Floristic Study of Vascular Plants in Typical Plant Communities in the Middle and Upper Reaches of the Yarlung Zangbo River

[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River,quadrat (line transect) method was applied to investigate the phytocoenoses in sample plots,and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results]① There are 96 species (including subspecies and variations),69 genera of 35 vascular plant families,accounting for 16.83%,5.48%,1.66% and 11.63%,2.02%,0.31% of total vascular plant families,genera and species in Tibet and China.② There are 24 monotypic-genus families,accounting for 68.57% of the total family number in the local area;22 monotypic-species families,accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict,such as Euphorbiaceae,Rubiaceae,Liliaceae and Ranunculaceae,they are all ancient primitive groups of the third flora and the fourth flora.③ Local vascular plant genera fall into 10 areal types and 8 variations.④ Temperate elements are much more than tropical elements,R/T is 0.19,indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera,but more endemic species to the local area,and these species are closely related,of which there are some transitional species,indicating that local flora is too young to experience more differentiation and specialization.⑤ There are 24 Chinese endemic species,accounting for 25% of total number of species in the local area;among which there are 12 endemic species to Tibet,accounting for 50% of endemic species to China,12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions]① There are scarce plant groups in the local area.② Among the obvious advantages,single-genus (species) families possess the absolute advantage,and the flora has ancient origins.③ The local flora has diversified distribution types,and the complicated geographical elements.④ Temperate species possess obvious advantages,and the flora is young.⑤ Rich unique and rare species have high species diversity protection and research value.

Analysis on Landscape Pattern in the Upper and Middle Reaches of Yarlung Zangbo River:Taking Zhongba County,Angren County, Rikaze City as Example

Taking Zhongba County, Angren County, Rikaze City located at the Upper and Middle Reaches of Yarlung Zangbo River as landscape units , this paper studied the difference of the landscape pattern under various degrees of human disturbance in the three areas. The results showed that： the three areas all reflected the same characteristic of landscape pattern in Qinghai-Tibet Plateau, the natural landscapes were in the absolute dominant position. However, from Zhangba to Rikaze, with human disturbance intensity increasing, anthropogenic features of landscapes became more and more outstanding, In Zhongba, the landscape structure appeared to be simpler with coarse grains and a less rich diversity, Conversely, in Rikaze, the landscape showed a complicated shape with finer grains and a relatively richer diversity, This reflected that the impact of human activities to natural landscape behaved a gradually-growing trend from the upper reach to the middle one of Yarlung Zangbo River Basin.

Unsteadiness of COD in the Upper and Middle Reaches of Minjiang River

This paper explores and identifies the rules of the unsteady evolution of COD in the upper and middle reaches of Minjiang River through multi-scale analysis on the weekly COD data for the last six years provided by the Water Quality Monitoring Station,Minjiang River Bridge,Leshan City,Sichuan Province.The results of the wavelet analysis indicate that the COD index oscillates alternatively and differently at each time-scale in an oneyear cycle,and the density of COD,subjected to the runoff volume,the effects of Wenchuan Earthquake and agricultural seeding and industrial construction,etc.,is high in winter and spring,mild in summer and autumn.

The SIA method for spatial analysis of precipitation in the upper-middle reaches of the Yangtze River

Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.

Reconstructing the extraordinary palaeoflood events during 3200-2800 a BP in the upper reaches of Hanjiang River Valley, China

Palaeoflood hydrology study is a leading subject in global change study. Through field investigation in the upper reaches of Hanjiang River, palaeoflood slackwater deposits （SWD） were found in the bedrock gorges of the Yunxi reach. The results of field observation, laboratory analysis including particle-size distribution and magnetic susceptibility, and com- parison with modern flood deposits, the SWD were identified as the most typical Holocene palaeoflood deposits of the Hanjiang River. By using stratig;aphic correlation and OSL dating method, the palaeoflood event was dated to be 3200-2800 a BP at the turn from the middle to late Holocene. According to the palaeoflood peak stage and hydraulic parameters, the peak discharges of the palaeoflood were reconstructed as 48,830-51,710 m3/s by using the slope-area method. At same time, the flood peak discharges of 1983, 2005 and 2010 severe floods were reconstructed with the same method and hydraulic parameters in the same cross section. The error between the reconstructed and gauged discharges was 1.99%-4.21%. This showed that the reconstructed palaeoflood peak discharges were reliable. The flood peak discharge-frequency relationship at 10,000-year time scale was established by a com- bination of the gauged flood, historical flood and palaeoflood hydrological data. These results are very important for hydraulic engineering and flood mitigation on the Hanjiang River.

