Showing 2 results for Quadrate
Mohammad Reza Vahhabi, Mehdi Bassiri, Jamaleddin Khajeddin,
Volume 1, Issue 1 (4-1997)
Abstract
Short-term changes (5 years) in canopy cover, species composition and forage production were studied under protection from grazing and grazed condition in 19 range sites in Fereydan region, Isfahan province. In this study, density, canopy cover and forage production data were obtained from quadrates inside and outside exclosures in the spring of 1983. These parameters were studied again in 1988 and compared with the previous data. Results indicated that species diversity in these range sites was relatively high up to 212 plant species were identified. Sixteen, 8.5 and 75.5 percent of these species were classified into I, II and III palatability classes respectively. After five years, comparison of inside and outside exclosures indicated an increase in the density of species of I, II and III palatability classes by 138.8, 120.8 and 51.5 percent inside exclosures, respectively. Density of all species had increased by 62 percent as a result of 5-year protection from grazing. Species composition data as canopy cover were used to construct 3 dendrograms to investigate the similarity among range Sites. Assuming 32% similarity as the threshold level, 19 range sites were classified into 10 vegetation types in 1983. After 5 years, these vegetation types decreased to 8 and increased to 11 under protection from grazing and grazed conditions, respectively. The average forage production inside exclosures was almost twice as much as in grazed sites (600 Vs. 315 kg/h). Three groups of range sites were recognized according to the time requirement for rehabilitation by grazing protection. The first group was improved considerably by the end of the 5-year protection Period. The second group improved relatively within five years of grazing exclusion. The third group did not improve by 5-year grazing protection and needed much longer protection period or some other range rehabilitation practices.
M. Mousaei Sanjerehei, M. Bassiri,
Volume 11, Issue 40 (7-2007)
Abstract
Selection of efficient indices is very important for detecting and measuring random, uniform and clumped distribution patterns of plants in different plant communities. To compare and evaluate indices of dispersion patterns of plants, three stands were selected in Nodushan, Yazd. A (50m*100m) area was selected within each stand for sampling. Sampling was randomly systematicly conducted. Measurements and counts were made at 50 points and (1 and 2m2) quadrats which were randomly selected along four 100m transects within each sampling area. Indices of dispersion using quadrate studied in this survey include: Standardized index of Morisita, Morisita's index, Green's index, Dispersion (variance/mean ratio) index , Lloyd's index of patchiness and distance indices of dispersion including Pielou, Hopkines, T square, Eberhardt , Hines, Johnson and Zimer and Holgate indices. Results showed that T square and Holgate indices were more powerful than the other indices for detecting intensity of small-scale and tightly clumped pattern of shrubs because the two indices could distinguish between single individuals and the individuals on the edges of dense and small clumps. Johnson and Zimer index and Standardized index of Morisita (in shrublands with plant cover greater than 5%) were more efficient than the other indices for determining spatial pattern of these small clumps and single individuals. Among studied indices of dispersion, Green's index had the highest precision and with the exception of this index, distance indices were more precise than the quadrate indices.
