Elevational diversity gradients across seed plant taxonomic levels in the Lancang River Nature Reserve： role of temperature, water and the mid-domain effect

It remains unclear whether the elevational diversity gradients observed in seed plants across different taxonomic levels （family, genus, and species） are driven by the same macro-environmental variables. In this study, seed plant elevational distribution data from the Lancang River Nature Reserve （Yunnan, China） were used to investigate spatial patterns in diversity and their environ- mental correlates, comparing across taxonomic levels. Environmental variables included energy availability, climate seasonality and environmental heterogeneity. All taxonomic levels （family, genus, and species） were found to have strong elevational richness gradients, with the strength of the gradient weakening at higher taxonomic levels. Spatial patterns in richness were explained by a combination of contemporary environmental variables and the mid-domain effect at all taxonomic levels. The independent effects of temperature- and precipitation-related variables were similar in explaining geographical patterns of family, genus and species richness. Energy, seasonality and heterogeneity variables influenced seed plant spatial richness at different taxonomic levels in similar ways.

Regional Mapping of Vertical Hydraulic Gradient Using Uncertain Well Data: A Case Study of the Toyohira River Alluvial Fan, Japan

Vertical hydraulic gradient (VHG) provides detailed information on 3D groundwater flows in alluvial fans, but its regional mapping is complicated by a lack of piezometer nests and uncertainty in conventional well data. Especially, determining representative depth of well screen in each well is problematic. Here, a VHG map of the Toyohira River alluvial fan, Sapporo, Japan, is constructed based on groundwater table elevation (GTE), using available well-data of various screen lengths and depths. The water-level data after 1988, when subway constructions are mostly completed in the city, are divided into those of shallow wells (≤20 m deep), and those of deep wells (>20 m deep). First, the GTE map is generated by kriging interpolation of shallow well data with topographic drift. Next, the individual VHG value of each deep well is calculated using its top, middle, and bottom elevations of the screen depths, respectively. The VHG maps of three cases are then obtained using neighborhood kriging. The VHG map of the bottom screen depths has proven most valid by cross-validation. The VHG map better visualizes that downward flows of groundwater are predominant over the fan. Positive area of VHG is mostly vanished around the fan-toe, indicating urbanization effect such as artificial withdrawals. A negative peak of VHG corresponds to recharge area, and is seen along the distinct losing section in the river. The negative peak also expands upstream to the fan-apex where a basement is suddenly depressed.

安宁河流域生态系统服务价值地形梯度分异及其驱动因素

探究安宁河流域生态系统服务价值(ecosystem service value,ESV)的地形梯度分布规律及其空间分异的驱动因子,对流域实施因地制宜的国土空间规划和生态环境保护策略具有积极意义。利用2000—2020年高精度土地利用数据,通过CA-Markov模型预测流域2030年土地利用结构,分析2000—2030年安宁河流域ESV变化,并借助地形因子和地理探测器分析ESV的地形梯度分布特征和空间分异驱动因素。结果表明:(1)2000—2020年安宁河流域ESV减少0.51%,2020—2030年预计受林地锐减影响,ESV将继续减少;(2)林地贡献了安宁河流域74%以上的ESV;气候调节和水文调节是ESV贡献率突出的生态系统服务功能,合计达47.79%以上;(3)总ESV和各项生态系统服务功能的ESV随海拔、坡度和地形起伏度增大呈先增后减的分布特征,坡向上分布较均匀;其中2300~2579 m海拔、30.92°~35.73°坡度、507~602 m地形起伏度和西坡分布最多;(4)流域ESV空间分异受自然和经济因子的共同作用影响,其中地形起伏度为主导因子。

西藏雅砻河流域生态系统服务价值地形梯度分异及驱动因素

[目的]分析雅砻河流域生态系统服务价值的变化,为流域生态文明建设提供科学依据。[方法]基于高精度土地利用数据,运用地形梯度分级、标准差椭圆和地理探测器,探究了近20年流域生态系统服务价值(Ecosystem service value,ESV)的时空演变和地形梯度分异特征。[结果](1)草地是流域主要的土地利用类型,占比达92.45%。研究期内林地、灌木和草地面积有所减少,其他类型有所增加;(2)流域ESV在研究期间增长了0.13%(0.16亿元),ESV在空间上呈现出东南部高西北部低的特征。随着海拔、坡度和地形起伏度的抬升,ESV呈先增后降的分布规律,坡向梯度呈阴坡高于阳坡的特征。(3)流域ESV的标准差椭圆和重心在研究期内逐渐向西南方向移动,并趋于聚集。ESV的空间分异主要受自然和经济因子的影响,其中年均地温是主导因子(q=0.24),任意因子交互均增强了其分异性。[结论]依据雅砻河流域ESV的时空和地形分布特征,采取因地制宜的生态保护措施,促进流域生态环境的可持续发展。

