Advertisement

Plant Ecology

, Volume 215, Issue 6, pp 581–595 | Cite as

The keystone saguaro (Carnegiea gigantea, Cactaceae): a review of its ecology, associations, reproduction, limits, and demographics

  • Taly Dawn Drezner
Braun-Blanquet Review

Abstract

This paper reviews the basics of a Sonoran Desert keystone cactus species, including the ecology of its establishment and high mortality, its association with nurse plants to provide ameliorated conditions for survival, and variability in longevity and reproduction over its range such as delayed reproduction in hotter and more arid populations where this delay is met with longer lifespans. The production of flowers, branches, and spines from areoles is reviewed, as well as current methods for estimating individual age despite great variability in growth rates, most notably linked to summer rainfall. Possible implications of anthropogenic influences that impact populations as well as global climate change are discussed as are implications for potential range shifts in the future. This paper also provides a table listing of over 100 birds, mammals, insects, reptiles, and other animal species that use Carnegiea and highlighting its keystone status.

Keywords

Cactus Carnegiea gigantea Keystone species 

References

  1. Adams JB, Mann ME, Ammann CM (2003) Proxy evidence for an El-Niño-like response to volcanic forcing. Nature 426:274–278Google Scholar
  2. Alcock J (2008) Territorial preferences of the hilltopping wasp Hemipepsis ustulata (Pompilidae) remain stable from year to year. Southwest Nat 53:190–195Google Scholar
  3. Alcorn SM, May C (1962) Attrition of a saguaro forest. Plant Dis Report 46:156–158Google Scholar
  4. Anderson EF (2001) The cactus family. Timber Press Inc., PortlandGoogle Scholar
  5. Baumgartner FM (1938) Courtship and nesting of the great horned owls. Wilson Bull 50:274–285Google Scholar
  6. Bennett PS, Kunzmann MR (1994) Suppression of saguaro cactus flower-bud formation by roosting vultures in Arizona. Southwest Nat 39:200–203Google Scholar
  7. Berry JW, Ho A, Steelink C (1960) Constituents of the saguaro (Carnegiea gigantea). I. Proximate analysis of the woody tissues. J Org Chem 25:1267–1268Google Scholar
  8. Booth PM (2005) “If we gave up the making of nawait, it would mean starvation”: Saguaro wine defenders of Tohono O’odham land and way-of-life. J Ariz Hist 46:375–396Google Scholar
  9. Bowers JE (1996) Environmental determinants of flowering date in the columnar cactus Carnegiea gigantea in the northern Sonoran Desert. Madrono 43:69–84Google Scholar
  10. Bowers JE (1997) Demographic patterns of Ferocactus cylindraceus in relation to substrate age and grazing history. Plant Ecol 133:37–48Google Scholar
  11. Bowers JE (2005) Influence of climatic variability on local population dynamics of a Sonoran Desert platyopuntia. J Arid Environ 61:193–210Google Scholar
  12. Bowers JE, Pierson EA (2001) Implications of seed size for seedling survival in Carnegiea gigantea and Ferocactus wislizeni (Cactaceae). Southwest Nat 46:272–281Google Scholar
  13. Bregman R (1988) Forms of seed dispersal in Cactaceae. Acta Bot Neerl 37:395–402Google Scholar
  14. Bruhn JG (1971) Carnegiea gigantea: the saguaro and its uses. Economic Bot 25:320–329Google Scholar
  15. Brum GD (1973) Ecology of the saguaro (Carnegiea gigantea): phenology and establishment in marginal populations. Madroño 22:195–204Google Scholar
  16. Butterfield BJ, Briggs JM (2009) Patch dynamics of soil biotic feedbacks in the Sonoran Desert. J Arid Environ 73:96–102Google Scholar
  17. Cannon WA (1911) The root habits of desert plants. Carnegie Institute Publ. 131, Washington, DCGoogle Scholar
  18. Clemensen AB (1987) Cattle, copper, and cactus: the history of Saguaro National Monument. National Park Service, DenverGoogle Scholar
