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07 November 2018, Volume 10 Issue 6 Previous Issue    Next Issue
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Research article
Stable isotope analysis of water sources for Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China
Jinhu ZHANG, Nai'ang WANG, Zhenmin NIU, Jie SUN, Chunyu DONG, LyuLyu ZHANG
Journal of Arid Land. 2018, 10 (6): 821-832.   DOI: 10.1007/s40333-018-0069-z
Abstract ( 458 )   HTML ( 15 )     PDF (505KB) ( 816 )  

The complex interactions in desert ecosystems between functional types and environmental conditions could be reflected by plant water use patterns. However, the mechanisms underlying the water use patterns as well as the water sources of Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China, remain unclear. This study investigated the water sources and water use patterns of T. laxa using the stable oxygen isotope method. The δ18O values of xylem water, soil water in different layers (0-200 cm), rainwater, snow water, lake water, atmospheric water vapor, condensate water, and groundwater were measured. The sources of water used by T. laxa were determined using the IsoSource model. The results indicate that T. laxa mainly relies on soil water. At the beginning of the growing season (in May), the species is primarily dependent on water from the middle soil layer (60-120 cm) and deep soil layer (120-200 cm). However, it mainly absorbs water from the shallow soil layer (0-60 cm) as the rainy season commences. In September, water use of T. laxa reverts to the deep soil layer (120-200 cm). The water use patterns of T. laxa are closely linked with heavy precipitation events and soil water content. These findings reveal the drought resistance mechanisms of T. laxa and are of significance for screening species for ecological restoration.

Sap flow characteristics and physiological adjustments of two dominant tree species in pure and mixed plantations in the semi-arid Loess Plateau of China
Yakun TANG, Xu WU, Yunming CHEN
Journal of Arid Land. 2018, 10 (6): 833-849.   DOI: 10.1007/s40333-018-0027-9
Abstract ( 383 )   HTML ( 16 )     PDF (546KB) ( 697 )  

It is essential to understand the water consumption characteristics and physiological adjustments of tree species under drought conditions, as well as the effects of pure and mixed plantations on these characteristics in semi-arid regions. In this study, the normalized sap flow (SFn), leaf water potential, stomatal conductance (gs), and photosynthetic rate (Pr) were monitored for two dominant species, i.e., Pinus tabuliformis and Hippophae rhamnoides, in both pure and mixed plantations in a semi-arid region of Chinese Loess Plateau. A threshold-delay model showed that the lower rainfall thresholds (RL) for P. tabuliformis and H. rhamnoides in pure plantations were 9.6 and 11.0 mm, respectively, and the time lags (τ) after rainfall were 1.15 and 1.76 d for corresponding species, respectively. The results indicated that P. tabuliformis was more sensitive to rainfall pulse than H. rhamnoides. In addition, strong stomatal control allowed P. tabuliformis to experience low gs and Pr in response to drought, while maintaining a high midday leaf water potential (Ψm). However, H. rhamnoides maintained high gs and Pr at a low Ψm expense. Therefore, P. tabuliformis and H. rhamnoides can be considered as isohydric and anisohydric species, respectively. In mixed plantation, the values of RL for P. tabuliformis and H. rhamnoides were 6.5 and 8.9 mm, respectively; and the values of τ were 0.86 and 1.61 d for corresponding species, respectively, which implied that mixed afforestation enhanced the rainfall pulse sensitivity for both two species, especially for P. tabuliformis. In addition, mixed afforestation significantly reduced SFn, gs, and Pr for P. tabuliformis (P<0.05), while maintaining a high leaf water potential status. However, no significant effect of mixed afforestation of H. rhamnoides was observed at the expense of leaf water potential status in response to drought. Although inconsistent physiological responses were adopted by these species, the altered water consumption characteristics, especially for P. tabuliformis indicated that the mixed afforestation requires further investigation.

