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Extent of Cropland and Related Soil Erosion Risk in Rwanda (卢旺达农田面积扩张带来的土壤侵蚀风险研究)
No full text在非洲，农田开垦是造成土壤侵蚀的主要原因。本研究以卢旺达为例，评估了该国当前的农田面积和土壤侵蚀情况。卢旺达是非洲最近十年人口增加和农田扩张最快的国家。我们利用 Landsat-8 影像，得到了卢旺达 2015 年的土地利用和覆被数据。基于降水、土壤性质、数字高程模型（DEM）、归一化植被指数（NDVI）和土壤保护因子数据，驱动 RUSLE（Revised Universal Soil Loss Equation）模型，评估了卢旺达的土壤侵蚀速率，空间分辨率是 30 米。模型结果显示，该国坡地的平均土壤侵蚀速率是 13.64 t ha-1y-1，每年土壤总流失量约为三千万吨。农田占总侵蚀面积的 60%，速率为 12.62 t·ha−1·y−1，占总流失量的 56%。约 93.49%的农田，其平均土壤流失率超过 1 t·ha−1·y−1。同时，土壤侵蚀率高（>10 t·ha−1·y−1）的农田有 42.94%位于坡度大（27-50%）和降水强（1119-1254 mm y-1）的地区。根据我们的研究，仅建造梯田就可以使土壤流失率减少 70%。控制火灾和减少人为干扰，如控制乱砍乱伐和牲畜的踩踏，可以减少森林和草地的土壤侵蚀风险。土壤侵蚀的减少能改善卢旺达的水体污染和粮食安全问题。该研究使用的方法可以帮助其他科学家和土地管理者评估实测数据缺乏地区的土壤侵蚀情况，指导人们采取合理的保护措施治理土壤
干旱区荒漠火烧迹地遥感特征分析研究—以古尔班通古特荒漠火灾为例
No full text西北干旱区受内陆极端干旱气候的影响，植被覆盖稀疏，生态结构简单，脆弱性明显。受自然和人为因素的影响，干旱区频繁发生的火灾已对当地经济的发展造成了沉重的压力与威胁，火灾对生态系统，尤其对干旱荒漠区生态系统的干扰特别明显。火灾是荒漠生态系统的重要影响因子，是荒漠生态系统突变的主要因素。因此，详细研究火烧迹地的发展与变化，提取火烧迹地信息对灾区生态建设与可持续发展具有重大意义，同时为有效防御火灾的发生提供科学依据，是实现当地经济与环境可持续发展的重要组成部分。传统的火烧迹地信息获取具有调查周期长、劳动强度大等弊端，得到广泛应用与发展的现代遥感技术及地理信息技术，能够弥补传统调查方式的严重不足。本论文以 2016 年 5 月底古尔班通古特荒漠自燃灾情为研究背景，首先借助轻小型无人机，按照测绘标准规范，对火灾大致位置进行航空摄影，由内业制作生成分辨率为 20cm 的数字正摄影像，精确定位火灾位置，目视解译过火区域边界；选取灾区 2013 年至 2016 年 Landsat 8 陆地成像仪(Operational Land Imager，OLI)卫星影像数据，按照 FLAASH 模型对 OLI 影像进行大气校正，对 4 年间火灾同期遥感影像进行温度反演，同时在 ENVI 软件下通过波段运算，对长时间序列植被指数和火烧植被指数进行提取，并对火烧指数进行差分运算。分析表明：干旱荒漠区每年 5、6 月份地表温度较高，研究区植被枝叶常年堆积形成的腐蚀层，是荒漠植被自燃的主要因素；干旱荒漠区的各种植被指数较其他湿润地区低，火灾在长时序植被指数上的变化不大，从生态学角度来说，火灾的发生有利于植被的恢复或者更替；差分指数对荒漠火灾的响应能力较单一指数好，单一指数而言，对荒漠火灾适应性最好的植被指数是亮温调整归一化燃烧率第一类型（NIR-SWIR-Temperature Version 1,NSTV1），差分指数中差分归一化燃烧率（Difference Normalized Burn Ratio, dNBR）的对荒漠火灾的适宜性最好；热红外波段对火灾前后的区分度最高，不同指数中归一化燃烧率（Normalized Burn Ratio, NBR）对火灾前后的区分度最高。本论文以火灾发生时的地表温度及植被指数作为切入点，提取火烧迹地面积，分析干旱荒漠区的火灾成因，探讨各种植被指数的适宜性，选择对干旱荒漠区火灾响应能力最强烈的植被指数
古尔班通古特沙漠南缘典型沙地土壤水分动态及模拟
No full textSoil moisture is the mainly limiting factor for the plant growth, vegetation succession and pattern change in arid desert area. The dynamics of soil moisture is affected by kinds of uncertainties, e.g., physical-chemical-biological processes,climate change, soil and vegetation differences. With randomness, it is more practical to simulate soil moisture evolution throughout time and space using a model based on probabilistic framework. Here, we selected the typical interdune at the southern edge of Gurbantunggut Desert as the study area in this thesis. This study was designed to investigate the soil moisture dynamics based on the field monitoring, laboratory experiment and model simulation. The relationship between the soil moisture dynamics and the precipitation characteristics was also analyzed. Using the measured soil moisture movement parameters, long-term soil moisture datasets and precipitation datasets, we simulated the soil moisture probability density function by stochastic Laio Model. The main conclusions are listed as follows.(1) Soil hydraulic parameters conformed to soil moisture dynamic chracteristics. Our results found that both the two models(VG and G) fit well with the measured soil water characteristic curves in this region. The saturated hydraulic conductivity of aeolian sandy soil in interdune was 1424.16 mm/d, which was determined using the one-dimensional horizontal infiltration method. There presented a monotonically increasing relationship between the unsaturated soil water diffusivity D(θ) and the soil water content θ.