This study evaluates the size frequency distribution of 11 trees and shrubs in the cloud forest in Wadi Garziz, southern Oman, in order to assess their current situation, which is affected by cutting, overgrazing and other constraints. A size class distribution and a vegetation structure analysis were applied in order to analyze the dynamics of this forest using census data from 51 plots selected across 5 transects covering the hill-slope andwadi-bed habitats. Some of the trees inhabiting the hill-slopes (e.g. Acacia senegal and Commiphora spp.) were found to exhibit an inverse J-shaped distribution with constant regeneration, whilst in the wadi bed these same trees exhibited a J-shaped distribution (i.e. of declining populations). On the other hand, Acacia etbaica inhabiting the hill-slopes exhibited a tendency towards a J-shaped distribution and an inverse J-shaped distribution in the wadi-bed. All the populations (i.e. inhabiting the hill-slopes and the beds) of Anogeissus dhofarica had a J-shaped distribution whereas all the populations of Blepharispermum hirtum had a more or less inverse J-shaped distribution. The Ziziphus spina- -christi and Acacia tortilis populations, meanwhile, exhibited the bi-modal shape of size distribution. The shrubs inhabiting the hill-slopes (e.g. Coroton confertus and Ormocarpum dhofarense) exhibited a tendency towards a J-shaped distribution; such distribution characterizes a declining population with a limited regenerational capacity. Overall, most of the examined populations, except those of Acacia etbaica in wadi-bed and Blepharispermum hirtum, seemed to be under stress from both environmental and human factors, particularly in the wadi bed. This type of study can provide a basis for the development of a management plan to support the conservation and sustainable use of forest vegetation in an arid region.
ANONYMOUS, 2004: Water resources in Sultanate of Oman. Ministry of Regional Municipalities, Environment and Water resources, Muscut, Sultanate of Oman.
BATANOUNY, K. H., 1987. Current knowledge of plant ecology in the Arab Gulf countries. Catena 14, 291-316.
BAXTER, W. J.,GETZ, M.,WAYNE, P., 2005: Amodel-farmed evaluation of elephant effects on tree, fire dynamics in Africa savannas. Ecological Application 154, 1331-1341.
BRIGGS, J. M., SCHAAFSMA, H. D., TRENKOV, D., 2007: Woody vegetation expansion in a desert grassland: Prehistoric human impact? Journal ofArid Environments 69, 458-472.
BRINKMANN, K., PAZELT, A.,DICKHOEFER, U., SCHLECHT, E.,BUERKERT, A., 2009: Vegetation patterns and diversity along an altitudinal and grazing gradient in the Jabal al Akhdar mountain range of northern Oman. Journal of Arid Environments 73, 1035-1045.
CASSWELL, H., 1986: Life cycle models for plants. Lectures on Mathematics in the Life Sciences 18, 171-233.
COOMES, D. A., ALLEN, R. B., 2007: Mortality and tree size distributions in natural mixed- -age forests. Journal of Ecology 95, 27-40.
CRISP, M. D., LANGE, R. T., 1976: Age structure, distribution and survival under grazing of the arid-zone shrub Acacia burkitii. Oikos 27, 86-92.
DANSEREAU, P., LEMS, K., 1957: The grading of dispersal types in plant communities and their ecological significance. Contributions de L'Institute Botanique Institute of Botany, University of Montreal 71, 1-52.
EL-BAZ, F., 2002:Wadis of Oman satellite image atlas. Center for Remote Sensing, Boston University; Office of the Advisor to His Majesty the Sultan for Cultural Affairs Publishing, Muscut, Sultanate of Oman.
EL-SHEIKH, M. A., 2005: Plant succession on abandoned fields after 25 years of shifting cultivation in Assuit, Egypt. Journal of Arid Environments 61, 461-481.
FETENE,M., 2003: Intra-and inter-specific composition between seedlings of Acacia etbaica and a perennial grass (Hyparrenia hirta). Journal of Arid Environments 55, 441-451.
FISHER, M., GARDNER, A., 1995: The status and ecology of a Juniperus excelsa subsp. polycarpos woodland in the northern mountains of Oman. Vegetatio 119, 33-51.
GHAZANFAR, S., 1998: Status of the flora and plant conservation in the Sultanate of Oman. Biological Conservation 85, 287-295.
GOLDBERG, D. E.,TURNER, R.M., 1986:Vegetation change and plant demography in permanent plots in the Sonoran desert. Ecology 67, 695-712.
GRAY, B., 1975: Size-composition and regeneration of Araucaria stands in New Guinea. Journal of Ecology 63, 273-289.
GREEN, D. F., JOHNSON, E. A., 1996: Wind dispersal of seeds from a forest into a clearing. Ecology 82, 595-609.