Relationships Between River Water Quality and Landscape Factors in Haihe River Basin, China: Implications for Environmental Management

River water plays a key role in human health, and in social and economic development, and is often affected by both natural factors and human activities. An in-depth understanding of the role of these factors can help in developing an effective catchment management strategy to protect precious water resources. This study analyzed river water quality, patterns of terrestrial and riparian ecosystems, intensity of agricultural activities, industrial structure, and spatial distribution of pollutant emissions in the Haihe River Basin in China for the year of 2010, identifying the variables that have the greatest impact on river water quality. The area percentage of farmland in study area, the percentage of natural vegetation cover in the 1000-m riparian zone, rural population density, industrial Gross Domestic Product(GDP)/km^2, and industrial amino nitrogen emissions were all significantly correlated with river water quality(P < 0.05). Farming had the largest impact on river water quality, explaining 43.0% of the water quality variance, followed by the coverage of natural vegetation in the 1000-m riparian zone, which explained 36.2% of the water quality variance. Industrial amino nitrogen emissions intensity and rural population density explained 31.6% and 31.4% of the water quality variance, respectively, while industrial GDP/km^2 explained 26.6%. Together, these five indicators explained 67.3% of the total variance in water quality. Consequently, water environmental management of the Haihe River Basin should focus on adjusting agricultural activities, conserving riparian vegetation, and reducing industrial pollutant emissions by optimizing industrial structure. The results demonstrate how human activities drive the spatial pattern changes of river water quality, and they can provide reference for developing land use guidelines and for prioritizing management practices to maintain stream water quality in a large river basin.

Phytoplankton Assemblage Structure Shaped by Key Environmental Variables in the Pearl River Estuary, South China

Spatial distribution and temporal dynamics of phytoplankton community and their relationships with environmental factors were studied in the Pearl River Estuary(PRE), South China, in three seasons. Salinity was considered as the key environmental variable controlling horizontal distributions of phytoplankton community composition. A transition from dominance of freshwater diatoms(Aulacoseira granulata and A. granulata v. angustissima) to estuarine species(Skeletonema costatum and Pseudonitzschia delicatissima) was observed in the high flow season(summer) along the estuary gradient; in the low flow season(spring), the inner estuary was relatively homogeneous and some typical estuarine species could be found near the river mouth. In the normal flow season(autumn), a potentially toxic bluegreen species, Microcystis spp. was predominant in the middle reaches of the estuary, which should be seeded from upstream and transported downstream by river discharges. Phytoplankton abundance was negatively correlated with suspended solid content and nutrient concentration in the PRE, suggesting that turbidity and nutrient availability were the crucial factors regulating the algal biomass. Phytoplankton abundance in the outer estuary was enhanced by increasing irradiance and continued to be enhanced until phosphorus-limitation.

Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary

Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor-and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water(salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield(ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching(NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water(salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon(14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.

Moraine-dammed glacial lake changes during the recent 40 years in the Poiqu River Basin,Himalayas

Glacier retreat is not only a symbol of temperature and precipitation change, but a dominating factor of glacial lake changes in alpine regions, which are of wide concern for high risk of potential outburst floods. Of all types of glacial lakes, moraine-dammed lakes may be the most dangerous to local residents in mountain regions. Thus, we monitored the dy- namics of 12 moraine-dammed glacial lakes from 1974 to 2014 in the Poiqu River Basin of central west Himalayas, as well as their associated glaciers with a combination of remote sensing, topographic maps and digital elevation models （DEMs）. Our results indicate that all monitored moraine-dammed glacial lakes have expanded by 7.46 km2 in total while the glaciers retreated by a total of 15.29 km2 correspondingly. Meteorological analysis indicates a warming and drying trend in the Nyalam region from 1974 to 2014, which accelerated glacier retreat and then augmented the supply of moraine-dammed glacial lakes from glacier melt. Lake volume and water depth changed from 1974 to 2014 which indicates that lakes Kangxico, Galongco, and Youmojanco have a high potential for outburst floods and in urgent need for continuous moni- toring or artificial excavation to release water due to the quick increase in water depths and storage capacities. Lakes Jialongco and Cirenmaco, with outburst floods in 1981 and 2002, have a high potential risk for outburst floods because of rapid lake growth and steep slope gradients surrounding them.

