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1.
Lilin Zheng Jinying Xu Dandan Wang Guoyu Xu Zhiqiang Tan Ligang Xu Xiaolong Wang 《水文研究》2021,35(2):e14026
The dynamic responses of wetlands to upstream water conservancy projects are becoming increasingly crucial for watershed management. Poyang Lake is a dynamic wetland system of critical ecological importance and connected with the Yangtze river. However, in the context of disturbed water regime in Poyang Lake resulting from human activities and climate change, the responses of vegetation dynamics to the Three Gorges Dam (TGD) have not been investigated. We addressed this knowledge gap by using daily water level data and Landsat images from 1987 to 2018. Landsat images were acquired between October and December to ensure similar phenological conditions. Object-oriented Artificial Neural Network Regression for wetland classification was developed based on abundant training and validation samples. Interactions between vegetation coverage and water regimes pre and post the operation of the TGD were compared using classification and regression trees and the random forest model. Since the implementation of the TGD in 2003, Poyang Lake has become drier, especially during the dry season. A more rapid plant growth rate was observed post TGD (44.74 km2 year−1) compared to that of the entire study period (12.9 km2 year−1). Average water level for the antecedent 20 days most significantly affected vegetation before 2003, whereas average water level for the antecedent 5 or 10 days was more important after 2003. The impoundment of the TGD after the flood season accelerated the drawdown processes of Poyang Lake, and the rapidly exposed wetlands accelerated vegetation expansion during the dry seasons, resulting in shrinkage and degradation of the lake area. This study deepens our knowledge of the influences of newly developed dams on lakes and rivers. 相似文献
2.
Gerald Schernewski 《洁净——土壤、空气、水》2003,31(2):152-161
Between 1989 and 1998 the small eutrophic stratified Lake Belau was investigated intensively and multidisciplinarily. This article is a short, comprehensive summary and re‐evaluation of the hydrochemistry of the lake, with focus on nitrogen and phosphorus. In several aspects the lake can be regarded as a typical example of the glacial north German lakes. The 1960's and 1970's are characterised by heavy nutrient inputs and fast eutrophication. During the last two decades the external nutrient load, especially the phosphorus load into Lake Belau was significantly reduced. But phosphorus‐rich sediments and large areas with summerly anoxic sediment surface conditions cause intensive release of phosphorus from older deeper sediment layers. Annual budgets reveal that despite an average sediment accumulation of 3 mm a?1 the lake has lost its function as net phosphorus sink and it is very likely that internal eutrophication by the sediments will keep the lake in its eutrophic state during the next decades. Despite that, monthly budgets of five vertical layers show that the main phosphorus supplier for the phosphorus depleted epilimnion during summer is the creek Alte Schwentine. The annual nitrogen budget indicates groundwater and interflow water as well as atmospheric input as additional important nitrogen sources. 36% (98 μmol m ?2 h?1 N) of all nitrogen input is lost to atmosphere mainly due to denitrification. The example of a heavy storm shows that about 10% of the annual nitrogen loss to the atmosphere can take place during a single day and in form of ammonia. The storm further made obvious that these unpredictable events can have strong impact on nutrient cycling and ecology in Lake Belau and the lake can become an unexpected nutrient source for downstream systems. 相似文献
3.
长江中下游典型湖泊营养盐历史变化模拟 总被引：2，自引：1，他引：1
湖泊营养盐变化在自然条件下受到气候水文因素控制,同时受到湖泊生态系统生物群落作用和反馈.作为动力机制探讨,本文试图基于水文和生态动力学方法,分别构建气候-流域水文作用于湖泊营养盐的外源模式和湖泊生物群落作用于湖泊营养盐的內源模式.针对长江中下游典型湖泊,经过控制实验和率定,发现营养盐模拟与观测数据在时间序列上达到90%百分位的正相关,因此用来模拟1640 1840 A.D.期间的营养盐演变历史.研究表明:(1)模拟的湖泊营养盐变化与沉积钻孔揭示的历史营养盐变化基本一致,沉积记录与模式模拟的7个湖泊的营养盐变化均显著相关;(2)气候因素是湖泊营养盐历史演变的主控因子,来自于湖泊生物群落的反馈作用贡献约占40%;(3)在温度和降水因子的驱动下,湖泊营养盐历史变化主要受降水控制,在极端干旱时期,60%的营养盐变化同步响应于降水变化.同时,面积在400 km2以下的湖泊营养盐对气候变化的响应比2000 km2以上的大湖更为敏感.研究结果对长江中下游湖泊营养状态的长期变化机理认识和趋势控制提供科学依据. 相似文献
4.