(2) Precipitation in the study area was dominated by small precipitation events(0-5 mm), accounted for 85.2% of the total events, and up to 44.7% of the total precipitation amount. The precipitation interval was dominated by 0-5 days,accounted for 53.2% of the total days without rainfall. And there showed 29.0% and 24.4% of intervals between precipitation events were from 11 days to 20 days and from 6 days to 10 days, respectively. As the precipitation intervals increased, the frequency of precipitation events decreased. (3) Soil moisture was relatively high at root-zone(0-100 cm) in the early growing season. With the temperature rising gradually, soil moisture decreased and reached the lowest basically(0.025 cm3 /cm3) at the end of the growing season. There were two distinct soil layers in the 400 cm depth. Soil water contents was significant variability in the upper 0-50 cm, and remained stable in 50-400 cm. (4) The soil moisture in sandy root-zone layer probability obeyed the T distribution with scale parameter and positional parameter in growing season. The distribution of probability density was basically unimodal, with a narrower width compared to the humid area. The peak value, position and scope of p(s) obtained by Laio model were similar to that of the measured values. Laio model had a good applicability in our study areas. For the thirteen parameters of Laio model, soil porosity, root depth, amount of precipitation intercepted by canopy cover for each rainfall event, soil moisture level below which plants begin closing their stomata, average daily evapotranspiration rate under unrestricted siol moisture conditions, average daily evaporation rate at permanent wilting point, mean of depth of rainfall events, arrival rate of rainfall events, soil moisture level below which water can not be extracted from the soil through evaporation and permanent wilting point were more sensitively, and mainly impacted the peak value of p(s) than paramater defining, along with saturated hydraulic conductivity, the relationship between soil moisture and hydraulic conductivity when an exponential law was used, saturated hydraulic conductivity, soil field capacity
新疆两种药用阿魏植物内生细菌多样性及抗病促生菌株筛选
No full textXinjiang, a region of high salinity and drought, is a host to many arid and semi-arid plants. Endophytes live within a plant for at least part of its life cycle without causing apparent disease. Many of these plants including Ferula spp. have indigenous pharmaceutical histories. As many of the medicinal properties of plants are in tandem with the associated microorganisms residing within the plant tissues, it is advisable to explore the endophytic potential of such plants. The present study involved the isolation of endophytes from different tissues of F. sinkiangensis K. M. Shen and F. songorica Pall. ex Spreng and analyzed the distribution pattern among the plant tissues. In addition, the plant growth promoting traits and their biocontrol potential ontaining proction of protease and cellulose, posphate solubilization, ntrogen fixation, sderophore production, indole acetic acid (IAA) synthesis and atagonism assay were studied. During the study, a total of 170 endophytic bacteria belonging to 3 phyla, 15 orders, 20 families, 27 genera and 58 species were isolated from F. songorica. 