Possible effects of residential development on streamflow, riparian plant communities, and fisheries on small mountain streams in central Arizona

Forest Ecology and Management, 3 3 / 3 4 ( 1 9 9 0 ) 351-361

351

Elsevier Science Publishers B.V., A m s t e r d a m - - P r i n t e d in The N e t h e r l a n d s

Possible effects of residential development on streamflow, riparian plant communities, and fisheries on small mountain streams in central Arizona Alvin L. Medina USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Forestry Sciences Laboratory, Arizona State University Campus, Tempe, AZ 85287-1304 (U.S.A.)

ABSTRACT Medina, A.L., 1990. Possible effects of residential development on streamflow, riparian plant communities, and fisheries on small mountain streams in central Arizona. For. Ecol. Manage., 33/34: 351-361. Increased residential development along small mountain streams within pine forests in central Arizona has surged in the last 20 years and presents a potential threat to riparian plant communities on these small mountain streams because it can alter the nature of streamflow from perennial to ephemeral. The change in streamflow increases water stress on riparian plants along these streams. Cultural activities associated with residential development that affect streamflow are water diversions, groundwater pumping, and changes in land use. Measurements of tree densities and stand composition of Arizona alder (Alnus oblongifolia ) and box elder (Acer negundo) showed that perennial stream reaches had greater tree densities in all diameter classes, compared with ephemeral stream reaches where small-diameter trees were absent. Xylem water-potential measurements decreased more rapidly on trees occupying ephemeral stream reaches than on trees of comparable reaches of perennial streams over time during the summer. The increase in water stress in trees growing along ephemeral stream reaches may be responsible for the lower plant densities and lack of seedling establishment measured. Trout populations also declined when perennial streamflow changed to ephemeral.

INTRODUCTION

Consumer interest in second-home development in rural areas of the Southwest has increased greatly in recent years. In Arizona, various economic and social aspects, including increased population growth, prosperity, and increased land value, influenced second-home development in the Mogollon Rim region (Lindquest, 1972; Bond and Dunikoski, 1977). Home and land subdivisions located along riparian zones of high-elevation pine forests are in greatest demand because of the aesthetics of the stream environment and water availability. Water consumption by home subdivisions increased proportionately with development, resulting in limited water supply for some commuElsevier Science Publishers B.V.

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nities and changes in streamflow conditions of perennial streams. Changes in streamflow pose potential threats to riparian vegetation and fishery resources, but these threats are difficult to assess either directly or indirectly (Bormann et al., 1970). Various researchers have examined water-related problems (i.e., quality, socioeconomic) associated with second-home development (Brickler and Utter, 1975; Segall, 1975; Morgan, 1978; Ponce and Dederick, 1979; Lewis, 1980). However, most studies were primarily concerned with impact assessment of water quality. Other studies (Johnson and Carothers, 1982) focused on recreational problems affecting riparian habitats. Information regarding the effects of home development and water consumption on riparian vegetation and aquatic habitats is scant and largely limited to unpublished reports (Bond and Dunikoski, 1977 ). This study specifically examined the impact of ( 1 ) water use by residential development along a small mountain stream in central Arizona on streamflow, riparian plant communities, and fisheries; and (2) the influx of residential development on ten streams. For the site-specific study on Pine Creek, data were collected on changes from perennial to ephemeral streamflow, xylem water-potentials on two tree species, and changes in aquatic habitat. For the general study, trends in home construction and water usage were determined for the region occupied by the eleven streams. Hydrological and biological measurements were then related to changes in water use by expanding residential communities along the sampled stream reaches. METHODS

Description of area The study area is near the geographic center of Arizona in northwestern Gila County, immediately below the Mogollon Rim escarpment on the Payson Ranger District, Tonto National Forest. Steep mountainous canyons dissect the landscape from east to west. Elevations range from 2350 m in the upper watersheds to about 1450 m in the pinyon/juniper zone. Precipitation is bimodal ( s u m m e r and winter) with localized monsoon s u m m e r showers and low-intensity winter storms. Nearly 65% of total precipitation occurs in winter, primarily as snow. Mean annual precipitation is 635 m m , with a range of 550-760. Mean annual temperature averages 14 °C and ranges from - 10 °C to 32°C. Base flows of 42.51 s - l are c o m m o n in most creeks, with peak flows as great as 170 cm s- ~ (Anonymous, 1966 ). The vegetation consists of Petran Montane Conifer Forest in the upper sections of the watersheds and Great Basin Conifer Woodland in the lower areas (Brown and Lowe, 1980). Interspersed within the woodland zone are stands of interior chapparal. Pine Creek is a first-order ephemeral stream draining southward into the

