气候变化条件下苦参在我国潜在分布区的预测分析

为了解气候变化情景下苦参在中国的潜在分布区变化,探讨生物气候因子与苦参适宜分布格局的关系.该文通过收集苦参的地理分布点并结合19项生态因子,运用最大熵模型(MaxEnt)和地理信息系统(ArcGIS)对末次盛冰期、当前气候、未来气候三种气候情景下苦参在我国适生区的分布格局进行模拟,并分析影响苦参生长的主导生态因子.结果...     

湖泊生态系统动力学模型研究进展

从系统分析在湖泊生态系统动力学研究中的作用出发,对湖泊生态系统的动力学建模过程、方法和软件等进行了总结.在此基础上,综述了国内外湖泊生态系统动力学模型的发展.从1960年代至今,湖泊生态系统动力学模型从简单的零维模型发展到复杂的水质水动力学生态综合模型和生态结构动力学模型,如LakeWeb模型.中国的湖泊生态系统动力学模型研究始于20世纪80年代,主要集中在滇池、太湖、东湖和巢湖等富营养化严重的湖泊以及其他水体.目前,已经开发一些软件用于湖泊生态系统动力学模拟,主要有CEQUALICM、WASP、AQUATOX、PAMOLARE、CAEDYM等,以及用来模拟湖泊能流的软件ECOPATH.湖泊生态系统动力学模型还在监测、数据共享和模型结构、参数选取和不确定性分析等方面存在不足,需在今后的研究中加以改进.     

星云湖硅藻群落响应近现代人类活动与气候变化的过程

随着人类活动的增强与全球气候变暖的持续,近年来云南湖泊的生态系统功能持续退化,而目前对云南湖泊生态系统的研究还主要集中于单一环境压力的生态效应。以星云湖为研究对象,通过沉积物记录与现代监测资料,识别在湖泊富营养化、气候变化以及人类强烈干扰下硅藻群落结构响应的过程,并甄别驱动群落变化的主要环境压力及其强度。结果显示随着湖泊生产力水平(如沉积物叶绿素a浓度)的增加,硅藻物种组成发生了明显的变化,主成分分析表明了水体富营养化是驱动群落变化的主要环境因子(r=-0.63,P0.001)。简约模型与方差分解的结果表明近200年来(钻孔长度38cm),湖泊营养水平和水动力是驱动星云湖硅藻群落变化的主要环境因子,分别解释了群落变化的18.8%和2.9%;而1951年以后,湖泊营养水平和温度分别解释了硅藻群落结构变化的31.4%和26.8%。研究结果表明了硅藻群落长期变化的主控因子是湖泊营养水平,而人类活动及气候变化等可以通过改变湖泊水动力及湖水温度来驱动硅藻群落的演替,同时抚仙湖-星云湖的连通性也对硅藻群落的演替产生了一定影响。     

气候变化与人类活动双重驱动的冷水湖泊富营养化

富营养化对水生生态系统造成的负面影响已在世界范围内广泛发生,尤其对淡水水源地湖泊的水环境质量影响深远,进而引起当地居民的饮用水安全与健康隐患。在人类活动和气候变化的双重驱动下,富营养化辐射的范围不断扩大,从过去主要集中于温带大型浅水湖泊已经扩展到寒冷地区的冷水湖泊。分析了近年来世界范围内高寒地区冷水湖泊富营养化的趋势特征与研究进展,探讨了气候变化、人类干扰(农业活动、畜牧业生产、管理措施不当等)在不同地区冷水湖泊富营养化进程中的作用。在未来的研究中,应进一步加强对冷水湖泊富营养化机制的探讨,并对已有富营养化症状的湖泊进行生态修复,以确保冷水湖泊生态系统健康并改善饮用水源地的环境质量。     