ANALYSIS OF THE MICROPHYSICAL STRUCTURE OF RADIATION FOG IN XUANEN MOUNTAINOUS REGION OF HUBEI,CHINA

Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle reaches of the Yangtze River, and compares them with findings in other areas. Results are as follows: radiation fog in Xuanen is evidently weaker in droplet number concentration and liquid water content than land fogs in other areas. Its liquid water content fluctuates obviously, 0.01g/m3 with visibility of 1,000 meters, which is quite different from that in urban areas, but similar to the Nanling Mountains. Bi-modal droplet distribution is likely to occur in Xuanen mountain radiation fog(MRF) events. Statistical analysis shows that the observed droplet size distribution can be piecewise described well by the Gamma distribution. There is a positive correlation between liquid water content, fog droplet concentration and mean radius, especially in the development and dissipation stage. Condensation growth and droplet evaporation are major processes of Xuanen MRF. The dissipation time coincided with the time when the grass temperature reached the peak value, which indicated that dew evaporation is a key role in maintaining Xuanen MRF. In the early stage of dense fog's growth, droplets with diameter of over 20 micrometers can be observed with visibility of800-1,000 m, which might be caused by the transportation of low cloud droplets to earth's surface by turbulence. Big droplets in the initial stage correspond to higher water content, leading to the higher observed value of water content of Xuanen MRF.

生态调度控制汉江中游入侵沉水植物过度生长效果研究

针对汉江中游江段入侵沉水植物伊乐藻(Elodea nuttallii)过度生长的问题,以2019年调查监测为基础,采用生物量、分布面积、流速、流量等指标,于2020-2021年在汉江丹江口水库联合王甫洲水利枢纽开展了控制伊乐藻过度生长的生态调度试验并评估其生态效果。结果表明:(1)丹江口−王甫洲区间适宜入侵沉水植物伊乐藻生长的水域面积达16.8 km^(2),主要分布在坝前两岸浅水区、泄水闸上游洲滩、水岸新城、中洲岛、木排港、羊皮滩等区域;(2)生态调度的控制效果显著,伊乐藻生物量和分布面积呈逐年减少趋势,其年度峰值生物量变化与春季萌发期1-3月流量极值比(r=-0.997)和生长旺盛期4−8月平均流量(r=-0.963)的相关系数均大于0.9,与全年平均流量(r=-0.748)和4−8月平均水温(r=0.732)的相关系数大于0.7,流量(流速)和水温是影响伊乐藻生物量的关键因子;(3)根据王甫洲坝前漂浮伊乐藻日打捞量与入库流量统计,可以对伊乐藻成熟团聚体产生明显冲刷影响的王甫洲入库流量(即丹江口水库下泄流量)条件为不小于1500m^(3)/s;丹江口水库峰值流量为3500m^(3)/s的单次汛期调度过程,可减少研究区间内约40%的伊乐藻生物量。

长江中上游重要渔业水域环境质量评估

为准确评估长江中上游重要渔业水域水环境质量现状及变化趋势,提高水质评价效率,本研究基于11个水质参数,采用水质指数法(water quality index,WQI)对2006-2021年长江中上游三个重要渔业水域水质进行了综合评价,建立WQI min综合评价模型。结果显示:(1)长江中上游重要渔业水域的水温和高锰酸盐指数呈上升趋势;基于地表水环境质量标准(GB38338-2002),单因素水质评价结果表明监测水域内整体水质处于地表水Ⅴ类水标准,部分年份达劣Ⅴ类,主要污染指标为总氮。(2)通过综合评价方法分析,长江中上游重要渔业水域整体为“良”;2006~2021年长江中上游重要渔业水域水质质量呈逐年改善的趋势,且上游保护区的改善较大。(3)基于WQI方法,确定了长江中上游重要渔业水域的关键水质参数为:总氮、高锰酸盐指数、汞、溶解氧、氨氮、悬浮物以及水温,分别构建了上游保护区、中华鲟保护区以及四大家鱼保护区的WQI_(min)模型;考虑权重和不考虑权重的WQI min模型对比分析表明,考虑权重的WQI min模型的水质评价结果更加准确,该方法可有效评估长江中上游重要渔业水域的水质变化特征并可扩展用于其他水域。

