جستجوی مقالات مرتبط با کلیدواژه « Principal Components Analysis » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

In order to study forage yield, seed yield and its components in two species of Stipa, 16 genotypes of S. barbata and 10 genotypes of S. hohenackeriana were collected from natural habitats in Esfahan province and evaluated with a completely randomized design with three replications in farm condition. Based on the results, there was a significant difference between two species for most of the important traits such as forage yield and seed yield. Rahmat Abad Khansar population of S.hohenackeriana and Polkale population of S. barbata showed higher forage yield (3333 and 3129 kg/ha, respectively). The first five components determined 73% of total variation. The first component named as yield factor, the second and the third factors as vegetative factors, the forth component as yield component factor and the fifth factor as dry weight/wet weight. Cluster analysis classified populations into two groups with distinct variations for seed yield and forage yield.

This study was carried out to evaluate 10 Stipa hohenackeriana populations based on forage and seed yield. Population seeds were collected from natural habitat of Esfahan province and were examined in a field condition using a randomized complete block design with 3 replications. Yield and yield components of seed and forage were studied. Populations showed significant differences for all traits. Rahmat abad Khansar had the highest forage and seed yield (1140 and 160 kg/ha, respectively). The first sixth components determined 97% of the total variation. Number of seeds in spike, spike seed weight, Plant height in spiking and spike length in spiking were the most important traits in the first component, seed weight of shrub, seed length and seed yield the second component, leaf length, stem height in maturing and canopy the third component, Shrub dry weight and forage yield in the fourth component, spike length in seed maturity 1000 seeds weight in the fifth component and dry weight/wet weight in the sixth component were important. Populations were classified into 3 groups and Rahmat abad Khansar, Soh, Ghalee Shahrokh and Gardane mola ahmad populations introduced as superior for forage and seed yield. The distribution of the populations based on (PCA) analysis was in agreement with cluster analysis results. Based on the results there is enough genetically variation between populations for seed and forage yield. Therefore it can use in restoring grasslands by selection indices and improvement programs.

This research aimed at studying the vegetation and investigating the effects of physiographic, edaphic and geological factors upon distribution of plant communities in Manesht district in Ilam province. Sampling was done based on plant types and land unit map. The number of samples was determined by Krebs method. In total, 125 square sampling plots of 400area were selected by random systematic method. To determine soil factors, two soil samples (0–30, 30-90 cm deep) were collected from each land unit and physico-chemical parameters were measured. Using TWINSPAN, vegetation of study area was classified and then PCA and CCA were used to investigate the relationship between vegetation and environmental factors. Based on TWINSPAN, four vegetation groups were recognized. According to TWINSPAN results, four ecological groups were identified that first and second groups with 31 and 46 sample plots, respectively and by Quercus barantti, Crataegus pontica and Acer monspessulanum, as indicator species, are more calciphiles than another groups. The first three axes of the PCA accounted for 62.83%, 23.45% and 13.72% of the total plant cover variability, respectively. Also based on Mont Carlo analysis, first and second axes with 0.68 and 0.48 eigenvalue, accounted for 28% and 19% of the variability, respectively and the correlation coefficient of axes and species is 0.98. According to PCA and CCA, Formation, organic matter and lime were the most important factors on establishing of ecological groups.

Vegetation and soil characteristics are highly affected by herbivores and exploring these relationships is essential for rangeland management. This study aimed to compare the plant composition and physico-chemical soil properties under livestock (sheep and goat) and wildlife (deer) grazing regimes in Kalmand-Bahadoran plain rangelands of Yazd province. A random-systematic method was used to collect the data from 10 randomly established transects with 100¬ meters lengths and 3 plots of 2 m2 were placed on each transect. CANOCO4 software was used to analyze the collected data. According to the results, livestock and wildlife grazing were identified as the most responsible factors, describing the sites places along the first axis of Redundancy analysis (RDA) plot. The frequency of some species such as Colchicum kotschyi, Stachys inflata, Iris songarica, Lolium rigidum, Boissiera squarrosa, Noaeae mucronata, Astragalus sp. and also stone percentage increased in the sites grazed by wildlifes. On the other hand, the frequency of Echinops sp., Scorzonera sp., Launaea acantodes, Zygophyllum eurypterum, Stipa barbata, Peganum harmala, litter and bare soil percentage raised in the sites grazed by livestock. livestock and wildlife grazing did not have any significant effects on the frequency of Artemisia sieberi as a dominant species, Lactuca sp. and Cousinia sp. Soil texture, soil moisture and soil organic carbon content did not varied significantly in the two studied areas but some soil characteristics such as EC, pH, TNV and soil bulk density were higher in the sites grazed by livestock than the other site. Wildlife grazing resulted to some positive changes in soil characteristics and vegetation composition, therefore it can be concluded that similar management practices experienced in sites grazed by wildlife can enhance the range condition of other sites.

