1R, and 2R were located on the Species typical of the shrub-type and ubiq- southern, most exposed tip of the mesa, sub- uit/occasional species showed little dispersal ject to warm, dry air rising from the canyon along DCA axis 2 (Fig. 4), whereas tree-type below. species (groups C–E) are well dispersed along With the possible exception of Eriogonum the axis. We interpret DCA axis 2 as possibly corymbosum (wild buckwheat), no plant species reflecting a gradient of soil textures. The in the shrub-type group could be interpreted agglomeration of species in group C (Yucca, as a differential species. The only abundant Poa, Coryphantha vivipara var. arizonica [pin- species in this group were the ubiquits dis- cushion cactus], and Fallugia paradoxa [Apache cussed above, which tended to reach their plume]) are more typical of sample sites with greatest levels of abundance here. Only Stipa rocky, clayey soils, often with bedrock close to comata (needle-and-thread), previously mis- the surface. Species comprising group E identified by Jameson et al. (1962) as S. spe- (Opuntia spp., Castilleja chromosa [Indian paint- ciosa, and Gutierrezia exhibited RC values in brush], Shepherdia rotundifolia, Pinus, and the 8–16% category (i.e., class 5 in Table 4). Lesquerella gordonii [Gordon bladderpod]) Thus, the shrub-type is defined more by the were observed to be more typical of fine- to absence of Pinus and Juniperus rather than moderately fine-textured soils. any special associations of differential species The stand ordination (Fig. 5) reflects the with a high preference for this vegetation same inferred ecological gradients as the type. TWINSPAN results and species abun- species ordination. All shrub-type elb arms dance and constancy patterns discussed above were clustered on the left of the ordination show a clear demarcation at the primary divi- (xeric), whereas tree-type elb arms were sion level between woodland (tree-type) species aggregated, though more loosely, on the right and samples and shrub-steppe (shrub-type) (less xeric). Elb 4R group II (Fig. 5) was some- species and stands. Not surprisingly, Pinus, what distinct from the main group of shrub- Juniperus, and Yucca form a distinct associa- type elbs (group I) just as it was in the tion within the tree-type. In the shrub-type TWINSPAN results (Table 4). Elb 4R was the 2001] RESURVEY OF FISHTAIL MESA 175

Fig. 6. Tree density and size (diameter) classes in centimeters for tree- and shrub-type elbs for Pinus and Juniperus. only shrub-type elb that had a substantial in density of Pinus beginning with the seed- amount of Pinus cover, and it may be undergo- ling class (<1 cm) declined smoothly, and a ing reoccupation or invasion. Relative cover of well-defined plateau region at the intermedi- both Pinus and Juniperus was high throughout ate size classes never occurred (Fig. 6). This this sample group, and soil textures varied in suggests only a moderate decline in mortality composition. between intermediate size classes. In other The depiction of tree reproduction in 1996 words, the Pinus population at Fishtail Mesa (Fig. 6) is that of a large number of Pinus may be approaching an all-aged condition, but seedlings and immature plants, with low it is not there yet. Assuming that no cata- reproduction of Juniperus. A clearer picture of strophic changes occur in the future, such as a the tree age-size relationship emerged when stand-replacing fire, the Pinus population in within-class tree density data were log10 trans- the tree-type vegetation of this relict area may formed (Fig. 6). The Pinus size-density rela- eventually become fully mature and all-aged. tionship approximated a “rotated sigmoid Almost all tree cores taken from tree-type curve” (Goff and West 1975, West et al. 1981) vegetation fell below the regression line in typical of an all-age stand with differential Figure 7 and therefore show some degree of recruitment from one size class to the next. growth suppression. This may indicate that Mortality is