Showing 7 results for Canopy
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.
A Shaabani, A Kamgar Haghighi, A Spaskhah, Y Emami, T Honar,
Volume 13, Issue 49 (10-2009)
Abstract
Oil seed rape (Brasica napus) is an important crop, which is cultivated in Iran for oil production. As a management practice deficit irrigation strategy is applied to cope with water shortages, especially during drought periods. This research was conducted to study the effect of water stress on physiological parameter of oil seed rape in the experimental research field of Collage of Agriculture (of shiraz university) during 2004- 2005 and 2005- 2006. Licord cultivar of oil seed rape was planted and experimental design was random block with five treatments and four replications. Treatments were full irrigation in all growth stages, water stress in vegetative stage in early spring, water stress in flowering and podding stages, water stress in grain filling stage and dry land treatment with supplemental irrigation in time of planting. Water stress caused decrease in water potential of plant, an increase in canopy temperature, and decrease in plant height especially in dry land treatment. Leaf area index decreased as water stress increased. The decrease in leaf area index was more severe in vegetative stage water stress treatment. At the end of water stress period leaf area index increased again. Rate of decrease in leaf area index at the end of the growing season was higher in grain filling stage of water stress treatment.
H. R. Owliaie, E. Adhami, H. Faraji, P. Fayyaz,
Volume 15, Issue 56 (7-2011)
Abstract
Trees in many forests affect the soils below their canopies. Analysis of the relationships between trees and soil is one of the basic factors in management and planning of forests. Zagros forest ecosystem is one of the main degrading forest ecosystems in Iran and plays an important role in soil protection. Quercus brantii is the most important woody species in these forests. This study was conducted to determine the influence of oak on selected physico-chemical properties of soils of three oak forests in Yasouj region. The experimental design was a factorial 332 (3 depths, 3 regions and 2 distances) in a randomized complete block design with four replications. Soil samples (0-20, 20-40 and 40-60 cm depth) were taken from beneath canopies and adjacent open areas. The results showed that oak canopy increased mostly organic carbon, total N, available K, P, EC, EDTA extractable Fe, Zn and Mn, while CCE, pH, and DTPA extractable Cu were decreased. Oak canopy had no significant effect on soil texture. Our results suggested that the presence of Quercus brantii individuals may be an important source of spatial heterogeneity in these forests.
P. Rostamizad, V. Hosseini, K. Mohammadi Samani,
Volume 22, Issue 2 (9-2018)
Abstract
Trees crown can be regarded as main factor contributing to the conservation and support of soil in many ecosystems including semiarid forests in Zagross. The aim of this study was to find out the effect of tree crown of pictachio (Pistacia atlantica Desf) on N, OC, P, pH, EC and the texture of the soil. Soil samples were collected in and outside the crown of 5 single pistachio trees on four directions of each tree in a northern slope from the 0-5 cm depth of soil in the Sarvabad region, Kurdistan. The results of this study showed that the amount of the soil organic carbon was decreased from 6.71% in the soil inside tree crowns to 4.73% in the soils outside the tree canopies. The soil inside trees had a higher concentration of soil nitrogen (0.406%) than the one outside (0.224%) the tree crown; the concentration of phosphorus was measured to be 32.7 mg/kg in the soil inside canopy, while it was 21.1 mg/kg in the soil of outside the tree canopy. EC under the tree crowns was more than that outside the canopy. The results, therefore, showed that soil texture was lighter inside the canopy, as compared to outside; however, the acidity of the soil was not affected by tree crowns and no significant differences were observed in different areas of the crown. Therefore, Persian turpentine trees have positive impacts on the soil properties in Zagros forests and eliminating them will lead to the significant loss of soil fertility and greater soil erosion.
