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题名: 长江中下游中小型湖泊预测湖沼学研究
作者: 王海军
答辩日期: 2007-06-06
导师: 刘建康 ; 王洪铸
授予单位: 中国科学院水生生物研究所
授予地点: 水生生物研究所
学位: 博士
关键词: 预测湖沼学 ; 整体性经验模型 ; 关键期模型 ; 最适放养量模型 ; 氮磷比 ; 滤食性鱼类 ; 藻类总量控制 ; 稳态转换 ; 长江流域浅水湖群
其他题名: PREDICTIVE LIMNOLOGICAL RESEARCHES ON SMALL- TO MEDIUM-SIZED LAKES ALONG THE MID-LOWER YANGTZE RIVER
摘要: 长江泛滥平原是世界上最重要的湿地之一。近几十年来,该区域许多湖泊面临着渔业资源过度利用和人为富营养化等各种问题。建立区域尺度的湖泊生态系统定量管理平台是解决这些问题的重要基础。传统湖沼学多针对特定水体进行中小尺度的系统分析,在理解生态机制方面有重要作用,但所得结果尤其是定量关系的外推性有限,对复杂系统宏观规律的把握亦显不足。预测湖沼学则在传统工作的基础上,通过大尺度比较寻求普适性的湖沼学规律。本文通过对46个中小型湖泊的实地调查,并运用部分文献资料,系统地开展了长江中下游浅水湖群的预测湖沼学研究,取得如下主要结果。 1. 提出了各种湖沼学参数合适的数据变换形式。统计分析一般要求数据呈正态分布,对于非正态数据须通过变换实现正态化。分析表明,湖水pH和温度呈正态分布,平均水深和透明度-水深之比接近于正态分布,可直接参与统计分析。螺类相对密度和生物量呈“U”形分布,难以通过直接变换实现正态化。湖盆发育系数呈左偏态分布,可通过x2和ex变换实现正态化。其余参数均呈右偏态分布,可通过log10(x),x0.5和x0.1变换实现正态化。由于数据样本量大,代表性好,所得结果可应用于长江水系的定量湖沼学研究。 2. 构建了沉水植物生物量关键期模型。构建沉水植物模型以预测生长趋势对长江流域湖泊的植被恢复工作十分必要。周年研究表明透明度-水深之比是影响沉水植物生长的最关键因子。进一步分析发现3-6月既是沉水植物的快速生长期,又是透明度-水深之比的关键作用期。相应地,以3-6月的透明度-水深之比为驱动变量建立了系列沉水植物生物量关键期模型(R2=0.75-0.81,n=15-18,p<0.001)。模型显示,3、4、5和6月的透明度-水深之比要分别达到0.66,0.47,0.55和0.45,沉水植物才有望正常生长。本模型预测力较强,为通过水位调控恢复沉水植被提供了定量依据。 3. 构建了沉水植物附生螺类的预测模型。附草螺类是浅水湖泊的重要生物类群,但过去缺乏系统的研究,尤其是模型工作。周年调查发现附草螺类群落以小型种类为主,如萝卜螺、扁蜷螺、长角涵螺和纹沼螺等。螺类平均体重为0.05 g/ind,99%的螺类小于0.2 g/ind。螺类密度和生物量分别为417±160 ind/m2 和18.05±7.43 g/m2,最高值均出现在8月。环境分析表明沉水植物生物量是影响螺类生长的关键因子。以此参数为驱动变量,建立了系列预测力较高的周年和各季度模型(周年:种数,R2=0.25-0.36,n=20,p=0.02-0.005;密度、生物量,R2=0.48-0.69,n=20,p<0.001。各季度:密度、生物量,R2=0.49-0.94,n=12-20,p<0.002)。分析还发现肺螺类偏好能接近水面的植物,而前鳃螺类偏好完全沉于水底的植物。研究结果对螺类资源的合理利用与保护有一定价值。 4. 初步构建底栖动物现存量预测模型。结果表明长江湖群寡毛类密度和生物量分别为403±225 ind/m2和1.12±0.39 g/m2,螺类密度和生物量分别为82±20 ind/m2和26.38±3.99 g/m2,摇蚊密度和生物量为356±62 ind/m2和1.86±0.58 g/m2,总计密度和生物量为847±248 ind/m2和29.41±3.97 g/m2。环境分析表明,影响底栖动物现存量的主要因子是水深、透明度、水温、总磷、浮游藻类叶绿素a和沉水植物生物量,并据此初步构建了底栖动物资源量预测模型。 5. 构建了河蟹最大产量模型和最适放养量模型。河蟹过度放养导致湖泊资源枯竭和水质恶化,故亟需建立蟹苗最适投放量的估算方法。周年研究表明沉水植物是影响河蟹产量的关键因子,但一般生产者难以测准其生物量,故选择简单易测准且与沉水植物生物量及河蟹产量均有密切关系的透明度-水深之比作为模型驱动变量。为使模型更具实际指导意义,遂基于投放季节(12月-5月)的透明度-水深之比构建了系列最大河蟹产量(CYMax,kg/ha)模型(R2=0.49-0.81,n=18,p<0.001)。独立数据验证表明这些模型有较强的预测力,准确率平均达70%。进一步根据最大可持续产量理论,结合成蟹规格(BW,g/ind)和回捕率(RR,%),构建了最适放养量(SROpt,ind/ha)模型:SROpt=(1000CYMax×50%)/(BW•RR)。根据模型,一般草型湖泊的河蟹(扣蟹,约10±5 g/ind)最适投放密度为700±60 ind/ha。本研究为湖泊河蟹的合理放养提供了简单实用的操作依据。 6. 否定了根据氮磷比指数判别藻类群落氮限制或磷限制的传统观点。传统上认为氮磷比(TN/TP)可判别湖泊浮游藻类群落为氮限制或磷限制,但该观点一直缺乏严格的统计检验。本文的系列回归分析表明周年和夏季浮游藻类叶绿素a最重要的影响因子为湖水总磷,其次是总氮。对不同氮磷比湖泊营养物-叶绿素a回归关系的比较发现,无论在各种特定氮磷比范围内还是在氮磷比全距上,总磷对叶绿素a变异的解释率均高于总氮。进一步分析发现单位总磷的叶绿素a产量(Chl a/TP)不受总氮浓度变化的影响(p>0.3),而单位总氮的叶绿素a产量(Chl a/TN)随总磷浓度的上升而迅速增加(p<0.001)。上述结果表明氮磷比不宜作为一个指数来判别限制性营养;无论氮磷比如何,总磷都是藻类群落的限制因子。自然藻类群落是由多个物种组成的,且不同物种最适氮磷比的差异甚大(淡水种类的变异范围为4.1-133.3)。显然,通过一个明确的阈值来判别多物种群落的营养限制类型是几乎不可能的。湖泊可通过生物和电离固氮补偿氮素不足,而磷素则没有相应的补偿机制,这使得磷素易于成为限制因子。本研究指出了氮磷比在湖泊管理中的误导作用,表明控磷对富营养化治理极为重要。 7. 证明滤食性鱼类不能控制湖泊浮游藻类的总量。过去对于滤食性鱼类能否控制浮游藻类总量存在争议,相关工作均为小尺度的模拟实验,难以反映实际情况。本研究根据鲢鳙鱼产量将70多组数据分为两类,以检验滤食性鱼类对浮游藻类总量(以叶绿素a衡量)的控制效果。结果表明,相对于滤食性鱼类产量低于100 kg/ha的湖泊,产量大于100 kg/ha的湖泊具有更高的叶绿素a (p<0.001)和更低的透明度(p<0.001)。这两类湖泊之间的总磷-叶绿素a回归关系(斜率差异t=0.40,截距差异t=0.52,n=70,p>0.50;t0.50, 70=0.68)和总磷-透明度回归关系(斜率差异t=0.67,截距差异t=0.22,n=78,p>0.50;t0.50, 80=0.68)的差异均不显著。这些结果表明滤食性鱼类不能降低叶绿素a,也不能提高透明度。主要原因是鱼类对于食物颗粒的选择性滤食,小型藻类在其竞争者(大型藻类)和摄食者(浮游动物)被鱼类滤除后将会迅速增殖。藻类群落的这种补偿机制将使藻类总量保持不降或持续上升。因此,滤食性鱼类不宜作为生物操纵手段来控制藻类总量。对于湖泊浮游藻类总量控制,建议首先削减营养负荷,然后设法恢复沉水植被和生态系统完整性。 8. 证实了浅水湖泊的多稳态性,确定了稳态转换的关键驱动因子及其阈值。研究湖泊生态系统的多稳态性和转换机制对于湖泊管理具有重要意义,可指导预防灾变、制定管理目标。目前国际上对湖泊多稳态性的研究基本上以实验模拟和模型推导为主,尚缺乏野外数据的系统证明。本文运用大时空尺度的野外数据证实,长江流域湖泊生态系统至少存在两种稳态,即沉水植物占优势的清水稳态和浮游藻类占优势的浊水稳态。进一步分析表明总磷是湖泊稳态转换最主要的驱动因子,清浊转换的总磷阈值为70-100 mg/m3,浊清转换的总磷阈值为20-30 mg/m3。本研究为我国制定长江流域湖泊的营养控制目标提供了定量依据,亦将促进湖泊多稳态理论的发展。 9. 发展了一套独特的实用模型构建方法,提出了关键期模型新概念。提出首先应分析预测变量的关键调控因子,进而寻找与之密切相关的可简单精确测量的参数作为模型驱动变量。如此,模型的预测力较高,且易推广使用。关键期模型以主作用期的参数为驱动变量,相对于传统的同步模型具有较高的预测能力,且可提前预测全年趋势,故更具实用价值。 总之,本文构建了一系列简单实用的整体性经验模型,验证了若干重要假说,提出了明确的、定量化的湖泊管理建议,并且创新研究策略,促进了区域湖沼学的发展。今后,将在长江流域和其他水系开展更为广泛更为深入的预测湖沼学研究,以期建立普遍适用的内陆水体管理专家系统。
