黃河三角洲濕地景觀演變驅動力淺析

1、黃河三角洲濕地景觀演變驅動力淺析江珍1 李淑貞2 陳呂平1 馬輝3（1黃委人勞局 2 黃河流域水資源保護局 3 黃委規(guī)劃計劃局）摘要：在1986年、1996年和2004年濕地時空變化規(guī)律的基礎上，研究分析黃河現(xiàn)代三角洲濕地景觀演變的主要驅動力。結果表明：黃河水沙資源變化是濕地景觀演變的根本動力，不合理的土地利用開發(fā)、水利工程建設、自然災害、文化因素是濕地景觀演變的主要驅動力。關鍵詞：景觀演變；驅動力；黃河現(xiàn)代三角洲濕地由于蘊藏著豐富的濕地資源，黃河現(xiàn)代三角洲已成為是國際上以保護黃河口新生濕地系統(tǒng)和珍稀瀕危鳥類為主體的重要濕地之一，同時還成為黃河河流健康的重要標志。但是，近20年來，隨著黃河入海

2、水沙量銳減、人類活動加劇及對濕地認識不足等，濕地原有的生態(tài)功能受到巨大的不同程度的破壞。因此，分析黃河三角洲濕地景觀時空演變演替規(guī)律，明確景觀演變驅動因子，確定濕地生態(tài)系統(tǒng)退化的驅動因子，將有助于更好地維持黃河河口生態(tài)系統(tǒng)的可持續(xù)管理。 1 濕地景觀本文是以與黃河來水聯(lián)系密切的黃河現(xiàn)代三角洲內(nèi)濕地作為研究區(qū)。黃河現(xiàn)代三角洲指以漁洼為頂點，北起挑河口，南至宋春榮溝的扇形地帶，面積約2,400km2，是由1976年黃河入海流路人工改道控制而成。黃河的填海造陸以及頻繁改道，形成了獨特的黃河河口濕地生態(tài)系統(tǒng)。黃河現(xiàn)代三角洲濕地總面積1570 km2。由于眾多季節(jié)性河流在此入?？诜植孑^多，故多為自然濕地

3、，其面積為892 km2，主要分布在東部和北部地區(qū)，尤其在南起小島河河口，北起徒駭河河口的東部地區(qū)多種濕地并存，集中連片。人工濕地面積為678 km2，主要為水稻田、水庫、人工鹽田等，多在中西部地區(qū)廣泛分布。從地區(qū)分布上，三角洲濕地在沿海地區(qū)分布較為集中，面積也較為廣闊，隨著向內(nèi)陸的推移，面積逐漸減少，分布也較零散。1.1 水文特性黃河是形成和維持本區(qū)水系的主導因素。據(jù)利津水文站實測資料計算，黃河入河口地區(qū)的年均徑流量為4.19*1010 m3，變幅相差10.6 倍；黃河河口地區(qū)年均流速為1330 m/s，最大可達10400 m/s，最小即斷流。黃河輸送到河口地區(qū)的年均沙量為1.049 *10

4、9t，平均含沙量為 25.53 kg/m3。近幾十年來，隨著黃河來水減少及黃河斷流的加劇，以及分水工程的增多，河流的徑流量和含沙量銳減。河口濕地生態(tài)系統(tǒng)處于水陸交界的生態(tài)脆弱帶上，特殊的水文條件決定了其易受自然和人為活動干擾，生態(tài)系統(tǒng)極易受到破壞，且破壞后難以恢復。1.2 生物特性作為東北亞內(nèi)陸和環(huán)西太平洋鳥類遷徙重要的“中轉站”、越冬地和繁殖地，黃河口特有的原生濕地系統(tǒng)和濕地生物資源，已成為國際上的重要濕地之一。為此，于1992年建立了以保護黃河口新生濕地系統(tǒng)和珍稀瀕危鳥類為主體的國家級濕地類型保護區(qū)，重點保護新生濕地生態(tài)系統(tǒng)和珍稀、瀕危鳥類。區(qū)內(nèi)有野生動物1543種，屬國家重點保護的9種。

5、鳥類資源豐富，達283種，屬國家一級保護的9種，屬國家二級保護的41種。植物393種，野生植物110種。 2 濕地景觀演變通過RS和GIS的支持，選取1986年、1996年和2004年的遙感衛(wèi)星CCD數(shù)據(jù)，在使用并建立景觀圖譜分析方法和景觀圖譜模型后，二十年來黃河現(xiàn)代三角洲濕地景觀格局時空演變的研究結果為：2.1 整個時序單元(1986-2004年)黃河現(xiàn)代三角洲濕地景觀呈現(xiàn)出兩個時空演變系列。一個是沿海岸帶到內(nèi)陸的濱海濕地->鹽堿地 -> 沼澤或草甸濕地（蘆葦）->人工濕地, 另一個是沿河床向外方向的河流濕地 ->草甸濕地（蘆葦）->沼澤->人工濕地。黃河