Seasonal differences in climatic controls of vegetation growth in the Beijing-Tianjin Sand Source Region of China
Lishan SHAN, Xiang YU, Lingxiao SUN, Bin HE, Haiyan WANG, Tingting XIE
Journal of Arid Land. 2018, 10 (6): 850-863.   DOI: 10.1007/s40333-018-0075-1
Abstract ( 444 )   HTML ( 11 )     PDF (913KB) ( 758 )  

Launched in 2002, the Beiing-Tianjin Sand Source Control Project (BTSSCP) is an ecological restoration project intended to prevent desertification in China. Evidence from multiple sources has confirmed increases in vegetation growth in the BTSSCP region since the initiation of this project. Precipitation and essential climate variable-soil moisture (ECV-SM) conditions are typically considered to be the main drivers of vegetation growth in this region. Although many studies have investigated the inter-annual variations of vegetation growth, few concerns have been focused on the annual and seasonal variations of vegetation growth and their climatic drivers, which are crucial for understanding the relationships among the climate, vegetation, and human activities at the regional scale. Based on the normalized difference vegetation index (NDVI) derived from MODIS and the corresponding climatic data, we explored the responses of vegetation growth to climatic factors at annual and seasonal scales in the BTSSCP region during the period 2000-2014. Over the study region as a whole, NDVI generally increased from 2000 to 2014, at a rate of 0.002/a. Vegetation growth is stimulated mainly by the elevated temperature in spring, whereas precipitation is the leading driver of summer greening. In autumn, positive effects of both temperature and precipitation on vegetation growth were observed. The warming in spring promotes vegetation growth but reduces ECV-SM. Summer greening has a strong cooling effect on land surface temperature. These results indicate that the ecological and environmental consequences of ecological restoration projects should be comprehensively evaluated.

Application and verification of simultaneous determination of cellulose δ13C and δ18O in Picea shrenkiana tree rings from northwestern China using the high-temperature pyrolysis method
Guobao XU, Xiaohong LIU, Weizhen SUN, Tuo CHEN, Xuanwen ZHANG, Xiaomin ZENG, Guoju WU, Wenzhi WANG, Dahe QIN
Journal of Arid Land. 2018, 10 (6): 864-876.   DOI: 10.1007/s40333-018-0070-6
Abstract ( 295 )   HTML ( 6 )     PDF (539KB) ( 719 )  

Stable isotopes in tree-ring cellulose provide important data in ecological, archaeological, and paleoenvironmental researches, thereby, the demand for stable isotope analyses is increasing rapidly. Simultaneous measurement of cellulose δ13C and δ18O values from tree rings would reduce the cost of isotopic commodities and improve the analytical efficiency compared with conventional separate measurement. In this study, we compared the δ13C and δ18O values of tree-ring α-cellulose from Tianshan spruce (Picea schrenkiana) in an arid site in the drainage basin of the Urumqi River in Xinjiang of northwestern China based on separate and simultaneous measurements, using the combustion method (at 1050°C) and the high-temperature pyrolysis method (at 1350°C and 1400°C). We verified the results of simultaneous measurement using the outputs from separate measurement and found that both methods (separate and simultaneous) produced similar δ13C values. The two-point calibrated method improved the results (range and variation) of δ13C and δ18O values. The mean values, standard deviations, and trends of the tree-ring δ13C obtained by the combustion method were similar to those by the pyrolysis method followed by two-point calibration. The simultaneously measured δ18O from the pyrolysis method at 1400°C had a nearly constant offset with that the pyrolysis method at 1350°C due to isotopic-dependence on the reaction temperature. However, they showed similar variations in the time series. The climate responses inferred from simultaneously and separately measured δ13C and δ18O did not differ between the two methods. The tree-ring δ13C and δ18O values were negatively correlated with standardized precipitation evapotranspiration index from May to August. In addition, the δ18O was significantly correlated with temperature (positive), precipitation (negative), and relative humidity (negative) from May to August. The tree-ring δ13C and δ18O values determined simultaneously through the high-temperature pyrolysis method could produce acceptable and reliable stable isotope series. The simultaneous isotopic measurement can greatly reduce the cost and time requirement compared with the separate isotopic measurement. These results are consistent with the previous studies at humid sites, suggesting that the simultaneous determination of δ13C and δ18O in tree-ring α-cellulose can be used in wide regions.

