分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 外泌体是细胞内源性囊泡样生物纳米级膜结构，直径大小在40-100 nm之间，可由各种类型的细胞分泌释放。外泌体具有许多功能，如蛋白质、mRNA、miRNA和脂类的细胞间运输和传递，以及抗原递呈，还可能具有致癌的能力。肿瘤细胞所分泌释放的外泌体在肿瘤的发生、发展以及迁移等生理和病理过程中发挥重要的作用。目前从肿瘤外泌体中寻找特异性标志物已成为肿瘤研究者重点关注的方向，对肿瘤早期诊断、疗效评价和预后分析具有重要的意义。本文作者就近年来外泌体在肿瘤研究和诊断中研究进展进行综述。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 通过目的基因的随机整合方式，构建得到的CHO表达细胞系，常会因为目的基因插入到染色体内不稳定区域，而在长期传代过程中出现表达不稳定的现象，这主要是由于位点效应所导致。为了解决这个问题，现利用CRISPR/Cas9技术介导的同源重组，将目的基因直接整合于CHO细胞染色体上稳定表达区域，以克服位点效应带来的CHO表达细胞系的长期表达不稳定。现总共利用该技术获得了2株外源基因（人白蛋白基因）定点整合细胞系；western blot结果显示，细胞上清液的产物具有人白蛋白抗原性；细胞在贴壁状态下，两株细胞系在第3、12、23、35、50代，细胞每日表达的HSA质量接近，且均维持在0.5 pg/cell/day；选取一株表达细胞系，经悬浮驯化后，在批次条件培养下，第1、25及50代的悬浮细胞，在摇瓶内的表达浓度均稳定在13-14 mg/L。本研究显示了将外源基因基因定点整合于CHO细胞基因组内的的可行性；且外源基因整合在稳定表达区域后，重组细胞系具有对外源基因长期表达的稳定性。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 环氧化物水解酶能够对外消旋环氧化物进行动力学拆分保留单构型的环氧化物。测定了菜豆环氧化物水解酶 (PvEH1) 针对苯基缩水甘油醚及其甲基衍生物的催化特性，并基于分子对接及多序列比对分析确定7个突变位点，通过单点和组合突变对PvEH1进行改造，以期改善PvEH1对邻甲基苯基缩水甘油醚 (1a) 的催化特性。底物谱分析表明PvEH1对1a的催化活性 (157.2 U/g湿细胞) 和对映选择性 (E = 5.6) 最高。单点突变结果显示E. coli/pveh1L105I和E. coli/pveh1V106I对1a的催化活性和对映选择性均有明显提高；L105I和V106I位组合突变菌株E. coli/pveh1L105I/V106I的催化活性 (493.8 U/g湿细胞) 是E. coli/pveh1的3.1倍，对映选择性 (E = 8.3) 也提高至E. coli/pveh1的1.5倍。纯化后PvEH1L105I/V106I的催化活性为17.6 U/mg是PvEH1的1.5倍，对1a的催化效率提高至PvEH1的2.1倍。SDS-PAGE分析表明提高了蛋白的可溶性表达量。利用E. coli/pveh1L105I/V106I全细胞催化100 mmol/L 1a水解动力学拆分获得手性纯 (R)-1a (ee > 96%) 的产率和时空产率分别为31.2%和5.12 g/L/h，因此，在手性纯 (R)-1a的制备中，E. coli/pveh1L105I/V106I是一种颇具潜力的生物催化剂。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 肿瘤免疫治疗是通过调节机体的免疫功能来控制和杀伤肿瘤的一种治疗手段。针对免疫检查点的治疗等一系列临床突破使得肿瘤的免疫治疗受到了广泛重视。目前，抗体治疗和过继性细胞治疗是肿瘤免疫治疗的主要方式，但是这些方法仍具有副作用较强，实体瘤治疗难以实现，治疗费用高昂等缺点。因此改进和发展更加高效、安全、低成本的新技术仍十分必要。适配体是利用指数富集的配体系统进化技术筛选得到的单链寡核苷酸，有核酸“抗体”之称。适配体具有低免疫原性，组织穿透力强，易于化学合成与修饰等优势，且与其靶标的结合具有较好亲和力和特异性，可像抗体一样实现肿瘤的免疫治疗。本文对适配体在肿瘤免疫治疗相关技术中的新应用作一综述，主要包括基于免疫检查点的抗肿瘤作用、双特异性适配体的肿瘤免疫治疗、适配体靶向递送siRNA的肿瘤免疫治疗和适配体联合抗体的肿瘤免疫治疗几个方面。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 利用甲醇营养型毕赤酵母生产猪干扰素（pIFN-），诱导过程一般在高细胞密度、定值控制甲醇浓度于5-10 g/L下进行，此时、溶解氧浓度（DO）自然下降到接近于0的水平。如果高好氧的毕赤酵母长期处在高甲醇/低DO的诱导浓度环境会导致其代谢活性恶化；胞内甲醇积累严重；pIFN-表达生产效率低。为此，提出了一种甲醇周期诱导控制策略来强化pIFN-生产。先将甲醇控制于高浓度达7 h；再降低甲醇流加速率、将DO控制在~20%约4 h，一共重复6个循环。采用上述周期控制策略，毕赤酵母代谢活性可以长期维持在较高水平；胞内甲醇处于极低水平（≤ 0.003 g/g-DCW）、解除了甲醇毒性效应；pIFN-活性达到3.90×107 IU/mL的最高水平，是定值控制甲醇浓度时的1.86倍。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 固定化酶作为一种绿色高效的生物催化剂，其性能远超游离酶。目前酶的固定化技术适用范围仍然较小，酶的研究范围多停留在模型酶阶段，扩大固定化酶的研究范围具有十分重要的意义。金属有机骨架材料（MOFs）作为酶固定化的载体在近些年得到了广泛的探索，但是具有生物功能的酶-MOFs复合材料的许多特性仍有待挖掘。本文采用仿生矿化的合成方法将5-羟甲基糠醛氧化酶（HMFO）固定到以沸石咪唑酯（ZIF-8）为代表的MOFs材料中，制备得到一种新的生物催化剂HMFO@ZIF-8，扫描电子显微镜表征其形态区别于经典的菱形十二面体。采用考马斯亮蓝法测定蛋白质浓度，计算得到酶的固定化效率达到89.0%。HMFO@ZIF-8催化5-羟甲基糠醛的转化率达到84.3%，收率和选择性均高于游离酶。本文拓展了MOFs固定化酶的研究范围，为研究其他生物大分子复合材料的生物催化剂提供一定的借鉴意义。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 目的：基于GC-FID法，对狂犬病疫苗生产过程中采用的β-丙内酯灭活剂进行了含量及稳定性研究。方法：气相色谱条件：采用Agilent DB-624（30 m×0.530 mm×3.00 μm）毛细管柱；升温程序：初始温度为80 ℃，保持1 min，以20 ℃/min的速率升温至200 ℃，保持3 min；色谱柱流量：3 mL/min；检测器温度：250 ℃；进样口温度：150 ℃；载气：氮气，线速度：25 cm/sec；进样量：1 μL，分流比为2:1，进样方式：手动进样。结果：以乙腈作为稀释剂，BPL在1:100～1:32000范围内线性关系良好（R2≥0.999）。在1:200、1:1000、1:8000 三个浓度水平下，加标回收率在95.04%～116.86%之间，相对标准偏差（RSD）为2.6%～3.2%，检测限为0.112 μg/mL。结论：该方法简便、专属性强、稳定且在室温条件下操作，大大降低了对试验条件和技术操作的要求，能够满足灭活狂犬病病毒工艺中对BPL检测的需求。