GRIME, J. P., 1979: Plant strategies and vegetation processes. Wiley, New York.
HALL, P.,BAWA, K., 1993:Methods to assess the impact of extraction of non-timber tropical forest products on plant populations. Economic Botany 47, 234-247.
HARPER, J. L., WHITE, J., 1974: The demography of plants. Annual Review of Ecology Evolution and Systematics 5, 419-463.
HARPER, J. L., 1977: Population biology of plants. Academic Press, London.
HILDEBRANDT, A., ELTAHIR, E. A. B., 2006: Forest on the edge: Seasonal cloud forest in Oman creates its own ecological niche. Geophysical Research Letter 33, L11401.
HILDEBRANDT, A.,ALAUFI,M.,AMERJEED,M.,SHAMMAS,M.,ELTAHIR, E.A. B., 2007. Ecohydrology of a seasonal cloud forest in Dhofar: 1. Field experiment. Water Resources Research 43, W10411.
HOU, J. H,MI, X. C.,LIU, C. R.,MA,K. P., 2004: Spatial patterns and associations in a Quercus-Betula forest in North China. Journal of Vegetation Science 15, 407-414.
HUSTON,M., 1986: Size bimodality in plant populations: an alternative hypothesis. Ecology 67, 265-269.
LYKKE, A. M., 1998: Assessment of species composition change in savanna vegetation by means of woody plant's size class distributions and local information. Biodiversity and Conservation 7, 1261-1275.
MAHMOUD, A., 1977: Germination of three desert Acacias in relation to their survival in arid environment. Proceedings 1 Conference of Saudi Biological Society, Riyadh, 47-94.
MANABE, T., NISHIMURA, N., MIURA, M., YAMAMOTO, S., 2000: Population structure and spatial patterns for trees in a temperate old-growth evergreen broad-leaved forest in Japan. Plant Ecology 151, 181-197.
MASAKI, T., SUZUKI, W.,NIIYAMA, K., IIDA, S., TANAKA, H.,NAKASHIZUKA, T., 1992: Community structure of a species rich temperate forest, Ogawa Forest Reserve, central Japan. Vegetatio 98, 97-111.
MILLER, A. G.,MORRIS, M., 1988: Plants of Dhofar, the southern region of Oman: Traditional, Economic and Medicinal uses. Office of the Adviser for Conservation of the Environment, Diwan of Royal Court Sultanate of Oman Publishing, Sultanate of Oman.
MILLER, G. M., 1994: Dhofar Fog Oasis, Oman and Yemen. In: DAVIS, S. D.,HEYWOOD, V. H.,HAMILTON,A. C. (Eds.), Centres of plant diversity, 1, 309-311.WorldWildlife Fund, International Union for Conservation of Nature, Gland.
NEWBERY, D. MCC., GARTLAN, J. S., 1996: Astructural analysis of rain forest at Korup and Douala-Edea, Cameroon. Proceedings of the Royal Society of Edinburgh 104B, 177-224.
NISHIMURA, T. B.,KOHYAMA, T., 2002: Formation and maintenance of community boundaries in a sub-alpine forest landscape in northern Japan. Journal of Vegetation Science13, 555-564.
NARUKAWA, Y., YAMAMOTO, S., 2002: Effects of dwarf bamboo (Sasa sp.) and forest floor microsites on conifer seedling recruitment in a subalpine forest, Japan. Forest Ecology and Management 163, 61-70.
OLIVER, C. D., 1980: Forest development in North America following major disturbances. Forest Ecology and Management 3, 153-168.
POORTER, L.,BONGERS, F., VAN ROMPAEY, R. S. A. R., DE KLERK,M., 1996: Regeneration of canopy tree species at five sites in west African moist forest. Forest Ecology and Management 84, 61-69.
PELISSIER, R., GOREAUD, F., 2001: A practical approach to the study of spatial structure in simple cases of heterogeneous vegetation. Journal of Vegetation Science 12, 99-108.
RICHARD, B., DANIEL, M., 2004: Advances in spatial, individual-based modeling of forest dynamics. Journal of Vegetation Science 15, 831-842.
RADCLIFFE-SMITH, A., 1980: The vegetation of Dhofar. in: Scientific Results of the Oman Flora and Fauna survey 1977 (Dhofar). The Journal of Oman Studies, Special Issue 2, 59-86.
SALE, J. B., 1980: The environment of the mountain region of Dhofar. Scientific results of theOman flora and fauna survey 1977 (Dhofar). The Journal ofOman Studies 2, 17-23.
SAKIO, H., 1997: Effects of natural disturbance on the regeneration of riparian forests in a Chichibu Mountains, central Japan. Plant Ecology 132, 181-195.