high and growth rates are slow in intraspecific competition, as described by the smaller size classes, resulting in a very Tausch and Tueller (1990), is an active factor steep curve. Recruitment to the canopy, how- within the Pinus population of the tree-type. ever, increases the growth rate and reduces Not surprisingly, the majority of Pinus cores mortality. As a result, the slope of the curve collected from the shrub-type lie above the decreases. High germination and seedling regression line, showing increased growth establishment followed by space and light rates over their woodland counterparts. competition result in rapid mortality and It has been shown that size-age patterns of reduced growth of young stems in older stands Pinus populations are more accurately reflected (West et al. 1981). On Fishtail Mesa the decrease when suppressed trees are removed from 176 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 7. Pinyon age-size relationship (A) using basal diameter and annual ring counts collected from trees adjacent to and outside all 8 elb arms and (B) according to shrub-type and tree-type. analysis (Tausch and Tueller 1990). In our re- 0.659). First, there was great improvement in search we felt the pattern of growth suppres- R2 values for the curve fits (R2 = 0.87 for the sion in relation to location and vegetation type shrub-type Pinus and R2 = 0.76 for the tree- was an important issue; thus, the entire data type Pinus). Second, Pinus growing within the set was retained. However, we did separate woodland communities on Fishtail Mesa were Pinus cores taken from the tree-type from generally growth-suppressed relative to site those taken from the shrub-type and removed location and community type, but only in com- the 5 elb 4 samples from the latter (Figs. 7a, parison to trees located within the shrub-type. 7b). Both data subsets were fitted to the Chap- Thus, different trees of similar age within the man-Richards function individually (R2 = study area may exhibit basal diameters that 2001] RESURVEY OF FISHTAIL MESA 177

Fig. 8. Landscape photographs of shrub-type elb 5, right arm, in (A) 1958 and (B) 1996. Note that Pinus density and size of individuals have increased throughout the depicted scene. Standing weathering snags in the mid-ground are still present. differ by as much as 20 cm. This is no doubt lyzed. Since 1850 is 146 years prior to our due to differences in microsite characteristics field research completed in 1996, the basal and perhaps competitive suppression from diameter estimate at 146 years ± the 95% con- adjacent dominant Pinus, as described by fidence limits is a reasonable value for attribu- Tausch and Tueller (1990). tion of presettlement, postsettlement, and in- Based on the evidence given in Figure 7b, determinate status. In the tree-type the basal and if 1850 is taken as a presettlement date, diameter (BD) estimate for a Pinus 146 years old ± then 5 Pinus core samples taken from the tree- (BDest[146]) is 22.4 4.7 cm. Pinus with BDs type and only 1 from the shrub-type represent greater than 27 cm are probably presettlement presettlement Pinus within the sample ana- trees, while those with BDs smaller than ca 17 178 WESTERN NORTH AMERICAN NATURALIST [Volume 61 cm are probably postsettlement trees. Trees studied details of 1940 and 1994 aerial pho- with BDs in between are indeterminate. Like- tographs of the south end of Fishtail Mesa, wise, for Pinus growing in the shrub-type, the where locations of individual tree canopies ± BD estimate (BDest[146]) is 30.9 7.4 cm. Pinus can be seen in both photographs. Patches in growing in the shrub-type with a BD greater the 1940 aerial photograph that lacked tree than ca 38 cm are probably presettlement cover supported Sagebrush Steppe vegetation. trees, and Pinus smaller than ca 23 cm are The same areas in the 1994 aerial photograph probably postsettlement trees. Trees with BDs showed tree canopies, suggesting that since in between are indeterminate. 