植物物候变化的全气候生产要素影响机制与模型研究

物候是气候变化的重要指示指标,不仅是植被动态模型的重要参数,也是陆地碳循环模型和大气环流模式的重要参数.本文从物候变化机制和物候模拟模型两方面综述了植物物候研究最新进展,剖析了物候研究趋势,指出当前物候研究大都仅考虑单一气候因子或少数几个气候因子的影响,涉及多气候因子相互作用影响的研究仍很少,还没有开展植物全气候生产要素相互作用影响物候的研究;受物候变化机制认识与研究物种的限制,现有物候模型仍不能反映植被生长的真实性,也不能有效模拟物候变化.本文指出,全面认识物候变化的机制迫切需要考虑影响植物物候的全气候生产要素及其相互作用,为物候模型发展提供依据.本文基于植物光合作用是最主要的物候影响因子的研究结论,提出采用气候生产潜力作为植物物候变化驱动因子,不仅体现气候环境因子对植物生产的综合作用及其在植物生长全过程中的一致性,还体现了生物因子、环境因子及其相互作用以及极端天气气候事件的影响,从而实现物候的准确模拟.本文提出的未来物候研究方向,有助于丰富物候认知、提升陆地碳循环和大气环流模式模拟的准确性.     

气候变暖与富营养化交互作用对浅水湖泊水-气界面N2O通量的影响

研究通过构建中尺度控温围隔模拟系统,模拟21世纪末气候变化与富营养化趋势,探讨未来气候变暖与富营养化趋势下浅水湖泊水-气界面N₂O交换过程的响应特征及机制。结果表明:(1)恒定与波动升温引起的代谢过程及生物间相互作用的改变显著促进了水-气界面间N₂O的排放及年累积释放量,而磷的添加可能因为影响了水体中反硝化代谢的效率而削弱了水-气界面N₂O排放及年累积释放量;(2)实验期间随季节转换,控制系统内优势的初级生产者由水生植物转变为浮游植物,水体中有机质含量亦不断积累,研究结果表明季节变化及初级生产者转换均对水-气界面N₂O排放量的增加起到了显著促进作用。在气候变化与富营养化趋势下浅水湖泊水-气界面的N₂O交换过程主要受到水体中氮磷含量及其比例的变化、水生植物与浮游植物的转换及有机质的积累过程的影响。因此,气候变暖(恒定和波动升温)能够促进湖泊N₂O排放量的上升,而变暖和营养盐的交互作用会使水-气界面N₂O交换更加复杂。     

基于管理目标的湖泊生态系统动力学

基于生态系统管理的目标,在对相关研究分析的基础上,依据生态系统生态学、淡水生态学的理论,提出了湖泊生态系统动力学研究的2个理论基础：生态系统管理和生态系统特征.在此基础上,分析得到湖泊生态系统动力学的研究方法体系,主要包括研究内容与技术路线、关键问题识别和动力学模拟、湖泊生态系统的适应性管理决策等部分.其中,湖泊生态系统结构和过程、湖泊中食物网营养动力学研究、生源要素循环、湖泊中关键过程的生态作用以及湖泊生态系统动力学模拟是研究的核心问题.此后,以P为主要的生源要素,将生态系统分为3个子过程：入流、出流和内部反馈,并以此建立了湖泊生态系统动力学的模型框架,以辅助于湖泊的生态系统管理.     

植物对气候变化生理生态响应的不确定性分析

生态系统对全球气候变化的响应模式有利于人类预测与适应未来生态环境变化,植物作为陆地生态系统的重要组成部分,对全球气候变化的响应具有重要作用.本文通过对近年来植物对气候变化的生理生态响应研究中(包括定点控制实验,空间代替时间样带),植物响应模式的复杂性、多样性及可变性等诸多不确定性进行分析.以探讨预测未来气候情景下植物的动态变化及生理生态响应过程.分析结果认为.造成这些不确定性的主要原因包括:(1)利用空间代替时间的样带研究中,往往忽略了植物的非线性响应,存在明显的阈值;(2)样带及定点研究中,由于各种气候因子的耦合.很难确定各种气候因子对植物生理生态学特性影响的权重;(3)定点控制实验中往往忽略了植物对气候变化的适应性,使实验结果很难代表更长时间尺度上的反映模式;(4)在相同的气候变化条件下,不同植物的响应有可能存在明显差异.提出了今后植物对气候变化生理生态响应研究的建议.     