6、現(xiàn)代三角洲濕地景觀不穩(wěn)定，約由66的濕地發(fā)生強烈的變化。濱海濕地和河流濕地是兩個未發(fā)生變化面積較大的濕地類型，多位于黃河故道入?？诟浇?，黃河現(xiàn)行河道入?？诟浇騼蓚?。第一大變化是從非濕地演變?yōu)辂}堿地、人工濕地和濱海濕地，第二大變化是從濱海濕地演變?yōu)榉菨竦?、人工濕地和鹽堿地。表明鹽堿地和人工濕地快速增長，33濱海濕地是面積轉移最大的濕地類型。2.2 第一個時序單元 (1986-1996年)非濕地顯著地演變?yōu)闉I海濕地、鹽堿地和草甸濕地，變化面積為655.41 km2。新增的濕地主要分布在黃河現(xiàn)行河道沙嘴，或在黃河故道兩側，或在黃河故道和現(xiàn)行河道之間。濱海濕地明顯地演變?yōu)辂}堿地，變化面積為192.1

7、7 km2。新增的鹽堿地主要分布在黃河故道和現(xiàn)行河道之間。黃河故道入?？诟浇臑I海濕地面積明顯地被侵蝕了74.32 km2。2.3 第二個時序單元(1996-2004年)各濕地類型顯著地演變?yōu)榉菨竦?，變化面積為412.18km2。其中黃河故道和現(xiàn)行河道之間的鹽堿地減少了189.20 km2，黃河故道和現(xiàn)行河道入海口附近的濱海濕地減少了189.20 km2。非濕地和鹽堿地明顯演變?yōu)橹行⌒偷娜斯竦?，變化面積為120.88 km2。其中新增的中型鹽田約占新增人工濕地的90%。由非濕地轉化來的人工濕地主要分布在黃河故道兩側或黃河現(xiàn)行河道的南面。由鹽堿地轉化來的新增人工濕地主要分布在黃河故道和現(xiàn)行河道

8、之間。濱海濕地明顯鹽堿化，變化面積為115.89 km2，主要分布在黃河故道兩側或現(xiàn)行河道南面。3 濕地演化驅動因子分析空間格局的成因可分為3種：非生物的(物理的)、生物的和人為的（鄔建國，2000）?，F(xiàn)在的黃河三角洲就是由黃河流路的改變過程、生物演替過程以及不斷加強的人類活動過程而產(chǎn)生的目前特有的景觀分異格局。其中,非生物因素中的水文因素直接影響濕地范圍及內(nèi)部生態(tài)過程,氣候土壤地貌等因素則相對比較穩(wěn)定.人為因素比較特殊，可直接或間接地改變濕地范圍及內(nèi)部生態(tài)特征. 而生物因素資料比較缺乏, 且對于濕地的作用相對較弱。因此,黃河三角洲濕地景觀演變的驅動因素分析,應圍繞濕地水文因素，重點考慮對濕地

9、有重要影響的自然因素和可以改變的、較為特殊的人為因素。3.1 黃河水沙資源變化是濕地景觀格局演變的根本動力黃河是三角洲唯一的客水資源，黃河水沙資源是黃河三角洲濕地賴以生存發(fā)育的根本，是形成和維持黃河三角洲原生濕地生態(tài)系統(tǒng)的主導因素，是三角洲濕地生態(tài)系統(tǒng)順向演替的根本動力。良好的黃河水沙資源基本能保證三角洲濕地面積有一定的增加。如: 在1976年1992年，相對較好的水沙資源保證了新增濕地面積為22.8 km2/a 。但進入九十年代以來，隨著黃河水沙資源的逐年減少,河口水沙量發(fā)生較大變化，黃河三角洲新增濕地面積增加趨勢趨緩甚至出現(xiàn)萎縮現(xiàn)象。如:在2004年河口出汊后由于入海水沙量的大量減少,河口

10、南汊新增的濕地明顯蝕退。但是如果有洪水存在, 三角洲濕地面積還可以有一定的增加, 如:1996年的濕地情況。黃河來水來沙的逐年減少，不僅造成了濕地面積萎縮,更使三角洲失去了維持本區(qū)水系和水文生態(tài)平衡的主導因素，導致河口濕地水文條件的改變，影響了整個濕地生態(tài)系統(tǒng)的發(fā)展方向。3.2 不合理的土地利用開發(fā)是導致濕地景觀變化的主要驅動力不合理的石油鹽田開發(fā)等土地利用開發(fā)導致濕地水文和生態(tài)系統(tǒng)發(fā)生了重大變化，加深了濱海濕地鹽堿地等的破碎化和中小斑塊的增多，破壞甚至喪失了濕地物種的生境條件。而且導致了新生陸地的大面積次生鹽漬化，鹽堿灘面積急劇增加。隨著不合理的土地利用開發(fā)的強度越來越大，人工鹽田油田等面積

