分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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 interspecific 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
XU Guobao
LIU Xiaohong
SUN Weizhen
CHEN Tuo
ZHANG Xuanwen
ZENG Xiaomin
WU Guoju
WANG Wenzhi
QIN Dahe
摘要： 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 13C and 18O 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 13C and 18O values of tree-ring -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 13C values. The two-point calibrated method improved the results (range and variation) of 13C and 18O values. The mean values, standard deviations, and trends of the tree-ring 13C obtained by the combustion method were similar to those by the pyrolysis method followed by two-point calibration. The simultaneously measured 18O 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 13C and 18O did not differ between the two methods. The tree-ring 13C and 18O values were negatively correlated with standardized precipitation evapotranspiration index from May to August. In addition, the 18O was significantly correlated with temperature (positive), precipitation (negative), and relative humidity (negative) from May to August. The tree-ring 13C and 18O 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 13C and 18O in tree-ring -cellulose can be used in wide regions.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： 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.
分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 正确认识区域产业同构状况及演变趋势，对于制定科学的经济发展政策，尤其是产业发展政策具有较为重要的现实意义。以陕北能源开发区—榆林市为研究对象，根据1995—2015年三次产业数据分析了榆林市产业结构模式，通过产业结构相似系数测度了榆林市产业同构，并从横向与纵向两个维度对产业同构进行对比分析，另采用R/S分析法，对未来产业同构的演变趋势进行预测。研究发现：（1）榆林市产业呈现典型的“二三一”产业结构模式，第二产业比重较大，成为推动全市经济发展的主导力量。（1）榆林市北六县和南六县内部产业结构趋同度属于较高层次，产业结构同质化现象十分严重；尤其以神木县-府谷县（0.976 2）和佳县-清涧县（0.967 5）最为突出，南六县与北六县绝大多数区县间产业同构度都低于0.9，产业趋同现象不明显。（3）榆林市南六县与北六县产业结构相似系数的H（1995—2015）=0.611 2>0.5，如果在原有的条件下继续发展，榆林市未来产业同构化程度将有所强化，但存在周期性变化。研究认为在相似的能源条件、经济交流与联系日益紧密及经济发展水平不断接近的条件下，榆林市产业结构的趋同发展具有一定必然性，在未来制定促进经济发展的政策时应有一个清醒的认识。
分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 对外开放是推动中国经济改革与发展的重要机制和动力，是国家繁荣发展的必由之路。本文以中国343个地级及以上行政单元为研究对象，通过构建熵值—突变系统模型从3个维度测算对外开放度；运用探索性空间数据分析、三维插值拟合分析及重心迁移、空间变差函数等方法，分析中国地级单元对外开放度的时空分异格局及演化的内在机理。结果显示：（1）中国地级单元对外开放度表现出明显的行政指向性、空间地带性和开放区域性等多重分异特征。对外开放度整体呈现东部>中部>东北>西部，南方>北方的特征；直辖市、副省级城市、省会城市、经济特区及沿海开放城市整体对外开放水平较高，地级市间差异较大；10a间，对外开放度总体差异逐渐减小。（2）对外开放度存在明显的空间依赖性，表现为“小分散大集聚”的空间俱乐部趋同特征；10a间，开放型纹理分散程度趋于提升，闭塞型纹理集聚程度趋于收敛，高原型整体呈破碎化分布。（3）中国对外开放度格局变异的随机成分在逐渐减小，空间自组织性和连续性较为显著，东北—西南方向均质性最好，东南—西北方向空间差异明显。科学剖析地级单元对外开放度时空格局分异及演化机理，对制定合理的对外开放战略和促进外向型经济与区域经济双轨融合发展具有重要的意义。