125 endophytic bacteria belonging to 3 phyla, 13 orders, 23 families and 29 genera were isolated from F. sinkiangensis. The genera Bacillus and Streptomyces constituted a major portion of the endophytic microbes associated with F. songorica and also F. sinkiangensis. The index values according to Shannon and Margalef were 4.02 and 16.55 respectively. Comparing the endophytes from different habitats, it was found that endophytes from Tacheng exhibited more abundant, but those from Shihezi showed more diverse. The 170 endophytes strains in F. songorica were distributed in 27 genera, but 125 endophytes strains in F. sinkiangensis were distributed 29 genera. During this study, root tissues were found to be a more suitable host for endophytic bacteria as compared to stem.Growth promotion assays indicate that most of the endophytes were able to promote plant growth. In this study, 88.0% of the total isolates from F. songorica were capable of grow in nitrogen-free medium, 79.4% and 75.8% of the isolates from F. sinkiangensis were able to produce IAA and fix nitrogen respectively, and 57.1 % of the strains were positive in siderophore production. Salt tolerant experiment of endophytes showed that 5 strains of endophytes grew normally under the condition of 7 % NaCl. Further research about growth promotion ability was carried out by seed germination of wheat.It demonstrated that endophytes bacteria could improve the germination rate of wheat seeds, increase the length and biomass accumulation under salt stress.During This study, there are some potential novel specises belonging to the genera Nocardioides, Paracoccus, Amycolatopsis and Porphyrobacter discovered. This research showed that the protcection of Ferula resource and endophytes in plant tissue were urgently required. This study revealed the great significant ecological adaptability of Ferula, and also the function of endophyes in improving plant disease resistance and stress toleration
塔里木盆地南缘不同土壤盐分生境下骆驼刺适应特性研究
No full textSoil salinization is one of the top ten threats to soil function. It seriously restricts the development of agriculture and animal husbandry. Tarim Basin is favorable for the occurrence of soil salinization due to its unique natural environment. The unreasonable land use and the construction of water conservancy projects have further aggravated the expansion and spread of saline land, which caused the serious damage to the natural vegetation near the oasis. Alhagi sparsifolia Shap. is a key species grown on the southern margin of the Tarim Basin. It plays an important role in maintaining ecological security and promoting economic development in this region. Therefore, it is of great significance to study the adaptive characteristics of A. sparsifolia.In this study, the dominant plant A. sparsifolia was studied under different salt conditions in the southern margin of Tarim basin. Through the combination of field observation and experimental analysis, we systematically studied the growth distribution, leaf traits, root ramet, ion distribution characteristics of A. sparsifolia under different salt conditions. In order to reveal the ecological adaptation of A. sparsifolia to different salinity environment, and provide scientific basis for regional degradation vegetation restoration and saline land resource management. Mainly results are as follows:(1) Growth distribution characteristics: There was a significant correlation between total salt of soil, soil organic carbon content, soil total nitrogen content, mineralization degree of groundwater and the growth distribution characteristics of A. sparsifolia; the correlation of groundwater depth with growth distribution characteristics was less significant while other indicators had no significant correlation with the plant’s