Known of ecosystem of range details and relation bet ween this details including soil and vegetation, is Necessary for optimum management of ranges. To determine the effect of some soil properties on species distribution of Dorema ammoniacum and Rheum ribes in ranges of Baghedar region, Information of vegetation were harvested with systematic-random method in the form of 40 plots and during 4 transects. After drilling soil profiles in beginning and end of each transect and samples of 0-10 and 110-80 cm, the parameters pH, EC, CaCo3, organic carbon, CaSo4, Co3, Hco3, Cl, So4, Ca, Mg, Na, Fe, Cu and soil classification grain distribution was determined in the laboratory. After Collection of data for Analysis, it was used Principal components analysis method. The results of analysis between soil variables and vegetation show that soil texture, CaCo3, EC, OC, CA, Mg, Cl and Na had more impact on distribution of vegetation types and Dorema ammoniacum and Rheum ribes.

In order to optimum management of ecosystem of range, need details and relation between this details including soil and vegetation known. To determine the effect of some soil properties on species distribution of Eryngium bungei in Baghedar summer Bafgh region, Information of three types of vegetative plants were identified Artemisia aucheri - Eurotia ceratoides, Artemisia aucheri - Eryngium bungei and Artemisia aAucheri - Stipa barbata in the form of 20 plots were harvested for each type in the desert. After drilling 27 soil profiles and samples of 0-30 and 30-60 cm, the parameters pH, EC, CaCo3, organic carbon, CaSo4, gravel and soil classification grain distribution was determined in the laboratory. Analysis of variance showed that clay and CaCo3 in the soil first depth and CaCo3 in the soil second depth in three vegetation types with significant differences are. Principal components analysis on 16 soil variables and percent slope showed that the first principal component included percent slope, clay in the second depth and CaCo3 and sand in the first depth, explain 61% of the variations and the second components included sand in the second depth and electrical conductivity and organic matter in the first depth, explain 38% of the variations. The results show that Eryngium bungei be seen on soil with more clay in lower layer and more CaCo3 and less organic carbon and EC in upper soil layers.

In order to investigate the variation and relationships among seed yield and its components under irrigation and dryland farming conditions، 12 populations of Festuca ovina were studied using a RCB design with three replications in Kheirabad agricultural research station in Zanjan province، Iran. Seed and forage yield and morphological traits were recorded and analyzed. There was significant variation in all traits in two farming conditions. The annual average values of seed and forage yield in irrigated condition were 215 and 2161 Kg/ha and were higher than 121 and 997 Kg/ha under rainfed conditions. The populations 3، 9 and 5 with average values of 208-227 Kg/ha seed production and populations 3، 4 and 11 with average of 1805-2172 Kg/ha forage yield had higher production for seed and forage yield in both farming conditions. According to results، the population 3، selected from Alborz rangelands was recommended for pasture and rangeland rehabilitation of Zanjan province. DM yield was negatively correlated with panicle emergence date and positively correlated with plant height، panicle number، panicle length، and panicle weight. Under irrigated conditions، the relationships among seed yield with all traits were positive and significant except panicle emergence date. Based on principal components analysis، the first three independent components with 55، 18 and 13% explained 86% of the total variation. Based on cluster analysis، all populations were placed in 3 groups. Finally، all genotypes in cluster 3 with higher values for seed and forage yield than two other clusters are recommended for use in breeding programs to improve synthetic varieties.

In order to study the grouping of Agropyron tauri populations, 13 populations were investigated in a randomized complete blocks design with three replications. The study was performed in research field of Islamic Azad University of Tabriz in 2010. In this study, a number of traits including plant height, tiller number, leaf number, flag leaf length, first leaf length, second leaf length, first internode length, second internode length, crown cover, fresh yield, dry yield, fresh weight of single plant and dry weight per plant were evaluated. Analysis of variance showed significant differences among populations for all measured traits. Thirteen populations were classified into three clusters by cluster analysis of standardized data, based on Euclidean distance and Ward method. This result was in consistent with the height of geographic regions from which populations were collected. In principal components analysis, four components were introduced, and the traits of fresh and dry yield showed high and positive coefficients in first component. Results of cluster analysis were confirmed by results of principal components analysis.

The purpose of current study is to investigate the effects of some of environmental factors on erosion value، to find the most important governing factors and the relation between erosion of working units and environmental factors (soil characteristics، slope، aspect، elevation، lithology، geomorphology faces and vegetation cover percentage). Working units map was prepared using geomorphology method. This map was derived by overlaying slop، aspect، elevation، lithology and geomorphology faces maps. In order to study plant cover random-systematic sampling in each working unit was conducted in 10 plots. Regarding the species type and distribution the area of each plot was determined based on the minimal area method. Canopy cover of species was determined in each plot. Furthermore، 5 profiles were sampled within the working units to study soil characteristics in 0-50 cm depth. Subsequently، the texture، percent of lime، organic matter، gravel، pH and EC were measured. Erosion value was determined in each working unit using E. P. M. method. Statistical analysis was done using the Principal Components Analysis (PCA) through PC-ORD4 software program. The results showed that among environmental factors، vegetation cover، slope، stone resistance، organic matter and aspect as the first set of factors determine the change in erosion value by 54. 35% while the second set of factors، including loam and clay percentage play contributes to the change by 26. 96%. These two sets of factors altogether explain 81. 31% of erosion value variation in Ghara aghaj basin.