利用Landsat系列卫星的MSS、TM和ETM+遥感数据,计算了研究区的归一化植被指数(NDVI),并以此为湿地植被活动的指标,研究1973 2011年间该湿地植被变化特征及年内季节变化特征,揭示植被活动在年内和年际变化的控制因子以及湿地植被对于气候变化、人类活动和极端干旱事件的响应特征.结果表明:(1)近40年来南四湖湿地植被各个季节的变化特征不尽相同.春季NDVI呈现先降低后增加的特征,主要先后受到研究区围垦、渔业养殖等人为活动和气候变化(增温)的影响;夏季和冬季的NDVI呈现显著降低趋势,主要受到围垦、渔业养殖等人类活动的影响;秋季NDVI的变化不显著.(2)年内季节变化方面,湿地植被面积和NDVI都呈现单峰的变化特征,从春季开始增加,在夏季末(全年的第202和205 d)达到最大值,然后开始下降,到冬季降至最低.植被的年内季节变化特征主要受到月均温度的控制.(3)干旱在一定程度上不是湖泊湿地NDVI增加的限制因子.干旱导致湖泊水位下降,滨湖滩地及湖底露出,可能会促进湿地植被生长和植被面积的扩大,使得湿地NDVI增加. 相似文献
5.
《国际泥沙研究》2022,37(5):563-575
Lacustrine sediment preserves high-resolution biogeochemical records of past variations in watershed processes controlling lake sedimentation. The current study explores historical variations in autochthonous and allochthonous sediment supplies to a large tropical freshwater lake system (Upper Lake, Bhopal) protected under the international Ramsar Convention of 2002 against anthropogenic pressures. For this purpose, multi-proxy biogeochemical data are presented for organic matter (total organic carbon, total nitrogen, phosphorous, and loss on ignition [LOI] at 550 °C), carbonate (LOI at 950 °C), lithic sediment (aluminum, titanium, iron, calcium, magnesium, sodium, potassium, manganese, zirconium, niobium, hafnium, tantalum, thorium, uranium, and rare earth elements), and anthropogenic inputs (lead) measured in a 38 cm long sediment core retrieved from the lake. In addition to the lacustrine sediment core, the samples of catchment bedrock, surface soils, major stream sediment, and eolian dust collected from the lake periphery also are analyzed. The systematic biogeochemical excursions in the upper core section (top ～8 cm) indicate increased anthropogenic inputs, watershed denudation by agricultural activities, artificially reduced fluvial sediment supply, relatively increased dust inputs and lake eutrophication in the last few decades. The current study underscores the roles of anthropogenic land-use and wetland conservation practices in the rapid alteration of autochthonous and allochthonous sediment supplies to open aquatic ecosystems. Further, rising lake eutrophication levels despite a managed reduction in allochthonous sediment supplies seem challenging to control due to dissolved nutrient supply from urban sewage discharge and runoff from agricultural land in the watershed. 相似文献
6.
龙感湖钻孔揭示的末次盛冰期以来的环境演化 总被引：4，自引：1，他引：4
通过龙感湖滩地钻孔24．4m深度以内的沉积物岩性、生物和物理指标分析，在^14C年代测定的基础上，对龙感湖末次盛冰期以来的环境演化进行了恢复，15．0kaBP前和10．0－6．3kaBP，龙感湖区发育河流沉积，以低生物量和高磁化率为特征；约15．0－10．0kaBP期间的晚冰期，龙感湖首次成湖，湖泊中生物量明显提高；现代龙感湖雏形始于约6．3kaBP后，至3．7kaBP后发展为稳定的湖泊环境，此外，花粉结果显示，龙感湖湿地相干被大致形成于3．3kaBP后，然后，龙感湖的成因和演化，及其与长江关系的研究，还必须重视对沉各物物源的追踪。 相似文献
7.