分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 随着气候变化日益加剧，碳排放及其影响越来越受到人们的关注。本文对我国30个省区2000—2015年终端能源消费产生的碳排放进行核算，分析中国能源消费碳排放的区域特征和时空差异，并通过STIRPAT模型和面板数据模型相结合的方法从碳排放量和碳排放强度两个视角对碳排放的驱动因素进行分析。研究发现，从全国层面来看，人口规模、人均GDP、能源强度以及城市化水平对碳排放量产生正向的驱动作用，即每提升1%，碳排放量将分别增加1.046 9%、0.938 6%、0.722 6%、0.411 6%，而产业结构对碳排放具有负向的驱动效应。对于碳排放强度而言，人均GDP和产业结构均产生负向的抑制作用。从区域层面来看，通过经济水平分组，东、中、西部三大区域由于经济发展水平的差异，各个因素对碳排放的影响也有所不同并表现出一定的规律性；城市化水平分组表现出随着城市化水平的提高，碳排放量也随之降低。通过研究，可为我国合理制定CO2减排的区域差异化政策提供参考依据。
分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 采用偏离-份额四分量模型，分解2010—2015年兰白西城市群41个县（区）经济增长结构；采用空间数据分析方法，分析41个县（区）经济增长总量及各分量空间特征。结果表明：（1）兰白西城市群呈现以兰州市和西宁市为双核心的“中心-外围”经济结构，兰州市的经济中心地位更为显著。（2）根据经济增长总量及各分量，将兰白西城市群41个县（区）分为经济快速增长型、经济滞后增长型、竞争力优势推动型和资源配置优势推动型等4种类型。（3）经济增长总量、份额偏离分量、产业结构分量在空间上存在集聚性特征，竞争力分量在空间上存在随机分布性特征，资源配置分量在空间上存在负相关性特征。（4）份额偏离分量、产业结构分量与经济增长总量的空间重合度较高，竞争力分量、资源配置分量与经济增长总量的空间重合度有待优化。
分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 农产品贸易是中国与“一带一路”沿线国家经济合作的重点领域之一。文章对中国与“一带一路”沿线国家农产品贸易规模、结构及其发展趋势进行研究，研究表明，中国与“一带一路”沿线国家农产品贸易规模及其增速存在区域间与区域内国家间双重差异性和阶梯性特征，东盟地区是沿线与中国农产品贸易额最高的区域，中亚地区是沿线与中国农产品贸易占比较低但增速较快的区域；改善贸易结构、优化贸易环境是实现沿线国家互动共赢共享发展的迫切要求。
分类： 地球科学 >> 大气科学 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 对上海市2012-2016年PM2.5质量浓度、气象因素数据资料进行整理统计，通过定性分析与定量计算相结合的方法，揭示近年来上海市PM2.5浓度的变化特征及其污染状况；进一步地，采用相关性分析，从温度、气压、相对湿度、风向、风速和降水量等方面探讨了PM2.5浓度与气象因素之间的关联性。结果表明，上海市近5年空气质量主要为优和良，污染天数所占全年比例在减少。PM2.5浓度呈现出夏季低，冬季高的季节特征，而且8月PM2.5浓度最低，处于16~36 μg m-3；PM2.5的日变化呈现出双峰双谷结构，浓度峰值出现于8时-9时和19-20时，且后者浓度更高。气温、气压、相对湿度的阈值分别出现在9.8 ℃、766.3 mm Hg、83 %，最大PM2.5在阈值处出现显著变化；最大PM2.5浓度与累积风速和降水量呈现出对数关系，并且东北风和东南风的累积风速达到350 m s-1以上时，PM2.5浓度基本减少至35 μg m-3；降水量越大，PM2.5浓度越低。
分类： 地球科学 >> 地理学 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 目前遥感监测土壤含水率的方法较多，本次研究选取了稳定性较好、应用较为广泛且所需气象资料少的三种监测方法——SWEPDI指数法、能量指数法与TVDI指数法。以2016年4月和9月两期中高分辨Landsat8数据为数据源，分别将SWEPDI光谱法、能量指数法与TVDI指数法按不同时间、不同土层深度与对应时间的土壤含水率野外实测数据进行线性拟合，并进行各模型之间的比较，选择出更加适当的模型。同时利用景观指数在斑块类型上分析2时相土壤水分的变化趋势。结果表明：TVDI法效果明显优于SWEPDI光谱法和能量指数法，同时该方法还解决了其他方法不能连续监测土壤含水量的问题，适用于各种植被覆盖条件下以及各种土层深度的土壤水分反演。此外，选用6个景观指数分析了2016年4月与9月不同旱情等级干旱等级的景观格局变化，发现4月份PLAND指数达到了58.76％，而9月份轻旱等级的PLAND指数达到了44.16％，都占据优势地位，其中LPI 、AREA_CV 、AI指数的值也都达到了最大，其旱情状况有了明显的改善。
分类： 地球科学 >> 水文学 提交时间： 2018-10-23 合作期刊: 《干旱区地理》
摘要： 祁连山自然保护区是河西地区重要的水源涵养区，而灌丛作为祁连山主要植被类型之一，对该区水源涵养功能具有举足轻重的作用。本文以黑河上游天涝池流域两种典型亚高山灌木为研究对象，基于2014 、2015 年野外观测和ArcGIS10.1分析功能，获得灌木生长季期间生态参数(叶面积、叶面积指数和比叶面积)的变化；同时，结合分辨率为0.5m×0.5m的LiDAR数据和Geoeye-1影像数据，估算研究区灌木叶面积指数的空间分布。研究结果表明：灌木在生长季期间比叶面积值在一定范围内波动；叶面积、叶面积指数变化较大。其中，在6月、7月份增加最明显，8月份趋于稳定，9月份叶片开始凋落。其次，随海拔梯度水热条件的不同，流域灌木叶面积指数空间异质性较大，以海拔3 400m为节点，在3 200~3 400 m 海拔带叶面积指数呈递增趋势，在3 400~3 750 叶面积指数呈递减趋势。
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