1951—2020年黄河上中游径流变化特征及归因分析

【目的】河川径流是地表重要的水资源,对其变化特征和原因进行解析,是流域水资源科学管理规划的前提。【方法】本文采用Mann-Kendall趋势检验、Pettitt突变检验、Budyko弹性系数法等方法分析了黄河上游和中游近70年(1951—2020年)径流变化的趋势和成因。【结果】(1)1951—2020年黄河上游年降水量呈不显著增加趋势(4.04 mm/(10 a),P> 0.05),中游呈不显著减少趋势(4.90 mm/(10 a),P> 0.05);上游、中游年潜在蒸散发均呈不显著增加趋势(1.77、2.23 mm/(10 a),P> 0.05);(2)黄河上游和中游1980—2020年土地利用/覆盖变化明显,主要表现在林草面积的增加,上游、中游年NDVI分别以0.025/(10 a)、0.042/(10 a)的速率显著增加(P <0.01);(3)1951—2020年,上游和中游年径流量分别以3.46、7.46 mm/(10 a)的速率显著减少(P <0.01),并分别在1986年、1990年发生突变;(4)上游和中游径流对降水变化最为敏感,其次是土地利用/覆盖变化、潜在蒸散发变化,且径流对各影响因子的敏感性逐年增强,即气候和土地利用/覆盖的变化将更容易引起径流的变化;(5)土地利用/覆盖变化是导致黄河上游和中游径流减少的主要原因,其次是降水和潜在蒸散,但各影响因子对径流变化的影响性质和程度在上游和中游不同区间存在一定的差异。其中,上游地区降水、潜在蒸散发、土地利用/覆盖变化对径流的影响性质和程度分别为-14.04%、1.30%、112.73%;中游地区分别为21.54%、3.63%、74.83%。【结论】1951—2020年黄河上游和中游径流变化是气候变化和土地利用/覆盖变化共同作用的结果,但主要影响因素为人类活动主导的土地利用/覆盖变化,且各因子对径流的影响在不同区间存在一定的差异。本研究结果可为黄河上游和中游不同区间的水资源管理和综合治理提供理论支持。

2022年夏季汉江中下游水华生消驱动因子及其贡献率量化研究

为探究2022年夏季长江流域“汛期反枯”极端水文条件下汉江中下游首次出现的蓝藻水华成因,选取叶绿素浓度为水华表征指标,考虑各环境因子间的多重共线性关系,采用偏最小二乘回归(PLSR)量化了不同环境因子对汉江中下游仙桃、宗关断面蓝藻水华生消的贡献率。结果表明:(1)仙桃断面叶绿素a浓度与水温、pH、溶解氧和总磷均呈显著正相关关系,与氮磷比呈显著负相关关系;宗关断面叶绿素a浓度与水温、pH、溶解氧均呈显著正相关关系,与日均水位、水位日变幅、流量、总磷和氨氮均呈显著负相关关系;(2)溶解氧、pH和水温对水华生消的贡献程度较高,对仙桃断面的贡献率分别为15.18%、13.68%和14.50%,对宗关断面的贡献率分别为18.06%、15.93%和15.65%;(3)基于偏最小二乘路径模型(PLS-PM)的环境因子解析显示,气象因子是2022年夏季汉江中下游蓝藻水华暴发的诱导因子,水华“萌发”时段可能与汉江中下游涝旱急转时段重叠。建议后续研究结合准确的中长期气象预报信息,在涝旱急转时段优化汉江中下游水华防控调度的下泄流量与下泄时机,提高水华防控效果。

晚清长江中上游民船运输状况——以《长江三峡及重庆游记》为中心的考察

1883年英国商人立德乐通过实勘实测的方法记录了其在长江中上游流域乘坐民船的航行情况,并留下数万字的旅行记录——《长江三峡及重庆游记》,生动再现了晚清我国长江中上游流域传统民船的运输状况。通过对行记的考察可以厘清我国民船的运输情形,自从清代前期长江流域全面贯通以来,逐渐积累了成熟的造船技术、完善的民船运营结构、丰富的行船经验等,都促进了长江民船运输专业化,高效率水运系统的形成。与近代轮船运输相比,传统民船在运输价格、航行范围、运营的灵活性上都具有优势,即使在晚清长江中上游开通轮船运输后,民船运输仍在持续发展。

基于文献计量分析的长江中上游鱼类资源研究综述

针对长江中上游鱼类资源领域研究,以主题“长江上游”“长江中游”“金沙江下游”“鱼类资源”“鱼类早期资源”为检索条件,筛选了2023年7月前中国知网及Web of Science核心合集数据库收录的503篇文献,利用CiteSpace进行文献计量分析并绘制科学知识图谱,在此基础上从文献数量分布、研究机构及代表作者分布、研究主题内容、研究热点及演变趋势方面对长江中上游鱼类资源领域研究进行了综述。结果表明:中国科学院和中国水产科学研究院等是该领域的领军机构;从发展趋势上看,该领域已形成了鱼类资源现状及变化趋势、鱼类资源的影响机制以及鱼类资源的保护对策3个重要的研究热点和方向。后面需进一步完善江段鱼类资源的长期动态监测方法、梯级开发背景下鱼类资源的变动情况以及鱼类资源的协同保护方法等方面的研究。