growth distribution characteristics. Synthesis analysis showed that mineralization degree of groundwater, groundwater depth, total salt of soil are main factors influencing growth distribution characteristics of A. sparsifolia. The increase of groundwater mineralization degree, soil total salt and groundwater table go against the growth of A. sparsifolia in saline habitat. (2) Leaf traits characteristics: With the increase of soil salinity, the area of A. sparsifolia leaf was "big - small - big" trend; Leaf thickness was "thin - thick - thin" trend; The specific leaf area, leaf dry matter content and leaf tissue density changed little; The change of total carbon content in the leaves of A. sparsifolia was less with the change of soil salinity, and the change of total nitrogen content and total phosphorus content was not obvious.(3) Root ramet characteristics: With the increase of soil salinity, the formation of A. sparsifolia seeds was restricted, and the way of reproduction by sexual reproduction and asexual reproduction coexist into only asexual reproduction, resulting in a reduction in the regeneration of the A. sparsifolia; The interval between the ramets increased gradually, and the depth of the ramets increased gradually, leading to the decrease of the number and ability of new plants; When the total salt content of soil is too high, there will be no new ramets, A. sparsifolia do not have a complete history of life, it can not carry out the natural breeding population. (4) Ion distribution characteristics: When grown on a light saline soil, Na+ distribution in different organs of A. sparsifolia followed the order of stem≈thorn>leaf>root; when grown on a severe saline soil, Na+ distribution followed leaf>stem≈thorn>root. The distribution of Ca2+ and Mg2+ followed leaf>thorn>stem>root. with the increase of soil salt level, Na+ content in different organs of A. sparsifolia increased, while K+ content in leave decreased; meanwhile the increasing soil salt level significantly decreased the K+/Na+ ratio in both root and leave, as well as the Ca2+/Na+ and Mg2+/Na+ ratios in all organs. The selective transportation coefficients for Ca2+-Na+（SCa,Na）and Mg2+-Na+ (SMg,Na) followed order of stem-leaf> stem-thorn> root-stem
气候波动下开都河流域的水文响应模拟及其不确定性分析
No full textThe socio-economic and ecological problems caused by climate change haveattracted worldwide attention. The arid region of central Asia is a typical ecologicallyfragile area, and its water resources are sensitive to climate change response. In thispaper, the Kaidu river basin in the typical mountainous region of Central Asia wastaken as the study area. Firstly, the applicability of CFSR reanalysis data in themodeling of arid mountainous hydrologic process was discussed. LOCI, Gamma andgamLOCI methods were used to correct for the bias of CFSR precipitation data, andthe daily runoff simulation results of the three methods were compared. Secondly,driven by the GCMs data and the statistical downscaling method, the hydrologicalmodel of the Kaidu river basin was used to simulate the hydrological response in theRCP4.5 and RCP8.5 scenarios. Finally, four kinds of GCMs were used as the rainfallinput data, and three kinds of hydrological models to simulate the runoff. Theuncertainty among the input data, model structure and model parameters wasanalyzed in the whole technical route. The main conclusions are as follows:(1) Compared with the observation, the overestimation for light rainfall andunderestimation for heavy