半干旱内陆地区的湖泊湿地是一种特殊的生态系统,季节和年际时间尺度上的湖泊水文变化对湖泊湿地生态结构和功能有着重要影响.近20年来,月亮泡湖泊湿地经历了自然和人为因素共同作用下的水文波动过程.为了实现大尺度地表生态年内/年际变化检测,更好地了解湖泊年际水淹范围及其水淹频次对内陆湖滨湿地生态的影响,基于1994—2018年Landsat TM/OLI影像数据(30 m),首先,计算提取月亮泡的年际水体信息和水淹频次,进而获取湖泊年际淹没范围.其次,采用综合生态指数变化检测法提取生态信息,选取3个标准观测年(1995、2006、2016年),从年内变化和年际变化视角分级评价了研究区生态变化,并分析了水淹频次与湿地生态变化的关系.最终,现有研究表明:湖泊年际水淹区主要分布在月亮泡的北侧与西侧尾闾,月亮泡湖泊湿地北侧的年际水淹频次更为显著.湖泊面积的扩展与自然湿地的减少是月亮泡水淹区域的主要变化类型.在这种变化情况下,研究区水体指数累积量的增加与植被指数累积量的衰减成为显著的生态变化特点.月亮泡湖泊年际水淹频次在一定时间和空间上影响着水淹区域的植被生产能力,水淹的低频波动是研究区植被累积量增加的关键因子.因此,在湿地生态恢复与管理过程中,维持合理的水文波动,恢复月亮泡北侧与西侧沼泽湿地是该区域内生态保护的核心措施. 相似文献
8.
Koenraad Muylaert Steven Declerck Jeroen Van Wichelen Luc De Meester Wim Vyverman 《Limnologica》2006,36(2):69-78
Phytoplankton and zooplankton were monitored during 2 years in four eutrophic shallow lakes (two turbid and two clear water) from two wetland reserves in Belgium. In each wetland, phytoplankton biomass was significantly higher in the turbid lake than in the clear water lake. Although total macrozooplankton biomass and the contribution of daphnids to total zooplankton biomass was comparable in the clear water and the turbid lakes, the grazing pressure of macrozooplankton on phytoplankton as estimated from zooplankton to phytoplankton biomass ratios was higher in the clear water lakes. Estimated grazing by daphnids in the clear water lakes was always high in spring. In summer, however, daphnid biomass was low or daphnids were even absent during prolonged periods. During those periods phytoplankton was probably controlled by smaller macrozooplankton or by submerged macrophytes through nutrient competition, allelopathic effects or increased sedimentation rates in the macrophyte vegetation. 相似文献
9.
In the northern glaciated plain of North America, the duration of surface water in seasonal wetlands is strongly influenced by the rate of infiltration and evaporation. Infiltration also plays important roles in nutrient exchange at the sediment–water interface and groundwater recharge under wetlands. A whole‐wetland bromide tracer experiment was conducted in Saskatchewan, Canada to evaluate infiltration and solute transport processes. Bromide concentrations of surface water, groundwater, sediment pore water and plant tissues were monitored as the pond water‐level gradually dropped until there was no surface water. Hydraulic head gradients showed strong lateral flow from under the wetland to the treed riparian zone during the growing season. The bromide mass balance analysis showed that in early spring, almost 50% of water loss from the wetland was by infiltration, and it increased to about 70% in summer as plants in and around the wetland started to transpire more actively. The infiltration contributed to recharging the shallow, local groundwater under the wetland, but much of it was taken up by trees without recharging the deeper groundwater system. Emergent plants growing in the wetlands incorporated some bromide, but overall uptake of bromide by vegetation was less than 10% of the amount initially released. After one summer, most of the subsurface bromide was found within 40–80 cm of the soil surface. However, some bromide penetrated as deep as 2–3 m, presumably owing to preferential flow pathways provided by root holes or fractures. Copyright © 2004 Crown in the Right of Canada. Published by John Wiley & Sons, Ltd. 相似文献
10.
L. Kalbe 《洁净——土壤、空气、水》1984,12(2):145-152
In the Galenbeck lake, a shallow lake covering 700 ha and having a nutrient load of 0.23 g/m2a P as well as 4.3 g/m2a N, in 1965 a stock of carp of 500 animals/ha was established and additionally fed with grain. This stock of carp resulted in a considerable whirling-up and redeposition of the soft lime sediments, the rich submersed vegetation disappeared and the phytoplankton reached maxima of 885,420 cells/ml, whereas the zooplanktion reached only 4530 ind./l. The chlorophyll contents increased to 464 mg/m3, the depth of visibility decreased to 10 cm. The total planktonic primary production is estimated at 500 g/m2a C at least. These changes are regarded as eutrophication, its cause being attributed mainly to the internal fertilization by an intensified recirculation of nutrients from the sediment, but also by the fertilization which is connected with feeding. When the fish rearing had ceased and the stock of carp had been fished off, in 1970 a reacreation of the lake began, and in 1974 the lake reached again its original state as a clear-water lake with an abundant contents of macrophytes, supported also by the P-retention in an upstream storage reservoir for spray-irrigation water. 相似文献