جستجوی مقالات مرتبط با کلیدواژه "water stress" در نشریات گروه "محیط زیست"

Water shortage stress is one of the factors affecting medicinal plants, and on the one hand, the role of mycorrhizal fungus is important in improving the performance of some medicinal plants faced with water shortage stress. Therefore, for this purpose, an experiment on the medicinal plant borage (Borago officinalis L.) in the form of chopped plots in the form of a completely randomized block design with three replications in the years 2014 and 2015 in Boyer Ahmad region (Chamkhani Yasouj Agricultural Research Station ), was implemented. Water stress as the main factor in irrigation levels after 30, 60, 90, 120, and 150 mm of water evaporation from evaporation pan class A and mycorrhiza fungus as a secondary factor in non-application levels, application of Glomus mosseae species and application of Glomus intraradices species was considered. Based on the average comparison results, in the conditions of irrigation levels after 60, 90, 120, and 150 mm of water evaporation from the evaporation pan, the application of Glomus mosseae and Glomus intraradices fungi compared to the absence of mycorrhizal mushroom application caused a significant increase in the relative water content. (17.29 and 13.83 percent), (13.60 and 16.76 percent), (7.87 and 8.97 percent), and (19.92 and 15.65 percent) became plants. It shows that in these irrigation levels, mycorrhizal symbiosis increases the level of root absorption and absorbs more and better water from the soil, leading to a change in the speed of water movement inside and outside the plant, affecting tissue water absorption and leaf physiology. Subsequently, it has caused an increase in the relative water content of borage under water stress conditions. The interaction of irrigation and mycorrhizal fungus on the water consumption efficiency of borage was also significant. Based on the results of this study, irrigation treatment after 90 mm of water evaporation from the evaporation pan and application of mycorrhizal fungus G. mosseae is recommended as water requirement.

Considering the not very suitable state of the country's water resources as well as the phenomenon of climate change and its effects, simulating the state of climate change in the future and evaluating its effects in order to reduce vulnerability and deal with it can be very important in future decisions. In this regard, in order to reduce the negative effects of climate change and benefit from its possible positive effects in watersheds, various adaptation strategies are presented.In this research, adaptation to climate change in the agricultural sector under the CMIP6-SSP climate change scenarios has been investigated and evaluated. Considering the characteristics of the Hashtgerd region and the risks that threaten agriculture in the region, this research tries to have a comprehensive view of this system. For this purpose, adaptation strategies to reduce the negative effects of climate change in the agricultural sector were evaluated.

 In this research, the SWAT model was used to simulate and evaluate the adaptive strategy in Hashtgerd region in 2018. To model climate change conditions in the region, the NorESM2-MM climate model related to the 6th IPCC report and different SSP scenarios (SSP1.26, SSP2.54, SSP3.70, SSP 5.85) were used and minimum and maximum temperature data and the precipitation were downscaled for the years 2020 to 2049. After calculating the changes in temperature and rainfall compared to the current conditions, the values ​​of these changes were applied to the SWAT model in order to investigate its effect on the water resources of Hashtgerd region. Finally, the values ​​of water stress and crop performance were estimated under the conditions of climate change.

The results indicated an average increase in water stress and also a decrease in yield of crops other than corn in all SSP scenarios. After evaluating the effects of climate change in the region, in order to adapt to these changes in the agricultural sector, two adaptation strategies were used 1) The strategy of changing the cultivation pattern from tomato and alfalfa crops to wheat and barley and 2) Changing the cultivation pattern from tomato and alfalfa to corn. These strategies were evaluated with criteria such as changes in water stress and yield of crops compared to BAU conditions.

The results showed that changing the cultivation pattern to wheat and barley has reduced the water stress of regional crops. In general, in the strategy of changing the cultivation pattern, the yield of all three crops, wheat, barley and corn, was increased compared to the BAU strategy. In the strategy of changing the cultivation pattern to corn, a significant reduction in water stress was estimated and, accordingly, the yield of this product was acceptable. This increase in performance is due to the reduction of water stress caused by the increase in available water.

One of the main limitations in arid and semi-arid regions is the allocation of water resources for green space development. Since water and drought stresses along with incorrect selection of species are the main factors that reduce seedling survival in the afforestation stages in arid and semi-arid regions, the aim of current study is to investigate the morphological characteristics of ash, Mullberry and ash leaved maple seedlings in the greenhouse and the feild under different water stress in Robat Karim town.

Robat Karim city is one of the towns of Tehran province with area of 275 square kilometers. To study the effect of water stress on morphological characteristics 20 saplings were planted in 4 repetitons in a completely randomized design. 5 saplings of each species were selected for water stress treatments. A total of 90 saplings including 5 repetitons and three drought levels (2, 4 and 6 days after reaching MAD point) were considered and tested for the above species in greenhouse and in field. The saplings that reached the MAD point were not irrigated immediately and were subjected to 3 drought stresses 2, 4 and 6 days after reaching the MAD point. Then the quantitative appearance characteristics of seedlings which include parameters of leaf numbers, leaf size, seedlings height, stem diameter, dry leaf weight, stem dry weight along with 2 qualitative characteristics of seedlings, which are leaf freshness and seedling health, were measured.

The results showed that the number of MAD period times in the greenhouse for Fraxinus rotundifolia Mill species was 29, Acer negundo 28 and Morus alba 32 and in the field for Fraxinus rotundifolia Mill species was 20, Acer negundo 20 and Morus alba 17 period times. Generaly, in all three studied species, in May, as the first month of research, the seedlings were in a very good condition. In other months, after being under different water stress (2, 4, 6 days), the number of leaves and leaf size have always decreased over time. In case of ash leaved maple, the number of leaves in the greenhouse area in August was zero (absolute defoliation).

Generaly, by increasing water stress, leaf number, leaf size, dry leaf weight, dry stem weight, leaf freshness and saplings health reduced. It seems that 6 days after reaching MAD point is the sutiable time to irrigate the saplings according to their Morphological characteristics. Considering to the appearance of seedlings during irrigation always helps to use water efficiently, prevent over-irrigation and under-irrigation of seedlings and save the relevant costs.