  19. Danzer S, Drezner TD (2010) Demographics of more than 12,000 individuals of a keystone species in the northern Sonoran Desert since the mid-1800s. Int J Plant Sci 171:538–546Google Scholar
  20. Dávila-Aranda P, Arias-Montes S, Lira-Saade R, Villaseñor JL, Valiente-Banuet A (2002) Phytogeography of the columnar cacti (Tribe Pachycereeae) in Mexico: A cladistic approach. In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 25–41Google Scholar
  21. Davis AJ, Jenkinson LS, Lawton JH, Shorrocks B, Wood S (1998) Making mistakes when predicting shifts in species range in response to global warming. Nature 391:783–786PubMedGoogle Scholar
  22. Dawson JW, Mannan RW (1991) Dominance hierarchies and helper contributions in Harris’ Hawks. Auk 108:649–660Google Scholar
  23. Dimmitt MA (2000) Cactaceae (cactus family). In: Phillips SJ, Comus PW (eds) A natural history of the Sonoran Desert. Arizona-Sonora Desert Museum Press, Tucson, pp 183–218Google Scholar
  24. Donnermeyer CJ, Drezner TD (2012) Cohort establishment on slopes: growth rates, demographic patterns, and the relationship to volcanic eruptions. J Arid Environ 76:133–137Google Scholar
  25. Drennan PM, Nobel PS (2000) Responses of CAM species to increasing atmospheric CO2 concentrations. Plant Cell Environ 23:767–781Google Scholar
  26. Drezner TD (2003a) Regional- and local-scale variations in plant distribution in the Sonoran Desert. Madrono 50:122–125Google Scholar
  27. Drezner TD (2003b) A test of the relationship between seasonal rainfall and saguaro cacti branching patterns. Ecography 26:393–404Google Scholar
  28. Drezner TD (2003c) Branch direction in Carnegiea gigantea (Cactaceae): regional patterns and the effect of nurse plants. J Veg Sci 14:907–910Google Scholar
  29. Drezner TD (2003d) Saguaro (Carnegiea gigantea, Cactaceae) age–height relationships and growth: the development of a general growth curve. Am J Bot 90:911–914PubMedGoogle Scholar
  30. Drezner TD (2004a) Saguaros and their nurses in the Sonoran Desert: a review. Desert Plants 20:3–10Google Scholar
  31. Drezner TD (2004b) Saguaro recruitment over their American range: a separation and comparison of summer temperature and rainfall. J Arid Environ 56:509–524Google Scholar
  32. Drezner TD (2004c) Saguaro patterns and ecology over Arizona: a closer look at rainfall. Desert Plants 20:24–32Google Scholar
  33. Drezner TD (2005) Saguaro (Carnegiea gigantea, Cactaceae) growth rate over its American range and the link to summer precipitation. Southwest Nat 50:65–68Google Scholar
  34. Drezner TD (2006a) Saguaro (Carnegiea gigantea) densities and reproduction over the northern Sonoran Desert. Phys Geogr 27:505–518Google Scholar
  35. Drezner TD (2006b) Plant facilitation in extreme environments: the non-random distribution of saguaro cacti (Carnegiea gigantea) under their nurse associates and the relationship to nurse architecture. J Arid Environ 65:46–61Google Scholar
  36. Drezner TD (2006c) Regeneration of Carnegiea gigantea (Cactaceae) since 1850 in three populations in the northern Sonoran Desert. Acta Oecol 29:178–186Google Scholar
  37. Drezner TD (2006d) The regeneration of a protected Sonoran Desert cactus since 1800 A.D. over 50,000 km2 of its range. Plant Ecol 183:171–176Google Scholar
  38. Drezner TD (2007) An analysis of winter temperature and dew point under the canopy of a common Sonoran Desert nurse and the implications for positive plant interactions. J Arid Environ 69:554–568Google Scholar
  39. Drezner TD (2008) Variation in age and height of onset of reproduction in the saguaro cactus (Carnegiea gigantea) in the Sonoran Desert. Plant Ecol 194:223–229Google Scholar
  40. Drezner TD (2010) Nurse tree canopy shape, the subcanopy distribution of cacti, and facilitation in the Sonoran Desert. J Torrey Bot Soc 137:277–286Google Scholar