EFFECTS OF RESIDENTIAL DEVELOPMENT ON SMALL MOUNTAIN STREAMS

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Verde River system of central Arizona. Its origin is effluent from the water table which emanates from the Coconino sandstone/shale contacts found on the south face of the Mogollon R i m escarpment at 2180 m. The perennial reach, approximately 8 km, extends from the headwaters to a geologic contact where sandstone formations give way to limestone at an elevation near 1675 m.

Deciduous trees characterize the riparian plant communities of Pine Creek and other creeks and include Arizona alder (Alnus oblongifolia), box elder (Acer negundo ) , and Arizona walnut ( Juglans major), bigtooth maple ( Acer grandidentatum ), and cherry ( Prunus serotina ). Ponderosa pine ( Pinus ponderosa), Gambel oak ( Quercus gambelii ) , Douglas fir ( Pseudotsuga menziesii), and white fir (Abies concolor) form vegetation mosaics with deciduous trees on terraces and streambanks. The region is a popular vacation, retirement, and recreation center. Summer residents exceed permanent residents by 2-3-fold. Commercial sectors are heavily dependent on tourism, s u m m e r residents, and recreationists (Anonymous, 1986 ). Settlement of the area, which started in the late 1800's, consisted mainly of cattle ranchers until recently. Stream water from Pine Creek is used locally for irrigation and domestic purposes, and little is returned to the main tributary. A detention dam constructed in 1965 in Pine Creek at an elevation of 1745 m diverts upstream water to the residential area below. Between May and October, most of the piped flow goes to residences for lawn and garden irrigation. This results in ephemeral stream conditions in the reaches below the detention dam during the s u m m e r months. Base flow during the s u m m e r is approximately 45 I s- l above the diversion (Anonymous, 1966). Other creeks in the area are also diverted for irrigation during the growing-season.

Sampling Pine Creek phase Densities and diameter-breast-height (Dbh) measurements of Arizona alder and box elder on perennial and ephemeral stream reaches of Pine Creek began at a point 200 m above and below the water detention dam, respectively. The ephemeral reach was that section of stream below the detention d a m where no surface flow persisted. At each reach, ten 10 × 30-m plots were systematically located 50 m apart from a randomly selected starting point within each area. The longitudinal side of each plot paralleled the streambank. Plots were limited to elevations between 1725 and 1775 m where both alder and box elder were present on sides of the stream channel. Differences between perennial and ephemeral reaches in total mean tree density, total mean density for alder and box elder, and total mean density between respective Dbh size classes of alder and box elder were determined using t-tests.

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Xylem water-potential measurements were made on paired alder and boxelder trees randomly located roughly 1 km apart on perennial and ephemeral reaches. Measurements were taken every four weeks beginning with ephemeral conditions in mid-May and ending mid-August. Measurements were made with a Scholander-type pressure bomb (Scholander et al., 1965 ) at 6-h intervals starting at 06:00 h. Samples were taken at the three daily time-periods to provide a more complete view of diurnal changes. Additionally, the trees have at least some roots within the phreatic zone and no major differences in waterpotential during pre-dawn hours were foreseen. Samples of xylem tissue were collected from terminal portions of the same branch ( 1.4-1.7 m from ground level) during all sample periods. If intermittent flows occurred from unusual rainfall events, measurements were taken at least five days after all pools in the ephemeral reach became dry. Nonparametric Tukey quick tests (Daniel, 1978 ) were used, for each daytime period across individual months, to ascertain if xylem water-potentials of paired alder and box- elder trees of perennial and ephemeral reaches were from the same subpopulations. Test results revealed no evidence that paired trees belonged to different populations. The hypothesis of identical water-potential subpopulation means was tested using t-tests of pooled tree data for each daytime period and across all months of paired trees. Streamflow was monitored with a water-level recorder on Pine Creek for two summers ( 1987 and 1988 ). Streamflow changes below the detention dam were recorded throughout the season. Rainbow trout (Salmo gairdneri) were visually counted in each reach every four weeks for two years ( 1987-1988 ) beginning with the onset of ephemeral conditions. Pools that paralleled each vegetation-study plot were searched for trout by hand-probing under banks and boulders.

