Supported by National Natural Science Foundation of China (41771199); Basic Research Project of Jiangsu Province, China (BK20171277).

1 Introduction

Suaedasalsa, an annual saline herb, is a kind of plant with very strong salt tolerance[1], mainly grows in the marsh saline environment[2], and is distributed in the Northeast, North China, northwest inland and coastal areas to the north of Yangtze River[3]. It also has stronger adaptation to the saline environment, called indicator plant of saline soil[4]. Thus, S. salsa is pioneer species of plant in coastal wetland. As it can absorb and accumulate much NaCl or Na2SO4 to reduce the soil salinity, it is awarded the title of an admirable breed of saline soil improvement, which exerts an important influence on maintaining ecological system stability and succession[5-8]. However, with increasingly intensive human management activities, and the success of the S. alterniflora’s introduction, the landscape evolution of Salsa marsh has changed apparently and imposed negative effects on regional biodiversity and eco-environment.

Yancheng coastal wetland, including two national reserves, Yancheng Nature Reserve and Dafeng elk nature reserve, is one of the typical original coastal wetlands in China and even in the world. And it keeps natural ecological system structure and function basically[8]. Under the natural and artificial circumstance, coastal wetlands landscape has apparently changed especially the trend of S. salsa marsh’s deviation from natural laws. S. salsa as an important part of local eco-system, is indigenous in Yancheng coastal wetland. At present, the research of S. salsa mainly focuses on the physiological characteristics, scale biological ecological adaptation, soil improvement and saline-alkali land ecological restoration from the aspect of ecological system[3-4, 10-13]. However, there are few researches on space-time evolution from the scale of landscape. By choosing Yancheng Nature Reserve core region as typical area and making a comparison between artificial administrative zones and the natural S. salsa marsh, this paper attempts to reveal the evolution characters of Yancheng coastal area under the artificial effects, and provide a reference for guiding coastal wetland’s ecological conservation.

2 Data sources and methods

2.1 Study area The study area is in the core zone of Yancheng National Nature Reserve, which is north to Xinyanggang River, south to Doulonggang River and west to seawalls and is regarded as the typical growth tidal flat of wetlands in Jiangsu with a total area of 1.740×104 ha. At present, the reserves are divided into north and south central parts (Fig.1).

调查的上海环城绿带植物群落的乔木层的 Shannon-Wiener 指数在 0～1.572之间,平均为0.750。群落的物种多样性指数整体偏小,乔灌草各层物种多样性变化没有明显规律,不同群落间的物种多样性有明显差异。该结果反映出百米林带植物群落在最初进行设计时,对群落的生态效应和稳定性未作充分考虑,从而表现出群落丰富度不够。

Fig.1 Location of study area

Fig.2 Landscape changes in the coastal wetlands in artificial area from 2000 to 2011

The northern area is about 0.540× 104 ha. As the reserves focus on protecting the key wintering habitat for red-crowned cranes, it is necessary to create a good habitat for red-crowned cranes and other rare species, and the artificial wetland and reed marsh restoration experiment in its core area has set up since 1993, becoming the typical artificial management area (Fig.2). Southern area is approximately 1.100×104 ha. The area by human disturbance is fragile, the landscape pattern as well as evolution is mainly affected by climate, topography, hydrology, soil, vegetation and other natural factors, becoming a typical wetland area under the control of natural conditions (Fig.3)[14].

Fig.3 Landscape changes in the coastal wetlands in natural area from 2000 to 2011

2.2 Data sources This research took three pictures of ETM+ images on May 4, 2000, May 21, 2006, and September 24, 2011 as the basic data sources. ETM+ images include 7 multi-spectral bands (resolution rate at 30 m) and one full-color band (resolution rate at 15 m) from the same sensor, and two kinds of resolution data can realize high precision fusion. To more accurately extract information, other auxiliary materials were used, including one diagram of 1∶400 000 coast land use map in Jiangsu province and the field investigation of 53 points GPS data. In ENVI 4.7, we used the non-supervision classification and decision tree classification method in combination with the field investigation to improve the interpretation precision, which reached 90% (Fig.2 and Fig.3). We used the ArcGIS9.3 to do overlay analysis of different images. The Fragstats 3.3 was used to calculate landscape index, and grid size was set to be 100 m. For unity in the study area, considering other landscape types of integrity at the same time, and on the basis of image in 2006 as a benchmark, 2000 and 2011 research area were cut in ArcGIS9.3.

