黄河三角洲湿地景观演变驱动力浅析

1、黄河三角洲湿地景观演变驱动力浅析江珍1 李淑贞2 陈吕平1 马辉3（1黄委人劳局 2 黄河流域水资源保护局 3 黄委规划计划局）摘要：在1986年、1996年和2004年湿地时空变化规律的基础上，研究分析黄河现代三角洲湿地景观演变的主要驱动力。结果表明：黄河水沙资源变化是湿地景观演变的根本动力，不合理的土地利用开发、水利工程建设、自然灾害、文化因素是湿地景观演变的主要驱动力。关键词：景观演变；驱动力；黄河现代三角洲湿地由于蕴藏着丰富的湿地资源，黄河现代三角洲已成为是国际上以保护黄河口新生湿地系统和珍稀濒危鸟类为主体的重要湿地之一，同时还成为黄河河流健康的重要标志。但是，近20年来，随着黄河入海

2、水沙量锐减、人类活动加剧及对湿地认识不足等，湿地原有的生态功能受到巨大的不同程度的破坏。因此，分析黄河三角洲湿地景观时空演变演替规律，明确景观演变驱动因子，确定湿地生态系统退化的驱动因子，将有助于更好地维持黄河河口生态系统的可持续管理。 1 湿地景观本文是以与黄河来水联系密切的黄河现代三角洲内湿地作为研究区。黄河现代三角洲指以渔洼为顶点，北起挑河口，南至宋春荣沟的扇形地带，面积约2,400km2，是由1976年黄河入海流路人工改道控制而成。黄河的填海造陆以及频繁改道，形成了独特的黄河河口湿地生态系统。黄河现代三角洲湿地总面积1570 km2。由于众多季节性河流在此入海口分叉较多，故多为自然湿地

3、，其面积为892 km2，主要分布在东部和北部地区，尤其在南起小岛河河口，北起徒骇河河口的东部地区多种湿地并存，集中连片。人工湿地面积为678 km2，主要为水稻田、水库、人工盐田等，多在中西部地区广泛分布。从地区分布上，三角洲湿地在沿海地区分布较为集中，面积也较为广阔，随着向内陆的推移，面积逐渐减少，分布也较零散。1.1 水文特性黄河是形成和维持本区水系的主导因素。据利津水文站实测资料计算，黄河入河口地区的年均径流量为4.19*1010 m3，变幅相差10.6 倍；黄河河口地区年均流速为1330 m3/s，最大可达10400 m3/s，最小即断流。黄河输送到河口地区的年均沙量为1.049 *

4、109t，平均含沙量为 25.53 kg/m3。近几十年来，随着黄河来水减少及黄河断流的加剧，以及分水工程的增多，河流的径流量和含沙量锐减。河口湿地生态系统处于水陆交界的生态脆弱带上，特殊的水文条件决定了其易受自然和人为活动干扰，生态系统极易受到破坏，且破坏后难以恢复。1.2 生物特性作为东北亚内陆和环西太平洋鸟类迁徙重要的“中转站”、越冬地和繁殖地，黄河口特有的原生湿地系统和湿地生物资源，已成为国际上的重要湿地之一。为此，于1992年建立了以保护黄河口新生湿地系统和珍稀濒危鸟类为主体的国家级湿地类型保护区，重点保护新生湿地生态系统和珍稀、濒危鸟类。区内有野生动物1543种，属国家重点保护的9

5、种。鸟类资源丰富，达283种，属国家一级保护的9种，属国家二级保护的41种。植物393种，野生植物110种。2 湿地景观演变通过RS和GIS的支持，选取1986年、1996年和2004年的遥感卫星CCD数据，在使用并建立景观图谱分析方法和景观图谱模型后，二十年来黄河现代三角洲湿地景观格局时空演变的研究结果为：2.1 整个时序单元(1986-2004年)黄河现代三角洲湿地景观呈现出两个时空演变系列。一个是沿海岸带到内陆的滨海湿地->盐碱地 -> 沼泽或草甸湿地（芦苇）->人工湿地, 另一个是沿河床向外方向的河流湿地 ->草甸湿地（芦苇）->沼泽->人工湿地。