分类： 生物学 >> 生物工程 提交时间： 2019-01-17 合作期刊: 《中国生物工程杂志》
摘要： 细菌中普遍存在L/D型氨基酸，与L-氨基酸（L-AAs）不同，D-氨基酸（D-AAs）不参与蛋白质合成，而与细胞壁肽聚糖的合成有关，直接影响细菌细胞壁的形状、数量和强度。D-AAs在细菌表征、药物抑菌性、靶标确定等方面具有重要的作用。目前，外源添加D-AAs参与肽聚糖合成的机制已有一些研究进展，其荧光衍生物已应用于细菌可视化，特异性探测细胞壁形成/重塑、细菌生长和细胞形态。但D-AAs如何影响细菌生长及其抗逆性的机制尚未研究清楚。本文对D-AAs的研究现状进行了综述，重点介绍了D-AAs在细菌中的生物合成和参与细胞壁合成的机制，非典型D-AAs对细菌的调控以及在细菌可视化中的应用，并对D-AAs未来研究方向进行了展望。
分类： 地球科学 >> 地理学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： This study explored the hydrological and economic feasibility of managed aquifer recharge (MAR) using tertiary treated wastewater (TWW) to mitigate salinity in the coastal aquifer of Jamma, Oman. A steady-state groundwater flow and transport model, using MODFLOW software, was developed and calibrated. Different managerial scenarios were simulated and the results reveal that the Jamma aquifer will be further deteriorated in the next 20 a if it remains unmanaged. The groundwater table will decline further by more than 3 m on average; and the iso-concentration salinity line of 1500 mg/L will advance 2.7 km inland, which will severely affect the farming activities in the area. However, MAR using TWW when integrated with the management of groundwater abstraction (e.g., using modern irrigation systems to reduce the abstraction rate) becomes hydrologically feasible to augment the aquifer storage and control seawater intrusion, and hence improves the farming activities. The results indicate that: (1) injecting TWW in the vicinity of irrigation wells (Scenario A2); (2) investing in smart water meters and online control of pumping from the wells to reduce the abstraction rate by 25% (Scenario B); and (3) a combination of both (Scenario B2) are feasible scenarios with positive net present values. Recharge in upstream areas is found not economically feasible because of the very high investment cost of the installation of pipes to transport the TWW over a distance of 12.5 km. Because of securing funds are challenging, Scenario B would be the best option and the second-best option is Scenario A2. Scenario B2 has the lowest net benefit investment ratio and is very attractive because it entails integrated demand and supply management of groundwater. It is required to reduce pumping and to invest in injecting TWW to improve groundwater quality in the vicinity of irrigation wells and to form a hydrological barrier to control seawater intrusion in the long run.
