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Modeling the contribution of abiotic exchange to CO2 flux in alkaline soils of arid areas
WenFeng WANG, Xi CHEN, GePing LUO, LongHui LI
Journal of Arid Land    2014, 6 (1): 27-36.   DOI: 10.1007/s40333-013-0187-6
Abstract1832)      PDF (1605KB)(2242)      
Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO 2 flux (F c). However, both the overall contribution of abiotic CO 2 exchange and its drivers remain unknown. Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to F c in alkaline soils of arid areas. An automated flux system was employed to measure F c in the Manas River Basin of Xinjiang Uygur autonomous region, China. Soil pH, soil temperature at 0–5 cm (T s), soil volumetric water content at 0–5 cm (θ s) and air temperature at 10 cm above the soil surface (T as) were simultaneously analyzed. Results highlight reduced sensitivity of F c to T s and good prediction of Fc by the model F c=R 10Q 10 (Tas–10)/10+r7q7(pH–7)+λT as+µθ s+e which represents F c as a sum of biotic and abiotic components. This presents an approximate method to quantify the contribution of soil abiotic CO 2 exchange to F c in alkaline soils of arid areas.
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Cited: Baidu(31)
Impact of climate change on the streamflow in the glacierized Chu River Basin, Central Asia
MA Changkun, SUN Lin, LIU Shiyin, SHAO Ming’an, LUO Yi
Journal of Arid Land    2015, 7 (4): 501-513.   DOI: 10.1007/s40333-015-0041-0
Abstract1849)      PDF (401KB)(2078)      
Catchments dominated by meltwater runoff are sensitive to climate change as changes in pre-cipitation and temperature inevitably affect the characteristics of glaciermelt/snowmelt, hydrologic circle and water resources. This study simulated the impact of climate change on the runoff generation and streamflow of Chu River Basin (CRB), a glacierized basin in Central Asia using the enhanced Soil and Water Assessment Tool (SWAT). The model was calibrated and validated using the measured monthly streamflow data from three discharge gauge stations in CRB for the period 1961–1985 and was subsequently driven by downscaled future climate projections of five Global Circulation Models (GCMs) in Coupled Model Inter-comparison Project Phase 5 (CMIP5) under three radiative forcing scenarios (RCP2.6, RCP4.5 and RCP8.5). In this study, the period 1966–1995 was used as the baseline period, while 2016–2045 and 2066–2095 as the near-future and far-future period, respectively. As projected, the climate would become warmer and drier under all scenarios in the future, and the future climate would be characterized by larger seasonal and annual variations under higher RCP. A general decreasing trend was identified in the average annual runoff in glacier (–26.6% to –1.0%), snow (–21.4% to +1.1%) and streamflow (–27.7% to –6.6%) for most of the future scenario periods. The projected maximum streamflow in each of the two future scenarios occurred one month earlier than that in the baseline period because of the reduced streamflow in summer months. Results of this study are expected to arouse the serious concern about water resource availability in the headwater region of CRB under the continuously warming climate. Changes in simulated hydrologic outputs underscored the significance of lowering the uncertainties in temperature and precipitation projection.
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Cited: Baidu(28)
Estimating total nitrogen deposition in agroecosystems in northern China during the wheat cropping season
ChunE HE, XueJun LIU, Christie PETER, Fangmeier ANDREAS, FuSuo ZHANG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00002
Abstract2473)      PDF (148KB)(1392)      
Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.
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Cited: Baidu(24)
Reconstructing the annual precipitation variation since 1899 based on tree-ring width in the western Hedong sandy land of Ningxia
YaJun WANG, ShangYu GAO, YuZhen MA, RuiJie LU, YanLi SANG, HongWei MENG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00286
Abstract2368)      PDF (366KB)(2275)      
Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.