rainfall of CFSR dataset were significant in Kaikong riverbasin. CFSR dataset is likely to underestimate heavy rainfall in high-altitudemountainous areas and to overestimate light rainfall in plains. There are too manysmall precipitation events for CFSR data both in high-altitude mountainous areas andplain areas. The deviation and correlation between CFSR precipitation data and theobservation are related to elevation and season. In general, the correlation of highaltitude mountainous area is better than that in plain area. The correlation in springand autumn is better than that in summer and winter. The deviation of high-altitudemountainous area and plain area is higher than that of middle-altitude area.Based on the results of three bias correction methods, the LOCI method cancorrect the wet day and wet rainfall intensity of the precipitation data, but it willdistort the extreme value of the precipitation change. The Gamma method can keepthe extreme value of the climate change signal, but cannot correct the wet dayfrequency and wet day precipitation intensity. The gamLOCI method synthesizes theadvantages of the LOCI and Gamma method, not only the wet-day frequency andprecipitation intensity of CFSR data could be corrected, but the extreme waspreserved. Three correction methods could equally and effectively improve thereliability of CFSR reanalysis data in plain area, while the correction effect withgamLOCI method was the best in mountainous region. Using the raw CFSR datasetas the precipitation input data of hydrological model, the simulation result of runoff istoo large, and the relative deviation is greater than 40%, and the spring flood peak getin advance and increased. Therefore, there exists obvious bias in reanalysisprecipitation datasets in Central Asia, the appropriate bias correction method has to beconsidered before applying these datasets in hydrological model of the aridmountainous area.The three bias correction methods, LOCI, Gamma and gamLOCI, have differentcharacteristics, but the results of runoff simulation show little difference. All of them can give a satisfied performance.(2)under background of global warming, the annual precipitation andtemperature in arid mountainous areas showed increasing trend, in agreement with thechange from "warm and dry" to "warm and humid‖. But the increase with months ofthe year was not consistent. Precipitation increases in both winter and summer, whilethat is not significant in spring and autumn. Temperatures is increasing all the year,but it increases faster in winter and summer, and slower in spring and autumn. Ingeneral, the volatility and uncertainty of precipitation in arid mountainous areas willincrease and precipitation will be more concentrated in the summer in the RCP8.5scenario. The distribution of precipitation in each month will be even more averagedin the RCP4.5 scenario.Affected by climate warming, the surface runoff, groundwater recharge andsnowfall will be reduced in the dry mountainous areas of Central Asia in future, whileprecipitation, actual evapotranspiration and potential evapotranspiration will increasesignificantly. By 2035,the runoff will increase in spring and autumn, and it willdecrease in winter and summer. The runoff during all seasons of the year will increaseby 2070. The water resources in Kaidu river basin is getting richer from 2016 to2023.The amount of annual runoff of Kaidu river basin is about 2 to 3.5 billion cubicmeters in the period from 2051 to 2070. The amount of