分类： 地球科学 >> 地理学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： In semi-arid region of northwestern China, underground mining subsidence often results in decreased vegetation coverage, impoverishment of soil fertility and water stress. In addition, the physical-chemical and biological properties of soil also change, resulting in more susceptible to degradation. In particular, subsidence causes disturbance of the symbioses of plant and microbe that can play a beneficial role in the establishment of vegetation communities in degraded ecosystems. The objective of this study was to evaluate the effects of revegetation with exotic arbuscular mycorrhizal fungi (AMF) inoculum on the chemical and biological properties of soil over time in mining subsidence areas. Soils were sampled at a depth up to 30 cm in the adjacent rhizosphere of Amorpha fruticose Linn. from five reclaimed vegetation communities in northwestern China. In August 2015, a field trial was set up with five historical revegetation experiments established in 2008 (7-year), 2011 (4-year), 2012 (3-year), 2013 (2-year) and 2014 (1-year), respectively. Each reclamation experiment included two treatments, i.e., revegetation with exotic AMF inoculum (AMF) and non-AMF inoculum (the control). Root mycorrhizal colonization, glomalin-related soil protein (GRSP), soil organic carbon (SOC), soil nutrients, and enzyme activities were also assessed. The results showed that mycorrhizal colonization of inoculated plants increased by 33.3%–163.0% compared to that of non-inoculated plants (P<0.05). Revegetation with exotic AMF inoculum also significantly improved total GRSR (T-GRSP) and easily extracted GRSP (EE-GRSP) concentrations compared to control, besides the T-GRSP in 1-year experiment and the EE-GRSP in 2-year experiment. A significant increase in SOC content was only observed in 7-year AMF reclaimed soils compared to non-AMF reclaimed soils. Soil total N (TN), Olsen phosphorus (P) and available potassium (K) were significantly higher in inoculated soil after 1–7 years of reclamation (except for individual cases), and increased with reclamation time (besides soil Olsen P). The exotic AMF inoculum markedly increased the average soil invertase, catalase, urease and alkaline phosphatase by 23.8%, 21.3%, 18.8% and 8.6%, respectively (P<0.01), compared with the control. Root mycorrhizal colonization was positively correlated with soil parameters (SOC, TN and soil available K) and soil enzyme activities (soil invertase, catalase, urease and alkaline phosphatase) in both AMF and non-AMF reclaimed soils (P<0.05), excluding available K in non-AMF reclaimed soils. T-GRSP (P<0.01) and EE-GRSP (P<0.05) were significantly correlated with the majority of edaphic factors, except for soil Olsen P. The positive correlation between root mycorrhizal colonization and available K was observed in AMF reclaimed soils, indicating that the AMF reclaimed soil with a high root mycorrhizal colonization could potentially accumulate available K in soils. Our findings concluded that revegetation with exotic AMF inoculum influenced soil nutrient availability and enzyme activities in the semi-arid ecosystem, suggesting that inoculating AMF can be an effective method to improve soil fertility and support restoration of vegetation communities under poor conditions like soil nutrient deficiency and drought.