Through the further analysis of landscape zone changes in salsa marsh by superimposing images of different periods, we can draw that artificial cofferdam accelerated the change of landscape zone. In 2000-2006, the average width of salsa marsh decreased from 2 570.800 m to 1 010.272 m in artificial area, decreasing by 60.70%. Compared with the natural areas, it decreased more than 23%; salsa marsh in artificial area showed the characteristics of contraction from two directions to center, but in natural area showed the contraction features to the sea directions. During 2006-2011, salsa marsh presented the properties from the sea and land two directions to center both in the south and north. But the average width of salsa marsh decreased by 67.320% in artificial area, decreased more than 23% compared with natural area.

1.3.1 阴道微生态检测 应用pH精密试纸法检测pH值；将分泌物置于滴有生理盐水的载玻片上，直接光镜下检查阴道清洁度，进行革兰染色并在显微镜下进行观察，检测阴道菌群，包括念珠菌感染(vulvovaginal candidiasis，VVC)、滴虫感染(trichomonal vaginitis，TV),采用阴道分泌物悬滴法，用快速细菌性阴道病(bacterial vaginosis，BV)试剂盒检测BV。

where X and Y are the weighted centroid coordinates according to the area; Xi and Yi are the centroid coordinates of S. salsa marsh’s patch; Ci is the No. i area of S. salsa marsh’s patch; n is the number of S. salsa marsh’s patches.

3 Results and discussions

Through the spatial-temporal analysis, this paper revealed the influence of artificial cofferdam and S. alterniflora expansion on the evolution of S. salsa marsh in Yancheng coastal wetland. We drew the following conclusions.

Table 1 Landscape features ofsalsa marsh in natural area and artificial area

LandscapeindexesArtificialareaMay2000May2006Sept．2011NaturalareaMay2000May2006Sept．2011PLAND22．3038．7652．86429．74818．46310．301PA＿MN(ha)389．33365．57121．429298．071112．60948．167AI96．78087．54265．45595．71690．62681．337A＿RAT(ha/a)118．16751．500-296．998214．822

2.3 Analysis methods Landscape index points to highly concentrated landscape pattern information, reflecting the structure and spatial configuration and some other characteristics of simple quantitative index, which can quantitatively describe and monitor landscape structure characteristics changing with time[15]. This study selected landscape type percentage (PLAND), the degree of polymerization index (AI), average plaques area (PA_MN) to describe the basic characteristics of landscape; and used annual change area (A_RAT) to compare the rate of change with different drivers in different period of landscape. The study method of the centroid change in land use was introduced to the space changes of landscape. The centroid changes of S. salsa marsh were used to reveal its spatial evolution rules[16-17]. Formula is as follows:

crease in S. alterniflora marsh, and makes the tide cross it and reach salsa marsh, S. alterniflora expands to the lower edge of salsa marsh along tide ditch. At the same time, because S. alterniflora has the characteristics of wide ecological range, it can settle down on the lower edge of salsa marsh, which results in the appearance of niche overlapping and interspecific competition. S. alterniflora has two modes of reproduction, namely sexual reproduction and asexual reproduction. Sexual reproduction has certain advantage in adapting to different environment, the offspring produced by asexual reproduction have the same genetic composition as the parent. However, the reproduction of salsa depends on seed dispersal. The plant is short and small, they have little chance to survive when the tide assault frequency is more than 20%. So in the competition of salsa and S. alterniflora, the growth space is easier to be used and occupied by S. alterniflora in the bottom edge of salsa marsh[19-20], which hasformed the evolution pattern of salsa marsh to S. alterniflora marsh. In addition, artificial cofferdams effectively play the corridor function, not only stopping S. alterniflora expansion to land direction, but also changing S. alterniflora’s expansion direction, and turning to expand in south to occupy the living space of salsa. Through the calculation of S. alterniflora landscape centroid in 2006 and 2011, we found that it was offset in south-east direction slightly by 223.169 m, accelerated the transformation from salsa marsh to S. alterniflora marsh (Fig.7).