1940 Pinus and/or Juniperus have colonized These findings strengthen our hypothesis the patches. We surmise that Artemisia will that Pinus are actively reoccupying the shrub- decline under the woodland canopy as well as type on Fishtail Mesa. Exceptions like elb 2 in the shrub-type, albeit perhaps more slowly are explained on the basis of site characteris- in the latter. In the long term of 100–300 years, tics involving the rim effect that creates a vegetation dynamically responds to fire or moisture gradient that is reflected in the vege- reflects changing climatic conditions. At this tation as revealed by indirect ordination (Figs. point in time, we consider Fishtail Mesa to be 4, 5). On an isolated mesa in the Grand Canyon, a Sagebrush Steppe with slowly expanding the most noticeable rim effect should be on Pinyon-Juniper Woodland patches. In the ab- the windward side. In the case of Fishtail sence of fire, Pinus and Juniperus could even- Mesa, this is the southwestern portion (Fig. 3, tually reoccupy most of the mesa and the extreme lower left). The southern tip of the Sagebrush Steppe would exist as patches near mesa is very narrow, without an interior, and the rim. for the most part dry and devoid of woodland. In conclusion, we found that several of the In general, throughout Fishtail Mesa wood- more important species components of Fish- land is noticeably denser away from the south- tail Mesa’s vegetation types have not signifi- west rim, strongly implicating the rim effect. cantly changed over the last 38 years. But, some Under the current climatic regime, it is un- species have undergone differential reduc- likely that Pinus would ever establish there. tions in cover, like Artemisia, or increases, like Juniperus and Pinus have possibly reoccu- pied the Sagebrush Steppe on Fishtail Mesa Poa. We surmise that Fishtail Mesa has experi- for millennia, and it appears that the mesa’s enced repeated waves of Juniperus establish- vegetation is presently in the middle of such a ment within the Artemisia-Poa steppe, fol- cycle. Fire has apparently not been an impor- lowed by a secondary wave of establishment tant factor for many years on Fishtail Mesa. by Pinus. Subsequently, reproduction of Junipe- Based upon the apparent stability of vegeta- rus in the densely wooded areas declined and, tion on Fishtail Mesa as seen by elb strip concomitantly, germination and seedling estab- methodologies, direct observation, and photo- lishment of Pinus increased in the maturing graphic interpretation, fires on Fishtail Mesa juniper woodland. Eventually Pinus may be- are apparently infrequent to rare. The last fire come dominant in number, height, and canopy on the mesa may date from the turn of the cover. Artemisia beneath the tree canopy will century or earlier. It is entirely possible that decline but, because of the relatively open remnant standing snags on the mesa could nature of the canopy, will always be an associ- actually be remnants of trees killed during the ate species and the dominant shrub. Following major drought which took place in the South- episodic events of drought, parasitism, disease, west during the 1950s (Neilson 1986). Also, or lightning-caused wildfire, wooded areas none of the 40+ Pinus cores collected for pop- will revert to a Sagebrush Steppe if residual ulation age-size determination showed any sagebrush plants or their seeds remain. Por- evidence of fire scarring. Fire may have tions of Fishtail Mesa are representative exam- caused the death of the original trees; how- ples of a dynamic, unmanaged, all-age stand (or ever, drought, mistletoe infestation, or insect nearly so) of Pinyon-Juniper Woodland. Arid- attack cannot be ruled out. ity near the mesa rim due to the rim effect will On a shorter time scale, aerial photographs ensure, at least during this climatic era, that provide corroboration of increasing tree cover some Artemisia-Poa steppe vegetation will on Fishtail Mesa over the last 50–60 years. We always persevere on Fishtail Mesa. 2001] RESURVEY OF FISHTAIL MESA 179