英文摘要: The Yangtze floodplain is one of the most important wetlands in the world. Many lakes in the region have suffered from fishery over-exploitation and man-made eutrophication for decades. To solve these problems, it is necessary to establish a regional-scale quantitative platform of lake ecosystem management. Traditional limnological researches were carried out in individual waters through small- to medium-scale analyses. Although these studies contributed greatly to our understanding of ecological mechanisms, the results, especially quantitative relationships are difficult to be extrapolated to real ecosystems or other waters, and the strategy is also insufficient to reveal macroecological patterns of complex systems. As a new approach, predictive limnology aims at finding general rules through large-scale comparative studies. In the present dissertation, predictive limnological researches on mid-lower Yangtze shallow lakes were carried out systematically in 46 small- to medium-sized lakes. The main results are as follows: 1. Suitable transformations of various limnological parameters have been recommended. Generally, data used in statistical analyses must follow a normal distribution and those with non-normal distributions must be normalized through transformations. The results showed that the frequency distributions of pH and water temperature are normal, and those of mean depth and ratio of Secchi depth to water depth are approximately normal; no transformation is needed for these four parameters. The frequency distributions of relative density and biomass of gastropods are U-shaped; so that they are difficult to be normalized through transformation. The coefficient of development of lake volume is right-skewed and can be normalized through x2 and ex transformations. All the other parameters are left-skewed and can be normalized through log10(x), x0.5 and x0.1 transformations. Since the data set is large and typical, the results are expected to be applied to quantitative limnological works on Yangtze waters. 2. Key-time models of submersed macrophyte biomass have been established. To recover the submersed vegetation in Yangtze lakes, the creation of models to predict growing tendency of vegetation is necessary. Annual investigations showed that the ratio of Secchi depth to water depth is the most important factor regulating the biomass of submersed macrophytes. Further analyses indicated that the months from March to June are not only the actively growing season for most macrophytes, but also the key time the key factor acts. Accordingly, a series of key-time models of submersed macrophyte biomass are generated using the ratio of Secchi depth to water depth during the key time as the driving variables (p<0.001): Mar.: BMac = - 3149 + 4854.6 ZSD/ZM R 2= 0.75 n = 15 Apr.: BMac = - 3396 + 7298.6 ZSD/ZM R2 = 0.76 n = 16 May: BMac = - 3490 + 6380.6 ZSD/ZM R2 = 0.77 n = 17 Jun.: BMac = - 3536 + 7900.6 ZSD/ZM R2 = 0.69 n = 18 Mar.-Jun.: BMac = - 3931 + 7072.9 ZSD/ZM R2 = 0.81 n = 18 Where, BMac (wet weight, g/m2) is annual biomass of submersed macrophytes, ZSD/ZM is the ratio of Secchi depth to water depth during the key period. According to the models, the ratio of Secchi depth to water depth should reach over 0.66, 0.47, 0.55 and 0.45 respectively in the four months during March-June to enable a normal growth of submersed macrophytes. These models have high predictive abilities and thus provide a quantitative tool for recovery of submersed macrophytes through regulation of water level. 