Inconsistent increasing of climate potential productivity resulting from global warming and land use transitions in the Dongting Lake Basin,from 2000 to 2020

In the face of global warming and increasing impervious surfaces,quantifying the change of climate potential productivity(CPP)is of great significance for the food production planning.Targeting the Dongting Lake Basin,which is a key area for food production in China,this paper uses meteorological data,as well as Climate Change Initiative Land Cover,and Shuttle Radar Topography Mission digital elevation model to investigate the CPP and its changes from 2000 to 2020.The suitability of land for cultivation(SLC),and the land use/land cover change(LUCC)are also considered.The results showed that the CPP varied from 9,825 to 20,895 kg ha^(-1).Even though the newly added impervious surfaces indirectly resulted in the decrease of CPP by of 9.81×10~8 kg,overall,the CPP increased at an average rate of 83.7 kg ha^(-1)a^(-1).Global warming is the strongest driver behind CPP increase,and CPP has played an important role in the conversions between cultivated land and other land types.The structure of land types tends to be optimized against this challenge.

The spatial-temporal changes of the land use/cover in the Dongting Lake area during the last decade

The research on the land use/cover change is one of the frontiers and the hot spots in the global change research. Based on the Chinese resource and environment spatial-temporal database, and using the Landsat TM and ETM data of 1990 and 2000 respectively, we analyzed the spatial-temporal characteristics of land use/cover changes in the Dongting Lake area during the last decade. The result shows that during the last ten years there were three land-use types that had changed remarkably. The cultivated land decreased by 0.57% of the total cultivated land. The built-up land and water area expanded, with an increase of 8.97% and 0.43% respectively. The conversion between land use types mostly happened among these three land-use types, especially frequently between cultivated land and water area. The land-use change speed of land-use type is different. Three cities experienced the greatest degree of land-use change among all the administrative districts, which means that the land use in these cities changed much quickly. The following changed area was the west and south of the Dongting Lake area. The slowest changed area is the north and east area.

Impact of LUCC on Ecosystem Service Value in the Up and Middle Reaches of Dongting Lake Basin,China

Supported by geographical information system,using Costanza method and referring to terrestrial ecosystem service value in China,the influence of land use and land cover change(LUCC)between 1980 and 2000 on ecosystem service value in the up and middle reaches of Dongting Lake basin was analyzed in this study.The results showed that the estimated value of ecosystem services decreased 8.416 9×108 CNY over a 21-year period,and the main reasons were that the land for forest use was exploited for cropland and construction land use in study area.Further analysis results showed that the value of single ecosystem service function such as gas regulation,climate regulation,soil formation and conservation,biodiversity conservation,raw materials as well as recreation decreased significantly;and that of provision of water conservation,waste treatment and food production increased obviously in the area.The results of coefficient sensitivity analysis indicated that these estimates were reliable.

Automated and refined wetland mapping of Dongting Lake using migrated training samples based on temporally dense Sentinel 1/2 imagery

Wetlands provide vital ecological services for both humans and environment,necessitating continuous,refined and up-to-date mapping of wetlands for conservation and management.in this study,we developed an automated and refined wetland mapping framework integrating training sample migration method,supervised machine learning and knowledge-driven rules using Google Earth Engine(GEE)platform and open-source geospatial tools.We applied the framework to temporally dense Sentinel-1/2 imagery to produce annual refined wetland maps of the Dongting Lake Wetland(DLW)during 2015-2021.First,the continuous change detection(CCD)algorithm was utilized to migrate stable training samples.Then,annual 10 m preliminary land cover maps with 9 classes were produced using random forest algorithm and migrated samples.Ultimately,annual 10 m refined wetland maps were generated based on preliminary land cover maps via knowledge-driven rules from geometric features and available water-related inventories,with Overall Accuracy(OA)ranging from 81.82%(2015)to 93.84%(2020)and Kappa Coefficient(KC)between 0.73(2015)and 0.91(2020),demonstrating satisfactory performance and substantial potential for accurate,timely and type-refined wetland mapping.Our methodological framework allows rapid and accurate monitoring of wetland dynamics and could provide valuable information and methodological support for monitoring,conservation and sustainable development of wetland ecosystem.