  41. Drezner TD (2013a) Variability in reproductive effort of a keystone species: age and height of branch establishment. Phys Geogr 34:136–148Google Scholar
  42. Drezner TD (2013b) The paradoxical distribution of a shallow-rooted keystone species away from surface water, near the water-limited edge of its range in the Sonoran Desert: seed-seedling conflicts. Acta Oecol 47:81–84Google Scholar
  43. Drezner TD (2014) How long does the giant saguaro live? Life, death and reproduction in the desert. J Arid Environ 104:34–37Google Scholar
  44. Drezner TD. In review. Regional environmental conditions affect microsite response in a keystone desert speciesGoogle Scholar
  45. Drezner TD, Balling RC Jr (2002) Climatic controls of saguaro (Carnegiea gigantea) regeneration: a potential link with El Niño. Phys Geogr 23:465–475Google Scholar
  46. Drezner TD, Balling RC Jr (2008) Regeneration cycles of the keystone species Carnegiea gigantea are linked to worldwide volcanism. J Veg Sci 19:587–596Google Scholar
  47. Drezner TD, Garrity CM (2003) Saguaro distribution under nurse plants in Arizona’s Sonoran Desert: directional and microclimate influences. Prof Geogr 55:505–512Google Scholar
  48. Drezner TD, Lazarus BL (2008) The population dynamics of columnar and other cacti: a review. Geogr Compass 2:1–29Google Scholar
  49. Engelmann G (1859) Cactaceae of the boundary. In: Emory WH, Report on the United States and Mexican boundary survey made under the direction of the Secretary of the Interior, vol 2, 34th Congress, 1st Session, House of Representative Executive Documents 135, Washington DCGoogle Scholar
  50. English NB, Dettman DL, Williams DG (2010) A 26-year stable isotope record of humidity and El Nino-enhanced precipitation in the spines of saguaro cactus, Carnegiea gigantea. Palaeogeogr Palaeoclimatol Palaeoecol 293:108–119Google Scholar
  51. Fleming TH (2002) Pollination biology of four species of Sonoran Desert columnar cacti. In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 207–224Google Scholar
  52. Fleming TH, Tuttle MD, Horner MA (1996) Pollination biology and the relative importance of nocturnal and diurnal pollinators in three species of Sonoran Desert columnar cacti. Southwest Nat 41:257–269Google Scholar
  53. Fleming TH, Sahley CT, Holland JN, Nason JD, Hamrick JL (2001) Sonoran Desert columnar cacti and the evolution of generalized pollination systems. Ecol Monogr 71:511–530Google Scholar
  54. Flesch AD (2003) Perch-site selection and spatial use by cactus ferruginous pygmy-owls in south-central Arizona. J Raptor Res 37:151–157Google Scholar
  55. Flores-Martínez A, Ezcurra E, Sánchez-Colón S (1994) Effect of Neobuxbaumia tetetzo on growth and fecundity of its nurse plant Mimosa luisana. J Ecol 82:325–330Google Scholar
  56. Flores-Martínez A, Ezcurra E, Sánchez-Colón S (1998) Water availability and the competitive effect of a columnar cactus on its nurse plant. Acta Oecol 19:1–8Google Scholar
  57. Franco AC, Nobel PS (1988) Interactions between seedlings of Agave deserti and the nurse plant Hilaria rigida. Ecology 69:1731–1740Google Scholar
  58. Franco AC, Nobel PS (1989) Effect of nurse plants on the micro-habitat and growth of cacti. J Ecol 77:870–886Google Scholar
  59. Garvie LAJ (2003) Decay-induced biomineralization of the saguaro cactus (Carnegiea gigantea). Am Mineral 88:1879–1888Google Scholar
  60. Geller GN, Nobel PS (1986) Branching patterns of columnar cacti: influences on PAR interception and CO2 uptake. Am J Bot 73:1193–1200Google Scholar
  61. Gill, LS, Lightle PC (1946) Analysis of mortality in saguaro cactus. Official report from the U.S. Department of Agriculture, Bureau of Plant Industry. Saguaro National Monument filesGoogle Scholar