3. Predictive models of epiphytic gastropods on submersed macrophytes have been established. Epiphytic gastropods are an important group in shallow lakes. However, little has been done previously in China, especially in the aspect of modeling. Annual investigations showed that the community is characterized by the constitution of small individuals, mainly represented by Radix spp., Planorbidae spp., Alocinma longicornis and Parafossarulus striatulus. The mean body weight was 0.05 g/ind and the dominant (99%) size was less than 0.2 g/ind. The average density and biomass were 417±160 ind/m2 and 18.05±7.43 g/m2, with maxima around August. Biomass of submersed macrophytes was found to be the important factor affecting epiphytic gastropods. Accordingly, a series of annual and seasonal predictive models yielding high predictive abilities are generated (Annual: species number, R2=0.25-0.36, n=20, p=0.02-0.005; density and biomass, R2=0.48-0.69, n=20, p<0.001. Seasonal: density and biomass, R2=0.49-0.94, n=12-20, p<0.002). Further analyses found that pulmonates prefer the macrophytes which can spread their terminal parts on the water surface, while prosobranchs prefer the macrophytes which are entirely submersed. The models are expected to benefit rational utilization and protection of gastropod resources. 4. Preliminary predictive models of benthos standing crops have been established. The results showed that oligochaetes of Yangtze lakes were 403 ± 225 ind/m2 in density and 1.12 ± 0.39 g/m2 in biomass, gastropods were 82 ± 20 ind/m2 and 26.38 ± 3.99 g/m2, chironomids were 356 ± 62 ind/m2 and 1.86 ± 0.58 g/m2, the total were 847 ± 248 ind/m2 and 29.41 ± 3.97 g/m2. Water depth, Secchi depth, water temperature, phytoplankton chlorophyll a and submersed macrophyte biomass were found to be the important factors affecting the standing crops of benthic animals. Accordingly, a series of predictive models of benthos are generated using these factors as the driving variables. 5. Maximum yield models and an optimal-stocking model of Chinese mitten crab have been established. Overstocking of Chinese mitten crab in lakes has resulted in exhaustion of resources and deterioration of water quality; thus it is necessary to establish a method to estimate the optimal stocking rate of crab juveniles. Annual analyses indicated that submersed macrophyte biomass is the key factor affecting the crab yield. For convenient applications in crab culture, the ratio of Secchi depth to mean depth, a parameter easy to be accurately measured and close to both submersed macrophyte biomass and crab yield is selected as the driving variable. The ratio of Secchi depth to mean depth during the crab planting season (Dec.-May) is used as the driving variable to generate a series of maximal yield (CYMax, kg/ha) models (n=18, p<0.001): Dec.-Jan. (1 month): CYMax = - 21.37 + 81.16 ZSD/ZM R2 = 0.61 Mar. (1 month): CYMax = - 1.22 + 63.9 ZSD/ZM R2 = 0.49 Apr. (1 month): CYMax = - 7.5 + 94.56 ZSD/ZM R2 = 0.64 May (1 month): CYMax = - 24.58 + 104.31 ZSD/ZM R2 = 0.70 Dec.-Mar. (2 months): CYMax = - 25.17 + 85.26 ZSD/ZM R2 = 0.65 Mar.-Apr. (2 months): CYMax = - 16.01 + 91.29 ZSD/ZM R2 = 0.71 Apr.-May (2 months): CYMax = - 23.21 + 109.26 ZSD/ZM R2 = 0.74 Dec.- Apr. (3 months): CYMax = - 32.37 + 103.18 ZSD/ZM R2 = 0.77 Mar.- May (3 months): CYMax = - 24.72 + 102.52 ZSD/ZM R2 = 0.75 Dec.