annual runoff in RCP8.5scenario ranges between 1 and 3.5 billion cubic meters. And the annual runoff of2051-2070 in RCP4.5 scenario is around 1.5 billion cubic meters. However, thefluctuation of the water resources amount in RCP4.5 scenario is more smaller thanthat in RCP8.0 scenario.The amount of snowmelt in the high mountainous areas of Kaidu river basin,which is vulnerable to climate change, is obviously increasing. While the amount ofsnowmelt in plains and low-altitude valleys of mountains is decreasing. This isbecause the temperature increases in the basin, and the snow line rises as the result.(3) The uncertainty of the bias correction methods in the process of hydrologicalresponse simulation to climate change is the smallest, and the input data, the modelstructure and the uncertainty of the model parameters mater indeed. The uncertaintyof the input data is relatively larger in wet seasons of the year than that in dry seasons;the uncertainty of model structure is large both in dry seasons and wet seasons. Butthe uncertainty of model structure in the flood formation and uplift stage is larger thanthat in flood regression stage
罗布泊湖相沉积物记录的全新世以来区域环境变化
No full text过去全球变化（PAGES）研究是全球变化研究的重要内容，对过去全球变化深入研究能够有效揭示其变化历史、演变规律及其成因机制，为预测未来环境变化提供科学依据。湖相沉积物是古环境信息的重要载体之一，蕴含大量的环境信息，具有较好的连续性和较高的分辨率。湖相沉积物被广泛用于重建不同时间尺度的古环境变化序列，探讨环境演变驱动机制，解析区域环境对全球变化的响应等。罗布泊地处塔里木盆地东端，地势低平，是整个塔里木盆地的汇流中心，沉积着以万年计的湖相沉积物，是区域古环境变化研究的理想场所。在历史上，罗布泊地区曾孕育出光辉灿烂的“楼兰文明”，为古丝绸之路重要的交通枢纽。本研究以罗布泊湖相沉积为研究对象，在“大耳朵”湖湖心位置以 1cm 分辨率连续采集了一个厚度为 378cm 的 LB 剖面（顶部 20cm 盐壳，以 10cm 间隔采样），并采集了 10 个 14C 年代学样品。首先通过加速器质谱仪（AMS）进行 14C 年代测试，建立了较高分辨率的年代–深度模型。然后对 LB 剖面样品进行粒度、磁化率、TOC、烧失量等各种环境代用指标测试分析，结合各代用指标的环境意义，重建了全新世以来罗布泊地区环境变化序列。最后与周边地区全新世环境变化特征比较，讨论罗布泊地区环境变化的驱动机制。获得以下主要结论和初步认识：（1）LB 剖面层理发育完善，层理清晰；剖面发育连续，韵律组合良好。各种环境代用指标之间如粒度、TOC、有机质烧失量、碳酸盐烧失量、磁化率等都发生同步变化，并与剖面现场观察记录有很好的对应关系。通过 14C 测年方法进行多层定年，基于沉积年代学理论建立了 LB 剖面年代–深度模型。罗布泊 14C 年代存在明显的碳库效应，LB 剖面碳库效应约为 3075 年，剖面各时期沉积速率较为接近，底部 378cm深度年代约为 9.1cal. ka BP。（2）罗布泊全新世以来主要表现为逐渐湿润的趋势。前人 C/N 比值数据显示全新世罗布泊湖相沉积有机质主要为外源成因的，因此代表流域的植被状况。TOC 和有机质指标在 9.1– 4.2 cal. ka BP 时段含量相对较低，流域环境较为干旱，并在 7.2 – 5.2cal. ka BP 期间最干旱；4.2 cal. ka BP – 1.1 cal. ka BP TOC 和有机质含量相对较高，处于全新世最湿润的阶段。1.1 cal. ka BP 以来转变为较干旱气候。（3）罗布泊全新世以来湖泊碳酸盐含量反映了湖泊盐度变化特征。9.1 – 8.5 cal. cal.ka BP 湖泊碳酸盐相对较低，矿化度低；8.5 – 4.2 cal. ka BP 期间，碳酸盐总体处于较高水平，湖水盐度较前期有所增加；4.2 cal. ka BP 以来，湖泊进入硫酸盐沉积阶段，盐度在 4.2 – 3.0 cal. ka BP；3.0 – 2.2 cal. ka BP；2.2 – 1.1 cal. ka BP 三个阶段出现旋回式升高，湖泊盐度波动式增加。1.1 cal. ka BP 以来，湖泊盐度有所降低，并在 0.6 cal.ka BP 出现低值，湖泊水量出现丰枯波动；0.4 cal. ka BP 以来为氯化物沉积阶段，湖泊处于最高盐度。（4）罗布泊地区全新世以来长期存在风沙活动，并发生多次风沙活动事件。罗布泊地区在 9.0 – 8.5 cal. ka BP，6.0 – 5.5 cal. ka BP， 4.4 – 3.9 cal. ka BP，3.1 – 2.7 cal. kaBP，2.3 – 1.7 cal. ka BP 和 1.1 ka BP 以来出现风沙活动较强烈时期，尤其是 9.0 –8.5cal. ka BP，4.4 – 3.9 cal. ka BP 和 1.1ka 以来风沙活动最强烈。罗布泊风沙活动响应北大西洋冷事件，在约 4.2 cal. ka BP、3.0 cal. ka BP、 2.2 cal. ka BP、1.1 cal. ka BP表现为冷干的气候特点。（5）罗布泊地区全新世气候主要受太阳辐射强度变化及其引起的西风环流强度、位置南北移动和流域山地冰雪补给量变化共同作用的结果。早、中全新世太阳辐射较强烈，西风带北移，流域降水较少，地表有效湿度较低，流域较为干旱，而冰雪融水补给较多，湖水矿化度较低。中、晚全新世太阳辐射强度减弱，地表有效湿度增加，西风带南移，降水增加，地表有效湿度较高，流域较为湿润；而冰川显著退缩，湖泊补给减少，湖水矿化度升高。另外，全新世北大西洋冷事件通过西风环流影响亚洲中部环流系统。冷事件爆发时增强了中纬西风环流和西伯利亚高压，促使区域风场加强，并通过塔里木盆地东灌气流影响罗布泊地区风沙活动
APEX 和 RWEQ 风蚀模型在塔里木盆地的适用性分析与改进