Dynamics of moisture regime and its reconstruction from a tree-ring width chronology of Pinus sylvestris in the downstream basin of the Selenga River, Russia
BELOKOPYTOVA Liliana, ZHIRNOVA Dina, KOSTYAKOVA Tatiana, BABUSHKINA Elena
Journal of Arid Land. 2018, 10 (6): 877-891.   DOI: 10.1007/s40333-018-0025-y
Abstract ( 305 )   HTML ( 6 )     PDF (438KB) ( 868 )  

Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August-July precipitation and annual water discharge of the Selenga River during the period 1767-2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains.

Impact of large-scale vegetation restoration project on summer land surface temperature on the Loess Plateau, China
Guohua HE, Yong ZHAO, Jianhua WANG, Qingming WANG, Yongnan ZHU
Journal of Arid Land. 2018, 10 (6): 892-904.   DOI: 10.1007/s40333-018-0105-z
Abstract ( 269 )   HTML ( 7 )     PDF (1551KB) ( 647 )  

A large-scale afforestation project has been carried out since 1999 in the Loess Plateau of China. However, vegetation-induced changes in land surface temperature (LST) through the changing land surface energy balance have not been well documented. Using satellite measurements, this study quantified the contribution of vegetation restoration to the changes in summer LST and analyzed the effects of different vegetation restoration patterns on LST during both daytime and nighttime. The results show that the average daytime LST decreased by 4.3°C in the vegetation restoration area while the average nighttime LST increased by 1.4°C. The contributions of the vegetation restoration project to the changes in daytime LST and nighttime LST are 58% and 60%, respectively, which are far greater than the impact of climate change. The vegetation restoration pattern of cropland (CR) converting into artificial forest (AF) has a cooling effect during daytime and a warming effect at nighttime, while the conversion of CR to grassland has an opposite effect compared with the conversion of CR to AF. Our results indicate that increasing evapotranspiration caused by the vegetation restoration on the Loess Plateau is the controlling factor of daytime LST change, while the nighttime LST change is affected by soil humidity and air humidity.

Simulating hydrological responses to climate change using dynamic and statistical downscaling methods: a case study in the Kaidu River Basin, Xinjiang, China
Wulong BA, Pengfei DU, Tie LIU, Anming BAO, Min LUO, HASSAN Mujtaba, Chengxin QIN
Journal of Arid Land. 2018, 10 (6): 905-920.   DOI: 10.1007/s40333-018-0068-0
Abstract ( 327 )   HTML ( 5 )     PDF (500KB) ( 649 )  

Climate change may affect water resources by altering various processes in natural ecosystems. Dynamic and statistical downscaling methods are commonly used to assess the impacts of climate change on water resources. Objectively, both methods have their own advantages and disadvantages. In the present study, we assessed the impacts of climate change on water resources during the future periods (2020-2029 and 2040-2049) in the upper reaches of the Kaidu River Basin, Xinjiang, China, and discussed the uncertainties in the research processes by integrating dynamic and statistical downscaling methods (regional climate models (RCMs) and general circulation modes (GCMs)) and utilizing these outputs. The reference period for this study is 1990-1999. The climate change trend is represented by three bias-corrected RCMs (i.e., Hadley Centre Global Environmental Model version 3 regional climate model (HadGEM3-RA), Regional Climate Model version 4 (RegCM4), and Seoul National University Meso-scale Model version 5 (SUN-MM5)) and an ensemble of GCMs on the basis of delta change method under two future scenarios (RCP4.5 and RCP8.5). We applied the hydrological SWAT (Soil and Water Assessment Tool) model which uses the RCMs/GCMs outputs as input to analyze the impacts of climate change on the stream flow and peak flow of the upper reaches of the Kaidu River Basin. The simulation of climate factors under future scenarios indicates that both temperature and precipitation in the study area will increase in the future compared with the reference period, with the largest increase of annual mean temperature and largest percentage increase of mean annual precipitation being of 2.4°C and 38.4%, respectively. Based on the results from bias correction of climate model outputs, we conclude that the accuracy of RCM (regional climate model) simulation is much better for temperature than for precipitation. The percentage increase in precipitation simulated by the three RCMs is generally higher than that simulated by the ensemble of GCMs. As for the changes in seasonal precipitation, RCMs exhibit a large percentage increase in seasonal precipitation in the wet season, while the ensemble of GCMs shows a large percentage increase in the dry season. Most of the hydrological simulations indicate that the total stream flow will decrease in the future due to the increase of evaporation, and the maximum percentage decrease can reach up to 22.3%. The possibility of peak flow increasing in the future is expected to higher than 99%. These results indicate that less water is likely to be available in the upper reaches of the Kaidu River Basin in the future, and that the temporal distribution of flow may become more concentrated.