Effects of the dispatch modes of the Three Gorges Reservoir on the water regimes in the Dongting Lake area in typical years

Based on the field-survey prototype hydrology data in typical years, the effect during the running periods of different dispatch modes of the Three Gorges Reservoir on the water regimes in Dongting Lake area is comparatively analyzed. The results are shown as follows. （1） The influence periods are from 25 May to 10 June, from 1 July to 31 August, from 15 September to 31 October and from December to the next April, among which the influence of the water-supplement dispatch in the dry season is not very sensitive. （2） During the period under the pre-discharge dispatch, the runoff volume slightly increases as well as both the average water level and the highest water level rise in the usual year. While in the wet and dry years, the average increase in the runoff volume is 40.25×1 08 m3 and the average rises of the average water level and the highest water level are both 1.06 m. （3） As for the flood-storage dispatch, the flood volume increases slightly, in the dry and wet years, the flood volume, the average water level and the highest water level averagely reduce by 444.02×108 m3, 2.64 m and 1.42 m respectively. （4） Under the water-storage dispatch, the runoff volume slightly in- creases and the water level heightens in a sort in the usual year. And in the dry and wet years the average decreases in the runoff volume, the average water leve/and the highest water levels are respectively 185.27×108 m3, 3.13 m and 2.14 m. （5） During the period under the water-supplement dispatch, the runoff volume, the average water level and the highest water levels averagely decline by 337.7×108 m3, 1.89 m and 2.39 m respectively in the usual and wet years. However, in the dry year, the runoff volume increases as well as the average and highest water levels slightly go up.

Variation of water body in Dongting Lake from in situ measurements and MODIS observations in recent decades

Identifying the spatiotemporal dynamics of the water body in Dongting Lake,the second largest freshwater lake in China,is crucial for water resource management.In this study,the variations of the water body were comprehensively analyzed based on remote sensing images and in situ measurements from 2000 to 2019.Four breakpoint detection approaches were integrated to analyze the change trends and explore the related driving forces behind the changes.The results showed that significant intra-and inter-annual fluctuations of the water body were found from 2000 to 2019.The water area and volume decreased at rates of 1.26 km^(2)/a and 16.65×10^(6)m^(3)/a,respectively.During the entire study period,the outflow at Chenglingji station(CLJ),the inflow from three outlets of the Yangtze River(Inflow2),and the inundation conditions during the last period(Arealag)made the largest relative contributions to the water area variation(around 25%,27%and 24%,respectively).A breakpoint was detected around 2004,corresponding to the operation period of the Three Gorges Dam(TGD).The regulation of TGD profoundly affected the hydrological characteristics at the three outlets and CLJ,and may have indirectly caused the water area to expand by 2.41 km^(2)/a during the dry seasons between 2004 and 2019.These results provide valuable insight into how natural and anthropogenic factors affect water body variation and may offer a practical reference for the local government to adjust management strategies.

Industrial Greening of the Dongting Lake Eco-economic Zone

Extensive industrial development is a major challenge to ecological civilization construction. Industrial energy consumption and environmental pollution reduction are desperately needed. The Dongting Lake district, located in Wuhan and the Changsha-Zhuzhou-Xiangtan(CZT)pilot zone, bears the responsibility to ensure national food security and watershed ecological security, and it is an urgent need for the Dongting Lake district to accept the ecological transition of industries. On the analysis of the industrial development status and problems of the Dongting Lake district, some proposals based on the characteristics and reality of the district are pointed out, such as industrial cooperation, proper space layout, ecological innovation, industrial structure upgrading, building of ecological parks, clean production, elimination of backward production capacity, heavy metals governance and so on, as to develop the industrial ecology of the Dongting Lake district.

