Future changes of the terrestrial ecosystem based on a dynamic vegetation model driven with RCP8.5 climate projections from 19 GCMs     

Miao Yu  Guiling Wang  Dana Parr  Kazi Farzan Ahmed 《Climatic change》2014,127(2):257-271

Future changes of terrestrial ecosystems due to changes in atmospheric CO₂ concentration and climate are subject to a large degree of uncertainty, especially for vegetation in the Tropics. Here, we evaluate the natural vegetation response to projected future changes using an improved version of a dynamic vegetation model (CLM-CN-DV) driven with climate change projections from 19 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The simulated equilibrium vegetation distribution under historical climate (1981–2000) has been compared with that under the projected future climate (2081–2100) scenario for Representative Concentration Pathway 8.5 (RCP8.5) to qualitatively assess how natural potential vegetation might change in the future. With one outlier excluded, the ensemble average of vegetation changes corresponding to climates of 18 GCMs shows a poleward shift of forests in northern Eurasia and North America, which is consistent with findings from previous studies. It also shows a general “upgrade” of vegetation type in the Tropics and most of the temperate zones, in the form of deciduous trees and shrubs taking over C3 grass in Europe and broadleaf deciduous trees taking over C4 grasses in Central Africa and the Amazon. LAI and NPP are projected to increase in the high latitudes, southeastern Asia, southeastern North America, and Central Africa. This results from CO₂ fertilization, enhanced water use efficiency, and in the extra-tropics warming. However, both LAI and NPP are projected to decrease in the Amazon due to drought. The competing impacts of climate change and CO₂ fertilization lead to large uncertainties in the projection of future vegetation changes in the Tropics.  相似文献   

Improving the spatial resolution of ground motion variability using earthquake and seismic noise data: the example of Bishkek (Kyrgyzstan)     

S. Ullah  D. Bindi  M. Pittore  M. Pilz  S. Orunbaev  B. Moldobekov  S. Parolai 《Bulletin of Earthquake Engineering》2013,11(2):385-399

Site response analysis plays an important role in seismic hazard and risk assessment, and in defining the optimal engineering design for civil structures. However, due to increasing urbanization, target areas are often too vast to be covered by standard approaches, resulting in large uncertainties in the spatial variability of the expected ground motion. Here, we propose a method to improve the spatial resolution of ground motion variability in terms of Standard Spectral Ratios (SSRs), using earthquakes recorded at a few selected sites for a relatively short amount of time, and seismic noise data collected over a denser grid, taking advantage of clustering and correlation analysis. The method is applied to Bishkek, Kyrgyzstan. Using the K-means clustering algorithm, three clusters of site response types have been identified, based on their similarity of SSRs. The cluster’s site responses were adopted for sites where only single station noise measurements were carried out, based on the results of correlation analysis. The spatial variability of the site response correlates well with the main geological features in the area. In particular, variability is noted from south to north, consistent with both the changes in the thickness of the sedimentary cover over the basin and in the Quaternary material outcropping at the surface. This method has therefore the potential to improve the estimation of site effects at the local scale in the future.  相似文献   

Development of a polder module in the SWAT model: SWATpld for simulating polder areas in south‐eastern China          下载免费PDF全文

Zhengqing Lai  Shuo Li  Yang Deng  Guonian Lv  Sana Ullah 《水文研究》2018,32(8):1050-1062

Polders are one of the most common artificial hydrological entities in the plain river network regions of China. Due to enclosed dikes, manual drainage, and irrigation intake operations, polders have had a significant impact on the hydrological processes of these areas. Distributed hydrological models are effective tools to understand and reproduce the hydrological processes of a watershed. To date, however, few models are able to simulate the drainage and irrigation intake interactions of polders at a watershed scale. This study develops a modified version of the Soil and Water Assessment Tool (SWAT) model, which is designed to better represent polders (SWATpld). The SWATpld model simulates drainage and irrigation intake processes by calculating the excess‐water storage in the inner rivers and irrigation schedule for paddy rice in the polder. Both SWAT and SWATpld models were tested for the Liyang watershed. SWATpld outperformed SWAT in simulating the daily discharge and intake of the experimental polder and predicting the monthly peak flow at the outlet of the Liyang watershed, which suggests that the modified model simulates the hydrological responses of the study watershed with polder operations more realistically than the original SWAT model does. Further evaluation at various locations and in various climate conditions would increase the confidence of this model.  相似文献   