Effect of soil management on soil erosion on sloping farmland during crop growth stages under a large-scale rainfall simulation experiment
Linhua WANG, Yafeng WANG, SASKIA Keesstra, ARTEMI Cerdà, Bo MA, Faqi WU
Journal of Arid Land. 2018, 10 (6): 921-931.   DOI: 10.1007/s40333-018-0016-z
Abstract ( 300 )   HTML ( 6 )     PDF (312KB) ( 552 )  

Soil erosion on farmland is a critical environmental issue and the main source of sediment in the Yellow River, China. Thus, great efforts have been made to reduce runoff and soil loss by restoring vegetation on abandoned farmland. However, few studies have investigated runoff and soil loss from sloping farmland during crop growth season. The objective of this study was to investigate the effects of soil management on runoff and soil loss on sloping farmland during crop growth season. We tested different soybean growth stages (i.e., seedling stage (R1), initial blossoming stage (R2), full flowering stage (R3), pod bearing stage (R4), and initial filling stage (R5)) and soil management practice (one plot applied hoeing tillage (HT) before each rainfall event, whereas the other received no treatment (NH)) by applying simulated rainfall at an intensity of 80 mm/h. Results showed that runoff and soil loss both decreased and infiltration amount increased in successive soybean growth stages under both treatments. Compared with NH plot, there was less runoff and higher infiltration amount from HT plot. However, soil loss from HT plot was larger than that from NH plot in R1-R3, but lower in R4 and R5. In the early growth stages, hoeing tillage was effective for reducing runoff and enhancing rainfall infiltration. By contrast, hoeing tillage enhanced soil and water conservation during the late growth stages. The total soil loss from HT plot (509.0 g/m2) was 11.1% higher than that from NH plot (457.9 g/m2) in R1-R5. However, the infiltration amount from HT plot (313.9 mm) was 18.4% higher than that from NH plot (265.0 mm) and the total runoff volume from HT plot was 49.7% less than that from NH plot. These results indicated that crop vegetation can also act as a type of vegetation cover and play an important role on sloping farmland. Thus, adopting rational soil management in crop planting on sloping farmland can effectively reduce runoff and soil loss, as well as maximize rainwater infiltration during crop growth period.

Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China
Tong HENG, Renkuan LIAO, Zhenhua WANG, Wenyong WU, Wenhao LI, Jinzhu ZHANG
Journal of Arid Land. 2018, 10 (6): 932-945.   DOI: 10.1007/s40333-018-0061-7
Abstract ( 364 )   HTML ( 5 )     PDF (1386KB) ( 733 )  

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0-200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Evaluating and modeling the spatiotemporal pattern of regional-scale salinized land expansion in highly sensitive shoreline landscape of southeastern Iran
SHAFIEZADEH Mohammad, MORADI Hossein, FAKHERAN Sima
Journal of Arid Land. 2018, 10 (6): 946-958.   DOI: 10.1007/s40333-018-0104-0
Abstract ( 255 )   HTML ( 3 )     PDF (2458KB) ( 599 )  

Taking an area of about 2.3×104 km2 of southeastern Iran, this study aims to detect and predict regional-scale salt-affected lands. Three sets of Landsat images, each set containing 4 images for 1986, 2000, and 2015 were acquired as the main source of data. Radiometric, atmospheric and cutline blending methods were used to improve the quality of images and help better classify salinized land areas under the support vector machine method. A set of landscape metrics was also employed to detect the spatial pattern of salinized land expansion from 1986 to 2015. Four factors including distance to sea, distance to sea water channels, slope, and elevation were identified as the main contributing factors to land salinization. These factors were then integrated using the multi-criteria evaluation (MCE) procedure to generate land sensitivity map to salinization and also to calibrate the cellular-automata (CA) Markov chain (CA-Markov) model for simulation of salt-affected lands up to 2030, 2040 and 2050. The results of this study showed a dramatic dispersive expansion of salinized land from 7.7 % to 12.7% of the total study area from 1986 to 2015. The majority of areas prone to salinization and the highest sensitivity of land to salinization was found to be in the southeastern parts of the region. The result of the MCE-informed CA-Markov model revealed that 20.3% of the study area is likely to be converted to salinized lands by 2050. The findings of this research provided a view of the magnitude and direction of salinized land expansion in a past-to-future time period which should be considered in future land development strategies.