近60年洞庭湖水位演变态势研究

辨析洞庭湖历史水位演变态势对保护湖泊生态系统健康运转以及确保长江中下游防洪安全和水资源利用均至关重要。为了定量评估洞庭湖近60年来水位变化特征、程度及规律,基于洞庭湖鹿角、杨柳潭和南咀水文站19612020年逐日水位监测数据,应用Mann-Kendall检验法、小波分析法、累积距平法、滑动t检验法等方法对洞庭湖水位变化趋势性、周期性、突变性进行分析,进而采用IHA-RVA法综合评价洞庭湖突变年前后各站点水位改变度和整体水位改变度。研究结果表明:(1)19612020年,鹿角站和杨柳潭站年均水位呈上升趋势,南咀站年均水位呈下降趋势;3个站点水位周期性变化较为明显,呈现4~5个时间尺度的周期变化规律,第一主周期为55~56年;鹿角站水位突变年份为1979、2003年,杨柳潭站水位突变年份为1978、2003年,南咀站水位突变年份为2003年,综合确定2003年为3个站点突变年份。(2)通过分析突变前后3个站点的水位、时间、频率、延时和改变率5组32个水位指标改变度,发现杨柳潭站水位改变度大于鹿角站和南咀站,鹿角、杨柳潭、南咀站的整体水位改变度分别为43%、48%、42%,均属于中度改变。该研究可为进一步解析洞庭湖水文情势演变规律以及为长江中下游通江湖泊水资源合理利用和水生态环境保护提供参考依据和数据支撑。

洞庭湖四水流域水库群联合防洪优化调度

针对多防洪控制点的混联水库群联合防洪调度中防洪目标难以协调的问题,构建了以多流域协调条件下合成洪水洪峰流量最小为目标的水库群联合防洪调度模型,并采用逐步优化-逐次渐进算法(POA-SA)优化求解。在洞庭湖四水流域开展实例研究,基于防洪需求及各水库的特性,以四水流域下游尾闾控制站洪峰流量最小和四水汇流至洞庭湖的合成洪水洪峰流量最小为目标,提出典型年四水流域水库群联合防洪优化调度方案。结果表明:①针对1998年和2017年两场洪水,水库群联合优化调度后的四水合成汇入洞庭湖的洪峰削峰率比四水单独优化调度分别提高了9.4%和4.5%;②资水的柘溪水库和沅江的五强溪水库通过补偿调节,较好地实现了入湖洪水的错峰。对洞庭湖四水流域水库群联合调度可以保障四水流域自身防洪安全,并为洞庭湖防洪减压,研究成果可为流域水库群联合防洪调度提供参考。

1960—2020年千岛湖流域蒸散发演变特征及驱动因素解析

为探究淡水湖库及其所属流域蒸散发演变特征,以及气象因子对蒸散发的影响规律。以长三角地区最大的淡水人工湖和重要的水源地--千岛湖为研究对象,采用Penman-Monteith等方法与WEP-L分布式水文模型,分别计算千岛湖流域1960-2020年潜在蒸散发(ET_(0))与实际蒸散发(ET_(a)),分析二者年际变化趋势及突变年份;采用偏微分方法分析气象因子对ET_(0)的敏感性和贡献度;采用归因分析法分析突变前后气象因子对ET_(a)变化的贡献度,并利用蒸发表面水分指数(EM_(1))解析流域蒸发互补关系。结果表明:ET_(0)与ET_(a)多年平均值分别为1021.7和857.5 mm,整体皆呈减少趋势,倾向率分别为-0.77和-1.03 mm/a,二者均在1980和2000年左右发生突变;ET_(0)对相对湿度变化最为敏感,ET_(0)增加的月份主要是由于相对湿度、平均气温的正贡献,风速呈负贡献但相对较小,ET_(0)减少的月份主要是由于日照时数和风速的负贡献,平均气温呈正贡献但相对较小;ET_(a)空间分布呈现东高西低格局,驱动因素按贡献率大小为相对湿度>风速>日照时数>气温;流域整体存在“蒸发悖论”现象,日照时数和风速的减小是引起ET_(0)近年来下降的主要原因;EM1愈趋近于1时,反映流域ET_(0)和ET_(a)取值愈加接近,蒸散发互补理论在千岛湖流域适用。