6、黄河现代三角洲湿地景观不稳定，约由66的湿地发生强烈的变化。滨海湿地和河流湿地是两个未发生变化面积较大的湿地类型，多位于黄河故道入海口附近，黄河现行河道入海口附近或两侧。 第一大变化是从非湿地演变为盐碱地、人工湿地和滨海湿地，第二大变化是从滨海湿地演变为非湿地、人工湿地和盐碱地。表明盐碱地和人工湿地快速增长，滨海湿地是面积转移最大的湿地类型。2.2 第一个时序单元 (1986-1996年)非湿地显著地演变为滨海湿地、盐碱地和草甸湿地，变化面积为655.41 km2。新增的湿地主要分布在黄河现行河道沙嘴，或在黄河故道两侧，或在黄河故道和现行河道之间。 滨海湿地明显地演变为盐碱地，变化面积为192

7、.17 km2。新增的盐碱地主要分布在黄河故道和现行河道之间。黄河故道入海口附近的滨海湿地面积明显地被侵蚀了74.32 km2。2.3 第二个时序单元(1996-2004年)各湿地类型显著地演变为非湿地，变化面积为412.18km2。其中黄河故道和现行河道之间的盐碱地减少了189.20 km2，黄河故道和现行河道入海口附近的滨海湿地减少了189.20 km2。 非湿地和盐碱地明显演变为中小型的人工湿地，变化面积为120.88 km2。其中新增的中型盐田约占新增人工湿地的90%。由非湿地转化来的人工湿地主要分布在黄河故道两侧或黄河现行河道的南面。由盐碱地转化来的新增人工湿地主要分布在黄河故道和现

8、行河道之间。滨海湿地明显盐碱化，变化面积为115.89 km2，主要分布在黄河故道两侧或现行河道南面。 3 湿地演化驱动因子分析空间格局的成因可分为3种：非生物的(物理的)、生物的和人为的（邬建国，2000）。现在的黄河三角洲就是由黄河流路的改变过程、生物演替过程以及不断加强的人类活动过程而产生的目前特有的景观分异格局。其中,非生物因素中的水文因素直接影响湿地范围及内部生态过程,气候土壤地貌等因素则相对比较稳定.人为因素比较特殊，可直接或间接地改变湿地范围及内部生态特征. 而生物因素资料比较缺乏, 且对于湿地的作用相对较弱。因此,黄河三角洲湿地景观演变的驱动因素分析,应围绕湿地水文因素，重点考

9、虑对湿地有重要影响的自然因素和可以改变的、较为特殊的人为因素。3.1 黄河水沙资源变化是湿地景观格局演变的根本动力黄河是三角洲唯一的客水资源，黄河水沙资源是黄河三角洲湿地赖以生存发育的根本，是形成和维持黄河三角洲原生湿地生态系统的主导因素，是三角洲湿地生态系统顺向演替的根本动力。良好的黄河水沙资源基本能保证三角洲湿地面积有一定的增加。如: 在1976年1992年，相对较好的水沙资源保证了新增湿地面积为22.8 km2/a 。但进入九十年代以来，随着黄河水沙资源的逐年减少,河口水沙量发生较大变化，黄河三角洲新增湿地面积增加趋势趋缓甚至出现萎缩现象。如:在2004年河口出汊后由于入海水沙量的大量减

10、少,河口南汊新增的湿地明显蚀退。但是如果有洪水存在, 三角洲湿地面积还可以有一定的增加, 如:1996年的湿地情况。黄河来水来沙的逐年减少，不仅造成了湿地面积萎缩,更使三角洲失去了维持本区水系和水文生态平衡的主导因素，导致河口湿地水文条件的改变，影响了整个湿地生态系统的发展方向。3.2 不合理的土地利用开发是导致湿地景观变化的主要驱动力不合理的石油盐田开发等土地利用开发导致湿地水文和生态系统发生了重大变化，加深了滨海湿地盐碱地等的破碎化和中小斑块的增多，破坏甚至丧失了湿地物种的生境条件。而且导致了新生陆地的大面积次生盐渍化，盐碱滩面积急剧增加。随着不合理的土地利用开发的强度越来越大，人工盐田油

