排序方式: 共有32条查询结果,搜索用时 15 毫秒
11.
Mojtaba Karami Birger Ulf Hansen Andreas Westergaard-Nielsen Jakob Abermann Magnus Lund Niels Martin Schmidt Bo Elberling 《Ambio》2017,46(1):94-105
The objective of this paper is to characterize the spatiotemporal variations of vegetation phenology along latitudinal and altitudinal gradients in Greenland, and to examine local and regional climatic drivers. Time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed to obtain various phenological metrics for the period 2001–2015. MODIS-derived land surface temperatures were corrected for the sampling biases caused by cloud cover. Results indicate significant differences between West and East Greenland, in terms of both observed phenology during the study period, as well as the climatic response. The date of the start of season (SOS) was significantly earlier (24 days), length of season longer (25 days), and time-integrated NDVI higher in West Greenland. The sea ice concentration during May was found to have a significant effect on the date of the SOS only in West Greenland, with the strongest linkage detected in mid-western parts of Greenland. 相似文献
12.
Hamideh Maleksaeidi Ezatollah Karami Gholam Hossein Zamani Kourosh Rezaei-Moghaddam Dariush Hayati Masoud Masoudi 《Environment, Development and Sustainability》2016,18(2):499-525
Water scarcity at an alarming rate has been a limiting factor for sustainable agriculture in arid and semi-arid environments of the world. It has resulted in a number of problems such as poverty and food insecurity among farm households. Therefore, building and improving resilience, as a way to mitigate the impacts of water scarcity, is important for farm households. But one of the significant steps for planning to improve farm households’ resilience under water scarcity is investigation of the current level of resilience of these households and understanding their variances. Therefore, this study offers a classification of farm households’ diversity based on resilience. Primary data were collected from 260 randomly selected farm households in 21 villages around Parishan wetland, Iran. Farm Household Resilience Scale was used to measure resilience. Cluster analysis suggested three groups: highly, medium-, and low-resilient farm households. The results of comparing three groups revealed that highly resilient farm households characterize with higher risk management, more agricultural water security, more positive psychological traits, and better knowledge management. Also, they had better water quality, attended more agricultural extension activities, and used modern irrigation systems. Farm households’ resilience map using GIS software illustrated that there is a relationship between resilience and farm location from the wetland. The findings of this study could be used by planner and policy-makers to improve farm households’ resilience in arid and semi-arid environments. Improvement in knowledge management system is recommended as one of the most effective policy instruments in building resilience. 相似文献
13.
Jakob Abermann Birger Hansen Magnus Lund Stefan Wacker Mojtaba Karami John Cappelen 《Ambio》2017,46(1):3-11
We investigated air temperature and pressure gradients and their trends for the period 1996–2014 in Greenland and compared these to other periods since 1958. Both latitudinal temperature and pressure gradients were strongest during winter. An overall temperature increase up to 0.15 °C year?1 was observed for 1996–2014. The strongest warming happened during February at the West coast (up to 0.6 °C year?1), weaker but consistent and significant warming occurred during summer months (up to 0.3 °C year?1) both in West and East Greenland. Pressure trends on a monthly basis were mainly negative, but largely statistically non-significant. Compared with other time windows in the past six decades, the period 1996–2014 yielded an above-average warming trend. Northeast Greenland and the area around Zackenberg follow the general pattern but are on the lower boundary of observed significant trends in Greenland. We conclude that temperature-driven ecosystem changes as observed in Zackenberg may well be exceeded in other areas of Greenland. 相似文献
14.
Hadi Hajizadeh Namaghi Gholam Hossein Karami Saeed Saadat 《Environmental monitoring and assessment》2011,174(1-4):573-583
In order to assess the chemical properties of groundwater and soil in ophiolitic zone of Firuzabad, in east of Shahrood, Iran, 10 soil samples with regard to sensitive points (vicinity to mine, ophiolitic rocks, and villages) and 10 groundwater samples including nine samples from springs, and also one sample from a well in a village of the study area were taken. These samples were analyzed in laboratories using inductively coupled plasma method. The soil samples were also evaluated for grain size. The obtained results show that most of heavy and major elements were exceeding the permissible levels in soil and water samples in the study area. On the subject of soil quality, concentrations of elements Cr, Mn, Fe, Ca, Mg, Ca, Ni, and Zn are above permissible levels. Enrichment factor and index of geoaccumulation have been calculated for heavy and major elements of all soil samples. According to the obtained results, it may be argued that soil samples are contaminated in relation to the above-mentioned indices. Comparing the concentrations of elements with results of grain size analysis illustrates that the concentrations of Cr, Ni, Fe, Mg, and Co are positively correlated with sand fraction and the concentrations of Al, P, Mn, and Pb are directly proportional with clay fraction in soil samples. The study on water contamination suggests that concentrations of elements Cr, Ni, and Mg in groundwater samples of the study area are above the permissible levels. Some indices like metal index and heavy metal pollution index show that most of the water samples include heavy metal contamination. 相似文献
15.