Regional phase Trends in home development since 1885 for the ten regional streams and Pine Creek were determined by examining county plat records (Anonymous, 1987 ) and recording the number of homes constructed yearly. Records were examined for the following 11 creeks (Fig. 1 ): Strawberry Creek, Pine Creek, Webber Creek, Bray Creek, Chase Creek, East Verde River, Dude Creek, Bonita Creek, Ellison Creek, Tonto Creek, and Christopher Creek. Only private homes located on or adjacent to stream environments were used in the analysis. Plots of construction trends were graphed to show differences among years. Total n u m b e r of lots available for additional development were also noted. Roughly 3370 ha of private land exist within the watersheds and most are subdivided for home development. Records from the local water company and data from a water-usage survey for the same area (Bond and Dunikoski, 1977 ) were used to derive estimates of water consumption for the community of Pine.

EFFECTS OF RESIDENTIAL DEVELOPMENT ON SMALL MOUNTAIN STREAMS

MOGOLLON

355

RIM

Fig. 1. Location of 11 stream study sites below the Mogollon Rim on the Payson Ranger District, Tonto National Forest. RESULTS

Streamflow in Pine Creek was continuous on all study sections from late August 1986 to mid May 1987 and from early September 1987 to early May 1988. Intermittent flows occurred occasionally during late summer as a result of watershed rainfalls that yielded more than 9 m m of rain per event. However, pools became dry within two days after the storm. Results of t-tests revealed significant differences in total tree density ( P < 0 . 0 0 1 ) and total density of alder ( P < 0 . 0 0 5 ) and box elder ( P < 0 . 0 1 ) among stream reaches. Total mean densities of alder and box elder were 315 ha-1 and 343 h a - i on the perennial reach and 138 ha-1 and 173 ha-~ on the ephemeral reach, respectively; major differences ( P < 0.05) in density oc-

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A.L.MEDINA

TABLE 1 Comparison of mean tree density (no. h a - t ) of alder and box elder trees by respective Dbh size classes between perennial and ephemeral stream reaches of Pine Creek Size class

Alder

Box elder

(cm) 1: < 2.5 2:2.5-10 3: > 10-20 4:>20-30 5:>30-40 6:>40-50 Total

Perennial

Ephemeral

Perennial

Ephemeral

491 427 375 218 75 109 315

306 (32) 73(10)* 75 (12)* 78 (16)* 78 (15) 88 (15) 138 (20)

494 344 250 94 62 343

356 (55) 89 (12)* 83(I0)* 83 (21) 94 (31) 173 (29)

(168) l (135)* (62)* (31)* (12) (30) (57)

(126) (89)* (50)* (31) (12) (56)

d

Standard errors. *Denotes significant differences for respective size classes between perennial and ephemeral reaches at P < 0.05.

curred between reach types only for smaller-Dbh size classes of < 30 cm (alder) and <20 cm (box elder) (Table 1 ). No significant ( P < 0.05 ) differences in water-potentials for respective daytime periods of paired trees of the perennial and ephemeral reaches were found, indicating that they were from respective subpopulations. However, ttests revealed significant ( P < 0.05 ) differences in the mean water-potentials of alder for two daytime periods, 12:00 and 18:00 h, between perennial and ephemeral reaches; significant ( P < 0 . 0 1 ) differences in mean water-potentials of box elder also occurred for these two periods between perennial and ephemeral reaches. Xylem water-potentials of both alder and box elder located within the ephemeral reach became more negative than those within the perennial reach over the course of the day and the summer (Table 2). Water-potentials were similar at 06:00 h throughout the season, but differences increased as daytime temperature increased. Water-potentials remained lower at 18:00 h for ephemeral reaches. Box elder attained lower waterpotentials than alder on both reaches. The number of rainbow trout observed within ephemeral stream reaches changed rapidly from month to month. In 1987, 47 trout were seen in 27 pools during the month of May; in June, 11 in four pools; none in July; and in August, four in one pool. Similarly, in May 1988, 29 occurred in 16 pools; in June, two in one pool; and none in July or August. Only small pools of about 500-600 c m 2 and approximately 10 cm in depth remained in July. A heavy rainfall in the upper headwaters raised the water level enough to go over the spillway and recharge ephemeral pools in August of 1987, possibly accounting for the trout found during that period.