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Cited: Baidu(14)
Identifying the influence of urbanization on soil organic matter content and pH from soil magnetic characteristics
YANG Han, XIONG Heigang, CHEN Xuegang, WANG Yaqi, ZHANG Fang
Journal of Arid Land    2015, 7 (6): 820-830.   DOI: 10.1007/s40333-015-0052-x
Abstract1568)      PDF (494KB)(1569)      
Soil magnetic characteristics are correlated with soil pH and organic matter content. Analyzing soil magnetic characteristics, organic matter content and pH can indirectly evaluate soil pollution caused by human activities. This study analyzed the soil magnetic characteristics, organic matter content and pH in surface soil samples from different land use types in Shihezi city, a newly and rapidly developing oasis city in Xinjiang of China. The aims of this study were to explore the possible relationships among the soil magnetic parameters and thereby improve the understanding of influence of urbanization on soil properties. Eighty surface soil samples at the depth of 0–10 cm were collected from 29 July to 4 August 2013. The results showed that the magnetic minerals in surface soil were dominated by ferromagnetic minerals. Spatially, the magnetic susceptibility ( χ LF), anhys-teretic remanent magnetization susceptibility ( χ ARM), saturation isothermal remanent magnetization (SIRM) and “soft” isothermal remanent magnetization (SOFT) were found to be most dominant in the new northern urban area B (N-B), followed by built-up areas (U), suburban agricultural land (F), and then the new northern urban area A (N-A). The values of χ LF, χ ARM, SIRM and SOFT were higher in the areas with high intensities of human ac-tivities and around the main roads. Meanwhile, the property “hard” isothermal remanent magnetization (HIRM) followed the order of U>N-B>F>N-A. Built-up areas had an average pH value of 7.93, which was much higher than that in the new northern urban areas as well as in suburban agricultural land, due to the increased urban pollutant emissions. The average value of soil organic matter content in the whole study area was 34.69 g/kg, and the values in the new northern urban areas were much higher than those in the suburban agricultural land and built-up areas. For suburban agricultural land, soil organic matter content was significantly negatively correlated with χ LF, and had no correlation with other magnetic parameters, since the soil was frequently ploughed. In the new northern urban areas (N-A and N-B), there were significant positive correlations of soil organic matter contents with χ ARM, SIRM, SOFT and HIRM, because natural grasslands were not frequently turned over. For the built-up areas, soil organic matter contents were significantly positively correlated with χ LF, χ ARM, SIRM and SOFT, but not significantly correlated with frequency-dependent susceptibility (χ FD, expressed as a percentage) and HIRM, because the soil was not frequently turned over or influenced by human activities. The results showed that soil magnetic characteristics are related to the soil turnover time.
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Cited: Baidu(13)
Impacts of land disturbance and restoration on runoff production and sediment yield inthe Chinese Loess Plateau
Ning AI, Tianxing WEI, Qingke ZHU, Fangfang QIANG, Huan MA, Wei QIN
Journal of Arid Land    2017, 9 (1): 76-86.   DOI: 10.1007/s40333-016-0088-6
Abstract922)   HTML1)    PDF (408KB)(1208)      

Land disturbance and land restoration are important factors influencing runoff production and sediment yield in the semi-arid loess regions of China.This study compared the runoff production and sediment yield during the early stage after land disturbance (ESLD) with those during restoring stage after land disturbance (RSLD). Grey relational analysis was used to analyse the importance of each one of the influencing factors (vegetation, rainfall, soil and topography) in affecting the runoff production and sediment yield. Our results showed that during ESLD, topography was the most critical factor controlling the runoff production, while soil was the most important factor controllingthe sediment yield. DuringRSLD, vegetation was more important in affecting runoff production, while rainfall was more important in affecting sediment yield. In additional, this study demonstrated that both the runoff production and the sediment yield can be effectively reduced by restoring vegetation on severely-disturbed lands, thus providing an important theoretical basis for better implementations of the Grain for Green Program.Our results revealed that the vegetation types of Hippophaerhamnoides+Pinustabulaeformis and H.rhamnoides are better plant selections for land restoration in this area, especially for relatively gentle slopes (i.e., less than 20 degrees).

