Desert Plants, Volume 22, Number 1 (June 2006)
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Desert Plants, Volume 22, Number 1 (June 2006) Item Type Article Publisher University of Arizona (Tucson, AZ) Journal Desert Plants Rights Copyright © Arizona Board of Regents. The University of Arizona. Download date 07/10/2021 05:58:59 Link to Item http://hdl.handle.net/10150/555918 Desert Volume 22, Number 1 June 2006 Published by The University ofArizona for Plants the Boyce Thompson Southwestern Arboretum Spotlight on a Global Biodiversity Hotspot- Namibia's Sperrgebiet Antje Burke 3 New Information on the Origins of Bottle Gourd (Lagenaria siceraria) Mary Wilkins Ellert 8 Singing the Praises of Gardening in the Shade Maggie Lee 18 Arboretum to Receive Research Grant Mark Biemer 27 Book Review Margaret Norem 28 Boyce Thompson Arboretum: Two Miles of Paths, 50 Acres of Wild flowers, Fall Color, Sonoran Desert Plants Rocky slopes support tremendous plant diversity, here on the west- Paul Wolterbeek 29 em slopes of Aurus Mountains in the eastern Sperrgebiet. 2 Desert Plants Desert Plants Volume 22, Number 1, June 2006 A journal devoted to broadening knowledge of plants Published by The University of Arizona indigenous or adapted to arid and sub-arid regions and to for the Boyce Thompson Southwestern Arboretum encouraging the appreciation of these plants. 37615 E. Highway 60 Superior, Arizona 85273-5100 MargaretA. Norem, Editor 2120 E. Allen Road Copyright 2006 Tucson, Arizona 85719 The Arizona Board of Regents on behalf of The University (520) 318-7046 of Arizona [email protected] The Boyce Thompson Southwestern Arboretum at Superior, Arizona is cooperatively managed by the Arizona State Parks Board, Boyce Thompson Southwestern Arboretum, Inc., and The University of Arizona. Underwriters 2006 Supporters 2006 1. Animas Foundation 1. Richard G. Beidleman 2. Arid Zone Trees 2. Jeanne Bensema 3. Josiah Austin 3. John M. Bridges 4. Walter Camp 4. Bronson Joy Brown 5. Colossal Cave Mountain Park 5. Jack Carter 6. Desierto Verde 6. Buford Crites 7. Frank W. Ellis 7. Robert D. Cross 8. Michal Glines 8. Theodore Esslinger 9. Charles and Janet Gray 9. Kay Fowler 10. Mary and Gary Irish I 0. Thomas Friedlander 11. James P. Mandaville 11. Brooke S. Gebow 12. Mr. and Mrs. Greayer Mansfield-Jones 12. Judith Gray 13. Edward H. Marshall 13. Herbert and Mary Hull 14. Lee J. Miller 15. Matthew B. Johnson and Patricia A. Rorabaugh 15. Victor Miller 15. Vernon and Diane Kliewer 16. Mountain States Wholesale Nursery 16. William J. Little 17. Nancy Norem 17. Christopher P. Marshall 18. Robert B. Pape 18. Edwin W. Minch 19. John Pierce 19. Elizabeth M. Moody 20. R. T. Ramage 20. Douglas R. Newton 21. Mark and Jean Siegwarth 21. Ken Pavlicek 22. E. Linwood Smith 22. Mr. and Mrs. N. Dean Ricer 23. Keith and Brenda Taylor 23. John H. Rumely 24. Les Wallach 24. David W. Steadman 25. Tom Wootten 25. Janice C. Swab 26. Brett Woywood 26. Cheryl Willis 27. Joe Wilkins 28. James R. Youse Burke Sperrgebiet 3 Conservation International and with tremendous local Spotlight on a global biodiversity support. has developed a long-tenn strategy for conservation hotspot-Namibia's Sperrgebiet and sustainable land use in the entire Succulent Karoo Biome. Spanning across over 2000 km on the south-western part of the African continent. geographic priority areas within the Antje Burke Succulent Karoo had to be assigned. For many reasons, the EnviroScience Sperrgebiet. the very northern tip of the Succulent Karoo Biome. is one such priority area. PO Box 1722 Oranjemund. Namibia Near natural conditions. vistas unimpeded by settlements. antj e. [email protected] roads and power lines and scenic landscapes may already have been enough to make the Sperrgebiet a prime candidate for a wilderness and conservation area. Add to this the .~fter many years of botanical exploring in the enigmatic tremendous diversity of arid-adapted plant and animal life Diamond Area- the "Sperrgebiet .. 011 the west coast ofthe and it becomes a biodiversity hotspot of global importance. southern .~fi·ican continellf- A11(je Burke gil·es an ac~ozmt of this hotspots natural riches and plans for the.fitture. Scientists still puzzle over the reasons for the tremendous di\·ersity in the Succulent Karoo Biome. In geological time frames a rather recent phenomenon. fluctuating climatic Diamonds. succulents that come in all forms. sizes. shapes conditions during the ice ages and a great diversity ofhabitats and colours. grandiose landscapes and deserted ghost towns and soil conditions on a local scale - sometimes within the come to mind when I think of the "Sperrgebief'. Locked up space of tens of centimetres - are believed to have fostered for nearly a century to public access. the Sperrgebiet is today the development of many new species within the main group one of Namibia's last wilderness areas and a natural asset of succulents. the midday tlowers (Mesembryanthemaceae ). which is appreciated by only few. 