Through the comparison of the two areas, during 2000-2006, 178 ha salsa marsh in the artificial area was transferred into S. alterniflora marsh, accounting for 15.24% of the area of salsa marsh in 2000, and compared with the natural area, the transferring rate was higher than 13%. From 2006 to 2011, 138 ha salsa marsh was transferred into S. alterniflora marsh, accounting for 30.07% of the area of salsa marsh in 2006, and under natural conditions, the transferring rate was nearly higher than 10% (Table 3). At the same time, due to the expansion of S. alterniflora marsh, it made the trend of salsa marsh fragmentation obvious, from 2000 to 2011, the average patch area of salsa marsh decreased by 94.50% in the artificial area, more than 11% than in the natural area; landscape gathering index in the artificial area dropped from 95.780 to 65.455, decreasing by 31.66%, more than 16% than in the natural area.

3.2 The effect of artificial cofferdams andS. alterniflora expansion onS. salsa marsh Landscape centroid changes in S. salsa marsh by human activities and natural processes from 2000 to 2011 were shown in Fig.4-5.

对于这个世界上所有喜欢英国车的人来说，他们想必也信奉纯粹的设计与我们的生活息息相关。毕竟设计的体现形式就是给人们带来愉悦的感受。这种愉悦既包含最浅层的目光所及的满足，也包含那种功能性层面的惺惺相惜。优秀的设计从来都不只有表面功夫，就像我本人非常喜欢的一句话，“Design Save The World”，设计的本质其实一直在推动着人类的发展与进步。

Fig.4 Landscape centroid changes inSuaedasalsa marsh by human activities from 2000 to 2011

Fig.5 Landscape centroid changes inSuaedasalsa marsh by natural processes from 2000 to 2011

The models in the artificial area are recovering reed marshes with artificial efforts and breeding mainly by building dams in north of the core region of Yancheng national natural reserve. The succession process from salsa marsh to reed marsh can be accelerated by man-made methods to further change the hydrological process and improve the environment of salsa with artificial cofferdam preventing the coming of tide and artificial breeding reeds. According to the results of soil and surface water salinity monitoring in Yancheng nature reserve in April 2011, we can see (Table 2) that: soil moisture in the artificial area was significantly higher than in the nature area; soil salinity in the artificial area was lower than in the nature area except S. alterniflora marsh. Through monitoring the salinity of the surface water in reed marshes both in the tide ditch in natural wetland and cofferdam area in artificial area, we can find that the salinity of the former was as high as 1.090%, while the latter was only 0.230%. So we can say that artificial cofferdam makes the hydrological conditions more conducive to the development of fresh water reed marshes in artificial area. At the same time, soil moisture increase and soil salinity decline in salsa marsh, changed the habitats of salsa which rendered it more conducive to the direction of the development of reed marshes.

Table 2 The contrast of soil moisture and salinity of coastal wetlands between natural area and artificial area

ArtificialareaSpartinamarshSalsamarshReedmarshNaturalareaSpartinamarshSalsamarshReedmarshMoisture47．36342．07638．83446．33240．70336．820Salinity2．0060．8170．3081．3280．9530．347

From 2000 to 2006, in the artificial area, through the artificial cofferdam, 539 ha salsa marshes changed into reed marshes and aquaculture ponds, accounting for 46.14% of salsa marsh area, and compared with natural conditions, the transfer rate was nearly 4% higher. From 2006 to 2011, 178 ha salsa marshes in the artificial area were transferred into reed marshes, accounting for 38.78% of salsa marsh area in 2006, compared with natural conditions, the transfer rate was nearly 20% higher (Table 3).