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Cited: Baidu(10)
Vertical distribution of sand-dust aerosols and the relationships with atmospheric environment
Jie ZHANG, XingMing LI
Journal of Arid Land    2012, 4 (4): 357-368.   DOI: 10.3724/SP.J.1227.2012.00357
Abstract2619)      PDF (1648KB)(2658)      
The vertical distribution of aerosols in the troposphere is important for determining their effects on cli-mate. The vertical distribution of aerosols under different atmospheric conditions in the free troposphere was di-rectly observed using a surface micro-pulse LIDAR (MPL) and a TP/WVP-3000 microwave radiometer at the Semi-Arid Climate & Environment Observatory of Lanzhou University (SACOL, 35.95°N, 104.10°E) in the western Loess Plateau, China, in the spring of 2008. The results showed two possible transportation paths of a sandstorm from May 1 to May 4 in 2008. In one path, sand-dust aerosols were transported toward the east from the Taklimakan Desert to the Badain Jaran Desert and the Tengger Desert by a westerly wind and then toward the southeast to Jingtai and Lanzhou. A weak aerosol index (AI) indicated another possible transport path toward the east from the Taklimakan Desert to the Qaidam Basin and through the Tibetan Plateau eastward to SACOL. The aerosol profile of sandstorm processes over the SACOL area displayed three patterns: a single peak distribution under stable at-mospheric conditions, indicating urban aerosol distribution; an exponential decrease under unstable atmospheric conditions in the presence of a sandstorm; and a slight change in the mixed layer during the first and last stages of the sandstorm, indicative of thorough mixing during lifting and deposition stages. Analyses of the aerosol layer height (ALH) showed that there are two types of ALH diurnal variation. The ALH during the first sandstorm stage was complex and disordered, and affected by atmospheric circulation. While the ALH had obvious diurnal variation in the other stage, the ALH and aerosol extinction coefficient (AEC) had a single peak, and was higher in the af-ternoon and lower in the morning. In the second case the ALH was in agreement with the atmospheric boundary layer height (BLH) variation. As a result of the development of the atmospheric boundary layer (ABL) during day and maintenance at night, ALH during sandstorm-free days showed obvious diurnal variations. Multiple vertical distribu-tion patterns of sand-dust aerosols will result in different climate effects; therefore, the vertical distribution patterns can be used to parameterize climate and aerosol models.
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Cited: Baidu(7)
Soil organic matter amendments in date palm groves of the Middle Eastern and North African region: a mini-review
Rawan MLIH, Roland BOL, Wulf AMELUNG, Nadhem BRAHIM
Journal of Arid Land    2016, 8 (1): 77-92.   DOI: 10.1007/s40333-015-0054-8
Abstract1474)      PDF (447KB)(1495)      
Countries in the Middle Eastern and North African (MENA) region are among the most water-scarce regions in the world, and their dryland soils are usually poor in organic carbon content (<0.5%). In this study, we summarize examples of how people in the few oases of the MENA region overcome environmental challenges by sustainably managing economically important date production. On the basis of the limited studies found in the existing literature, this mini-review focuses on the role of traditional soil organic matter amendments beneath the soil surface as a key tool in land restoration. We conclude that soil organic matter amendments can be very successful in restoring soil water and preventing the soil from salinization.
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Cited: Baidu(6)
Sand mining disturbances and their effects on the diversity of arbuscular mycorrhizal fungi in a riparian forest of Iran
Journal of Arid Land    2017, 9 (6): 837-849.   DOI: 10.1007/s40333-017-0028-0
Abstract450)   HTML5)    PDF (398KB)(736)      

The major objective of this study was to evaluate the effects of sand mining disturbances on the diversity of arbuscular mycorrhizal fungi (AMF). In addition, the proportional changes in the diversity of AMF to the distances from riverbanks were assessed. For this purpose, the riparian forest of the Maroon River, Iran was divided into three locations with a 200-meter wide zone in between. Thus, the locations studied were named Distance I (riverbank), Distance II (intermediate), and Distance III (farthest from riverbank). In each of these distances, 10 Tamarix arceuthoides and Populus euphratica of each species were randomly selected. At the same time, soil and root samples were collected from the rhizosphere of the tree species studied. Results indicated that totally 13 AMF species were observed in T. arceuthoides and 19 AMF species were recorded in P. euphratica rhizosphere belonging to 6 genera and 6 families. In these AMF species, Glomus segmentatum, G. geosporum, G. rubiforme, G. nanolumen, G. spinuliferum, Claroideoglomus drummondii, Gigaspora gigantea and Acaulospora paulinae appeared only in P. euphratica rhizosphere, while G. multiforum and Claroideoglomus claroideum were observed only in T. arceuthoides rhizosphere. Moreover, Distance II had the least AMF species both in T. arceuthoides and in P. euphratica rhizospheres, and also the least spore density and root colonization rate. Our results are important in that they provide a list of resistant AMF species that could be used in the conservation of biodiversity.