No full textAPEX 和 RWEQ 作为目前通用的土壤风蚀预报模型，在许多国家和地区得到了广泛的应用。本文选取塔里木盆地阿克苏绿洲的枣园、棉田和沙漠（荒漠绿洲过渡带）三种典型的下垫面对比分析了 APEX 和 RWEQ 在该研究区的适用性。在多场大风事件中，通过野外试验监测，获得 APEX 和 RWEQ 模型参数、以及土壤流失量和风蚀沙通量的实测值。再通过参数率定，模型模拟，获得土壤流失量和风蚀沙通量的模拟值。对比实测值和模拟值，对模型进行模型适用性分析。结果显示：1. 两个模型在不同下垫面的预测精度各异。初始的 APEX 模型对棉田点（模型一致性指数 (d)=0.81, R2=0.50）和荒漠绿洲过渡带（d=0.81, R2=0.91）的土壤流失量模拟较好。然而，初始的 APEX 模型在枣园点对土壤流失量和沙通量模拟性能欠佳，其首要原因可以归结为该模型高估了植被在风沙运动中的保护作用（过程参数 VCF 偏小）。2. 在所选取的三个下垫面中，初始的 RWEQ 模型对土壤流失量的模拟均表现不佳。模型对土壤流失量和风蚀沙通量的预测值偏低。在棉田下垫面，预测值偏低可以归因于该模型对 S（试验地长度制约参数）的模拟性能不佳。在枣园点，该模型对风蚀沙通量的模拟性能预报不佳可以归因为对 Qmax的预报精度不够。3. 不区分下垫面，合并分析 23 个大风事件，我们发现初始的 APEX 模型模拟土壤侵蚀（包括土壤流失量和风蚀的沙通量）的性能要高于 RWEQ 模型。对比其它主要风蚀区域的模拟性能，例如美国华盛顿州的哥伦比亚高原的休耕轮作的小麦下垫面，初始的 APEX 模型对土壤流失量模拟效果也不理想，模型一致性指数为 0.18，低于该模型在塔里木盆地的模拟效果。初始的 RWEQ 模型模拟土壤流失量的性能良好，模型一致性指数 0.76，回归的拟合优度（R2）为0.40，高于该模型在塔里木盆地的模拟效果。模型参数校准是提高模型模拟性能的一个重要方法。本文选取的 APEX 和RWEQ 模型均包含大量的经验参数，这些非可测量的经验参数是模型本地应用精度不高的原因之一，也是模型率定的重点。本文运用模型参数暴力破解校准法 (brute force calibration technique)对模型参数进行校准，为更好的比较 APEX和 RWEQ 两个模型在不同下垫面的模拟性能，选取同样的大风事件来校准APEX 和 RWEQ 模型的过程参数。模型校准的结果显示： 通过模型过程参数的校准，除了在枣园下垫面的 RWEQ 模型，APEX 和 RWEQ 两个模型在所选取的其它下垫面，均有较高的模型性能。校准后的 APEX 和 RWEQ 模型，在棉田和荒漠绿洲过渡带点的模拟性能良好。APEX 和 RWEQ 模型在研究区适用性的提高，可以更好地为塔里木盆地的风蚀预报及沙尘治理工作服务。风洞试验可以定量控制风蚀影响因子，包括风速，沙源，边界条件等在短时间内取得较多的观测数据，本文利用可移动野外风蚀风洞在不同种农田耕作方式下测试了RWEQ 模型的性能。RWEQ 模型的一些积分方程和模型参数源自风洞试验，所以相对于野外实测的风蚀试验，RWEQ 模型在风洞试验中对土壤损失量的模型模拟性能更好（d>0.65 , 且 R2>0.90）
卫星降水产品在天山的适用性评价及降尺度研究
No full textHigh accuracy precipitation data is very important for regional climate andhydrological research. Based on 199 meteorological stations, we evaluated 3 sets ofsatellite precipitation datasets (CMORPH, GPM, TRMM) in Tishan mountains usingvarious statistical method. And put forward a new downscaling method based onprecipitation intensity, the precipitation distribution information from GPM and PTPLSGeographic-Precipitation correlation model. Finally, we analyzed the temporal andspatial variation of precipitation in Tianshan mountains based on the downscaledprecipitation data. The main conclusions are as follows:(1) The satellite precipitation data perform better in summer and autumn, amongwhich, GPM has the highest correlation coefficients and minimum relative errors(PB≈10%) with meteorological records. GPM has the minimum error in each elevationzones. In addition, satellite datasets has a better skill to capture weak precipitationevents. In a word, GPM could capture the precipitation changes accurately in Tianshanmountains, and can be applied to the ecology and hydrology research.(2) The annual precipitation of downscaled TRMM data is consistent with theobserved values, with the value of R2 above 0.7, reduce the average error of originalTRMM data effectively, but there is obvious differences between the rainy season (4-10 months) and dry season (11-3 months). The simulated runoff driven by downscaledTRMM data could accurately reflect the change of runoff in Akesu Basin, with thecorrelation coefficient >0.82 and the NS coefficient of 0.48.(3) Precipitation in the northern slope of Tianshan mountains behaves moreregular, with little differences through the whole year, however, The precipitation ofsouthern slope has remarkable seasonality. The results of M-K test show that: there areless precipitation in central and western part of Tianshan, while the precipitation in east,south Tianshan and Yili valley are increase. The PRCPTOT, R95p, R99p and R10mmhave been significantly reduced in the past 20 years, while Rx1d, CWD showed asinificant increase trend. As a whole, the amount and frequency of extreme precipitation in Tianshan are decreasing
齿肋赤藓四个 ScDREBs 基因特性及抗逆功能分析