11、田等面积显著增长,而自然湿地将趋向减少和不断萎缩。这种变化趋势将使本区湿地景观的天然性降低，湿地生态系统良性循环受到威胁。3.3 水利工程建设是改变湿地水文的重要因素大型水利工程建设这类高强度的人类活动改变了河口地貌、沉积相分布与水动力条件，对河口湿地景观格局和河口湿地水文状况具有显著影响。其中,黄河上游水利工程建设改变了河口湿地的水文周期、水文过程，影响了湿地正常发育，加深湿地破碎化程度，导致湿地面积萎缩。河口水库的修建，改变了湿地的水文条件，导致湿地出现盐碱化现象,导致芦苇面积的萎缩和破碎化程度的加深，使湿地生境丧失和片断化，从而威胁生物多样性。另外，堤防工程和防潮工程建设，改变了湿地的水

12、文周期和水文特征，使湿地水文周期由长变短，导致湿地植物群落的逆向演替、生态系统平衡失调、生物多样性降低。为了协调工程建设与湿地保护之间关系，河口堤防建设、防潮工程以及入海流路治理工程应充分考虑湿地水文周期和水文条件要求，在适当的位置预留口门或建设生态闸，在植物生长季节有计划地向堤外湿地进行补水，以维持淡水湿地和滨海湿地生态系统的良性循环。3.4 自然灾害加剧了湿地景观的逆向演替黄河口三角洲是发生风暴潮最严重的地区之一。每次风暴潮浸没纵深达几十公里，给三角洲湿地生态系统造成很大破坏和威胁。同时风暴潮是滩涂湿地和重盐碱荒地土壤盐分的主要来源，加剧了土地盐碱化程度，致使湿地生态系统向着重盐碱荒地和光

13、板地生态系统演替，破坏了湿地生态系统的发展。3.5 文化因素是人类改变湿地景观格局的重要驱动力思想、意识、法律、管理等文化因素是人类改变湿地景观格局的重要驱动力。人口、技术、政治经济体制、政策等人为因素的影响在一定程度可减缓或加剧湿地景观格局的改变。土地开发、水利工程建设等导致了湿地面积的萎缩，改变了湿地的水文条件，加深了湿地的破碎化程度等。但严格的立法、湿地科学的普及、高水平的管理等措施，可加大对湿地的保护力度和强度，在一定程度上减缓、遏制湿地逆向演替速度和趋势，促进湿地生态系统的良性循环。黄河三角洲自然保护区的建设以及河口湿地恢复工程的实施初步遏制了淡水湿地面积萎缩的趋势就是一个很好的说明

14、。Study on driving forces of Wetland Change in the Yellow Rivers Modern DeltaJiang Zhen1, Liu Shuzhen2, Chen lvping1, Ma Hui3 (1. Department of Personnel, YRCC; Zhengzhou)2. Water Protection Bureau, YRCC; Zhengzhou3. Department of Planning, YRCC; Zhengzhou)Abstract：On the basis of the autumn data of

15、remote sensing in 1986, 1996 and 2004, the spatial and temporal changes of wetland landscape are described using the approach of landscape graph spectrum, then the driving forces of wetland change is investigated in the Yellow Rivers Modern Delta during the past 20 years. The results show that water

16、 and sediment resources of the Yellow River, overexploitation of land-use, construction of hydraulic engineering, storm tides and knowledge are the main driving forces of wetland change in the Yellow Rivers Modern Delta.Key words: wetland change; driving force; the Yellow Rivers Modern DeltaThe wetl

17、and in the Yellow Rivers Modern Delta (YRMD) is provided with abundant new-born wetland and rare birds. Accordingly, the wetland in the YRMD has become not only one of the international important wetlands, but also the crucial symbol to maintain healthy river. However, in the last 20 years, the wetl

18、and ecosystem in the YRMD has suffered tremendous degradation due to the sudden decreased discharge in the river, the increasing human activities and the lack of wetland science etc. Therefore, it is beneficial to the sustainable management of ecological system, if we investigate the driving forces

19、of wetland change in the YRMD. 1 Wetland landscapeThis study is focusing on the wetland in close relation to the water coming from the Yellow River in the YRMD. Generally, YRMD starts from Yuwa point, with the Diaokou river in the north and Songchunrong ditch in the south, and was shaped by the man-

20、made changing of the watercourse of the Yellow River entering to the sea in 1976. As known, the unique wetland ecosystem in the YRMD comes into being by filling-up and frequent fluctuation of tail channel of the Yellow River. The total area of wetland in the YRMD is about 1570 km2. Most of the wetla