H. Karimi Avargani, A. Rahimikhoob, M. H. Nazarifar,
Volume 23, Issue 3 (12-2019)
Abstract
In recent years, a lot of research has been done on the Aquacrop model, the results show that this model simulates the product performance for deficit irrigation conditions. But this model, like other models, is sensitive to values of independent variables (model inputs). In this research, the sensitivity of the Aquacrop model was analyzed for 4 input parameters of reference evapotranspiration, normalized water productivity, initial canopy cover percentage and maximum canopy cover for barley. Irrigation treatments included full irrigation and two deficit irrigation treatments of 80% and 60%, the experiment was done in 2014-15 growing season in the field of Abourihan College. The values of measured biomass were used as the base values for treatments. The Beven’s method (Beven et al., 1979) was used for sensitivity analysis of Aquacrop model. The results showed that the model is most sensitive to the reference crop evapotranspiration, So the sensitivity coefficient for this parameter for full irrigation treatments, 80% full irrigation and 60% full irrigation were -1.1, -1.2 and -2.3 respectively. The negative sign indicates that if the value of reference evapotranspiration input is exceeded the actual value into the model, Yield performance is simulated less than actual value. In the meantime, the higher the degree of deficit irrigation, the greater the sensitivity of the model.
M. Abedinzadeh, A. Bakhshandeh, Mr B. Andarziyan, Mr S. Jafari, M Moradi Telavat,
Volume 25, Issue 3 (12-2021)
Abstract
Iran is located in the dry belt of the earth and is predicted to face water stress in the next half-century. Currently, the area of sugarcane cultivation in Khuzestan is over 85,000 hectares and due to the high water needs of sugarcane and drought conditions, optimization of water consumption and irrigation management is necessary to continue production. Therefore, in this study, the values of soil moisture, canopy cover, biomass yield in five treatments and irrigation levels (start of irrigation at 40%, 50%, 60%, 70%, and 80% soil moisture discharge) during 2 planting dates in the crop year 2015-2016 on sugarcane cultivar CP69-1062 in Amirkabir sugarcane cultivation and industry located in the south of Khuzestan was simulated by AquaCrop model. The measured data on the first culture date (D1) and the second culture date (D2) were used to calibrate and validate the model. The results of NRMSE statistics in canopy cover simulation in calibration and validation sets with values of 2.1 to 15.6% and 3.8 to 18.3%, respectively, and in biomass simulation with values of 6.2 to 15.2%, and 9.5 to 12.6%, respectively and coefficient of determination (R2), range 0.98 to 0.99 indicated that the high ability of the AquaCrop model in simulation canopy cover and biomass yield. whereas, the values of NRMSE of soil depth moisture in the calibration and validation sets ranged from 11.6 to 23.8, and 12.2 to 22.7, respectively, with a coefficient of determination (R2), 0.73 to 0.96 (calibration) 0.8 to 0.93 (validation) showed less accuracy of the model in the simulation. The best scenario is related to the third proposal that water consumption, water use efficiency, and yield are 1710 mm, 1.53, and 42.27 tons per hectare, respectively, which shows a reduction in water consumption of 360 mm.
M.r. Bahadori, F. Razzaghi, A.r. Sepaskhah,
Volume 26, Issue 3 (12-2022)
Abstract
Inefficient use of limited water resources, along with increasing population and increasing water demand for food production has severely threatened agricultural water resources. One way to overcome this problem is to improve water productivity by introducing new crops that tolerate water stresses such as quinoa. In this study, the effect of water stress at different stages of plant growth (vegetative, flowering, and grain filling) was studied on plant parameters, yield, and water productivity of quinoa (cv. Titicaca). This study was conducted under field conditions and the treatments were performed as a block experiment in a completely randomized design with four replications. Experimental factors were: treatment without water stress or full irrigation (F) and water stress treatment (D) at 50% of the need for full irrigation at different stages of quinoa growth. The application of deficit irrigation during different stages of plant growth decreased stomatal conductance, leaf area index, leaf water potential, seed yield, and water productivity, while deficit irrigation increased the green canopy temperature. According to the results of the present study, the flowering stage of quinoa was very sensitive to water stress leading to produce lower yield compared with the amount of yield obtained when vegetative and or grain filling stages are under water stress conditions.