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Cited: Baidu(6)
Interactions between wind and water erosion change sediment yield and particle distribution under simulated conditions
TUO Dengfeng, XU Mingxiang, ZHAO Yunge, GAO Liqian
Journal of Arid Land    2015, 7 (5): 590-598.   DOI: 10.1007/s40333-015-0128-7
Abstract1498)      PDF (201KB)(2138)      
Wind and water erosion are among the most important causes of soil loss, and understanding their interactions is important for estimating soil quality and environmental impacts in regions where both types of erosion occur. We used a wind tunnel and simulated rainfall to study sediment yield, particle-size distribution and the fractal dimension of the sediment particles under wind and water erosion. The experiment was conducted with wind erosion firstly and water erosion thereafter, under three wind speeds (0, 11 and 14 m/s) and three rainfall intensities (60, 80 and 100 mm/h). The results showed that the sediment yield was positively correlated with wind speed and rainfall intensity ( P<0.01). Wind erosion exacerbated water erosion and increased sediment yield by 7.25%–38.97% relative to the absence of wind erosion. Wind erosion changed the sediment particle distribution by influencing the micro-topography of the sloping land surface. The clay, silt and sand contents of eroded sediment were also positively correlated with wind speed and rainfall intensity ( P<0.01). Wind erosion increased clay and silt contents by 0.35%–19.60% and 5.80%–21.10%, respectively, and decreased sand content by 2.40%–8.33%, relative to the absence of wind erosion. The effect of wind erosion on sediment particles became weaker with increasing rainfall intensities, which was consistent with the variation in sediment yield. However, particle-size distribution was not closely correlated with sediment yield ( P>0.05). The fractal dimension of the sediment particles was significantly different under different intensities of water erosion ( P<0.05), but no significant difference was found under wind and water erosion. The findings reported in this study implicated that both water and wind erosion should be controlled to reduce their intensifying effects, and the controlling of wind erosion could significantly reduce water erosion in this wind-water erosion crisscross region.
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Cited: Baidu(6)
Monophyly and infrageneric variation of Corispermum L. (Chenopodiaceae), evidence from sequence data psbB-psbH, rbcL and ITS
JuanJuan XUE, MingLi ZHANG
Journal of Arid Land    2011, 3 (4): 240-253.   DOI: 10.3724/SP.J.1227.2011.00240
Abstract3351)      PDF (1766KB)(5879)      
Corispermum is one of the most problematic taxonomic genera in Chenopodiaceae. To understand the phylogeny and infrageneric variation of Corispermum, we sequenced the nuclear ribosomal ITS region and two chloroplast DNA regions (rbcL and psbB-psbH) of 22 species and three varieties of Corispermum and the related genus Agriophyllum. Several representative species of Salsola, Suaeda, Chenopodium, Kalidium and Camphorosma served as outgroups. Our phylogenetic trees confirm that the tribe Corispermeae is monophyletic, Corispermum and Agriophyllum have a close relationship. Corispermum is demonstrated to be monophyletic, and contains at least four clades which, consequently, are served as the foundation of the infrageneric sectional variation of Corispermum, in terms of a combination of molecular data and morphological characters. The evolution of morphological characters for fruit wing and apex, two important characters in generic classification, is consistent with the sectional division of Corispermum, especially to the East Asian and Chinese taxa.
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Cited: Baidu(5)
Effects of freezing intensity on soil solution nitrogen and microbial biomass nitrogen in an alpine grassland ecosystem on the Tibetan Plateau, China
YANG Zhaoping, GAO Jixi, YANG Meng, SUN Zhizhong
Journal of Arid Land    2016, 8 (5): 749-759.   DOI: 10.1007/s40333-016-0012-0
Abstract1230)      PDF (235KB)(1253)      
The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem; however, the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention. In this study, the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments. The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River. In the experiment, the soil samples were cultivated at –10°C, –7°C, –5°C, –3°C and –1°C, respectively for three days and then thawed at 2°C for one day. The results showed that after the freeze-thaw process, the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased. When the freezing temperature was below –7°C, there was no significant difference between the content of nitrogen components, which implied a change of each nitrogen component might have a response threshold toward the freezing temperature. As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem, more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.