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EFFECTS OF RESIDENTIAL DEVELOPM ENT ON SMALL MOUNTAIN STREAMS

TABLE 2 Actual xylem water-potentials ( - MPa) of two each alder and box elder trees within perennial and ephemeral stream reaches of Pine Creek during the summer of 1987 Time

Alder

Box elder

Perennial

Ephemeral

Perennial

Ephemeral

1

2

1

2

1

2

1

2

06.00 12.00 18.00

-0.08 -1.06 -1.02

-0.09 -1.17 -1.03

-0.14 -1.46 -1.04

-0.22 -1.54 -1.06

-0.0 -1.57 -1.60

-0.0 -1.63 -1.70

-0.0 -1.67 -1.71

-O.O1 -1.76 -1.93

June 06.00 12.00 18.00

-0.11 -1.39 -1.14

-0.13 -1.45 -1.16

-0.12 -1.50 -1.15

-0.24 -1.60 -1.35

-0.02 -1.67 -1.93

-0.03 -1.75 -2.01

-0.01 -1.72 -1.99

-0.05 -1.94 -2.11

July 06.00 12.00 18.00

-0.11 -1.55 -1.19

-0.15 -1.64 -1.23

-0.22 -1.61 -1.71

-0.32 -1.91 -2.03

-0.04 -1.67 -1.92

-0.06 -1.75 -2.01

-0.05 -1.93 -2.12

-0.13 -2.01 -2.30

August 06.00 12.00 18.00

-0.14 -1.84 -1.31

-0.16 -1.89 -1.34

-0.27 -2.20 -1.85

-0.39 -2.36 -1.91

-0.04 -1.89 -1.70

-0.08 -1.92 -1.78

-0.08 -2.51 -2.28

-0.18 -2.63 -2.40

May

1200 PINE CREEK 1000

~_.

-- -- -

OTHER CREEKS

.....

REGION TOTAL

~. r

-

,,

800

0 1-

-

600

~t

rr I.U 400

7= 2OO

. . \%/I .;7

-

......

. . . . . 1900

.F:/ 1920

1940

,'-.,/ 1960

1980

YEAR

Fig. 2. Trends in home development for Pine Creek and the 10 stream study areas below the Mogollon Rim, Gila County, Arizona.

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A.L. MEDINA

Average water-consumption rate per household per m o n t h was roughly 10 730 1 for the period 1975-1985, based on an average of 1602 Pine Creek area households. Winter and s u m m e r consumption rates approximated 8500 1 and 12 950 1, respectively. Regional housing-development trends are shown in Fig. 2. Very little development occurred between 1885 and 1940; this increased 77% between 1940 and 1950 and 394% between 1950 and 1960. From 1960 to 1970, housing development remained at about 110%, but increased to nearly 231% from 1970 to 1985. The total number of homes built between 1885 and 1985 was 3829, occupying approximately 47% of all home lots available or subdivided in the region. The potential for additional home development in the region is at least 2-fold, since large private parcels remain unsubdivided. DISCUSSION

Reductions in tree densities between perennial and ephemeral reaches of Pine Creek may be a result of changes in water status from the construction of the water-detention dam in 1965. Differences in density occurred only between tree saplings (Dbh> 2.5 cm) and young trees with Dbh < 30 cm. This size range coincides with about 27 years of expected normal tree growth, and results in a general representation of trees in each size class, as seen in the perennial reach. Tree mortality resulting from past disturbance may be a factor in the unequal densities in each size class (Medina, 1986), but other influences, such as infrequent reproduction, growth rates, periodic production of seeds, plant competition, shade tolerance, and succession, may also be operative (Harcombe and Marks, 1978 ). Evidence of human-caused tree mortality, direct or indirect, from cultural activities such as wood harvesting or grazing were lacking. Factors such as infrequent reproduction or seed production were discounted, because no difference in reproduction (size class < 2.5 cm) between reaches was evident. Additionally, I found no evidence from examinations of individual sites to suspect factors such as shade tolerance, succession, or competition to be causal as all sites had the same general species composition and stand structure (own unpublished data, 1986). Hence, I hypothesize that tree mortality and subsequent reduced growth-rates reflect differences observed in density and size-class distribution, which were a result of reduced water availability. Examination of xylem water-potentials supports the assumption that tree mortality may have resulted from the change in streamflow. Xylem waterpotentials were significantly more negative for trees along ephemeral stream reaches (Table 2), and reflect conditions of water-stress. It is reasonable to assume that trees within the perennial reach have adequate water available for carrying on normal physiological processes and that their water-potentials represent the normal condition. Hence, water-potentials that significantly