No full textDREB transcription factor, belonging to the AP2 / EREBP family, is specificallypresent in plants and can regulate the expression of a series of downstream genes related todrought, salinity, low temperature and high temperature stresses, which plays vital roles inresponse to external adverse environmental factors, and are extensively investigated invarious plants. Syntrichia caninervis Mitt., an extremely dessication tolerance moss, isconsidered as a good candidate species for gene mining because of its outstanding drought,heat and UV resistant tolerance. In the past research, we build dehydration-rehydrationtranscriptome profile of S. caninervis and screened DREB family genes, and analyzed ongene expression pattern and gene abiotic function by yeast system of ten ScDREBs. In thisstudy, we selected four potential key ScDREBs genes and delve on further stress tolerancefunctional in Arabdopsis system. The work will shed light on the extremely stress tolerancemechanism of the moss, and will benefit for further development and utilization of thegene resources in crop breeding. The main conclusions are as follows:(1) Subcellular location assay of four ScDREBs proteins showed that all the fourScDREBs were located in both the nucleus and the cytoplasm of the onion or tobaccocells;(2) Transactivation activity assay of four ScDREBs proteins showed that ScDREB10,ScDREB3and ScDREB6 had transactivation activity except that ScDREB8 showed notransactivation activity;(3) Four ScDREBs genes were stably transformed into Arabidopsis by floral dipmethod, and the positive T3 generations were obtained for further gene function validation.Under the drought, salt, cold and heat treatment, the phenotypic change (root length andfresh weight) were observed, the physiological response (ROS level, determination ofantioxidant enzymes and proline content) were monitored and downstream gene expressionpattern were detected. The results showed that:Under the drought, salt and heat treatment, the Overexpressing-ScDREB10 lines had significantly higher seed germination rate and seedlings survival rate of transgenic linesthan wild type (WT). The transgenic lines also showed lower ROS level and higher SODand POD activities than those of WT at seedling stage. In addition, the expression ofScDREB10 gene could positively regulated a series of downstream stress toleranceassociated genes expression, which indicated that overexpressing-ScDREB10 increasedrought and salt tolerance in Arabidopsis; Under the salt treatment, the germination rate and seedlings survival rate ofoverexpressing-ScDREB8 gene lines were significantly higher than WT. The level of ROSin transgenic lines was significantly lower than that in WT, and the activity of antioxidantenzyme (SOD、POD) and proline content were significantly higher at seedling stage. Inaddition, ScDREB8 positively regulated a series of downstream stress tolerance associatedgenes expression. All results indicated that ScDREB8 increased salt tolerance inArabidopsis; Under the drought, high salt, cold and heat treatment, the overexpressing-ScDREB3lines had no significantly higher seed germination rate than the WT, but the survival ratewas significantly higher than that of the wild type under the extreme cold treatment(-20 ℃)at the seedling stage, showing that overexpressing-ScDREB3 gene might increase coldtolerance in Arabidopsis;Under the drought, high salt treatment, ScDREB6 transgenic lines showed nosignificant differences compared with the wild type, indicating that ScDREB6 might haveno abiotic stress tolerance ability. While the transgenic Arabidopsis showed significantlonger hypocotyl and a faster growth cycle phenotype at the seedling stage, implyingstrong hypocotyl elongation and growth-promoting function