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Cited: Baidu(5)
Runoff of arid and semi-arid regions simulated and projected by CLM-DTVGM and its multi-scale fluctuations as revealed by EEMD analysis
NING Like, XIA Jun, ZHAN Chesheng, ZHANG Yongyong
Journal of Arid Land    2016, 8 (4): 506-520.   DOI: 10.1007/s40333-016-0126-4
Abstract1241)      PDF (802KB)(1577)      
Runoff is a major component of the water cycle, and its multi-scale fluctuations are important to water resources management across arid and semi-arid regions. This paper coupled the Distributed Time Variant Gain Model (DTVGM) into the Community Land Model (CLM 3.5), replacing the TOPMODEL-based method to simulate runoff in the arid and semi-arid regions of China. The coupled model was calibrated at five gauging stations for the period 1980–2005 and validated for the period 2006–2010. Then, future runoff (2010–2100) was simulated for different Representative Concentration Pathways (RCP) emission scenarios. After that, the spatial distributions of the future runoff for these scenarios were discussed, and the multi-scale fluctuation characteristics of the future annual runoff for the RCP scenarios were explored using the Ensemble Empirical Mode Decomposition (EEMD) analysis method. Finally, the decadal variabilities of the future annual runoff for the entire study area and the five catchments in it were investigated. The results showed that the future annual runoff had slowly decreasing trends for scenarios RCP 2.6 and RCP 8.5 during the period 2010–2100, whereas it had a non-monotonic trend for the RCP 4.5 scenario, with a slow increase after the 2050s. Additionally, the future annual runoff clearly varied over a decadal time scale, indicating that it had clear divisions between dry and wet periods. The longest dry period was approximately 15 years (2040–2055) for the RCP 2.6 scenario and 25 years (2045–2070) for the RCP 4.5 scenario. However, the RCP 8.5 scenario was predicted to have a long dry period starting from 2045. Under these scenarios, the water resources situation of the study area will be extremely severe. Therefore, adaptive water management measures addressing climate change should be adopted to proactively confront the risks of water resources.
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Cited: Baidu(5)
A cladistic scenario of Southern Pacific biogeographical history based on Nothofagus dispersal and vicariance analysis
Journal of Arid Land    2011, 3 (2): 104-113.   DOI: 10.3724/SP.J.1227.2011.00104
Abstract2509)      PDF (253KB)(2180)      
Nothofagus is regarded as a key group for interpreting Southern Pacific biogeographical history. Based on a molecular phylogenetic tree, a quantitative dispersal-vicariance analysis (DIVA) of the genus is presented. The results indicate that the ancestral area of Nothofagus is a broad realm almost including the total extant distribution pattern of the genus rather than a so-named center of origin. Integrated with the paleogeography, the time of origin and subsequent diversification is inferred to have started in the Late Cretaceous. Most vicariance and dispersal events should be contained in that period. Vicariance events versus dispersal events play a dominant rule in speciation. The dispersal events are hypothesized to happen from the Late Cretaceous to Eocene in terms of the geological history. Rich fossils are collected in the Eocene. South America, comprising three subgenera of Nothofagus, should be considered as a diversification region, in which the distribution of the species of subgenus Fuscospora and subgenus Nothofagus are explained by dispersal events during the Late Cretaceous-Late Eocene.