EFFECTS OF RESIDENTIAL DEVELOPMENT ON SMALL MOUNTAIN STREAMS

359

differ from the n o r m are evidence of water-stress. Water-stress often limits growth and physiological processes in forests because it affects growth and many physiological processes (Zahner, 1968; Hale and Orcutt, 1987; Kramer, 1987 ). Water-stress decreases cell enlargement, which decreases leaf area, which decreases width of annual rings and results in smaller trees (Kramer, 1987 ). Mortality can also occur in response to water-stress. Hence, given repeated water-stress periods during the growing-season throughout a 27-year period, tree growth is likely suppressed and tree mortality increases, although this alone may not be responsible for differences in species distributions (Robertson et al., 1978). H o m e development trends in the Pine Creek area are similar to those of the region (Fig. 2). These trends reflect an increasing d e m a n d for water from streams capable of supplying only a limited a m o u n t of water. Bond and Dunikoski ( 1977 ) reported considerable variation in average water-usage patterns throughout the region. The heaviest use (mean = 45.1%) occurred during the s u m m e r between June and August; this coincides with the period of no streamflow in Pine Creek and also with the influx of s u m m e r residents (Anonymous, 1986 ). Bond and Dunikoski ( 1977 ) estimated an average annual use of 74 409 1 household- 1 and a s u m m e r usage rate of 11 570 1 househ o l d - ~m o n t h - ~for a residential area in Pine. This estimate is lower than the 12 950 1 household-~ summer-month-1 reported herein. Using the reported average number of 1602 households and a summer use rate of 12 9501 household -~ m o n t h -~ for the Pine Creek area, water usage is about 20.7× 105 1 s u m m e r - m o n t h - ~, or roughly 20 746 m 3. The flow of 135 1 s- 1 from the detection d a m provides about 5832 m 3, or about 25%, of the estimated s u m m e r demand. The deficit is made up from 126 groundwater wells. These calculations show the c o m m u n i t y may be using more water than base flows in the stream provide during the summer months. In addition, about 47% of all home tracts sold have houses, hence the potential d e m a n d for water could exceed 2-fold, or about 41 500 m 3. The fishery resource was also affected by the streamflow duration. Trout occupied ephemeral stream reaches of Pine Creek during high flow (October t h r o u g h April). Trout are either transported downstream or relocated during periods of high perennial flow in the fall or winter, but they become isolated during the summer in small pools. Rinne and Medina ( 1988 ) reported a mean width of 2.5 m, mean depth of 17 cm, and mean trout density of 1.0/2 m 2 with a mean biomass of 10.7 g m -2 for the perennial reach. Estimates offishery habitat and trout loss in the human-induced ephemeral reach, which extends 2.2 km below the detention dam, is about 3500 m 2 of surface stream and 1750 trout or a biomass of 58.85 kg, respectively. This resource, along with other aquatic biota, is probably affected by the change in water levels.

360

A.L. MEDINA

CONCLUSIONS Tree density and size classes of young alder and box-elder trees were found to differ when measured between perennial and ephemeral stream reaches of Pine Creek. Measurements of xylem water-potentials reflected greater waterstresses for alder and box-elder trees within the ephemeral stream reach created by a water-detention dam. I hypothesize that repeated water-stress over a 27-year period resulted in reduced tree growth and increased tree mortality, leading to unequal size-class distributions and reduced density o f young trees. H o m e - d e v e l o p m e n t rates have continually increased since 1940. Increasing water use paralleled h o m e development, so c o n s u m p t i o n rates exceeded the a m o u n t provided by stream base flows. C o n s u m p t i o n during the s u m m e r was greater because s u m m e r residency increased 2-3-fold. Differences in tree density between reaches cannot be directly or indirectly attributed to changes in water conditions, as conditions before construction of the detention d a m are not known. However, the potentials for negative effects, resulting from reduced water availability, are present. Reduction in water availability m a y result from various factors other than domestic consumption - climatic changes in temperature or precipitation, changes in vegetation density, or other p h e n o m e n a affecting groundwater characteristics. Nonetheless, the change in streamflow conditions below the detention d a m has resulted in negative changes in the structure of the riparian plant communities and fishery habitat. ACKNOWLEDGEMENTS I gratefully acknowledge the assistance o f Penny Medina, Scott Medina, and Joyce Medina in the performance o f this study.