'With well over 1600 species recognised today. these are comparable in diversity to the cactus family (Cactaceae) in Diamonds have been the areas blessing and curse. the New World. Coupled with a shift to a drier climate in Discovered nearly one hundred years ago. at the time the southern Africa some ten to five million years ago, area \vas quickly pegged by mining companies and all public morphological features that helped to withstand water stress access restricted to this vast stretch of desert. some 100 by developed rapidly in some species and many found different 250 km in extent. Although mining concentrates on deposits solutions to common environmental problems. One of these along the coast and on ancient terraces along the Orange solutions is wide-band tracheids - water pipes of plants - River. Namibia's southern border. a vast butTer zone to which are more robust than more primitive tracheids and protect the industry from diamond smugglers has remained manage to keep the plants upright. even when they are under in place for nearly a century. Even today. diamond smuggling drought stress and the water pressure in their cells is low. is a threat and is costing diamond companies millions of Another solution is the reduction in leaf surface area, a very dollars every year. Mining has no doubt left some obvious adaptation to reduce water loss. Small. perfectly irrecoverable scars. largely along the southern coast. but is round or cylindrical leaves are therefore favoured by many otherwise confined to localised areas. Yet. without the species. Their mode of seed dispersal is also very diamond riches and the associated security restrictions. this sophisticated- a mastennind of nature to perfectly time seed wilderness area would not exist in its present fonn. Livestock release. The more advanced midday flowers are in evolution. fanning would have altered this diverse succulent shrub land the more intricate are their seed capsules. Midday flowers as elsewhere in the Succulent Karoo Biome and its succulent have in common that they retain their seeds on the plant and riches may have been plundered by unscrupulous collectors. do not disperse them immediately once they are ripe. The more primitive ones have capsules that disintegrate within a Not equalled by comparable areas elsewhere. southern year or so. capsules of more advanced species have many Africa ·s Succulent Karoo Biome is one of the world's top compartments with several layers of covering and hinging 25 biodiversity hotspots- and the only one in an arid region. structures to aid seed dispersal. Within a capsule there are Remarkable plant diversity and a very high level of endemism expanding keels. covering membranes. closing bodies and -plants and animals restricted to this area- have contributed valves - the tenninology alone indicates the sophisticated to the biome ·s world class conservation value. Much attention mechanism. All these respond to changes in humidity and has been paid to this area recently and conservation planning the mechanical impact of raindrops in different ways. As a studies arc underway to ensure that part of its magnificent result air. humidity and the force of raindrops have to be natural riches arc prcscn·cd for future generations. Biomc exactly right to induce the plant to release its seeds. widc. the "Succulent Karoo Ecosystem Plan". an initiative Furthem1ore. not even tmsting this sophisticated mechanism. supported by the Critical Ecosystem Partnership Fund. only a few seeds arc dispersed at one time. The remainder is kept for the next season. just in case the conditions were 4 Desert Plants still not entirely right to ensure successful germination and Plants and animals had to adapt to these desiccating survival, or too many hungry animals are around that may conditions and have evolved numerous innovative means to relish the tender, juicy new plants. escape the onslaught of the wind. Some succulents remain entirely underground and only their leaf tips emerge at the Almost all midday flowers occur in southern Africa, with surface to catch some sunlight, keeping their metabolism the exception of few genera such as sour figs ( Carpobrotus) going. Others catch sand grains with a sticky substance on and ice plants (Mesemb1yanthemum) which have also made their leaf and stem surfaces. This provides an effective shield it to the Mediterranean and the west coasts ofAustralia, North against damage from sand storms and the partially sealed America and South America. Since many are popular garden surface reduces water loss through transpiration. Larger plants in drier areas, some sour fig species (for example the animals such as antelopes (e.g. springbok and gemsbok) South African Carpobrotus edulis), have now also spread from which are plentiful in this area, have extensive home ranges their initial homes in gardens - for example in California. and simply migrate to where the environmental conditions are favourable, and food and water are found.