  62. Gill LS (1951) Mortality in the giant cactus at Saguaro National Monument, 1941–1950. Official report of the U.S. Department of Agriculture, Bureau of Plant Industry. Saguaro National Monument filesGoogle Scholar
  63. Gill LS, Lightle PC (1942) Cactus disease investigations: an outline of objectives, plans, and accomplishments on project J-2-8. U.S. Department of Agriculture, Bureau of Plant Industry, Forest Pathologist, Albuquerque. Saguaro National Monument filesGoogle Scholar
  64. Goad MS, Mannan RW (1987) Nest site selection by elf owls in Saguaro National Monument, Arizona. Condor 89:659–662Google Scholar
  65. Goldsmith SK, Alcock J (1993) The mating chances of small males of the Cerambycid beetle Trachyderes mandibularis differ in different environments (Coleoptera: Cerambycidae). J Insect Behav 6:351–360Google Scholar
  66. Halloy S (2008) Exponential growth and survival in cardon (Echinopsis atacamensis subsp. pascana) at its altitudinal limit (Tucuman, Argentina). Ecologia en Bolivia 43:6–15Google Scholar
  67. Hastings JR, Alcorn SM (1961) Physical determinations of growth and age in the giant cactus. J Ariz Acad Sci 2:32–39Google Scholar
  68. Hutto RL, McAuliffe JR, Hogan L (1986) Distributional associates of the saguaro (Carnegiea gigantea). Southwest Nat 31:469–476Google Scholar
  69. Johnson DS (1924) The influence of insolation on the distribution and on the developmental sequence of the flowers of the giant cactus of Arizona. Ecology 5:70–82Google Scholar
  70. Jordan PW, Nobel PS (1982) Height distributions of two species of cacti in relation to rainfall, seedling establishment, and growth. Bot Gaz 143:511–517Google Scholar
  71. Kerpez TA, Smith NS (1990a) Competition between European Starlings and native woodpeckers for nest cavities in saguaros. Auk 107:367–375Google Scholar
  72. Kerpez TA, Smith NS (1990b) Nest-site selection and nest-cavity characteristics of Gila woodpeckers and northern flickers. Condor 92:193–198Google Scholar
  73. Kiontke E, Sudhaus W (1996) Diplogaster (Diplogastrellus) Cerea Sp. Nov. from saguaro cactus rot and a revision of the subgenus Diplogastrellus (Nematoda: Diplogastridae). Nematologica 42:173–197Google Scholar
  74. Korol JJ, Hutto RL (1984) Factors affecting nest site location in Gila woodpeckers. Condor 86:73–78Google Scholar
  75. Lewis DA, Nobel PS (1977) Thermal energy exchange model and water loss of a barrel cactus, Ferocactus acanthodes. Plant Physiol 60:609–616PubMedCentralPubMedGoogle Scholar
  76. Lightle PC, Standring ET, Brown JG (1942) A bacterial necrosis of the giant cactus. Phytopathology 32:303–313Google Scholar
  77. M’Closkey RT (1997) Response of a lizard species to the senescence of a dominant plant in the Sonoran Desert. Ecoscience 4:43–47Google Scholar
  78. Mader WJ (1978) A comparative nesting study of red-tailed hawks and Harris’ hawks in southern Arizona. Auk 95:327–337Google Scholar
  79. Mahall BE, Callaway RM (1992) Root communication mechanisms and intracommunity distributions of two Mojave Desert shrubs. Ecology 73:2145–2151Google Scholar
  80. McAuliffe JR (1984) Sahuaro-nurse tree associations in the Sonoran Desert: competitive effects of sahuaros. Oecologia 64:319–321Google Scholar
  81. McAuliffe JR (1996) Saguaro cactus dynamics. In: Halvorson WL, Davis GE (eds) Science and ecosystem management in the National Parks. University of Arizona Press, Tucson, pp 96–131Google Scholar
  82. McAuliffe JR, Hendricks P (1988) Determinants of the vertical distributions of woodpecker nest cavities in the sahuaro cactus. Condor 90:791–801Google Scholar
  83. McAuliffe JR, Janzen FJ (1986) Effects of intraspecific crowding on water uptake, water storage, apical growth, and reproductive potential in the sahuaro cactus, Carnegiea gigantea. Bot Gaz 147:334–341Google Scholar