分类： 生物学 >> 生态学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： Soil water content (SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate change. However, there is a knowledge gap regarding the large-scale spatial distribution of SWC in this region. The specific objectives of this study were to determine the spatial distribution patterns of SWC across the Hexi Corridor and identify the factors responsible for spatial variation of SWC at a regional scale. This study collected and analyzed SWC in the 0–100 cm soil profile from 109 field sampling sites (farmland, grassland and forestland) across the Hexi Corridor in 2017. We selected 17 factors, including land use, topography (latitude, longitude, elevation, slope gradient, and slope aspect), soil properties (soil clay content, soil silt content, soil bulk density, saturated hydraulic conductivity, field capacity, and soil organic carbon content), climate factors (mean annual precipitation, potential evaporation, and aridity index), plant characteristic (vegetation coverage) and planting pattern (irrigation or rain-fed), as possible environmental variables to analyze their effects on SWC. The results showed that SWC was 0.083 (±0.067) g/g in the 0–100 cm soil profile and decreased in the order of farmland, grassland and forestland. The SWC in the upper soil layers (0–20, 20–40 and 40–60 cm) had obvious difference when the mean annual precipitation differed by 200 mm. The SWC decreased from southeast to northwest following the same pattern as precipitation, and had a moderate to strong spatial dependence in a large effective range (75–378 km). The SWC showed a similar distribution and had no significant difference between soil layers in the 0–100 cm soil profile. The principal component analysis showed that the mean annual precipitation, geographical position (longitude and latitude) and soil properties (soil bulk density and soil clay content) were the main factors dominating the variance of environmental variables. A stepwise linear regression equation showed that plant characteristic (vegetation coverage) and soil properties (soil organic carbon content, field capacity and soil clay content) were the optimal factors to predict the variation of SWC. Soil clay content could be better to explain the SWC variation in the deeper soil layers compared with the other factors.
分类： 生物学 >> 生态学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： Soil salinization is a serious ecological and environmental problem because it adversely affects sustainable development worldwide, especially in arid and semi-arid regions. It is crucial and urgent that advanced technologies are used to efficiently and accurately assess the status of salinization processes. Case studies to determine the relations between particular types of salinization and their spectral reflectances are essential because of the distinctive characteristics of the reflectance spectra of particular salts. During April 2015 we collected surface soil samples (0–10 cm depth) at 64 field sites in the downstream area of Minqin Oasis in Northwest China, an area that is undergoing serious salinization. We developed a linear model for determination of salt content in soil from hyperspectral data as follows. First, we undertook chemical analysis of the soil samples to determine their soluble salt contents. We then measured the reflectance spectra of the soil samples, which we post-processed using a continuum-removed reflectance algorithm to enhance the absorption features and better discriminate subtle differences in spectral features. We applied a normalized difference salinity index to the continuum-removed hyperspectral data to obtain all possible waveband pairs. Correlation of the indices obtained for all of the waveband pairs with the wavebands corresponding to measured soil salinities showed that two wavebands centred at wavelengths of 1358 and 2382 nm had the highest sensitivity to salinity. We then applied the linear regression modelling to the data from half of the soil samples to develop a soil salinity index for the relationships between wavebands and laboratory measured soluble salt content. We used the hyperspectral data from the remaining samples to validate the model. The salt content in soil from Minqin Oasis were well produced by the model. Our results indicate that wavelengths at 1358 and 2382 nm are the optimal wavebands for monitoring the concentrations of chlorine and sulphate compounds, the predominant salts at Minqin Oasis. Our modelling provides a reference for future case studies on the use of hyperspectral data for predictive quantitative estimation of salt content in soils in arid regions. Further research is warranted on the application of this method to remotely sensed hyperspectral data to investigate its potential use for large-scale mapping of the extent and severity of soil salinity.
