Journal of Arid Environments (1 995) 31: 15-1 9 Effect of wind on a Ferocactus fordii var. fordii population on Piedra Island, Baja California Sur, Mexico Alfredo Ortega-Rubio, Heidi Romero-Schmidt, Cerafina Arguelles-Méndez & Aradit Castellanos-Vera Centro de Investigaciones Biológicas del Noroeste, S. C. Apdo. Postal No. 128, CP 23000, La Paz, Baja California Sur, México (Received 20 November 1993, accepted 14 March 1994) A census was taken of the Ferocactus fordii var. fordii population at Piedra island, Baja California Sur, México and the growing form of their individuals recorded. The population consisted of 114 individuals, growing, on average, in clusters of nine. Most of these clusters (77%) were located in the southern part of the island. Al1 Ferocactus fordii var. fordii individuals showed morphological responses to the effect of the dominant wind direction and showed different degrees of prostration directly related to their size. 01995 Academic Press Limited Keywords: Ferocactus fordiz' var. fordii; Baja California Sur; México; growth; wind Introduction The effect of wind on vegetation has been well documented in the literature (Foster & Boose, 1992; Schneidt & Webwerling, 1993). The wind speed, persistence, dominance and violence could produce vexy different effects on vegetation (Greene et al., 1992; Nemoto & Lu, 1992). The effects on the vegetation range fiom growth form modifications (Schneidt & Webwerling, 1993), to drastic modifications of the total community. For instance, catastrophic winds could produce severe damage to the vegetation, causing uprooting and breakage (Foster, 1988; Foster & Boose, 1992). Wind could affect vegetation directly and indirectly; indirect effects could be associated with the change of substrate topography (Nakanishi & Fukumoto, 199 l), modification of soil-sediment units by soil erosion (Doering & Reider, 1992), and humidity availability by increasing soil desiccation (Isard, 1986). In many habitats the wind is one of the major restrictive factors determining vegetation growth and biomass, shaping entire landscapes (Bayíield, 1984; Sonesson & Callaghan, 1991; Nemoto & Lu, 1992), and even determining growth and structure of aquatic vegetation (Yen & Myerscough, 1989). In spite of the importante of wind on growth modifications of plants, there have been no previous studies concerning such effects on members of the Cactaceae. 0140-19631951010015 + 05 $12.0010 O 1995 Academic Press Limited
A. ORTEGA-RUBIO ET AL. Material and methods Study site The work was conducted at Piedra island (Stony Island), located at 27'42'18" N latitude and 114'09'36'' W longitude, within Laguna Ojo de Liebre (Eye of the Jack Rabbit) also known as Scammon's Lagoon, the southern and by far the largest and most important of the three lagoons that open into the Bahía Sebastián Vizcaíno (Fig. 1). Piedra island appears to be the remnants of old lagoon barriers formed from nverborne sediments deposited over 30,000 years ago (Bostic, 1975). It is 2500 m long and 350 m wide. The total annual precipitation is 110.4 mm and the mean annual temperature is 18.4' C (Table 1). North-westerly winds persist throughout the year round, blowing at an average speed of 1.8 m S-' (6.48 km. h-'; Table 1). The island vegetation is mainly composed of small shrubs (Atn'plex sp., Lycium sp., Frankenia sp., and Fouquieria sp.); Cactaceae (Stenocereus gummosus(enge1m.) Gibson & Morak) and annual herbs (Spartina sp. and Salicornia sp.) (Bostic, 1975). 114"09'36' Figure 1. Location of Piedra island.
WIND EFFECT ON FEROCACTUS FORDII 17 Table 1. Monthly temperatures, precipitation, wind speed (rn.s-l) and direction in Piedra Zsland Month Temperature ("C) Precipitation (mm) Wind speed Wind direction The species Ferocactus fordii (Orcutt) Britton & Rose var. fordii (Firkin cactus) is a small, prominently ribbed cactus with rose-coloured flowers, and crochet needle-like spines that display daily growth rings. This cacti was originally named by Lyrnan Ford, who imponed specimens from Baja to his San Diego nursery in the 1900s (Bostic, 1975). Individuals form large, globular plants of grayish-green, up to 38 cm high, and slightly depressed in the centre. The 21 ribs have gray, woolly aureoles set at 2 cm intervals and bearing about four centrals, one hooked, up to 4 cm long. The flowers, which occur in summer are diurnal, are up to 4 cm long (Innes & Glass, 199 1). F. fordii var. fordii is endemic to the Vizcaíno Desert of Baja California México. In spite of its endemic status there has been no previous study concerning the ecology of the populations, the only references are on their taxonomy (Wiggins, 1980; Innes & Glass, 1991). Methods During Febmary and April of 1993 we traversed the island plotting every individual Ferocactus fordii var. fordii and recording the following data: total length (including prostrate portion), height (size of the plant from the soil up to the point of bending), average diameter and growth orientation. Growth orientation was taken with a compass and the percentage prostration estimated by measuring the portion of the plant inclined along the compass bearing, i.e. total length minus the height. Resuits The total population of Ferocactus fordii var. fordii on the island was 114 individuals. There were no isolated individuals, al1 the plants were clustered. The average cluster consisted of nine (8.76) individuals, growing in an average area of 5 m', most of the clusters (10) were located in the north-eastern part of the island. There was a consistent growth orientation of the individual cacti, al1 were orientated
18 A. ORTEGA-RUBIO ET AL. Table 2. Giowng direction and degree of prosrratimi of Ferocactus fordii var fordii individuak; at Isla Piedra. Height - size classes: 1 = O to 20 cm; 2=21ro4Ocm;3=>4Ocm Height size classes Growth orientation Average percent of prostration to the south-east, in the direction of the dominant winds. The degree of growth orientation was also related to the size of the individuals (Table 2). Discussion There have been no previous studies on the size Ferocactus fordii var. fordii populations on Piedra island with which to compare our results. Certainly, the density found and the relative easy accessibility of the island (during short periods in winter it is easily reached from the mainland because of the shallowness of the lagoon and the wide tidal movement), suggest the vulnerability of the populations to furtive collectors and invasion by competing species. The cluster growth form could be explained as a result of vegetative reproduction or as result of nurse-plant effect of the seed parent: in each cluster we found 15% of the individuals in size class 2, 30% in size class 3 and 55% in size class 1. Because members of the genus Ferocactus reproduce, probably exclusively, by seeds it is very unlikely that the grouping of individuals observed is a result of vegetative reproduction and more likely due to the nurse-plant effect of the seed parent. Figure 2. Flowenng individual of F. fordii var. fordii, showing wind prostration effect.