-May (4 months): CYMax = - 36.60 + 110.69 ZSD/ZM R2 = 0.81 Validation based on an independent data set indicated that these models have high predictive powers, with a mean accuracy of 70%. Based on the theory of MSY (Maximum Sustainable Yield), in combination with body-weight (BW, g/ind) and recapture rate (RR, %) of adult crabs, a general optimal-stocking model is formulated: SROpt=(1000CYMax×50%)/(BW•RR). According to the models, the optimal stocking rates of crab juveniles (yearlings, about 10±5 g/ind) in macrophytic lakes are generally 700±60 ind/ha. The models provide a simple and practical tool for rational crab culture. 6. The traditional viewpoint to use TN/TP ratio as an index to identify phytoplankton as nitrogen- or phosphorus-limited has been disproved. Traditionally, growth of phytoplankton in lakes have been regarded as limited by total phosphorus if TN/TP was relatively large, limited by total nitrogen if TN/TP was relatively small and co-limited by total nitrogen and total phosphorus when TN/TP was intermediate. However, this viewpoint has never been proved by strict statistical tests. Serial regression analyses in the present research indicated that total phosphorus was the primary affecting factor and total nitrogen the second affecting factor for both annual and summer phytoplankton chlorophyll a. In separate nutrient-chlorophyll a regression analyses for lakes of different TN/TP ratios, total phosphorus is also superior to total nitrogen in explaining the variation of chlorophyll a at all particular TN/TP ranges and over the entire TN/TP spectrum. Further analyses found out that chlorophyll a varied regardless of the changes of TN for a given amount of TP (annual, p=0.33; summer, p=0.81), but increased rapidly with an increase of TP for a given amount of TN (annual and summer, p<0.001). These results suggest that TN/TP ratio is inappropriate as an index to identify limiting nutrients and that TP is the primary nutrient limiting phytoplankton over the entire TN/TP spectrum. Natural phytoplankton communities are ones of multiple-species. Optimal N/P ratios vary greatly from species to species (ranging from 4.1-133.3 among various freshwater species). Obviously, it is almost impossible to set a specific “cut-off” ratio to identify a limiting nutrient(s) for a multiple-species community. In lakes, biological and lightning nitrogen fixation may correct for nitrogen deficiency. On the other hand, relevant mechanism is lack for phosphorus, resulting in the wide occurrence of phosphorus limitation. This study pinpoints the misleading of TN/TP ratio in lake management and highlights the vital importance of phosphorus abatement in eutrophication control. 7. Planktivorous fishes have been found to fail to control total phytoplankton. Previously, there has long been a controversy on whether planktivorous fishes could effectively control total phytoplankton. The controversy is mainly due to the fact that that all the experiments were too small in spatio-temporal scales and difficult to reflect the real ecosystems. In the present research, to test the effects of planktivorous fishes on total phytoplankton (measured as chlorophyll a), more than 70 sets of data were used and divided into two groups with fish yields (silver and bighead carp, the species native to China) greater than and less than 100 kg/ha. The results showed that, lakes with yields of planktivorous fish greater than 100 kg/ha have significantly higher phytoplankton chlorophyll a (p<0.001) and lower Secchi depth (p<0.001) than those with yields less than 100 kg/ha. Total phosphorus- chlorophyll a (slope difference, t=0.40; intercept