11、顯著增長,而自然濕地將趨向減少和不斷萎縮。這種變化趨勢將使本區(qū)濕地景觀的天然性降低，濕地生態(tài)系統(tǒng)良性循環(huán)受到威脅。3.3 水利工程建設是改變濕地水文的重要因素大型水利工程建設這類高強度的人類活動改變了河口地貌、沉積相分布與水動力條件，對河口濕地景觀格局和河口濕地水文狀況具有顯著影響。其中,黃河上游水利工程建設改變了河口濕地的水文周期、水文過程，影響了濕地正常發(fā)育，加深濕地破碎化程度，導致濕地面積萎縮。河口水庫的修建，改變了濕地的水文條件，導致濕地出現(xiàn)鹽堿化現(xiàn)象,導致蘆葦面積的萎縮和破碎化程度的加深，使?jié)竦厣硢适Ш推瑪嗷?，從而威脅生物多樣性。另外，堤防工程和防潮工程建設，改變了濕地的水文周期和

12、水文特征，使?jié)竦厮闹芷谟砷L變短，導致濕地植物群落的逆向演替、生態(tài)系統(tǒng)平衡失調(diào)、生物多樣性降低。為了協(xié)調(diào)工程建設與濕地保護之間關系，河口堤防建設、防潮工程以及入海流路治理工程應充分考慮濕地水文周期和水文條件要求，在適當?shù)奈恢妙A留口門或建設生態(tài)閘，在植物生長季節(jié)有計劃地向堤外濕地進行補水，以維持淡水濕地和濱海濕地生態(tài)系統(tǒng)的良性循環(huán)。3.4 自然災害加劇了濕地景觀的逆向演替黃河口三角洲是發(fā)生風暴潮最嚴重的地區(qū)之一。每次風暴潮浸沒縱深達幾十公里，給三角洲濕地生態(tài)系統(tǒng)造成很大破壞和威脅。同時風暴潮是灘涂濕地和重鹽堿荒地土壤鹽分的主要來源，加劇了土地鹽堿化程度，致使?jié)竦厣鷳B(tài)系統(tǒng)向著重鹽堿荒地和光板地生態(tài)

13、系統(tǒng)演替，破壞了濕地生態(tài)系統(tǒng)的發(fā)展。3.5 文化因素是人類改變濕地景觀格局的重要驅動力思想、意識、法律、管理等文化因素是人類改變濕地景觀格局的重要驅動力。人口、技術、政治經(jīng)濟體制、政策等人為因素的影響在一定程度可減緩或加劇濕地景觀格局的改變。土地開發(fā)、水利工程建設等導致了濕地面積的萎縮，改變了濕地的水文條件，加深了濕地的破碎化程度等。但嚴格的立法、濕地科學的普及、高水平的管理等措施，可加大對濕地的保護力度和強度，在一定程度上減緩、遏制濕地逆向演替速度和趨勢，促進濕地生態(tài)系統(tǒng)的良性循環(huán)。黃河三角洲自然保護區(qū)的建設以及河口濕地恢復工程的實施初步遏制了淡水濕地面積萎縮的趨勢就是一個很好的說明。Stu

14、dy on driving forces of Wetland Change in the YellowRivers 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 remote

15、 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 and s

16、ediment 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 wetland in

17、 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 wetland ec

18、osystem 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 of wet

19、land 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-made c

20、hanging 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 wetland is

21、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 thecontrast, artificial wetland, mainly including paddy fiel

22、d, 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 characteristicsTh

23、e 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, rangi

24、ng 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, the in

25、creases 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 undergo

26、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 around wes

27、tern 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 nature re

28、serve 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 vegetation. M

29、oreover, 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 birds are

30、 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 fauna an

31、d 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 During th

32、e 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 of RW to

33、 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 largest ch

34、anges 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 transferring ar

35、ea.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 the Yell

36、ow 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 mouth of p

37、revious 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 watercourse and c

38、urrent 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 salty field

39、s 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 thecurrent watercourse of the Yellow River. The increasing AW from OW is mainly situated between the previous watercourse and current wate

40、rcourse 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 pattern can

41、 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-biotic (p

42、hysical) 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 scope of w

43、etland 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 factors, in cl

44、ose relation to the hydrologic factors of wetlands.3.1 Water and sediment resources of the Yellow RiverThe 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 River is the basi

45、c 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 the YRMD. E.g.

46、 the annual2new-born wetlands is about 22.8 km per year due to more water and sedimentresources 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., the coastland

47、s 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 unbalance of water sy

48、stem and hydrological ecology in the YRMD.The evolution of wetland landscape has obviously been influenced.3.2 Overexploitation of land-useUnreasonable exploitation of land-use is the main driving forces of the evolution of space-time pattern of wetland landscape in the YRMD. Because these kinds of

49、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 addition, saline lagoon h

50、as 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 these changes will sur

51、ely cause the continuous decrease of natural wetlands and imperil the positive evolution of wetland ecosystems in the YRMD.3.3 Construction of hydraulic engineeringThe construction of hydraulic engineering is an important factor for the changes of wetland hydrology, because this kind of human activi

52、ties 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 and