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Cited: Baidu(4)
Dynamic changes of a typical linear dune in the Tengger Desert
KeCun ZHANG, KenJi KAI, JianJun QU, YuQuan LING, QingHe NIU
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00272
Abstract2810)      PDF (622KB)(2361)      
The dynamical processes of a typical linear dune including morphological features, dune ridge swing range and crest height were investigated at different monitoring periods in the hinterland of Tengger Desert. The results indicated that the development of linear dune depends on not only the northwesterly prevailing wind, but also the winds from northeast and southwest. The dune ridge swayed along its fundamental strike and took on an eastward movement gradually. The original dune strike was NW70° on August 3, 1994, and then changed to NE15° on April 21, 2001. The dune crest increased by 1.8 m longitudinally, which manifested strong wind-blown sand activities in this region. Wind erosion frequently occured at the bottom of sand dune, while sand accumulation appeared on its mid-upper section. The mean wind erosion depth was 25 cm on the bottom of linear dune and the height difference of the control points on the dune’s ridge was 1.13 m. Although the linear dune swayed laterally, the horizontal displacement of its ridge moved eastward 5.8 m averagely. The swing range of the dune crest line is very distinct, with a maximum value of 13.2 m. The highest site on the K-profile swayed on both sides of the dune ridge and the heights were 19.88 m at the control point K5, 19.61 m at K6 and 19.05 m at K7, respectively. The results indicated that the lateral swing of the linear dune was distinct under the northwesterly wind and it moved toward east gradually.
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Cited: Baidu(3)
Endemics and endangered species in the biodiversity hotspot of the Shada Mountains, Saudi Arabia
THOMAS Jacob, A EL-SHEIKH Mohamed, A ALATAR Abdulrehman
Journal of Arid Land    2017, 9 (1): 109-121.   DOI: 10.1007/s40333-016-0025-8
Abstract826)   HTML2)    PDF (535KB)(1712)      

Shada Mountains in Saudi Arabia, separated by Maleel Wadi into twin mountains (i.e., Shada Alalah and Shada Asfal), are rich in biodiversity. We investigated the diversity of endemics and endangered species of the mountains based on the data collected from 38 stands falling in 8 elevational zones ranging from 500 to 2215 m a.s.l. Results indicated that 495 plant species falling in 314 genera and 76 families occurred in the Shada Mountains, including 19 endemic species and 43 endangered species, and accounting for 22% of the total flora in Saudi Arabia. Canonical correlation analysis indicated that physiographic features, particularly altitude play an important role in the frequency and abundance of species. Endemics were not evenly distributed in the Shada Mountains and mostly restricted in the elevation zone of 1000-1500 or >1500 m a.s.l. When the altitude reached up to 2000 m a.s.l., the endemics decreased substantially due to the significantly low temperature. The endangered species existed three different distribution patterns: (i) most endangered species distributed in the altitudes of 1000-1800 m a.s.l.; (ii) endangered trees, lianas, and shrubs occupied the altitudes 1000-1300 m a.s.l.; and (iii) endangered subshrubs and herbs inhabited the altitudes 1500-2100 m a.s.l. The results demonstrated that the biodiversity of endangered species in the Shada Mountains is high and undisturbed by invasive species, and protective measures should be taken against human disturbances to the small-scale hotspot.

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Cited: Baidu(2)
Evaluating land subsidence by field survey and D-InSAR technique in Damaneh City, Iran
Journal of Arid Land    2017, 9 (5): 778-789.   DOI: 10.1007/s40333-017-0104-5
Abstract596)   HTML1)    PDF (1708KB)(1320)      

Based on the data from piezometers, well logs, geophysical surveys and the interferometric synthetic aperture radar (InSAR) technique, this study investigates the main causes of land subsidence in Damaneh City, Iran. The size, openings and direction of fissures were measured by micrometer and compass. The locations of fissures and wall cracks were determined by GPS. The geoelectrical data were used to determine the composition, thickness, depth and shape of lower parts of the aquifer. Groundwater fluctuations were evaluated by available piezometers. The InSAR technique was used to measure land deformation from space and to map the dense changes of surface displacements. The results indicate that the main cause of ground subsidence is the decline of groundwater heads and changes in composition and thickness of compressible lacustrine sediments. The subsidence map obtained from the radar data of ASAR sensor of ENVISAT satellite shows that the subsidence zone is mainly in northern city that is underlain by very thick fine sediments. The subsidence rates from March to December 2005 and from July 2011 to January 2012 are 6.7 and 7.0 cm/a, respectively. The results also show good correlations among the formation of earth features, decline in groundwater head and thickness of fine-grained sediments. We recommend that the groundwater withdrawal for agricultural and industrial sectors should be restricted and urban expansion in the northern part of the city should be constrained.

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Cited: Baidu(2)