WIND EFFECT ON FEROCACTUS FORDII 19 Conclusion We conclude that there is a determinant wind effect on Ferocactus fordii var. fordii individuals: they become prostrate due to the persistency and direction of the dominant wind. Furthermore, the degree of prostration is correlated with the size of the individuals, and older individuals, subjected to the wind effects for longer periods of time, are more affected than the younger ones. Inclusively, severa1 individuals of F. fordii var. fordii resemble individuals of a very particular endemic cacti of Baja California Sur: the Chirinola (devil creek or walking cactus, Stenocereus eruca(brandegee) Gibson & Horak) (Cancino et al., 1995). Further comparative studies of this species are required in other localities, as well as similar studies on other members of the cacti familv. However. we can conclude that wind speed and direction has a direct effect on the growth shape of individual Ferocactus fordii var. fordii cacti on Piedra island. This work was supported by the Centro de Investigaciones Biológicas del Noroeste, the Secretaria de Educación Pública and the Consejo Nacional de Ciencia y Tecnología of México. We would like to thank Dr G.E. Wickens and one anonyrnous referee for their kind comments and suggestions to an early version of the manuscript; to J. Castellanos for her help in the fieldwork, to Biol. César Salinas who provided us with the climatological data and to D. Vázquez and V. Hirales who provided expert secretaria1 assistance. References Bayfield, N. G. (1984). The dynamics of heather (Calluna vulgans) stripes on the Cairngorn Mountains, Scotland. Journal of Ecology, 72: 5 15-527. Bostic, D. L. (1975). A Natural History Guide to the Pacific Coast and North Central Baja California and Adjacent Islands. Biological Educational Expeditions, San Diego, CA. 184 PP. Cancino, J., Romero-Schmidt, H., Ortega-Rubio, A. & León de la Luz, J. L. (1995). Observations on distnbution and habitat charactenstics of the endangered Mexican endemic cacti Stenocereus eruca. Journal of And Environments, 29: 55-62. Doering, W. & Reider, R. (1992). Soils of Cinnabar Park, Medicine Bow Mountains, Wyoming, U.S.A.: indicators of park origin and persistence. Arctic Alpine Research, 24: 27-39. Foster, D. R. (1988). Species and stand response to catastrophic wind in Central New England. U.S.A. Journal of Ecology, 76: 135-151. Foster, D. R. & Boose, E. R. (1992). Pattern of forest damage resulting from catastrophic wind in central New England, U.S.A. Journal of Ecology, 80: 79-98. Greene, S. E., Harcombe, P. A., Harmon, M. E. & Soycher, G. (1992). Patterns of growth, mortality and biomass change in a coastal Picea sitchensis-tsuga herpetophilla forest. Journal of Vegetation Science, 3: 697-706. Innes, C. & Glass, Ch. (1991). Cacti. New York: Portland House. 320 pp. Isard, S. A. (1986). Factor influencing soil moisture and plant community distribution on Niwot Ridge, Front Range, Colorado, U.S.A. Arctic Alpine Research, 18: 83-96. Nakanishi, H. & Fukumoto, H. (1991). Zonation of sand dune vegetation and depositional topography in the San-in District, western Honshu, Japan. Japan Journal of Ecology (Kyoto), 41: 225-235. Nemoto, M. & Lu, X. (1992). Ecological characteristics of Agriophyllum squarrosum, a pioneer annual on sand dunes in eastern Inner Mongolia, China. Ecological Research, 7: 183-186. Schneidt, J. & Webwerling, F. (1993). Studies on growth forms in the Paramo of Costa Rica: 111. Studies on species of Ericaceae. Flora o), 187: 403-427. Sonesson, M. & Callaghan, T.V. (1991). Strategies of survival in plants of the Fennoscandian tundra. Arctic, 44: 95-105. Wiggins, I.L. (1980). Flora of Baja California. Stanford, CA: Stanford University Press. pp. 596-597. Yen, S. & Myerscough, P. (1989). Co-existence of three species of amphibians plants in relation to spatial and temporal variation: field evidence. Australian Journal of Ecology, 14: 291-303.