300年来鄱阳湖营养盐演化重建与模拟

水体富营养化已经成为全球性的问题而受到广泛关注,然而其发生的过程和机制尚未完全明了。在湖泊营养演化过程中,水文和生态是两个最基本的制约因素。相对于短期的和试验性的研究,长时间尺度的营养盐变化过程能更全面地揭示营养盐的演化机制。以我国最大的淡水湖——鄱阳湖为例,采用湖泊水体交换周期模型和湖泊生态-营养盐动力耦合模型,重建鄱阳湖营养盐的长期变化,并利用沉积钻孔代用指标加以验证。在此基础上探讨其演化机制,模拟的时间序列中营养盐变化对气候水文与生态系统存在两种不同的响应模式。敏感因子分析显示:典型同步响应期中(1812—1828 AD),气候水文因子的贡献率达79.1%,生态因子为20.9%;典型异步响应期中(1844—1860 AD),两者贡献率分别为36.4%和63.6%。在模拟的营养盐变化时间序列中同步期占62.5%,说明气候因子在营养盐演化过程中起重要的作用;异步期虽只占12.5%,但对湖泊营养盐作用、营养盐反馈生物量同样至关重要。相关分析结果显示,生物量增长与TP含量基本呈线性关系,但存在一个阈值。在没有超过阈值前,生物量对TP具有较好的调节作用;当超过阈值之后,生物量的调节作用减弱。     

云南程海湖泊系统响应富营养化与水文调控的长期模式

流域开发和气候变化背景下,逐渐增强的人类活动已经显著影响湖泊系统演替及功能。本研究以云南程海为研究对象,通过对程海湖泊沉积物记录与现代调查数据相结合,重建了程海近250年来的生态环境变化过程,探讨了程海湖泊系统在富营养化以及水文波动等多重环境压力影响下的长期响应模式。结果表明: 1970年之前程海营养水平整体偏低,1970—2000年间缓慢增长,2000年后快速增加,初级生产力呈长期上升趋势。1993—2000年期间,引水工程显著增加了湖泊水动力强度和物种扩散能力,促进了直链藻和菱形藻的增加。程海沉积物记录的碳循环变化主要受内源输入的长期影响。富营养化是硅藻群落长期演替的主要驱动因子,其次是湖泊水动力条件的波动。对程海的生态修复与流域管理不仅需要关注水体营养盐的富集与流域污染物的控制,同时还要考虑到湖泊水文调控和水位波动的影响。     

Effect of eutrophication on culm architecture of lakeshore Phragmites reeds

The eutrophication of lakes in central Europe has been assumed to be at least partly responsible for a widespread die-back of fringing Phragmites australis reeds. To test the ‘eutrophication hypothesis’ on a broad data basis, lakeshore reed stands at 41 lakes of known trophic status and 10 stands in waste water and sludge treatment plants in Denmark and north Germany (North data subset, n=26), and south Germany, Switzerland and Austria (South data subset, n=25) were investigated. A total of 24 culm performance variables in three different shoot classes were analyzed by two-way ANOVA with the geographic origin and the ‘relative trophic index’ as factors. The geographic origin had a pronounced influence on culm architecture, whereas the effect of the trophic level mostly failed to be significant in the ANOVA. The culms from the North reed stands showed a weaker performance throughout than those from the South stands for a given trophic level. However, some of the morphometric traits in the North stands were significant positively correlated with the trophic level but very few significant cases were observed in the South data subset. Three hypotheses are discussed to explain the geographic effect: climatic effects, geochemistry of lake water and sediments, and trophic history of the lakes. It is concluded that lake eutrophication does not influence the culm performance negatively and that eutrophication cannot be regarded as a general cause in reed decline.     