21、nd is natural, as lots of seasonal rivers branches off in rivers mouths to the sea. Especially, many natural wetlands coexist and concentrate in the eastern zone from the Xiaodao river mouth in the south to the Tuhai river mouth in the north. On the contrast, artificial wetland, mainly including pad

22、dy field, reservoir and salty field, widely spreads in the Midwest of the total wetland in the YRMD. In the sight of spatial distribution, the wetlands in the YRMD vastly centralize in littoral zone, but taper gradually and scatter spatially when shifting into the inlands.1.1 Hydrological characteri

23、sticsThe Yellow River is the basic factor to maintain the water system in this region. According to observation by Linjin hydrological station, the mean annual run-off is 41.9 billion m3 in the mouth of the Yellow River, with the discharge difference of 10.6 times. The average discharge is 1330 m3/s

24、, ranging from10400 m3/s to zero. The Yellow River is also the river with highest sediment concentration in the world. The average annual river load is 1.049 billion tons and the average sediment concentration is 25.53 kg/m3. Recently, with the water flow of the Yellow River, the abrupt flow reduce,

25、 the increases of water diversion works and so on, the run-off and the river load decreased abruptly by about 60%.Generally, the wetland ecosystem is situated in the fragile ecological region between land and water. Thus, particular hydrological condition determines that the wetlands are liable to u

26、ndergo the disturbances by the nature and human activities. Correspondingly, the wetlands are difficult to be restored once destructed in the YRMD.1.2 Ecological characteristicsAs the exceptional habitat of breeding, migrating, and wintering for bird migration in the inland of northeast Asia and aro

27、und western Pacific Ocean, the unique natural wetlands and abundant biological resources in the YRMD have been one of the most crucial wetlands in the world. Accordingly, in this region, the national nature reserve was established and authorized in 1990 and 1992 respectively. The main aims of the na

28、ture reserve focus on the conservation of new-born wetland ecosystem and rare endangered birds.In the reserve, there are total 393 species (varieties) of plants, mainly including 271 species of angiosperm. Most vegetation is natural with the area of 50915hm2, accounting for 77.9% of the total vegeta

29、tion. Moreover, therere 1466 species of wild animals recorded, consisting of 300 species of terrestrial vertebrates, 583 species of terrestrial invertebrates, 223 species of terrestrial aquatic animals and 418 species of marine aquatic animals. In terms of national priority wildlife, 7 species of bi

30、rds are listed as the 1st class priority, and 33 species as the 2nd class priority, including Grus japonensis, Circus cyaneus cyaneus etc. In addition, 7 species of birds are in the annex, 26 species in annex and 7 species in annex of convention on international trade in endangered species of wild f

31、auna and flora.2 Wetland changeOn the basis of the autumn data of remote sensing in 1986, 1996 and 2004, the spatial and temporal changes of wetland landscape are investigated in the Yellow Rivers Modern Delta during the past 20 years, using the approach of landscape graph spectrum as follows.2.1 Du

32、ring the whole period (19862004)Landscape pattern of wetlands in the YRMD presents two series of transition in the space-time scale during the whole period. One is the transition of CW to OW (saline lagoon) to SW or MW (reeds) to AW from the coastland to the inland, and the other is the transition o

33、f RW to MW (reeds) to SW to AW from the riverbed to the outward. Landscape pattern of wetlands is unstable in the YRMD. About 66% of the wetlands in the YRMD have changed intensely due to the fragile ecosystems. CW and RW are the two wetland classifications with the larger unchanged areas.The 1st la

34、rgest changes of wetland classifications are the process from non-wetland (NW) to OW, AW and CW, and the 2nd largest changes are the process from CW to NW, AW and OW. It is shown that OW (saline lagoon) and AW have increased rapidly, and that CW is the wetland classification with the largest transfe

35、rring area.2.2 During the first temporal sequence (19861996)The non-wetland has dominantly changed into CW, OW and MW with the area of 655.41 km2. The increasing wetlands are mainly located in the sand spit of the current watercourse of the Yellow River, on the both sides of previous watercourse of

36、the Yellow River, or between the previous watercourse and current watercourse of the Yellow River.The CW has obviously changed into OW with the area of 192.17 km2. The increasing OW is mainly located between the previous watercourse and current watercourse of the Yellow River. And the CW near the mo