REFERENCES

Anonymous, 1966. Hydrologicanalysis and report for the Pine Canyon watershed, Payson Ranger District, Tonto National Forest. USDA For. Serv. Tonto Nat. For., Phoenix, AZ Rep. (unpubl.), 34 pp. Anonymous, 1987. Gila County, Arizona. Real Estate Data Inc., Miami, FL, Microfiche, 1987: E0 l-E09. Anonyumous, 1986. Pine/Strawberry community profile. Arizona Dep. of Commerce, Dep. of Economic Security, Phoenix, 2 pp. Bond, M.E. and Dunikoski, R.H., 1977. Impact of second-home development on water availability in north central Arizona. Arizona State University, Bureau of Business and Economic Research, Tempe, AZ, 88 pp. Borman, F.H., Siccama, T.G., Likens, G.E. and Whittaker, R.H., 1970. The Hubbard Brook

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Ecosystem study: composition and dynamics of the tree stratum. Ecol. Monogr., 40: 373388. Brickler, S.K. and Utter, J.G., 1975. Impact of recreation use and development on water quality in Arizona: an overview. USDA For. Serv., Rocky Mount. For. Range Exp. Stn., Eisenhower Consortium Bull., 1: 195-201. Brown, D.E. and Lowe, C.H., 1980. Biotic communities of the southwest. USDA For. Serv., Rocky Mount. For. Range Exp. Stn., GTR-RM-78 map. Daniel, W.W., 1978. Applied Nonparametric Statistics. Houghton Mifflin, Boston, MA, 503 PP. Hale, M.G. and Orcutt, D.M., 1987. The Physiology of Plants under Stress. Wiley, New York, 206 pp. Harcombe, P.A. and Marks, P.L., 1978. Tree diameter distributions and replacement processes in southeast Texas forests. For. Sci., 24:153-166. Johnson, R.R. and Carothers, S.W., 1982. Riparian habitats and recreation: interrelationships and impacts in the Southwest and Rocky Mountain region. USDA For. Serv., Rocky Mount. For. Range Exp. Stn., Eisenhower Consortium Bull., 12, 31 pp. Kramer, P.J., 1987. The role of water stress in tree growth. J. Arboric., 13: 33-38. Lewis, G.D. (Compiler), 1980. The Eisenhower Consortium for western environmental research: research highlights, 1972-1980. USDA For. Serv., Rocky Mount. For. Range Exp. Stn, Eisenhower Consortium Bull., 8, 31 pp. Lindquest, L.A. (Compiler), 1972. Mogoilon Rim area - land use planning study. USDA Forest Service, Tonto National Forest, Phoenix, AZ. Medina, A.L., 1986. Riparian plant communities of the Fort Bayard watershed in southwestern New Mexico. Southwest. Nat., 31: 345-359. Morgan, J.N., 1978. Economic and ecological impact of second home developments on local areas. USDA For. Serv., Rocky Mount. For. Range Exp. Stn., Eisenhower Consortium Final Rep. 16-597-GR, 60 pp. Ponce, S.L. and Dederick, J., 1979. Impact of second home developments on water quality in areas of low precipitation. USDA For. Serv., Rocky Mount. For. Range Exp. Stn, Eisenhower Consortium Final Rep. 188 (unpubl.), 94 pp. Rinne, J.N. and Medina, A.L., 1988. Factors influencing salmonid populations in six headwater streams, central Arizona, USA. Pol. Arch. Hydrobiol., 35:515-532. Robertson, P.A., Weaver, G.T. and Cavanaugh, J.A., 1978. Vegetation and tree species patterns near the northern terminus of the southern floodplain forest. Ecol. Monogr., 48: 249-267. Scholander, P.F., Hammel, H.T., Bradstreet, E.D. and Hemmingway, E.A., 1965. Sap pressure in vascular plants. Science, 148: 339-346. Segall, B.A., 1975. The effects of second home and related vacation development use on water quality in Arizona. USDA For. Serv., Rocky Mount. For. Range Exp. Stn, Eisenhower Consortium Bull., 1: 221-226. Zahner, R., 1968. Water deficits and growth of trees. In: T.T. Kozlowski (Editor), Water Deficits and Plant Growth, Vol 2. Academic Press, New York, pp. 191-254.