Grain Cadmium and Zinc Concentrations in Maize Influenced by Genotypic Variations and Zinc Fertilization   总被引：2，自引：0，他引：2       下载免费PDF全文

Shah Fahad  Saddam Hussain  Shah Saud  Shah Hassan  Darakh Shan  Yutiao Chen  Nanyan Deng  Fahad Khan  Chao Wu  Wei Wu  Farroq Shah  Bashir Ullah  Muhammad Yousaf  Saqib Ali  Jianliang Huang 《洁净——土壤、空气、水》2015,43(10):1433-1440

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Evaluating the impact of classification algorithms and spatial resolution on the accuracy of land cover mapping in a mountain environment in Pakistan     

Sami Ullah  Muhammad Shafique  Muhammad Farooq  Muhammad Zeeshan  Matthias Dees 《Arabian Journal of Geosciences》2017,10(3):67

Satellite images of various spatial resolutions and different image classification techniques have been utilized for land cover (LC) mapping at local and regional scale studies. Mapping capabilities and achievable accuracies of LC classification in a mountain environment are, however, influenced by the spatial resolution of the utilized images and applied classification techniques. Hence, developing and characterizing regionally optimized methods are essential for the planning and monitoring of natural resources. In this study, the potential of four non-parametric image classification techniques, i.e., k-nearest neighbor (k-NN), support vector machine (SVM), random forest (RF), and neural network (NN) on the accuracy of LC classification was evaluated in the Hindu Kush mountains ranges of northern Pakistan. Moreover, we have assessed the impact of the spatial resolution of the utilized satellite imagery, i.e., SPOT-5 with 2.5 m and Landsat-8 with 30 m on the accuracy of the derived LC classification. For the classification of LC based on SPOT-5, we have achieved the highest overall classification accuracy (OCA) = 89% with kappa coefficient (KC = 0.86) using SVM followed by k-NN, RF, and NN. However, for LC classification derived from Landsat-8 imagery, we achieved the highest OCA = 71% with KC = 0.59 using RF and SVM followed by k-NN and NN. The higher accuracy derived from SPOT-5 versus Landsat-8 indicated that the results of LC classification based on SPOT-5 are more accurate and reliable than Landsat-8. The findings of the present study will be useful for the classification and mapping task of LC in a mountain environment using SPOT-5 and Landsat-8 at local and regional scale studies.  相似文献   

Fractal geometry of faults in relation to the 12 October 1992 Cairo earthquake     

Nimr Arab  Asadullah Kazi  Herman H. Rieke 《Natural Hazards》1994,10(3):221-233

The aim of this study is to demonstrate how the 12 October 1992 Cairo earthquake relates to the spatial geometry of the northern Egyptian fault systems. A box-counting algorithm was used, in a focused down approach (from regional to local scales) to analyze the fractal dimensions of the existing faults. The results indicate that these faults display fractal geometries that are self-similar over two to three orders of magnitude. It is shown that the northwest-southeast (Northern Red Sea) trending fault system has the lowest fractal dimension value. Coincidentally, this fault trend is the one that the fault plane solution shows to be active.  相似文献   

Hydrogeology of Wadi Al-Yammaniyah, Saudi Arabia     

Bashir A. Memon  Asadullah Kazi  Abdulghafar S. Bazuhair 《Ground water》1984,22(4):406-411