difference, t=0.52; n=70,p>0.50, t0.50, 70=0.68) and total phosphorus-Secchi depth (slope difference, t=0.67; intercept difference, t=0.22; n=78, p>0.50, t0.50, 80=0.68) relationships are not significantly different between lakes with yields greater than or less than 100 kg/ha. These results indicated that the fish fail to decrease chlorophyll a yield, and also fail to enhance Secchi depth. The main reason is the selective filter-feeding on larger food particles. Small-sized species would develop quickly when their competitors (large-sized phytoplankton) and grazers (zooplankton) are eliminated. Therefore, silver carp and bighead carp are not recommended as a biotic agent for phytoplankton control in lake management if the goal is to control the total phytoplankton and to enhance water quality. For lake management concerning total phytoplankton control, nutrient abatement should be carried out first, and then try to recover submersed macrophytes and ecosystem integrity. 8. The regime multiplicity of shallow lakes has been proved; the primary factor and its thresholds triggering the regime shifts have been determined. Researches on multiplicity of lake regimes and mechanism triggering regime shift are important to lake management. They may help to prevent catastrophic events and define targets in lake management. However, in previous studies, the multiplicity of lake regimes was analyzed mainly by the means of experiments and models. Little evidence has been obtained from field data. In the present research, large-scale field data were used. It is proved that there are at least two ecosystem regimes in Yangtze lakes: one of clear water with submersed vegetation-dominance and one of turbid water with phytoplankton-dominance. Total phosphorus is determined as the primary factor triggering the regime shifts. The threshold of total phosphorus is determined as 70-100 mg/m3 for the clear-turbid shift, and 20-30 mg/m3 for the turbid-clear shift. The results provide quantitative references to define targets of nutrient control in Yangtze lakes. They are also expected to make a contribution to the theory of multiple regimes. 9. A special approach to practical models has been developed and the new concept “key-time model” has been defined. It is suggested that modelers should first determine regulating factors of target variables, and then seek for driving variables which are correlated closely with the regulating factors and easy to be accurately measured. Models generated like this are expected to have higher predictive powers and to be more practical. Key-time models are based on driving variables during the functioning period. They have higher predictive capacity than traditional synchronic models in general, and enable us to predict annual tendency in advance; thus are of greater value in application. In summary, in the present dissertation, a series of simple and practical holistic empirical models have been established; several important hypotheses have been tested; some explicit and quantitative suggestions for lake management have been given; a new approach of predictive modeling has been developed. To create an expert management system of inland-waters in China, predictive limnological work will be carried out more extensively and intensively in the Yangtze Basin and other regions in the future.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ihb.ac.cn/handle/342005/12120
Appears in Collections:中科院水生所知识产出(2009年前)_学位论文

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长江中下游中小型湖泊预测湖沼学研究.王海军[d].中国科学院水生生物研究所,2007.20-25
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