立体空间视角下景观生态风险时空演化及影响因素分析

综合探究修河流域景观生态风险时空演化特征及其影响因素对构筑区域国土空间生态屏障,优化生态风险管理机制具有重要意义。该研究以平原山地混合分布典型区修河流域为例,以2002、2007、2012、2017、2022年为研究时点,在测度景观生态风险指数的基础上,借助空间自相关、地形梯度分级等模型综合探究区域景观生态风险时空演化特征,并采用最优参数地理探测器识别其影响因素。结果表明:1)2002—2022年,修河流域景观生态风险指数呈下降趋势,低风险与中-低风险区域共增加491.89 km^(2),高风险与中-高风险区域共减少926.17km^(2),生态风险基本由高风险向低风险等级转移。2)修河流域景观生态风险在水平尺度上呈空间正相关性,局部集聚特征主要以“高-高”“低-低”为主;垂直空间上,景观生态风险呈明显地形梯度效应,高风险区在低地形梯度范围内呈优势分布,低风险区在中高地形梯度范围内呈优势分布。3)景观生态风险易受多维因素的影响,各时期地形因子、人类干扰指数、年均温等因素的影响效应始终较强;因子间的交互作用后对景观生态风险的解释力显著增强。研究结果可为流域生态风险管控及生态空间布局优化提供有益参考。

伊犁河谷草地生物量碳的变化研究

通过研究不同海拔高度下草地生物量碳的分布规律,可以评估不同海拔高度下生态系统的碳储量,为生态系统碳平衡和碳管理提供科学依据。探究了伊犁河谷不同海拔高度下草地地上生物量碳与土壤环境因子的分布特征及相关关系,结果表明:①随着海拔上升,土壤温度呈现波动下降趋势,土壤含水量与盐分呈波动上升趋势。H1-H10(海拔1000~2500 m)土壤温度、含水量与盐分分别处于10.87~19.97℃、8.42%~40.17%与0~1.31 g/kg。②草地地上生物量碳储量在5月份随着海拔的升高,呈“降低-增加-降低”的变化趋势,H9(海拔2100~2200 m)时最大,为234 gC/m^(2),7月份呈“增加-降低-增加”的变化趋势,H2(海拔1200~1300 m)时最大,为296.44 gC/m^(2);空间分布上,5月份地上生物量碳储量呈现“西高东低”分布,7月份呈相反趋势。③H8(海拔2000~2100 m)时地上生物量碳储量与土壤温度呈显著负相关,与土壤水分和植被叶面积指数都呈显著正相关(P<0.05)。

云南红河流域土地利用变化的地形梯度效应及其功能分区

明确土地利用情况及其地形梯度分布格局,并进行功能分区,是云南红河流域土地资源可持续利用和土地利用规划优化调整的基础.基于RS和GIS技术,使用地形分布指数、地形位指数方法系统分析了2000、2010年和2020年云南红河流域土地利用变化在高程、坡度和地形位梯度上的时空分异特征,并基于分析结果开展了云南红河流域土地利用功能区划分.结果表明:(1)林地(56.46%)和耕地(29.34%)是云南红河流域主要的土地利用类型,其次是草地(6.93%)和灌木地(6.17%),而湿地、水体和人造地表所占面积比例均不到1%.2000—2020年云南红河流域耕地和人造地表面积扩张明显,而林地持续减少,存在林地被侵占的现象;(2)云南红河流域土地利用类型分布呈现明显的地形梯度特征.耕地、人造地表受到高地形位开发难度的限制,优势位处于中低地形位的河谷、山腰区域,湿地、水体高度汇集在低地形位,草地、灌木地在中低地形位较为集中,林地则广泛分布于中高地形位;(3)基于土地利用地形分异规律,将云南红河流域划分为4个土地利用功能区,即河谷集约发展区、陡坡综合治理区、高山潜在开发区和山顶生态调控区.

1961—2020年长江下游地区夏季降水趋势分析

近几十年来长江下游地区夏季(6—8月)降水量呈现出显著上升的变化趋势,利用1961—2020年夏季台站降水资料,通过降水项分解法,定量分析了该降水趋势的可能影响因素。结果表明:1)长江下游地区夏季降水的上升趋势主要是由日降水量显著增加造成,而日降水量显著增加主要与整层水汽垂直梯度增大和垂直上升速度增强所导致的降水增加有关;2)长江下游地区对流层低层大气温度因地面升温的加热作用而显著上升,高层大气温度受亚太振荡相位正转负的影响而下降,使得高、低层大气的温差变大,低层大气比湿升高、高层大气比湿降低,导致整层水汽垂直梯度增加,为局地降水的增强提供了充沛的水汽条件;低层大气异常辐合加之显著增长的不稳定能量为垂直上升运动的增强和对流性降水的增加提供了有利的动力和热力条件,从而造成了长江下游地区夏季降水的显著上升趋势。