Activity patterns and resource partitioning: seven species at watering sites in the Altun Mountains, China
Yadong XUE, Jia LI, Guli SAGEN, Yu ZHANG, Yunchuan DAI, Diqiang LI
Journal of Arid Land. 2018, 10 (6): 959-967.   DOI: 10.1007/s40333-018-0028-8
Abstract ( 217 )   HTML ( 3 )     PDF (404KB) ( 586 )  

As part of a larger project to examine the richness and distribution of wildlife in Kumtag Desert area, we conducted camera trapping surveys during the period 2010-2012 at seven watering sites in an arid region of the Altun Mountains in western China. Information on activity patterns of the wild bactrian camel (Camelus ferus), kiang (Equus kiang), goitered gazelle (Gazella subgutturosa), argali (Ovis ammon), blue sheep (Pseudois nayaur), red fox (Vulpes vulpes), and wolf (Canis lupus) was obtained. We found that the wild camel, kiang, goitered gazelle, argali, and blue sheep were predominantly diurnal at watering sites, whereas red fox and wolf were nocturnal. Five herbivores partitioned the use of watering sites in a temporal manner to minimize the risk of predation by carnivores. The wild camel was the dominant herbivorous species at the watering sites. The kiang, goitered gazelle, argali, and blue sheep displayed adaptive water use by altering spatial or temporal patterns based on the presence or absence of wild camel, to minimize the risk of interspeci?c strife. These results are suggestive of the differences in activity patterns that might modulate water partitioning by different species, and provide insights for the development of conservation strategies for integrated species and decisions regarding water development in the Altun Mountains.

Report
Comparing phreatic evaporation at zero water table depth with water surface evaporation
Shunjun HU, Yongde GAN, Yongbao CHEN
Journal of Arid Land. 2018, 10 (6): 968-976.   DOI: 10.1007/s40333-018-0108-9
Abstract ( 263 )   HTML ( 4 )     PDF (389KB) ( 556 )  

Salt-affected soils are mostly found in irrigated areas within arid and semi-arid regions where the groundwater table is shallow. Soils of this type have become an increasingly severe problem because they threaten both the environment and the sustainable development of irrigated agriculture. A tool to estimate phreatic evaporation is therefore urgently required to minimize the salinization potential of salt-affected areas. In this context, phreatic evaporation at zero water table depth (E0) is a key parameter for establishing a model for calculating phreatic evaporation. The aim of this study was to explore the law of phreatic evaporation and to develop structurally rational empirical models for calculating phreatic evaporation, based on E0 data of six types of soil (i.e., gravel, fine sand, sandy loam, light loam, medium loam, and heavy loam) observed using the non-weighing lysimeter and water surface evaporation (E601) data observed using a E601 evaporator of same evaporation area with a lysimeter-tube at the groundwater balance station of the Weigan River Management Office in Xinjiang Uygur Autonomous Region, China, during the non-freezing period (April to October) between 1990 and 1994. The relationship between E0 and E601 was analyzed, the relationship between the ratio of E0 to E601 and the mechanical compositions of different soils was presented, and the factors influencing E0 were discussed. The results of this study reveal that E0 is not equal to E601. In fact, only values of the former for fine sand are close to those of the latter. Data also show that E0 values are related to soil texture as well as to potential atmospheric evaporation, the ratio of E0 to E601 and the silt-clay particle content (grain diameter less than 0.02 mm) is negatively exponentially correlated, and that soil thermal capacity plays a key role in phreatic evaporation at E0. The results of this analysis therefore imply that the treatment of zero phreatic depth is an essential requirement when constructing groundwater balance stations to study the law of phreatic evaporation.