SAKIO, H., KUBO, M., SHIMANO, K., OHNO, K., 2002: Coexistence of three canopy tree species in a riparian forest in the ChichibuMountains, central Japan. Folia Geobotanica 37, 45-61.
SHALTOUT, K. H.,AYYAD,M. A., 1988: Structure and standing crop of Egyptian Thymelaeahirsuta populations. Vegetatio 47, 137-142.
SHALTOUT, K. H.,MADY, M. A., 1993: Current situation of the raudha's woody plant populations in the Central Saudi Arabia. Feddes Repertorium 104, 503-509.
SHALTOUT, K. H.,SHEDED,M. G.,EL-KADY, H. F.,AL-SODANY, Y.M., 2003: Phytosociology and size structure of Nitraria retusa along the Egyptian Red Sea coast. Journal of Arid Environments 53, 331-345.
SHALTOUT, K, SHEDED, M. G., SALEM, A. H., 2009: Population structure of common shrubs and trees in Wadi Allaqi Biosphere Reserve, South-East Egypt. Feddes Repertorium 120, 343-354.
SHEDED, M. G. PULFORD, I. D.,HAMED, A. I., 2006: Presence of major and trace elements in seven medicinal plants growing in the South Eastern Desert, Egypt. Journal of Arid Environments 66, 210-217.
SKARPE, C., 1990: Structure of woody vegetation in disturbed and undisturbed arid savanna, Botswana. Vegetatio 78, 11-18.
STEWART, G. H., ROSE, A. B., 1990: The significance of life history strategies in the development history of mixed beech (Nothofagus) forests, New Zealand. Vegetatio 87, 101-114.
STOHLGREN, T. J., BACKAND, R. R., ONAMI, Y., BINKLEY, D., 1998: Species-environment relationships and vegetation patterns: effects of spatial scale and tree life-stage. Plant Ecology 135, 215-229.
TAKAHASHI, K., 1994: Effect of size structure, forest floor type and disturbance regime on tree species composition in a coniferous forest in Japan, Journal of Ecology 82, 769-773.
TAKAHASHI, K. HOMMA, K.,VETROVA, V. B.,FLORENZEV, S.,HARA, T., 2001: Stand structure and regeneration in a Kamchatka mixed boreal forest. Journal of Vegetation Science 12, 627-634.
TANAKA, H., SHIBATA, M.,MASAKI, T., IIDA, S.,NIIYAMA, K.,ABE, S.,KOMINAMI, Y.,NAKASHIZUKA, T., 2008: Comparative demography of three coexisting Acer species in gaps and under closed canopy. Journal of Vegetation Science 19, 127-138.
TOLSMA, D. L., ERNST, W. H. O., VERWEIJ, R. A., VOOIJST, R., 1987: Seasonal variation of nutrient concentrations in a semi-arid savanna ecosystem in Botswana. Journal of Ecology 75, 755-770.
VEBLEN, T. T., 1992: Regeneration dynamics. In: GLENN-LEWIN, D. C. PEET, R. K.,VEBLEN, T. T. (eds), Plant succession: theory and prediction, 152-187. Chapman and Hill, London.
WANG, W.,MA, K. P., LIU, C. R., 1999: Removal and predation of Quercus Liaotungensis acorns by animals. Ecological Research 14, 225-232.
WANG, W.,MA, K. P., LIU, C. R., 2000: Seed shadow of Quercus Liaotungensis Koidz. in a broad-leaved deciduous forest in Dongling Mountain. Acta Botanica Sinica 42, 195-202.
WERNER, P. A., CASSWELL, H., 1977: Population growth rates vs. stage distribution models for teasel (Dipsacus sylvestris Huds.). Ecology 58, 1103-1111.
WEINER, J., 1985: Size hierarchies in experimental populations of annual plants. Ecology 66, 746-752.
WEINER, J., 1986: How competition for light and nutrients affects size variability in Ipomoeatricolor populations. Ecology 67, 1425-1427.
WELDEN, C. W, HEWETT, S. W., HUBBELL, P. S., FOSTER, R. B., 1991: Sapling survival, growth, and recruitment: relationship to canopy height in a neotropical forest. Ecology 72, 35-50.
WEISSENHOFER, M. A., 2005: Structure and vegetation dynamics of four selected one hectare forest plots in the lowland rain forests of the Piedras Blancas National Park, Costa Rica, with notes on the vegetation diversity of the Golfo Dulce region. Ph.D. Thesis, University of Wienna.
WILSON, J. B., AGNEW, A. D. Q., 1992: Positive-feedback switches in plant communities. Advances in Ecological Research 23, 263-336.