右江航道整治工程河段比降观测方法探讨

针对右江航道整治工程比降观测要求,对比降观测的方法进行探讨。采用纵比降与河心比降相结合的实施方案,重点对河心比降水准测量方法进行论证。通过在竹筏上设置可调节管状水准尺的水面比降器,采用水准测量的方法测量河心水面高程,结合全球卫星导航系统-载波相位差分技术(GNSS-RTK)测得的坐标等信息,提高河心比降观测精度。结果表明,水准观测的方法可实现毫米级观测精度,比GNSS-RTK观测河心比降的精度更高。

钢模台车在引江补汉输水隧洞出口渐变段中的应用

引江补汉输水隧洞出口渐变段顶拱受不良地质条件的影响,出现了出口边坡变形过大引起不收敛的问题。由于施工合同工期短,若采用传统支架平面模板的方式浇筑边顶拱,则该出口段施工工期不能达到合同要求。阐述了应用定制钢模台车成功完成该输水隧洞出口渐变段边顶拱混凝土衬砌施工的过程,较平面模板的施工方式节约工期7 d。采用钢制模板施工其混凝土,外观质量优于传统平面大模板衬砌渐变段边顶拱混凝土,不仅节约了施工成本,而且为后续隧洞掘进争取了时间,所取得的经验可供类似工程借鉴。

特高含水期条带砂体挖潜策略研究

BS油田明化镇组下段条带砂体稠油油藏,储层以分流河道为主,采用沿河道方向注采相间的“一字型”井网投入开发。进入特高含水期后,沿河道方向水驱效率降低,局部含水上升快、整体采出程度低。针对这一问题,在系统分析条带砂体非均质性特征基础上,通过建立顶平底凸的典型条带砂体模型,从研究渗流特征入手,引入渗流系数定量表征不同宽度河道径向流和线性流在河道内的占比,根据流动形态及压力场传导规律,建立了压力梯度随渗流距离变化的关系图版,为挖潜策略制定提供了依据。根据条带砂体内的流动形态及压力梯度变化,提出了不同河道及河道不同部位的强化注采、调剖调驱、井间和边部加密的挖潜策略。现场实施加密井8口,取得初期日增油280 t,累增油48.2×104t的成果,同时释放潜力井位23口。特高含水期条带砂体仍然可以通过重建井网和重组流场,进一步提升开发效果,为条带砂体特高含水期深化挖潜指明了新的方向,为类似条带油田在特高含水期提高采收率提供了参考。

闽江河口湿地土壤磷形态变化对盐度增加的响应及其影响因素

以闽江河口湿地为研究对象,沿自然盐度梯度分别采集不同盐度区的短叶茳芏湿地(有植被)和光滩(无植被)土壤样品,对不同盐度条件下土壤理化性质、植物生物量及土壤磷形态等进行研究,以评估盐度增加对湿地土壤磷形态变化的影响及其调控因子。结果表明:①不同盐度条件下,土壤全磷和各形态磷含量大体表现为短叶茳芏湿地高于无植被的光滩,尤其在淡水条件下最为显著。总体上,随盐度增加,土壤全磷和有机磷含量逐渐减低,无机磷和氢氧化钠磷含量表现为先降低后增加,而盐酸磷含量则逐渐增加。无机磷是闽江河口不同盐度湿地土壤全磷的主要赋存形态,分别占全磷的74%、77%和83%,占比随盐度增加而增大。②不同植被条件下,短叶茳芏湿地土壤全碳、全氮含量和氮磷比均显著高于光滩土壤(P<0.05)。不同盐度条件下,淡水区土壤全碳、全氮含量和碳氮比均显著高于咸水湿地,并且高盐区大于中盐区(P<0.05)。③地上和地下植物生物量沿盐度梯度呈现明显不同的趋势,地上生物量表现为随盐度增加而增大,地下生物量在淡水区高于咸水区,尤其是显著高于中等盐度区。④相关分析显示,盐度及其关联的地上/地下生物量、全碳、全氮和有机质含量等的变化共同调控了土壤磷形态和有效性的变化。研究表明,滨海河口湿地盐度的增加通过改变土壤有机质含量和地上/地下植物生物量,调控了土壤磷的形态和转化,进而影响湿地生态系统的养分循环和化学计量平衡。