洞庭湖营养盐赋存及对水沙情势变化响应综述

洞庭湖水环境营养状况与水沙情势密切相关,水沙情势变化使湖区营养盐赋存状态发生改变,进而对长江中下游流域的水生态安全造成影响。梳理了20世纪50年代以来洞庭湖区水沙情势与营养盐赋存状况的变化特征,总结了水沙条件与营养盐赋存关系的相关研究进展。结果表明:受下荆江裁弯、葛洲坝截流、三峡水库运行等因素影响,荆江三口分流分沙减少,洞庭湖泥沙淤积趋缓,同流量下湖区水位下降。近30 a洞庭湖水体氮磷污染程度加深,沉积物氮磷污染未见显著恶化。三口分流量的减少直接导致水环境容量减小,使总氮浓度升高;分沙量的减少降低了湖区颗粒态磷含量,使总磷浓度减小、溶解态磷占比升高;洞庭湖淤积泥沙营养盐释放是影响湖区水体氮、磷含量的重要因素;湖区水位变化引起的洲滩干湿交替及水生植物群落改变,促进了沉积物中氮、磷蓄积并增加上覆水体营养盐含量。研究成果可为水沙与水环境耦合关系研究提供支撑,为面向湖区水环境改善的水沙调控提供参考。

2010—2019年间洞庭湖流域生态环境状况时空动态特征及影响因素

洞庭湖流域是长江中下游重要生态区,开展其生态环境状况定量监测与评价是进行区域生态保护、修复及治理的先决条件。该文采用2010—2019年MODIS遥感数据产品,基于绿度、湿度、干度和热度4个生态指标构建了洞庭湖流域遥感生态环境指数(remote sensing ecological index,RSEI),并在此基础上研究了流域生态环境状况时空动态特征及其影响因素。结果表明:①2010—2019年洞庭湖流域绿度指标呈增长趋势,湿度指标呈下降趋势,而干度和热度指标变化较为平稳;②洞庭湖流域整体生态环境状况较好,RSEI多年均值为0.58,并呈波动增长,空间上则表现为西部优于东部、四周优于中部的分布格局;③降水、气温、高程以及土地覆盖与RSEI均具有较强相关性。其中,林地RSEI(0.65)最高,建筑用地RSEI(0.31)最低;在流域2种主要土地转化类型中(草地→林地、耕地→草地),“草地→林地”转化有助于促进区域生态环境(ΔRSEI=0.0025,贡献率为46.3%),而后者则有可能导致生态环境恶化(ΔRSEI=-0.0004,贡献率为44.44%)。研究结果有助于深刻把握流域生态环境时空特征及其内在驱动机制,辅助开展科学的土地规划与生态环境治理,因而具有较强的理论与实践意义。

广东省河湖库水域系统时空变化特征及驱动力分析

为研究广东省河湖库水域系统历史变迁发展规律,对其1980—2021年时空变化、景观格局、土地利用转移特征进行分析,并结合相关性系数分析水域变化的驱动因素。结果表明:(1)1980—2021年河流面积持续缩减而水库面积不断增长,二者变化趋势均于1995年发生突变;(2)水域景观格局表现出破碎化、复杂化、离散化的趋势;(3)近40 a内水域周边50 m土地利用的变化主要为河流向水库的转化,同时1995—2021年有大面积的河湖库水域转为城乡、工矿、居民用地;(4)年平均气温、常住人口密度以及经济产值是水域面积及景观格局变化的主要驱动因子。该研究成果明确了广东省河湖库水域的变化特征,可为针对性的水域保护政策制定提供一定的依据。

四川省大型湖泊和水库水体长时序时空变化分析

采用2000—2020年欧盟委员会联合研究中心发布的逐年地表永久水体和季节水体数据集,分析了四川省30个大型湖泊和102个大型水库(水体面积在1 km^(2)以上)的水体时空变化特征,探究了水体与降水和陆地水储量的关系。研究结果表明,2000—2020年大型湖泊和水库整体均呈永久水体面积增加、季节水体面积减少的变化趋势;从个体尺度来看,12个大型湖泊的永久水体面积显著增加,7个大型湖泊的季节水体面积显著减少,89个大型水库的永久水体面积显著增加,43个大型水库的季节水体面积显著减少。大型湖泊和水库的永久水体与年降水量、陆地水储量均存在较高的正相关性,相关系数分别达到0.68和0.90。