Maryam Ghadiri Khanaposhtani Mohammad Kaboli Mahmoud Karami Vahid Etemad Saeedeh Baniasadi 《Environmental management》2013,51(3):750-758
In the Hyrcanian forests of northern Iran, reduced-impact silviculture systems, (single-tree and group-tree selection) were applied over a large area, which generated different local habitat structures. The aim of this study was to assess the differences between treated and untreated areas of forest and their effect on avian richness, abundance and diversity (R.A.D). Birds were surveyed during the breeding season in 2009 by 100-point counts, equally distributed in the treated and untreated area. Avian R.A.D was significantly different and higher in the untreated area. Generally, forestry practices cause noticeable changes in canopy percentage, tree composition, snags and shrub number. Treated forest habitats in the area of study had a much more developed understory, fewer snags and fewer large diameter trees. The results highlighted the importance of forest maturity and showed that preventing silvicultural disturbances may not be the best solution for conserving and enhancing biodiversity. Rather, methods such as selective cutting seem an appropriate and sustainable way of forest management. It is suggested that forests should be managed to conserve structural elements which create favorable habitat for bird species, preventing future species losses due to logging practices. 相似文献
16.
17.
18.
Micro-habitat characteristics of breeding display Sites (Leks) of Caucasian Black Grouse (Tetrao mlokosiewiczi) were studied in the mountains of Arasbaran Region, East Azerbaijan, from October 2006 to June 2008. We quantified micro-habitat characteristics around active and inactive Caucasian black grouse lek sites and random points in the 3 areas (Biosphere reserve, Kalan protected area (one of core zones of Arasbaran biosphere reserve) and unprotected areas)). Our objective was to compare micro-habitat characteristics among these sites. We also developed a logistic regression model to identify micro-habitat factors have important effect in the active lek sites. In the micro-habitat scale, we measured both biotic factors (canopy cover (%), height (cm) and frequency of vegetations) and abiotic (physical) factors (slope (%), altitude (m), aspect and etc.). Slope and altitude were different significantly between sampling sites (p = 0.05). Mean of slope in the active leks (= 57.9%) and inactive leks (= 52.0%) were higher than random sites (= 40.1%). The mean aspect differed between active leks ( $ \bar X $ = 284°, S.D = 54.1°) and random sites ( $ \bar X $ = 33°, S.D = 76.18°) (Watson’s U2-test, U 0.05, 22, 27 2 = 0.717). Also, variance analysis (ANOVA) revealed that grasses and forbs cover, frequency of deciduous shrubs and forbs, canopy cover and frequency of deciduous woody plants > 12 cm diameter at breast height were different significantly between sampling sites. The best model for discriminating between active lek and random sites included rock-pavement cover (parameter estimate [B] = 0.286, SE = 0.219), canopy cover of grasses (parameter estimate [B] = 0.880, SE = 0.453), distance to the nearest tree (parameter estimate [B] = ?0.047, SE = 0.027). 相似文献
19.
Emamgholizadeh Samad Seyedzadeh Amin Sanikhani Hadi Maroufpoor Eisa Karami Gholamhosein 《Environment, Development and Sustainability》2022,24(1):558-575
Environment, Development and Sustainability - The water advance time (Ta) is needed for designing and evaluating surface irrigation systems. This study employed artificial neural networks (ANNs)... 相似文献
20.
Statistical source identification of major and trace elements in groundwater downward the tailings dam of Miduk Copper Complex, Kerman, Iran 总被引:2,自引:0,他引:2
Kargar M Khorasani N Karami M Rafiee G Naseh R 《Environmental monitoring and assessment》2012,184(10):6173-6185
Identifying the possible sources of potential harmful metals in groundwater systems plays a crucial role in evaluating the potential risks to residents and local plant cover. An attempt was made to define the origin of Al, Cd, Cu, Fe, Mo, Ni, and Pb in groundwater using multivariate statistic approaches [principal component analysis (PCA), hierarchical cluster analysis], and tailings sequential extraction by the method of Tessier et al. The concentrations of studied elements were measured in 42 samples collected from 15 stations surrounding and downward the tailings dam of Miduk Copper Complex, central province of Kerman, Iran. According to the PCA results, confirmed by cluster dendrogram and metal content measurement of tailings sequential extracts, two components accounting for nearly 73% of the total variance, controlled the heavy metal variability and classified the possible source of groundwater contamination into two categories: (1) upper seepage which controls the variability of Cd, Cu, Fe, Ni, and Pb and (2) toe seepage of tailings dump affecting on Mo and Al concentration in downstream groundwater. 相似文献