Quaternary alluvium, ranging in thickness from a few to 100 meters underlain by Precambrian rocks of metamor-phic and igneous origin, constitutes an important source of ground water in Wadi Al-Yammaniyah, Saudi Arabia. The purpose of this report is to assess the hydraulic properties, quality of water, and estimated change in storage in waterbearing rocks in the area. The results of eight pumping tests carried out in hand-dug, large-diameter wells, indicate that the hydraulic conductivity of the alluvial aquifer ranges from 5.6 × 10⁻⁵ to 1.85 × 10⁻³ cm/second (3.36 × 10⁻⁵ to 1.11 × 10⁻³ m/minute) and that its storativity varies from 8.23 × 10⁻² to 1.17 × 10⁻¹. The aquifer is replenished by sporadic but intensive rainfall of short duration. The present withdrawal is only about 10 percent of the annual recharge which is estimated at 52 × 10⁶ m³. It is shown that there is a substantial potential for the future development of potable ground water which would be required for the development of the area.  相似文献   

Comparative study on three-dimensional statistical damage constitutive modified model of rock based on power function and Weibull distribution     

Song Chen  Chunsheng Qiao  Qing Ye  Muhib Ullah Khan 《Environmental Earth Sciences》2018,77(3):108

According to the characteristics of the microscopic unit strength of rock with random distribution, the power function distribution, and the Weibull distribution which is widely used in the past as the distribution function of the strength of the rock. Based on the theory of rock damage and statistical strength theory, two damage constitutive models established under three different confining pressures are modified. Then, the damage constitutive modified model of two kinds of distribution is verified and compared with the existing three axis test data. The results show that: (1) In the stage of elastic deformation of rock, the two theoretical damage constitutive model curves are in high agreement with the three axis test curve; (2) The rock at the plastic stage (hardening and softening), damage constitutive model established by Weibull probability distribution and experimental curve fits better than the damage constitutive model established by power function distribution. Especially in high confining pressure, damage constitutive model based on Weibull distribution can well describe the rock deformation from brittle to ductile transition process and power function is not; (3) In the residual strength in rock, damage variable D of damage constitutive model based on power function distribution appeared more than 1, which is deviation from the actual one and damage constitutive model based on Weibull distribution is not deviating. To summarize, using Weibull distribution statistical probability model to describe the microscopic unit strength of rock is more reasonable.  相似文献   

The evolution of an electrical fittings industrial cluster in Pakistan     

Ullah  Sana  Majeed  Muhammad Tariq  Arif  Babur Wasim 《GeoJournal》2021,86(6):2657-2670

GeoJournal - This study provides an evolution process of electrical fittings industrial cluster in Pakistan by using two rounds of survey dataset (2008 and 2017) taken from the electrical fittings...  相似文献   

Chromium uptake by giant reed under rhizobacterial inhibition     

S. Shaheen  Q. Mahmood  A. Pervez  N. Mirza  Z. A. Bhatti  T. Hayat  S. S. Meryem  F. Ullah 《International Journal of Environmental Science and Technology》2016,13(6):1581-1590

The role of rhizospheric microbes of giant reed (Arundo donax L.) in Cr uptake from hydroponic culture was investigated. The control group was exposed to Cr in range of 25–100 mg L^?1 containing a control itself (with no metal addition). The experimental group received same Cr treatments, but in addition was exposed to antibiotic treatment in order to inhibit rhizospheric bacteria. The range of Cr accumulated in the roots was 3–7.65 mg L^?1; in stem it ranged 2.15–42.4 mg kg^?1; while in leaves, the range of Cr content was 13.7–15 mg kg^?1. Overall, Cr uptake in A. donax (without rhizobacterial inhibition) was root < leaf < stem. However, the amount of Cr uptake in plants with rhizobacterial inhibition was significantly less (~4.6-folds in 100 mg L^?1 Cr treatment) than those without such inhibition clearly highlighting that rhizobacterial inhibition decreased the Cr uptake. The experimental results clearly demonstrated that the inhibition of the rhizobacterial populations had great influence on the Cr uptake. However, Cr uptake could not be completely inhibited as some metal uptake was observed after the rhizobacterial inhibition although it was significantly less than the Cr uptake of plants without such inhibition.  相似文献