基于多情景模拟的洞庭湖流域LUCC与生境质量耦合演变分析

以洞庭湖流域为研究区域,本文设定自然发展(情景1)、快速发展(情景2)、耕地保护(情景3)、生态保护(情景4)和可持续发展(情景5)5种情景模式,利用PLUS模型和InVEST模型模拟2030年5种不同情景下的土地利用和生境质量格局,并采用耦合协调度模型探究不同情景下LUCC与生境质量耦合协调特征.研究结果表明:1)土地利用变化模拟结果基本符合情景设置的要求,能较好地反映洞庭湖流域土地利用的演变规律和规划方向.2)2030年洞庭湖流域生境质量水平为:情景4>情景5>情景3>情景1>情景2.3)2030年情景1、情景2和情景3耦合协调发展水平呈下降趋势,且情景3下降程度略高于情景1和情景2;而情景4和情景5呈上升趋势,且情景4上升程度略高于情景5.4)结合情景设置原则,可以发现情景5为洞庭湖流域LUCC与生境质量耦合协调发展空间格局优化提供了规划发展可行性.

1980—2020年洞庭湖流域土地利用变化及其碳效应

[目的]探查粮食主产区土地利用变化规律及其碳效应,为土地利用结构调整及低碳经济发展提供依据。[方法]基于1980,2000,2020年3期土地利用现状数据,在网格采样法、土地利用动态度模型、碳排放系数法以及空间自相关分析模型支持下,揭示1980年以来洞庭湖流域土地利用变化规律及其碳效应的空间异质性特征。[结果]①洞庭湖流域土地利用阶段性变化。1980—2000年综合动态度为0.02%,其中动态度最大的是建设用地,未利用地次之。2000—2020年综合动态度增至0.18%,建设用地面积增长加快。②净碳效应表现为碳汇,但由1980年的5.93×10^(7)t下降到2020年2.82×10^(7)t,而由土地利用变化引起的碳效应呈现碳排放变化量大于碳汇变化量特点,并导致净碳排放量增加了6.08×10^(5)t,且空间上净碳排放相对高值区呈“H”型分布特点,低值区逐渐扩张。③洞庭湖流域集水小区净碳排放的空间自相关性特征显著。1980—2000年主要聚集类型为高—高型和低—低型,低—高型分布零散,2000—2020年高—高型分布更加集中连片,低—低型主要在湘江流域北部。[结论]在洞庭湖流域,应坚持“碳增汇,碳减排”定位,保持林地的碳汇稳定状态,科学引导高碳排放土地的开发利用,并依据空间自相关特点关注不同集水区的碳排放“同化”作用。

洞庭湖地形变化对洪水过程的影响研究

为了更好地理解地形变化对湖泊洪水过程的影响,采用已构建的长江-洞庭湖二维水动力模型,在洞庭湖2003及2011年实测地形的基础上,以2003年型洪水为例,定量分析了湖泊地形变化对洞庭湖洪水过程的影响。结果表明:2003—2011年洞庭湖超过40%的区域地形下降值大于0.10 m,特别是湘江洪道,其深泓线地形高程平均下降了5.72 m。通过对2003年洪水过程模拟发现,相比于2003年,在2011年地形情况下,以“四水”来流为主导的洪水过程中,南洞庭湖内洪峰水位下降超过0.40 m,西洞庭湖内洪峰水位下降约0.20 m,东洞庭湖内仅在南部地形变化较大区域的水位变化明显;斗米咀-城陵矶河段水面坡降变缓,南洞庭湖内洪道水面坡降变陡。而对于以长江来流为主导的洪水过程,由于长江洪水位的顶托作用,洞庭湖内洪峰水位下降了0.15 m,斗米咀-城陵矶河段及南洞庭湖内水面坡降下降不明显。因此,2003—2011年洞庭湖地形变化对“四水”来流型洪水影响较大,湖盆下切导致湖容增大,可有效缓解洞庭湖内防洪形势,但对长江来流主导的洪水影响较小。研究结果可为洞庭湖内疏浚扩容等防洪工程的开展提供参考。