  84. McGregor SE, Alcorn SM, Kurtz EB Jr, Butler GD Jr (1959) Bee visitors to saguaro flowers. J Econ Entomol 52:1002–1004Google Scholar
  85. McGregor SE, Alcorn SM, Olin G (1962) Pollination and pollinating agents of the saguaro. Ecology 43:260–267Google Scholar
  86. Medeiros AS, Drezner TD (2012) Vegetation, climate, and soil relationships across the Sonoran Desert. Ecoscience 19:148–160Google Scholar
  87. Meyer JM, Fogleman JC (1987) Significance of saguaro cactus alkaloids in ecology of Drosophila mettleri, a soil-breeding, cactophilic drosophilid. J Chem Ecol 13:2069–2081PubMedGoogle Scholar
  88. Niering WA, Whittaker RH, Lowe CH (1963) The saguaro: a population in relation to environment. Science 142:15–23PubMedGoogle Scholar
  89. Nobel PS (1980) Morphology, nurse plants, and minimum apical temperatures for young Carnegiea gigantea. Bot Gaz 141:188–191Google Scholar
  90. Nobel PS (1988) Environmental biology of agaves and cacti. Cambridge University Press, CambridgeGoogle Scholar
  91. Nobel PS (1999) Physiochemical and environmental plant physiology, 2nd edn. Academic Press, San DiegoGoogle Scholar
  92. Nobel PS (2002) Physiological ecology of columnar cacti. In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 189–204Google Scholar
  93. Nobel PS, Bobich EG (2002) Plant frequency, stem and root characteristics, and CO2 uptake for Opuntia acanthocarpa: elevational correlates in the northwestern Sonoran Desert. Oecologia 130:165–172Google Scholar
  94. Nobel PS, Israel AA (1994) Cladode development, environmental responses of CO2 uptake, and productivity for Opuntia ficus-indica under elevated CO2. J Expert Bot 45:295–303Google Scholar
  95. Nobel PS, Loik ME (1999) Form and function of cacti. In: Robichaux RH (ed) Ecology of Sonoran Desert plants and plant communities. University of Arizona Press, Tucson, pp 143–163Google Scholar
  96. Olson CA (2000) Insects and the saguaro. In: Phillips SJ, Comus PW (eds) A natural history of the Sonoran Desert, pp. 353–356Google Scholar
  97. Olsson AD, Betancourt J, McClaran MP, Marsh SE (2012) Sonoran Desert ecosystem transformation by a C4 grass without the grass/fire cycle. Divers Distrib 18:10–21Google Scholar
  98. Parker KC (1989) Nurse plant relationships of columnar cacti in Arizona. Phys Geogr 10:322–335Google Scholar
  99. Parker KC (1993) Climatic effects on regeneration trends for two columnar cacti in the northern Sonoran Desert. Ann Assoc Am Geogr 83:452–474Google Scholar
  100. Pierson EA, Turner RM (1998) An 85-year study of saguaro (Carnegiea gigantea) demography. Ecology 79:2676–2693Google Scholar
  101. Pierson EA, Turner RM, Betancourt JL (2013) Regional demographic trends from long-term studies of saguaro (Carnegiea gigantea) across the northern Sonoran Desert. J Arid Environ 88:57–69Google Scholar
  102. Pinto R (2007) Conservation status of Eulychnia iquiquensis (Schumann) Britton and Rose (Cactaceae) in the northernmost Chile. Gay Bot 64:98–109Google Scholar
  103. Rebman JP, Pinkava DJ (2001) Opuntia cacti of North America: an overview. Fla Entomol 84:474–483Google Scholar
  104. Rehfeldt GE, Crookston NL, Warwell MV, Evans JS (2006) Empirical analyses of plant–climate relationships for the western United States. Int J Plant Sci 167:1123–1150Google Scholar
  105. Rogers GF (1985) Mortality of burned Cereus giganteus. Ecology 66:630–632Google Scholar
  106. Schiermeier Q (2005) Pall hangs over desert’s future as alien weeds fuel wildfires. Nature 435:724PubMedGoogle Scholar
  107. Schmidt JO, Buchmann SL (1986) Floral biology of the saguaro (Cereus giganteus) I: Pollen harvest by Apis mellifera. Oecologia 69:491–498Google Scholar
  108. Schmidt-Nielson KS (1964) Desert animals: physiological problems of heat and water. Clarendon, Oxford 277 ppGoogle Scholar
  109. Schupp EW (1995) Seed-seedling conflicts, habitat choice, and patterns of plant recruitment. Am J Bot 82:399–409Google Scholar