分类： 生物学 >> 植物学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： Vegetation roots contribute to soil fixation and reinforcement, thus improving soil resistance against erosion. Generally, the amount of soil fixation presented by roots mainly depends on root density and tensile strength. In the present study, we conducted the research in order to further understand the biotechnical properties of Haloxylon persicum and also to quantify its role in increasing soil cohesion in arid lands of Iran. Ten H. persicum shrubs were randomly selected for root distribution and strength investigations, in which five samples were set on flat terrain and other five samples on a moderate slope terrain. The profile trench method was used to assess the root area ratio (RAR) as the index of root density and distribution. Two profiles were dug around each sample, up and downslope for sloped treatment and north and south sides for flat treatment. The results showed that RAR increased with increasing soil depth and significantly decreased in 40–50 cm layers of downhill (0.320%) and 50–60 cm for uphill (0.210%). The minimum values for the northward and southward profiles were 0.003% and 0.003%, respectively, while the maximum values were 0.260% and 0.040%, respectively. The relationship between the diameter of root samples and root tensile strength followed a negative power function, but tensile force increased with increasing root diameter following a positive power function. The pattern of increased cohesion changes in soil profile was relatively similar to RAR curves. The maximum increased cohesion due to the presence of roots in uphill and downhill sides were 0.470 and 1.400 kPa, respectively. In the flat treatment, the maximum increased cohesions were 0.570 and 0.610 kPa in northward and southward profiles, respectively. The analysis of variance showed that wind and slope induced stresses did not have any significant effect on the amount of increased cohesion of H. persicum. The findings served to develop knowledge about biotechnical properties of H. persicum root system that can assist in assessing the efficiency of afforestation and restoration measures for erosion control in arid lands.
分类： 生物学 >> 生态学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： With the aim to investigate if the halophyte Halothamnus iraqensis Botsch. can be suitable for re-vegetation and remediation of salt-affected lands, this study evaluated (1) the effects of photoperiod, thermoperiod, storage period and wings' presence on its seed germination, and (2) the ability of its seeds to have successful germination recovery after salt stress. Germination tests in different photoperiods (12 h light/12 h darkness and total darkness) and thermoperiods (15°C/20°C and 20°C/25°C) were conducted for seeds collected in 2012, 2013, 2014, 2015 and 2016. The seeds collected in 2016 were sown under different salinity levels (0, 100, 200, 400 and 600 mM NaCl) to assess the salinity tolerance during the germination. Wings' presence highly inhibited seed germination of this species in both photoperiods and thermoperiods under all salinity level treatments. In addition, the germination recovery occurred well when seeds were deprived of their wings. The photoperiod of 12 h light/12 h darkness and the thermoperiod of 15°C/20°C were the best conditions for seed germination. Germination percentages of H. iraqensis seeds decreased with the increasing storage duration, especially after three years of the collection. In addition, H. iraqensis seeds were able to germinate under different salinity levels, and their germination percentages decreased with increasing salinity levels. H. iraqensis seeds have the ability to recover their germination after alleviating the salt stress, irrespective of photoperiod, highlighting the halophilous character of this species.
分类： 生物学 >> 生态学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： Intraspecific trait variation and heritability in different environmental conditions not only suggest a potential for an evolutionary response but also have important ecological consequences at the population, community, and ecosystem levels. However, the contribution of quantitative trait variation within a grassland species to evolutionary responses or ecological consequences is seldom documented. Leymus chinensis is an important dominant species in semi-arid grasslands of China, which has seriously suffered from drought and high temperature stresses in recent decades. In the present study, we measured variation and heritability of 10 quantitative traits, namely the number of tillers, maximum shoot height, number of rhizomes, maximum rhizome length, rhizome mass, aboveground mass, root mass, maximum net photosynthetic rate (Pmax), specific leaf area (SLA), and leaf length to leaf width ratio (LL/LW), for 10 genotypes of L. chinensis under one non-stress (Ck) condition and three environmental stress conditions (i.e., drought (Dr), high temperature (Ht), and both drought and high temperature (DrHt)). Result indicated that (1) the interaction of genotype and environmental condition (G×E) was significant for 6 traits but not significant for the other 4 traits as shown by two-way analysis of variance (ANOVA), suggesting that different selection forces were placed for different traits on the factors dominating phenotypic responses to different environmental conditions. Moreover, these significant G×E effects on traits indicated significantly different phenotypic adaptive responses among L. chinensis genotypes to different environmental conditions. Additionally, individuals could be grouped according to environmental condition rather than genotype as shown by canonical discriminant analysis, indicating that environmental condition played a more important role in affecting phenotypic variation than genotype; (2) by one-way ANOVA, significant differences among L. chinensis genotypes were found in all 10 traits under Ck and Dr conditions, in 8 traits under DrHt condition and only in 4 traits under Ht condition; and (3) all 10 traits showed relatively low or non-measurable broad-sense heritability (H2) under stress conditions. However, the lowest H2 value for most traits did not occur under DrHt condition, which supported the hypothesis of 'unfavorable conditions have unpredictable effects' rather than 'unfavorable conditions decrease heritability'. Results from our experiment might aid to improve predictions on the potential impacts of climate changes on L. chinensis and eventually species conservation and ecosystem restoration.