南水北调中线供水区水域面积变化遥感分析

为更好地研究调水对供水区域水域面积的影响,利用遥感技术研究了南水北调中线工程调水前后供水区及其下游四季的水域面积变化情况及其动因。研究表明:在调水工程实施之后,汉江中下游区域出现了水域面积大幅度下降的情况,汉江流域水域面积从2011年到2015年整体减少,尤其是春夏季水域面积减少最多,春季减少52.6km^(2),夏季减少65.8km^(2),减少比例达到17.3%,秋季和冬季水域面积减少幅度较小,秋季水域面积减少23.4km^(2),冬季水域面积减少最少,为4.2km^(2)。

汉江中下游重要支流目标生态流量分期控制研究

为有效推进河湖生态流量保障体系建设,采用Qp法、Tennant法、近10 a最枯月法、频率曲线法等方法计算分析确定了汉江中下游重要支流控制断面基本生态流量,采用适配法确定各断面生态流量分月泄放目标。研究表明:(1)汉江中下游重要支流控制断面的基本生态流量为1.16~7.50 m^(3)/s,占年均流量的5%~15%。除南河谷城断面受金盆沟电站发电引水导致满足度偏低外,其他断面满足度均高于90%,可作为生态流量管控依据。(2)各断面生存流量分月控制目标为1.16~55.00 m^(3)/s,年泄放量占年均径流量的20%,月均满足度可达80%以上。研究成果可为健全法规体系、强化工程生态调度、汉江流域水资源保护及监督管理提供参考依据。

韩江中上游地区的崩岗分布特征

选取韩江中上游地区2016—2022年的Sentinel-1/2卫星星座遥感影像和其他辅助数据,基于机器学习方法进行区域尺度的崩岗识别和崩岗影响因子测度。结果表明:1)分类模型的总体精度达到84%,Kappa系数为0.8。其中,崩岗识别的用户精度和生产者精度都超过95%,且其FScore为0.97。2)截至2022年,韩江中上游地区的崩岗侵蚀面积共有435.5 km^(2),各县(市、区)崩岗侵蚀面积差异明显,年变化趋势不一。其中,五华县崩岗侵蚀面积最多(199.2 km^(2)),其年平均变化率为16.29 km^(2)/a。梅江区崩岗侵蚀面积最少(1.6 km^(2)),其年平均变化率为0.18 km^(2)/a。3)韩江中上游地区崩岗发生概率与高程、坡度、植被覆盖、地质类型、人口密度、大气压、降雨量、经向风速、纬向风速和风速等10个因素存在显著相关性(P<0.001)。在一定的变化范围内,高程、坡度、地质类型、大气压、经向风速、纬向风速和风速对研究区崩岗发生为正向影响,植被覆盖、人口密度和降雨量对崩岗发生为负向影响。

淮河中上游地区新石器时代中期文化影响研究

淮河中、上游地区处于我国地理单元上的过渡中心,也是史前文化交流碰撞的“漩涡地带”。新石器时代中期两区域以淮河及其支流为纽带开启了文化上的互动交流,并逐步增强。两者之间的文化交流互动直接促进了淮系文化的形成与发展,并对淮河上游所在中原地区文化传播与扩散及早期中国各地考古学文化由分散、孤立走向交流、融合形成相对的文化共同体产生了积极的影响。

汉江中下游皇庄站年最低水位变化及成因分析

近年来汉江中下游多次出现特枯低水位,为探究其原因,分析了1950~2022年汉江中下游干流皇庄站年最低水位变化趋势,并分析了断面、流量、含沙量等引起年最低水位变化的影响因素。结果表明:1950~2022年,皇庄站年最低水位呈明显波动下降趋势。皇庄站历年年最低水位的最高值出现在1954年的1月,为43.59 m;最低值出现在2022年的10月,为38.47 m;多年平均值为41.29 m。最高值与最低值之间变幅为5.12 m。河段的持续冲刷下切是影响皇庄站年最低水位变化的最显著因素;受上游水库群的调蓄及河段内丁坝等航道整治工程影响,皇庄站过水断面持续冲刷下切,导致皇庄站年最低水位变化。

生态环境保护与农业经济高质量发展的协调性--以黄河中上游四省(区)为例

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