Between 2010 and 2011 a field survey dedicated to Dracaena cinnabari (DC) population was conducted in Firmihin, Socotra Island (Yemen). It’s main goal was to collect data that would make it possible to unbiasedly estimate main characteristics of the local DC population. Our motivation was to provide reliable information to support decision-making processes as well as other research activities. At the same time we were not aware of a survey which could provide this kind of statistical-sound estimates for the whole population covering an area of almost 700 ha.
This article describes how the survey has been planned and carried out in practice. In addition, we also provide a set of preliminary estimates of the main DC population figures - totals and per hectare densities of stems, overall and partitioned according to predicted crown age. Among estimated parameters there are also mean crown age and proportions of predefined age classes on the total number of living DC stems. These estimates provide an explicit information on age structure of the whole DC population in Firmihin.
Although we collected data on more than one hundred randomly located plots, the reported accuracy of our estimates is still rather limiting. We discuss several possibilities to obtain more accurate results or at least to approach the supposedly lower true variance that can’t be calculated by approximate techniques applied here.
The design and concept of our survey makes it possible to evaluate changes over time on stem by stem bases and to generalize these stem-level details to the whole population. Mortality, regeneration and even change of population’s mean crown age can be estimated from a future repeated survey, which would be extremely useful to draw firm conclusions about the dynamic of the whole DC population in Firmihin.
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Adolt, R., & Pavliš, J. (2004). Age structure and growth of Dracaena cinnabari populations on Socotra. Trees, 18, pp. 43-53.
Adolt, R., Habrová, H., & Maděra, P. (2012). Crown age estimation of a monocotyledonous tree species Dracaena cinnabari using logistic regression. Trees, 26, pp. 1287-1298.
Attorre, F., Francesconi, F., Taleb, N., Scholte, P., Saed, A., Alfo, M., & Bruno, F. (2007). Will dragonblood survive the next period of climate change? Current and future potential distribution of Dracaena cinnabari (Socotra, Yemen). Biological conservation, 138(3-4), pp. 430-439.
Axelrod, D.I. (1975). Evolution and biogeography of madrean-tethyan sclerophyll vegetation. In: Annals of the missouri botanical garden. Missouri Botanical Garden Press.
Barabesi, L., & Franceschi, S. (2010). Sampling properties of spatial total estimators under tessellation stratified designs. Environmetrics, (on-line publication).
Bellhouse, D., R. (1988). A brief history of random sampling methods. In: Krishnaiah, P., R., & Rao, C., R. (eds): Handbook of statistics, (pp. 1-13), sampling. 6, North Holland.
Brown, G., & Mies, B.A. (2012). Vegetation ecology of Socotra. Plant and Vegetation 7., Springers, 382 pp.
Buckland, S. T., Anderson, D. R., Burnham, K. P., & Laake, J. L. (1993). Distance sampling: Estimating abundance of biological populations. Chapman and Hall, London.
Cassel, C.M., Särndal, C.E., & Wretman, J.H. (1977). Foundations of inference in survey sampling. John Willey & Sons, New York. 192 p.
Cochran, W. G. (1977). Sampling techniques. Willey series in probability and mathematical statistics - applied. John Willey & Sons.
Cooper, C.6. (2006). Sampling and variance estimation on continuous domains. Environmetrics, 17, pp. 539-553.
Cordy, C., B., & Thompson, C., M. (1995). An application of the deterministic variogram to design-based variance estimation. Mathematical geology, 27, pp. 173-205.
Cordy, C. B. (1993). An extension of the Horwitz-Thompson theorem to point sampling from a continuous universe. Statistics and probability letters, 18, pp. 353-362.
De Sanctis, M., Adeeb, A., Farcomeni, A., Patriarca, Ch., A., Saed, & Attorre, F. (2013). Classification and distribution patterns of plant communities on Socotra Island, Yemen. Applied vegetation science, 16(1), pp. 148-165.
Godambe, V.P. (1955). An unified theory of sampling from finite populations. Journal of the Royal Statistical Society, series b, 17, pp. 269-278.
Gregoire, T. G., & Valentine, H. T. (2008). Sampling strategies for natural resources and the environment. Chapman and Hall/CRC.
Haber, S. (1966). A modified Monte Carlo quadrature. Math. comput., 20, pp. 361-368.
Haber, S. (1967). A modified Monte Carlo quadrature 2. Math. comput., 21, pp. 388-397.
Habrová, H. (2004). Geobiocoenological differentiation as a tool for sustainable land-use of Socotra Island. Ekologia, 23, pp. 47-57.
Habrová, H., & Maděra, P. (2004). Ecology of Dracaena cinnabari communities on Socotra. In: Polehla, P. (ed): Geobiocoenological papers, (pp. 120-126), vol. 9. MUAF in Brno.
Habrová, H., Čermák, Z., & Pavliš, J. (2009). Dragon’s blood tree - threatened by overmaturity, not by extinction: Dynamics of a Dracaena cinnabari woodland in the mountains of Socotra. Biological conservation, 142(4), pp. 772-778.