  110. Shreve F (1910) The rate of establishment of the giant cactus. Plant World 13:235–240Google Scholar
  111. Shreve F (1911) The influence of low temperatures on the distribution of the giant cactus. Plant World 14:136–146Google Scholar
  112. Simmons NB, Wetterer AL (2002) Phylogeny and convergence in cactophilic bats. In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 87–121Google Scholar
  113. Sosa VJ, Fleming TH (2002) Why are columnar cacti associated with nurse plants? In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 306–323Google Scholar
  114. Steenbergh WF, Lowe CH (1976) Ecology of the saguaro I: the role of freezing weather in a warm-desert plant population. In: Research in the Parks, pp. 49–92. National Park Service Symposium Series No. 1. Washington D.C.: National Park ServiceGoogle Scholar
  115. Steenbergh WF, Lowe CH (1977) Ecology of the Saguaro: II: reproduction, germination, establishment, growth, and survival of the young plant. National Park Service Scientific Monograph Series No. 8., National Park Service, Washington D.CGoogle Scholar
  116. Steenbergh WF, Lowe CH (1983) Ecology of the Saguaro: III: Growth and Demography. National Park Service Scientific Monograph Series No. 17, National Park Service, Washington D.CGoogle Scholar
  117. Stelfox JG, Vriend HG (1977) Prairie fires and pronghorn use of cactus. Can Field Nat 91:282–285Google Scholar
  118. Thornton B (2008) How many saguaros? Cactus Succul J 80:160–169Google Scholar
  119. Turnage WV, Hinckley AL (1938) Freezing weather in relation to plant distribution in the Sonoran Desert. Ecol Monogr 8:529–550Google Scholar
  120. Turner RM (1990) Long-term vegetation change at a fully protected Sonoran Desert site. Ecology 71:464–477Google Scholar
  121. Turner RM, Alcorn SM, Olin G, Booth JA (1966) The influence of shade, soil, and water on saguaro seedling establishment. Bot Gaz 127:95–102Google Scholar
  122. Turner RM, Bowers JE, Burgess TL (1995) Sonoran desert plants: an ecological atlas. The University of Arizona Press, TucsonGoogle Scholar
  123. Turner RM, Webb RH, Bowers JE, Hastings JR (2003) The changing mile revisited: an ecological study of vegetation change with time in the lower mile of an arid and semiarid region. University of Arizona Press, TucsonGoogle Scholar
  124. Valiente-Banuet A, Bolongaro-Crevenna A, Briones O, Ezcurra E, Rosas M, Núñez H, Barnard G, Vázquez E (1991) Spatial relationships between cacti and nurse shrubs in a semi-arid environment in central Mexico. J Veg Sci 2:15–20Google Scholar
  125. Van Devender TR (2002) Environmental history of the Sonoran Desert. In: Fleming TH, Valiente-Banuet A (eds) Columnar cacti and their mutualists. University of Arizona Press, Tucson, pp 3–24Google Scholar
  126. Vandermeer J (1980) Saguaros and nurse trees: a new hypothesis to account for population fluctuations. Southwest Nat 25:357–360Google Scholar
  127. Wolf BO, del Río CM (2000) Use of saguaro fruit by white-winged doves: isotopic evidence of a tight ecological association. Oecologia 124:536–543Google Scholar
  128. Wolf BO, del Río CM (2003) How important are columnar cacti as sources of water and nutrients for desert consumers? A review. Isot Environ Health Stud 39:53–67Google Scholar
  129. Yeaton RI, Travis J, Gilinsky E (1977) Competition and spacing in plant communities: the Arizona Upland Association. J Ecol 65:587–595Google Scholar
  130. Yeaton RI, Karban R, Wagner HB (1980) Morphological growth patterns of saguaro (Carnegiea gigantea: Cactaceae) on flats and slopes in Organ Pipe Cactus National Monument, Arizona. Southwest Nat 25:339–349Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Department of GeographyYork UniversityTorontoCanada

Personalised recommendations