37、uth of previous watercourse has been obviously eroded with the area of 74.32 km2.2.3 During the second temporal sequence (19962004)The wetland classifications have dominantly changed into non-wetland (NW) with the area of 412.18km2. The OW has decreased with 189.20 km2 between the previous watercour

38、se and current watercourse of the Yellow River. The CW has reduced by 189.20 km2 near the mouth of previous watercourse and the southern mouth of current watercourse of the Yellow River.The NW and OW have obviously changed into middle or small sized AW with the area of 120.88 km2. The increasing sal

39、ty fields accounts for 90% of the increasing AW of middle size. The increasing AW from NW is mainly located on the both sides of previous watercourse and in the south of the current watercourse of the Yellow River. The increasing AW from OW is mainly situated between the previous watercourse and cur

40、rent watercourse of the Yellow River.The CW has obviously changed into OW with the area of 115.89 km2, and is mainly located on the two sides of previous watercourse and in the south of the current watercourse of the Yellow River.3 Driving forcesGenerally speaking, the driving forces of landscape pa

41、ttern can be identified into three types, namely a-biotic (physical) factors, biologic factors and artificial factors. The special pattern of wetland landscape has evolved by the fluctuation of watercourse of the Yellow River, the biological succession and intensified human activities. For all the a

42、-biotic (physical) factors, the hydrological factor directly influences the scope of wetland and its inner ecological process in the YRMD, while the other factors are relatively stable, e.g. climate, soil and topography etc. As special factors, human activities can directly or indirectly change the

43、scope of wetland and its inner ecological process in the YRMD. For the biological factors, the information is lacking and the influences are relatively weak. Therefore, the discussion of driving factors should focus on the important a-biotic (physical) factors and changeful or special artificial fac

44、tors, in close relation to the hydrologic factors of wetlands. 3.1 Water and sediment resources of the Yellow River The changes of water and sediment resources of the Yellow River is the essential driving factors for the of space-time pattern of wetland landscape in the YRMD. Because the Yellow Rive

45、r is the basic factor to maintain the water system in this region, and the water and sediment resources are the leading factor to maintain the natural wetland ecosystems in the YRMD. In general, more water and sediment resources of the Yellow River can guarantee the increase of new-born wetlands in

46、the YRMD. E.g. the annual new-born wetlands is about 22.8 km2 per year due to more water and sediment resources during the 19761992. However, along with the decrease of water and sediment resources at Linjin station of the Yellow River, the new-born wetlands has been shrunk and even disappeared. E.g

47、., the coastlands near the mouth of the previous watercourse and the southern mouth of the current watercourse have been obviously disappeared.Therefore, the decreased water and sediment resources of the Yellow River have resulted in not only the shrinkage of the wetlands, but also the serious unbal

48、ance of water system and hydrological ecology in the YRMD. The evolution of wetland landscape has obviously been influenced. 3.2 Overexploitation of land-use Unreasonable exploitation of land-use is the main driving forces of the evolution of space-time pattern of wetland landscape in the YRMD. Beca

49、use these kinds of activities have led to important changes of wetland hydrology and its ecosystems, fragmentized the wetlands with the increasing middle or small patches, e.g. coastal wetland, saline lagoon etc. And even the habitats of species of wetland have been damaged or disappeared. In additi

50、on, saline lagoon has dramatically increased during the whole period of 19862004.At the same time, with the increasingly unreasonable exploitation of land-use, the salty fields and oil fields etc. have evidently raised, while the natural wetlands have relatively reduced and shrunk. The trends of the

51、se changes will surely cause the continuous decrease of natural wetlands and imperil the positive evolution of wetland ecosystems in the YRMD.3.3 Construction of hydraulic engineering The construction of hydraulic engineering is an important factor for the changes of wetland hydrology, because this

52、kind of human activities can notably influence the landscape pattern and the hydrological characteristics of wetlands in the YRMD.Actually, the construction of hydraulic engineering in the upper reaches can change the hydrological cycle and process of wetlands in the lower reaches of the Yellow River. Therefore, the evolution of wetland landscape is unbalanced with the fragmentation and shrinkage of wetlands in the YRMD. Moreover, the construction of reservoirs leads to more saline lagoon a