Retaining examples of pristine natural envi- D. Smith, associate editor, Western North ronments is one of the National Park Service’s American Naturalist, as well as those from one missions. It is important for inspiration, edu- anonymous reviewer. Funds for the publica- cation, and interpretation, as well as for park- tion of this manuscript were provided by a based and academic study of research natural grant from the Grand Canyon Association areas. These relict areas offer baselines for through the 1999 Annual Grants Program gauging impacts occurring elsewhere, defining administered by Grand Canyon National Park. productive potentials of woodlands, providing sanctuaries for native species, and studying LITERATURE CITED ecological processes (Hanson 1939, Callahan 1984, 1991, Van Pelt and Tuhy 1991). The AXELROD, D.I. 1950. Evolution of desert vegetation in western North America. Pages 217–298 in D.I. Axel- study of dynamic ecology, or succession, is rod, editor, Studies in Late Tertiary paleobotany. often hampered because of the length of time Carnegie Institute of Washington Publication, Wash- involved, the absence of control over desirable ington, DC. communities, and the difficulty of securing BEGON, M., J.L. HARPER, AND C.R. TOWNSEND. 1996. Ecology: individuals, populations, and communities. long-term management cooperation (Clements Blackwell Science, Oxford, U.K. 1930). Fishtail Mesa offers an excellent natural BETANCOURT, J.L. 1990. Late Quaternary biogeography of area research site or benchmark for long-term the Colorado Plateau. Pages 259–292 in J.L. Betan- study and surveillance of a Pinus-Juniperus court, T.R. Van Devender, and P.S. Martin, editors, Packrat middens, the last 40,000 years. University of woodland and Artemisia-Poa steppe. Its large Arizona Press, Tucson. size makes it particularly well suited for such BEYMER, R.J., AND J.M. KLOPATEK. 1992. Effects of graz- an effort. The descriptive historical record ing on cryptogamic crusts in pinyon-juniper wood- begins in the 1930s, with aerial photography lands in Grand Canyon National Park. American Midland Naturalist 127:139–148. available from 1940. Permanent study areas BLACKBURN, W.H., AND P. T. T UELLER. 1970. Pinyon and with fixed photo sites were established in juniper invasion in black sagebrush communities in 1958. Our study recorded additional vegeta- east-central Nevada. Ecology 51:841–848. tion, soil, faunal, and GPS data. Furthermore, BONHAM, C.D. 1989. Measurements for terrestrial vegetation. Wiley and Sons, New York. field data, notes, photography, herbarium speci- CALLAHAN, J.T. 1984. Long-term ecological research. Bio- mens, rectified maps, and electronic data are Science 34:363–167. archived in the Grand Canyon National Park’s ______. 1991. Long-term ecological research in the United Museum Collections where they will receive States: a federal perspective. Pages 9–21 in P. G . Risser, editor, Long-term ecological research: an inter- permanent curatorial care. We hope that future national perspective. Wiley and Sons, New York. surveys will build upon these efforts to pro- CANFIELD, R. 1941. Application of line interception in vide further insight into changes in naturally sampling range vegetation. Journal of Forestry 39: functioning ecosystems of the Pinyon-Juniper 388–194. CLEMENTS, F.E. 1930. The relict method in dynamic ecol- Woodland and Sagebrush Steppe. ogy. Ecology 22:39–67. CLUTTER, J.L., J.C. FORTSON, L.V. PIENAR, G.H. BRISTER, ACKNOWLEDGMENTS AND R.L. BAILEY. 1983. Timber management, a quantitative approach. Wiley and Sons, New York. DESPAIN, D.W. 1989. Radial growth relationships in Utah The resurvey of Fishtail Mesa benefited from juniper ( Juniperus osteosperma) and pinyon pine the interest, enthusiasm, and participation of (Pinus edulis). Doctoral dissertation, University of Donald (Don) Jameson, the previous, princi- Arizona, Tucson. pal ecologist. Don was actively involved, first DRISCOLL, R.S. 1958. A loop method for measuring ground cover characteristics on permanent plots. Journal of during the 2 years of correspondence about Range Management 11:94. the study and then during the week of data GOFF, F.G., AND D.C. WEST. 1975. Canopy-understory inter- collection in May 1996. He collected all Parker action effects on forest population structure. Forest loop data and answered numerous questions Science 21:98–108. GREEN, C.R., AND W. D. S ELLERS. 