长江流域城镇化对生境质量的影响梯度差异研究

作为我国最大的流域,长江流域城镇化对生境质量的影响呈现出明显的沿江梯度差异。揭示城镇化对生境质量影响的梯度差异对长江大保护以及生境修复差异化管控措施的制定具有重要意义。然而,城镇化对生境质量影响的沿江梯度差异规律仍然不清楚。基于此,沿长江建立了三个缓冲梯度,并基于多源数据,借助一系列动态分布和空间回归分析方法分析了2000年、2010年和2020年城镇化对生境质量影响的梯度差异规律。结果表明:(1)长江流域的生境质量沿缓冲梯度先减少后增加,且在不同梯度区间内均随时间发生恶化,而城镇化水平沿缓冲梯度不断降低,但在不同梯度区间随时间发生了剧烈增长;(2)不同梯度区间生境质量的区域内差异以及区域间差异均不断增加,超变密度是区域差异的主要来源,且不同梯度区间生境质量的转移趋势也具有较大差异;(3)城镇化水平与生境质量以负相关为主,且城镇化对生境质量的负向影响沿着缓冲梯度不断增强,但随时间均有所减弱。针对长江流域地区的生境治理,应当充分考虑生境质量及其影响因素的梯度差异,以支持差异化生境保护政策与措施的制定与实施。

塔里木河中、下游胡杨林种内竞争对比研究

为探究塔里木河中、下游胡杨(Populus euphratica Oliv.)种内竞争差异及其对水分梯度的响应规律,以塔里木河下游阿拉干断面以及中游国家自然保护区胡杨种群为研究对象,在每个区域分别选取3条样带,每条样带依照水分梯度布设3个样方,共18个样方,利用Hegyi单木竞争模型探究塔里木河中、下游水分梯度下胡杨林种内竞争变化特征.结果表明:1)塔里木河中游胡杨最适竞争范围为8 m,下游最适竞争范围为10 m;2)胡杨竞争指数与胸径服从幂函数关系(P<0.001),胡杨竞争指数随对象木胸径的增加而逐渐减小,当胡杨胸径在塔里木河下游达20 cm以上、中游达30cm以上时,胡杨竞争指数逐渐稳定;3)随水分梯度的降低胡杨种群竞争指数呈下降趋势,且塔里木河中游的胡杨竞争压力高于下游的胡杨.立地水文条件是控制塔里木河流域胡杨竞争强度的决定性因子;在胡杨林分管理中,应充分考虑胡杨种内竞争与水分梯度之间的关系.

釜溪河自贡城区段季节性低氧成因研究

釜溪河为沱江一级支流,在自贡城区段设有国考碳研所断面。收集碳研所断面近10年来水质自动站数据,分析溶解氧(DO)变化特征,采样调查釜溪河自贡城区段水质及河道底泥污染状况,采用相关性分析、数值模拟等,研究分析釜溪河自贡城区段溶解氧分布特征及碳研所断面季节性低氧成因。研究结果表明,碳研所断面的溶解氧质量浓度变化特征呈现春末夏初最低,白天高晚上低的特征。釜溪河碳研所断面河水耗氧类污染物质量浓度较沱江流域内其他断面高,耗氧强度较大,溶解氧质量浓度较沱江流域其他断面偏低;其次,研究河段中釜溪河污水厂以下河段受污水厂低氧水排入和金子凼堰底层低氧水下泄影响,其溶解氧水平整体较污水厂以上河段低;最后,河段底泥有机质含量较高,春夏季气温升高将导致微生物分解活性增强大量消耗溶解氧,同时,闸坝和外来水体排入的水文扰动造成污水厂以下河段水温梯度弱,表层溶解氧易受底层低氧水影响,促使断面形成季节性低氧现象。溶解氧预测模型结果也进一步证实了温度变化和垂向温度梯度弱是碳研所断面溶解氧质量浓度季节性偏低的主要因素。

平原河网区水力坡降对城市内涝的影响分析

嘉兴市位于太湖流域下游的平原河网城市,城区内地面标高整体较低。嘉兴市雨水管渠的排出口一般淹没在河道水面以下,排水条件较为不利。因此,合理的水力坡降对减小城市的内涝风险十分重要。综合水面率、河网密度及雨水管渠入河前的流动距离等因素,选取能够代表嘉兴市总体排水特点的典型排水分区,借助MIKE水力模型软件,研究不同河道最高控制水位对应的内涝风险情况,分析出当水力坡降大于20cm时,能基本保障嘉兴市平原河网区在设计重现期下的排水安全。研究结果可为城市水利调度和开发建设中地面标高的控制提供参考和指导。