Resource ratio and human impact: how diatom assemblages in Lake Maggiore responded to oligotrophication and climatic variability

Diatoms have been often used to track trophic changes from sedimentary records: recent studies demonstrated that these organisms can even be valuable indicators of climatic variability, although it is often difficult to discriminate the role of trophic and climatic drivers. Moving from the hypothesis that oligotrophication and climate affected the composition of the diatom assemblages by changing the resource ratio, we analysed the vernal diatoms succession in Lake Maggiore, between 1984 and 2007, using multivariate techniques (cluster analysis, canonical correspondence analysis, multivariate regression trees), in order to single out the oligotrophication effects from those attributable to climatic variability. Our results point out that Si, TP, temperature and wind emerged as key explanatory variables in species selection, with a stronger link between trophic and climatic drivers after the lake reached a stable oligotrophic status. Peculiar climate-driven events (deep mixing and floods) affected the in-lake Si:P ratio, giving an advantage to diatoms that are excellent P, but poor Si competitors. The classical role of Fragilaria and Tabellaria as early-warning indicators of eutrophication should be reconsidered, taking into account that both can be useful indicators of climate change, when links between their physiological resource needs and environmental data coming from robust limnological investigations can be established.     

Ecosystem services of Lake Võrtsjärv under multiple stress: a case study

This study is the first attempt at the European scale to make an inventory of ecosystem services (ESS) of a large lake. We analysed a set of ESS indicators against the annual mean values of environmental parameters for 2006–2013. According to principal component analysis, the trophic state- and hydrology-related factors explained about 70% of the environmental variability of the lake and showed strong relationships with some ESS. Among the provisioning ESS, the annual eel catch and the total fish catch were positively related to different eutrophication indicators while the catches of pike, bream, and burbot depended rather on hydrological factors. Reed harvesting efficiency was related to the lake’s water level. The indicators of regulating, maintenance, and cultural ESS showed very high variability in different years, the latter depending on socio-economic conditions rather than environmental factors. We discovered numerous trade-offs between ESS benefitting from higher trophic state or regulated water level of the lake and the goals of good ecological status of the lake. Our analysis showed a clear need for rules prioritizing life supporting regulatory services against other ESS.     

Using aquatic macrophyte community indices to define the ecological status of European lakes

Defining the overall ecological status of lakes according to the Water Framework Directive (WFD) is to be partially based on the species composition of the aquatic macrophyte community. We tested three assessment methods to define the ecological status of the macrophyte community in response to a eutrophication pressure as reflected by total phosphorus concentrations in lake water. An absolute species richness, a trophic index (TI) and a lake trophic ranking (LTR) method were tested at Europe-wide, regional and national scales as well as by alkalinity category, using data from 1,147 lakes from 12 European states. Total phosphorus data were used to represent the trophic status of individual samples and were plotted against the calculated TI and LTR values. Additionally, the LTR method was tested in some individual lakes with a relatively long time series of monitoring data. The TI correlated well with total P in the Northern European lake types, whereas the relationship in the Central European lake types was less clear. The relationship between total P and light extinction is often very good in the Northern European lake types compared to the Central European lake types. This can be one of the reasons for a better agreement between the indices and eutrophication pressure in the Northern European lake types. The response of individual lakes to changes in the abiotic environment was sometimes represented incorrectly by the indices used, which is a cause of concern for the use of single indices in status assessments in practice.     

应用支持向量机评价太湖富营养化状态

根据湖库富营养化程度评价标准,随机生成大量学习样本,运用支持向量机（SVM）算法建立富营养化评价模型。采用太湖2012年7—9月的监测数据,分别应用SVM模型和线性插值评分法(SCO)对太湖33个监测点的富营养化状况进行了评价。结果表明太湖在2012年7—9月共出现3种营养类型,其中,中营养主要分布于东部湖区,轻度富营养主要分布于湖心区和东部沿岸区,中度富营养主要分布于西北部湖区,太湖水体整体表现为轻度到中度富营养水平。通过SVM和SCO结果的对比分析,发现两种评价方法的结果一致率为78.8%,出现不一致的个例均属于相邻营养等级,表明该SVM模型是有效的,能够应用于太湖的富营养化评价,且具有更好的收敛性和泛化性。     

Long‐term changes in hypoxia and soluble reactive phosphorus in the hypolimnion of a large temperate lake: consequences of a climate regime shift

