عنوان مقاله [English]
Vegetation studies measuring the accuracy of the results is important. The purpose of this study is to compare shape and distribution plots on different levels for species richness measurements.Thiscomparison was in three design Whittaker, Stohlgern and a new design (Ariz) in Ariz, Sanandaj.Designed proposition (Ariz) obtainedon base changes in the size and distribution plotin design Stohlgern species richness is designed to measure accurately. This study was conducted with three replications in grassland vegetation type. Compare plans were originally wooden and rope was walking in the area, and then proceed to the species in the plots were counted. Data analysis and statistical methods in factorial completely randomized design was performed using spss software version 17.
The results showed that the three estimates of species richness are having a significant difference in the estimation of species richness and Stohlgern plan and Whittaker are significantly different in the level 0.01. Whittaker plans and proposal (Ariz) in this study are the significantly different in the level 0.01 But Stohlgern plan and Ariz design are significantly different in the level 0.05.
 Bourdeau, P.F., 1953. A test of random versus systematic ecological sampling. Journal of Ecology, 34, 499-511.
 Clapham, A.R., 1932. The form of the observational unit in quantitative ecology. Journal of Ecology, 20, 192-197.
 Condit, R., Hubbell, S.P., Lafrankie, J.V., Sukumar, R., Manokaran, N., Foster,R.B., Ashton, P.S., 1996. Speciesareaand species-individual relationships fortropical trees:a comparison of three 50-ha plots. Journal of Ecology, 84, 549-562.
 Curtis, J., McIntosh, R., 1950. The enterrelations of certain analytic and synthetic phitosociological. Journal of Ecology, 41, 434-445.
 Dengler, J., Lobel. S., Dolnik, Ch., 2009. Species constancy depends on plot size- a problem for vegetation classification and how it can be solved. Journal of vegetation Science, 20, 754-766.
 Gifford, E.L., Benee F.S., Georage W.T., 1998. Species diversity and diversity profiles concept meaturement and application to timber and range management. Journal of Range Management, 41, 466-469.
 Gregi-Smith, P., 1964. Quantitative Plant ecology. Butterworth Science Publication Londan. England
 Hikman, K.R., Hartnett, D.C., Owensby, C.E., 2004. Grazing management effect on plant species diversity in tallgrasspraivie.Journal Range Management, 57, 58_65.
 Brummer, J., Nichols, T., Russel, K., 1994. Efficiency of different quadrat sizes and shapes for sampling standing crop. Journal of Range management, 47, 84-89.
 Keeley, Jon E., Fotheringham, C.J., 2005. Plot shape effects on plant species diversity measurements. Journal of Vegetation Science, 16, 249-256.
 Kenkel, n.c., podani, j., 1991. Plot size and estimation effecioncy in plant community studies. Jeurnal of vegetation science, 2, 539-544.
 Kent, M., Coker, p., 1992. Vegetation description and analysis. M. Mesdaghi (Translator). mashhad University publications. (In Persian)
 Kunin, W.E., 1997. Sample shape, spatial scale and speciescounts:Implications for reserve design. Biology Conserv, 82, 369-377.
 Mesdaghi, M., 2003. Range management in Iran. University of Mashhad press.336p. (In Persian).
 Mesdaghi, M., 2005. Plant ecology. University of Mashhad press.187p. (In Persian).
 Moghaddam, M. R., Ghorbani, J., 2001. A comparison of different plot size and shape efficiency to estimate of standing crop in steppe, high- steppe and semi- steppe ragions of Iran. Iranian journal Natural Research, 54, 191-204.
 Moghaddam, M. R., 2008. Quantitative Plant Ecology, 26-31P.(In Persian)
 Mohamadi, A., 1997. Basins assessed in order to obtain a birth certificate watersheds Kurdistan province. Institute of Soil Conservation and Watershed Management Research Project Final Report.
 Mohammed, A., Kalkhan, T., Stohlgren, j., 2000. Usingmulti scale sampling and spatial cross correlation to inverstigate patterns of plant species richness. Environmental Monitoring and Assessment, 64, 591–605.
 Mirdeilami, Z., sepehri, A., 2011. The comparing of plot size in estimating the quantitative characteristics of species in enclosure and non enclosure rangelands of Calpush plain. Iranian journal of Watershed Management Research, 91, 37-42.
 Myers, E., Chapman, V.J., 1953. Statistical analysis appliedto a vegetation type in New Zealand. Ecology, 34, 175-185.
 Pound, P., Clements, F. E., 1898. A method of determining the abundance of secondary species. Minn. Bot. stud, 2, 19-24.
 Shmida, Avi., 1984. Whittakers Plant Diversity Sampling Method. Israel Journal of Botany, 33,41-46
 Stohlgern,T.J., Kelly, A.B., Yuka, D., 1998 Comparison of rangeland vegetation sampling techniques in the central grassland. Journal of Range Management, 51, 164-172.
 Stohlgern, T.J., Flakner, M.B., Schell, L.D., 1995. A Modified-Whittaker nested vegetation sampling method Vegetation, 117, 113-121.
 Taya., A., 2006. Comparison of Whittaker and Modified-Whittaker plots to estimate species richness in Saluk. Masters dissertation Range Management. university of Natural Resources Sari.
 Wilson, S.D., Tilman, D., 2002. Quadratic variation in old-field species richness along gradients of disturbance and nitrogen. Ecology 83, 492–504.
 Yazdi Samadi, B., Rezai. A., Valizade. M., 2011. The statistics in agricultural research. University of Tehran press.764p. (In Persian).