1964. Arizona climate. about methodology. His participation, experi- University of Arizona Press, Tucson. ence, and historical perspective made this HANSON, H.C. 1939. Check areas as controls in land use. resurvey especially meaningful. We were sad- Science Monthly 48:130–146. dened when Don passed away on 30 August HALVORSON, W.L. 1972. Environmental influence on the pattern of plant communities along the North Rim of 1998. We appreciate the constructive comments the Grand Canyon. American Midland Naturalist of our reviewers, Robert M. Webb and Stanley 87:223–235. 180 WESTERN NORTH AMERICAN NATURALIST [Volume 61

HELTSCHE, J.F., AND N.E. FORRESTER. 1983. Estimating USDA Soil Conservation Service Technical Bulletin species richness using the jackknife procedure. Bio- 1169. metrics 39:1–11. PEARL, R. 1928. The rate of living. Knopf, New York. HERMANN, R. 1989. Long-term monitoring for environ- SCHMUTZ, E.M., A.E. DENNIS, A. HARLAN, D. HENDRICKS, mental change in national parks. Abstract, Ecologi- AND J. ZAUDERER. 1976. An ecological survey of cal Society of America Annual Meeting, Toronto, Wide Rock Butte in Canyon de Chelly National Ontario. Monument, Arizona. Journal of Arizona Academy of HILL, M.O. 1979a. TWINSPAN: a FORTRAN program for Science 11:114–125. arranging multivariate data in an ordered two-way SCHMUTZ, E.M., C.C. MICHAELS, AND B.I. JUDD. 1967. table by classification of the individuals and attri- Boysag Point: a relict area on the North Rim of Grand butes. Microcomputer Power, Ithaca, NY. Canyon in Arizona. Journal of Range Management ______. 1979b. 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Accepted 11 April 2000 2001] RESURVEY OF FISHTAIL MESA 181

APPENDIX. Alpha code index for scientific and common names for plants listed in Figure 3. Alpha code Scientific name Common name Ach.hym Achnatherum hymenoides Indian ricegrass Ara.per Arabis perennans Rock cress Arc.div Arceuthobium divaricatum Pinyon dwarf mistletoe Art.tri Artemisia tridentata Big sagebrush Ast.cal Astragalus calycosus Gray’s locoweed Ast.new Astragalus newberryi Newberry milk-vetch Ast.pin Astragalus pinonis var. atwoodii Pinyon milk-vetch Atr.can Atriplex canescens Four-wing saltbush Bou.gra Bouteloua gracilis Blue grama Cas.chr Castilleja chromosa Indian paint brush Chr.gre Chrysothamnus greenei Green’s rabbit brush Col.ram Coleogyne ramosissima Black brush Cor.viv Coryphantha vivipara var. arizonica Pincushion cactus Cow.mex Cowania mexicana var. stansburiana Cliff rose Ech.tri Echinocactus triglochidiatus Hedgehog cactus Eph.tor Ephedra torreyana Torrey joint-fir Eri.con Erigeron concinnus Tidy fleabane Eri.cor Eriogonum corymbosum Wild buckwheat Eup.fen Euphorbia fendleri var. chaetocalyx Fendler spurge Fal.par Fallugia paradoxa Apache plume Gut.sar Gutierrezia sarothrae Snakeweed Hym.ric Hymenoxys richardsonii Pinque Jun.ost Juniperus osteosperma Utah juniper Kra.lan Krascheninnikovia lanata Winter fat Les.gor Lesquerrella gordonii Gordon bladderpod Leu.eri Leucelene ericoides White aster Lom.nev Lomatium nevadense Parish wild parsley Opu.pol Opuntia polyacantha Prickly pear Pen.spp Penstemon sp. Beard tongue Phl.lon Phlox longifolia Phlox Pho.jun Phoradendron juniperinum Mistletoe Pin.edu Pinus edulis Pinyon pine Poa.fen Poa fendleriana Mutton grass She.rot Shepherdia rotundifolia Roundleaf buffalo berry Sit.hys Sitanion hystrix Squirrel tail Sph.gro Sphaeralcea grossulariaefolia Globe mallow Sti.com Stipa comata Needle-and-thread Sti.spe Stipa speciosa Desert needlegrass Str.ari Streptanthus arizonicus Twist flower Yuc.bac Yucca baccata Banana yucca