The (Lower) Lake of Zurich provides an ideal system for studying the long‐term impact of environmental change on deep‐water hypoxia because of its sensitivity to climatic forcing, its history of eutrophication and subsequent oligotrophication, and the quality and length of its data set. Based on 39 years (1972–2010) of measured profiles of temperature, oxygen concentration and phosphorus (P) concentration, the potentially confounding effects of oligotrophication and climatic forcing on the occurrence and extent of deep‐water hypoxia in the lake were investigated. The time‐series of Nürnberg's hypoxic factor (HF) for the lake can be divided into three distinct segments: (i) a segment of consistently low HF from 1972 to the late‐1980s climate regime shift (CRS); (ii) a transitional segment between the late‐1980s CRS and approximately 2000 within which the HF was highly variable; and (iii) a segment of consistently high HF thereafter. The increase in hypoxia during the study period was not a consequence of a change in trophic status, as the lake underwent oligotrophication as a result of reduced external P loading during this time. Instead, wavelet analysis suggests that changes in the lake's mixing regime, initiated by the late‐1980s CRS, ultimately led to a delayed but abrupt decrease in the deep‐water oxygen concentration, resulting in a general expansion of the hypoxic zone in autumn. Even after detrending to remove long‐term effects, the concentration of soluble reactive P in the bottom water of the lake was highly correlated with various measures of hypoxia, providing quantitative evidence supporting the probable effect of hypoxia on internal P loading. Such climate‐induced, ecosystem‐scale changes, which may result in undesirable effects such as a decline in water quality and a reduction in coldwater fish habitats, provide further evidence for the vulnerability of large temperate lakes to predicted increases in global air temperature.     

Lake eutrophication associated with geographic location,lake morphology and climate in China

Lake eutrophication is influenced by both anthropogenic and natural factors. Few studies have examined relationships between eutrophication parameters and natural factors at a large spatial scale. This study explored these relationships using data from 103 lakes across China. Eutrophication parameters including total nitrogen (TN), total phosphorus (TP), TN:TP ratio, chemical oxygen demand (COD_Mn), chlorophyll-a (Chl-a), Secchi depth (SD), and trophic state index (TSI) were collected for the period 2001–2005. Sixteen natural factors included three of geographic location, five of lake morphology, and eight of climate variables. Pearson correlation analysis showed that TP and TSI were negatively related to elevation, lake depth, and lake volume, and positively related to longitude. All eutrophication parameters, except for COD_Mn and Chl-a, showed no significant correlation with climate variables. Multiple regression analyses indicated that natural factors together accounted for 13–58% of the variance in eutrophication parameters. When the 103 study lakes were classified into different groups based on longitude and elevation, regression analyses demonstrated that natural factors explained more variance in TN, TP, COD_Mn, Chl-a, and TSI in western lakes than in eastern lakes. Lake depth, volume, elevation, and mean annual precipitation were the main predictors of eutrophication parameters for different lake groups. Although anthropogenic impacts such as point- and nonpoint-source pollution are considered as the main determinants of lake eutrophication, our results suggest that some natural factors that reflect lake buffer capacity to nutrient inputs can also play important roles in explaining the eutrophication status of Chinese lakes.     

Palaeoenvironmental Changes Inferred from Biological Remains in Short Lake Sediment Cores from the Central Alps and Dolomites

In this paper we review research on eutrophication, acidification and climate change based on studies of lake sediments in the Alps. Studies on fossil diatoms, chrysophytes, plant pigments, Cladocera and carbonaceous particles in a number of high altitude lakes in Italy and Switzerland have been used to track environmental changes. We present an original study on fossil Cladocera in sediment cores from 29 lakes that have shown changes in biodiversity from the pre-industrial period (ca. pre AD 1850) to the present. These data show that altitude, ca. 60 years of acidification impacts and fish stocking are the most important factors that affect their distribution and abundance. We review further case studies from two morphometrically and chemically different lakes (Tovel and Paione Superiore). Their lake sediment records span 400 and 150 years, respectively; multi-core, multi-proxy analyses show their pH, trophic and climatic evolution over time.