分类： 地球科学 >> 地理学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： This study aimed to investigate the interaction between regions with different climatic conditions (arid vs. semi-arid) and management (protected vs. unprotected) on the turnover and nestedness of vegetation in relation to physical, chemical and biological properties of soils in the Ilam Province of Iran. In each of the two regions, we sampled 8 sites (4 managed and 4 unmanaged sites) within each of which we established 4 circular plots (1000 m2) that were used to investigate woody species, while two micro-plots (1 m×1 m) were established in each 1000-m2 plot to analyze herbaceous species. In each sample unit, we also extracted three soil samples (0–20 cm depth) for measuring soil properties. The results indicated that the interaction between region and conservational management significantly affected the percent of canopy cover of Persian oak (Quercus brantii Linddl), soil respiration, substrate-induced respiration, as well as beta and gamma diversities and turnover of plant species. The percent of oak canopy cover was positively correlated with soil silt, electrical conductivity, available potassium, and alpha diversity, whereas it was negatively correlated with plant turnover. In addition, plant turnover was positively related to available phosphorus, while nestedness of species was positively related to organic carbon and total nitrogen. According to these results, we concluded that physical, chemical, and biological characteristics of limited ecological niche generally influenced plant diversity. Also, this study demonstrated the major contribution of the beta diversity on gamma diversity, especially in semi-arid region, because of the higher heterogeneity of vegetation in this area.
分类： 地球科学 >> 地理学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： Snowfall is one of the dominant water resources in the mountainous regions and is closely related to the development of the local ecosystem and economy. Snowfall predication plays a critical role in understanding hydrological processes and forecasting natural disasters in the Tianshan Mountains, where meteorological stations are limited. Based on climatic, geographical and topographic variables at 27 meteorological stations during the cold season (October to April) from 1980 to 2015 in the Tianshan Mountains located in Xinjiang of Northwest China, we explored the potential influence of these variables on snowfall and predicted snowfall using two methods: multiple linear regression (MLR) model (a conventional measuring method) and random forest (RF) model (a non-parametric and non-linear machine learning algorithm). We identified the primary influencing factors of snowfall by ranking the importance of eight selected predictor variables based on the relative contribution of each variable in the two models. Model simulations were compared using different performance indices and the results showed that the RF model performed better than the MLR model, with a much higher R2 value (R2=0.74; R2, coefficient of determination) and a lower bias error (RSR=0.51; RSR, the ratio of root mean square error to standard deviation of observed dataset). This indicates that the non-linear trend is more applicable for explaining the relationship between the selected predictor variables and snowfall. Relative humidity, temperature and longitude were identified as three of the most important variables influencing snowfall and snowfall prediction in both models, while elevation, aspect and latitude were of secondary importance, followed by slope and wind speed. These results will be beneficial to understand hydrological modeling and improve management and prediction of water resources in the Tianshan Mountains.
分类： 地球科学 >> 地理学 提交时间： 2019-01-17 合作期刊: 《干旱区科学》
摘要： The countries of Central Asia are collectively known as the five ''-stans'': Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan and Kazakhstan. In recent times, the Central Asian region has been affected by the shrinkage of the Aral Sea, widespread desertification, soil salinization, biodiversity loss, frequent sand storms, and many other ecological disasters. This paper is a review article based upon the collection, identification and collation of previous studies of environmental changes and regional developments in Central Asia in the past 30 years. Most recent studies have reached a consensus that the temperature rise in Central Asia is occurring faster than the global average. This warming trend will not only result in a higher evaporation in the basin oases, but also to a significant retreat of glaciers in the mountainous areas. Water is the key to sustainable development in the arid and semi-arid regions in Central Asia. The uneven distribution, over consumption, and pollution of water resources in Central Asia have caused severe water supply problems, which have been affecting regional harmony and development for the past 30 years. The widespread and significant land use changes in the 1990s could be used to improve our understanding of natural variability and human interaction in the region. There has been a positive trend of trans-border cooperation among the Central Asian countries in recent years. International attention has grown and research projects have been initiated to provide water and ecosystem protection in Central Asia. However, the agreements that have been reached might not be able to deliver practical action in time to prevent severe ecological disasters. Water management should be based on hydrographic borders and ministries should be able to make timely decisions without political intervention. Fully integrated management of water resources, land use and industrial development is essential in Central Asia. The ecological crisis should provide sufficient motivation to reach a consensus on unified water management throughout the region.
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