三峡水库运行前后长江中下游干流及两湖的径流过程变化

为探索三峡水库运行前后长江中下游干流及两湖径流过程的变化及其驱动因素,利用宜昌、监利、大通、七里山、湖口共5个水文站的流量资料,分析了各站径流过程的变化特征及其成因。结论:(1)各站年径流量均减少,但除七里山站之外,其它各站减少比例均小于10%且变化不显著;(2)干流各站月径流量最大减幅发生在10月,而七里山站、湖口站分别发生在7月、4月;(3)干流各站月径流量最大增幅发生在3月,而七里山站、湖口站分别发生在1月、6月;(4)宜昌站,1-4月径流量增加是三峡水库入库径流增加和水库调度的共同作用结果,6-8月径流量减少的主因是三峡水库入库径流量减少,5、9、10月径流量变化的主因是三峡水库调度;(5)监利站,径流量的变化与宜昌站表现出高度的一致性,但冬季各月径流量的增幅均大于宜昌站;(6)大通站,4-6月径流量变化方向与湖口站一致,其它月份变化方向均与宜昌站一致。(7)七里山站,7月径流量减少的主因是洞庭湖流域来水减少,9、10月径流量减少的主要原因是荆江分流减少,但洞庭湖流域来水减少也是重要原因。(8)湖口站,4、5月径流量减少的主因是流域降水减少,9、10月径流量减少的主要原因是鄱阳湖汛期水位降低、低水位提前、蓄水量减少。

洞庭湖区土地利用变化特征及驱动力分析模拟研究

以2000、2005、2010、2015、2020年洞庭湖区的土地利用现状和相关的社会经济数据为研究对象,运用Binary-Logistic二元回归模型分析了不同影响因子与各类用地类型在空间布局上的关联性,借助CA-Markov、MCR模型对研究期内洞庭湖区的土地利用变化、特征以及驱动因子进行了研究与分析。结果表明:(1)2000—2020年洞庭湖区6种地类变化幅度和活跃度均有所提高,其中建设用地占用耕地的程度明显,林地面积呈小幅减少趋势;(2)分析各地类分布与11个影响因子之间的关系,结果表明:ROC检验值均大于0.8,解释能力最好的因子包括坡度、植被覆盖率等;(3)2035年的土地利用模拟情况与2020年的相比,耕地、林地和草地均保持下降趋势,而水域、建设用地和未利用地均保持上升趋势。

洞庭湖流域生境质量对LUCC的动态响应

【目的】探究洞庭湖流域生境质量对土地利用变化的响应机制,为该流域生态环境保护和可持续发展提供参考依据。【方法】基于洞庭湖流域1980—2018年土地利用数据,运用InVEST模型进行生境质量定量评估,并采用地理加权回归模型探究生境质量变化对耕地、林地、草地、水域和建设用地的响应。【结果】1)近40年间洞庭湖流域土地利用类型以耕地和林地为主,呈现出耕地持续萎缩、林地基本稳定和建设用地持续扩张等主要特征,以耕地与林地之间的内部转移及向建设用地转移为主要变化方向;2)洞庭湖流域生境质量水平虽整体处于较高水平,但持续变差,东南西三面环山地带生境质量最高,环洞庭湖平原、湘中南丘陵地区和武陵—雪峰山脉山地生态农业带生境质量次之,各大中城市和小城镇的建成区生境质量最低;3)生境质量对各地类的响应具有显著的时空异质性,林地、草地和水域总体对生境质量产生正面影响,耕地和建设用地与生境质量基本上呈负相关,但各地类在局部地区均存在反向影响。【结论】三面环山地带生境质量变化主要受林地变化的影响,洞庭湖及“湘、资、沅、澧”四水的河谷湖盆和冲积平原生境质量变化的主导地类则为耕地和建设用地。因此,在制定洞庭湖流域生态环境保护政策时,三面环山地带应以生态保护为首要任务,耕地分布较广区域应加快发展生态农业和循环农业,城市化地区应注重土地利用结构生态型和稳定性的提升。