Heikkinen, J. (eds. Kangas A. & Maltamo M.). (2006). Forest inventory, methodology and applications. Springer Verlag. Chap. Assessment of Uncertainty in Spatially Systematic Sampling, pp. 155-176.
Hubálková, I. (2011). Prediction of dragon’s blood tree (Dracaena cinnabari Balf.) stand sample density on Socotra Island (key study). Journal of Landscape Ecology, 4(2), pp. 5-20.
Kangas, A., Gove, J. H., & Scott, T. Ch. (eds. Kangas A. & Maltamo M.). (2006). Forest inventory, methodology and applications. Springer Verlag. Chap. Introduction, pp. 3-8.
Král, K., & Pavliš, J. (2006). The first detailed land cover map of Socotra Island by Landsat/ETM+ data. International Journal of Remote Sensing, 27(15), pp. 3239-3250.
Kürschner, H., Hein, P., Kilian, N., & Hubaishan, M.A. (2006). Diversity and Zonation of the forests and woodlands of the Mountains of Northern Socotra, Yemen. Englera, 28, pp. 11-55.
Laplace, P.S. (1783). Sur les naissances, les mariages et les morts. In: Histoire de l’académie royale des sciences, année 1783. Académie Royale des Sciences, Paris. Mandallaz, D. (1991). An unified approach to sampling theory for forest inventory based on infinite population and superpopulation models. Ph.D. thesis, Swiss-Federal Institute of Technology (ETH), Zurich.
Mandallaz, D. (2007). Sampling techniques for forest inventories. Chapman and Hall/CRC.
Marrero, A., Almeida, S.R., & Martín-González, M. (1998). A new species of the wild dragon tree, Dracaena (Dracaenaceae) from Gran Canaria and its taxonomic and biogeographic implications. Botanical Journal of the Linnean Society, 128(3), pp. 291-314.
Matérn, B. (1960). Spatial variation. Ph.D. thesis, Statens Skogsforskningsinstitute.
Mies, B., & Beyhl, F.E. (1996). The vegetation Ecology of Soqotra. In: Dumont, H.J. (ed): Proceedings of the first International Symposium on Soqotra Island, (pp. 35-82). Aden, NY. United Nations Publications.
Miller, A., & Cope, T.A. (1996). Flora of the Arabian Peninsula and Socotra. Vol. 1., Edinburgh University Press.
Miller, A., & Morris, M. (eds). (2000). Conservation and sustainable use of the biodiversity of soqotra archipelago. Royal Botanic Garden Edinburgh.
Miller, A.G., Morris, M., Diccon, A., & Atkinson, R. (2004). Ethnoflora of the Soqotra Archipelago. Royal Botanic Garden Edinburgh.
Neyman, J. (1934). On the two different aspects of the representative sampling: the method of stratified sampling and the method of purposive sampling. Journal of the Royal Statistical Socienty, pp. 558-606.
Quenouille, M. H. (1949). Problems in plane sampling. Annals of Mathematical Statistic, 20, pp. 335-375.
R Core Team. (2013). R: A language and environment for statistical computing.
R Foundation for Statistical Computing, Vienna, Austria.
Rao, J. N. K. (2003). Small area estimation. Wiley.
Razdorskij, F., V. (1954). Anatomie rostlin. ČSAV. Praha.
Ripley, B. D. (2004). Spatial statistics. John Willey & Sons.
Scholte, P., & De Geest, P. (2010). The Climate of Socotra Island (Yemen): A first-time assessment of the timing of the monsoon wind reversal and its influence on precipitation and vegetation patterns. Journal of Arid Environments, 74, pp. 1507-1515.
Scholte, P., Al-Okaishi, A., & Suleyman, A.S. (2011). When conservation precedes development: A case study of the opening up of the Socotra Archipelago, Yemen. Oryx, 45(3), pp. 401-410.
Stevens, D. L. Jr. (1997). Variable density grid-based sampling designs for continuous spatial populations. Environmetrics, 8, pp. 167-195.
Stevens, D. L. Jr., & Olsen, A. R. (2003). Variance estimation for spatialy balanced samples of environmental resources. Environmetrics, 14, pp. 593-610.
Stevens, D. L. Jr., & Olsen, A. R. (2004). Spatialy balanced sampling of natural resources. Journal of the American Statistical Association, 99, pp. 262-278.
Särndal, C. E., Swensson, B., & Wretman, J. (2003). Model assisted survey sampling. Springer.
Van Damme, K., & Banfield, L. (2011). Past and present human impacts on the biodiversity of Socotra Island (Yemen): implications for future conservation. biodiversity conservation in the Arabian Peninsula zoology in the Middle East, Heidlberg: Kasparek Verlag. Supplementum 3: pp. 31-88.
Zimmermann, M., H., & Tomlinson, P., B. (1969). The vascular system in the axis of Dracaena fragrans (Agavacea). Journal of the Arnold Arboretum, 50, pp. 370-383.