Table 3 Landscape transition matrix by natural processes and human activities

LandscapetransitionHumanactivities2000—20062006—2011Area∥haTransitionrate∥%Area∥haTransitionrate∥%Naturalprocesses2000—20062006—2011Area∥haTransitionrate∥%Area∥haTransitionrate∥%Ponds15713．4400370．8900Reed marsh38232．717838．78173241．5151419．85Spartinamarsh17815．2413830．07882．1153820．77Suaedamarsh45138．6114231．15231655．5153859．38

At the same time, due to the impact of human during 2000-2006, nearly 50% of salsa marshes were transferred into reed marshes, aquaculture ponds and dams. However, during 2006-2011, there was no new cofferdam area, salsa marsh in the cofferdam area disappeared, all transferred into reed marshes and aquaculture ponds, so the change rate of salsa marsh in this period slowed down. Therefore, the evolution rate of salsa marsh under the artificial cofferdam presented the obvious characteristics of being fast at first and then getting slower afterwards. In addition, the centroid change of salsa marsh and reed marsh has consistency in artificial area. In 2000-2006, reed marshes in south-east direction were offset 429.720 m; in 2006-2011, reed marshes in northwest direction were slightly offset 199.246 m (Fig.6).

S. alterniflora was introduced in the 1980s in Jiangsu coastal wetlands, and formed a large community in the 1990s, then its area expanded quickly, becoming the dominant wetland salt vegetation of marine marsh. S. alterniflora was distributed in the upper intertidal zone, and the top edge to the mean high tide, the lower edge to the mean sea-level, tide assault frequency was between 20% and 80%[18]. Because S. alterniflora has very strong function of promoting deposition, which causes the elevation in-

Fig.6 Landscape centroid changes in reed marsh by human activities from 2000 to 2011

（1）薪酬独立，独立董事在上市公司就职期间获得的薪金报酬必须与他人利益相互独立，互不牵连。此外，除薪资外不得以任何方式获取不恰当利益。

Fig.7 Landscape centroid changes inSpartinaalterniflora marsh by human activities from 2000 to 2011

The landscape centroid of salsa marsh in different times was calculated by using the formula one. We can see that the spatial evolution direction changed in salsa marsh under artificial cofferdam. During 2000-2006, the centroid of salsa marsh migrated by 1 042.710 m to north-east under the control of natural conditions. Under the influence of human, the centroid of salsa marsh migrated to south-east by 666.350 m. From 2006 to 2011, the centroid of salsa marsh migrated 88.329 m to the east and 320.029 m to the north in natural area, the main migration to the north. However, under the influence of human, it migrated 502.474 m to the east, 67.276 m to the north, to the east primarily.

4 Conclusions

3.1 Spatial-temporal evolution of landscape structure insalsa marshes Due to the different drivers, in the southern and northern parts of the study area, there was obvious differentiation in spatio-temporal changes. The area of salsa marsh in these two areas decreased overall. Comparing the two area we found that the salsa marsh area of northern artificial zone was reduced 87.16%, almost a decrease of nearly 22% compared with southern natural area. At the same time, the average patch area of salsa marsh was reduced 94.50% in artificial area, nearly 11% more than that in the southern area. AI in the artificial zone fell from 95.780 to 65.455 and fell from 95.716 to 81.337 in natural area during 2000-2011. In addition, from the rate of landscape changing, we saw that the rate of salsa marsh evolution changes was accelerated in artificial area, but under the control of natural conditions, the rate changed little. From 2000 to 2006, the area was reduced to 296.998 ha/a. the evolutional rate of salsa marsh was 214.822 ha/a in natural area during 2006-2011, but in artificial area, the evolutional rate of salsa marsh obviously increased rapidly first and then slowly from 2000 to 2006, the area was reduced to 118.167 ha, only 51.500 ha/a during 2006-2011.

Artificial cofferdam affected the landscape evolution in salsa marsh. Artificial cofferdam made artificial area transform into freshwater ecosystem, and meanwhile the freshwater reed marsh did benefit a lot from it. During the year 2000 to 2006, in the artificial area, by artificial cofferdam, 539 ha salsa marsh was transferred into reed marshes and aquaculture ponds, of which the transformation rate was nearly 4% higher than in the natural area. While from 2006 to 2011, the transformation rate was 20% higher than in the natural area, 178 ha salsa marsh was transferred into reed marsh. In the artificial management area, the consistency of landscape centroid change between reed marsh and salsa marsh showed that artificial cofferdam was an important factor for salsa marsh evolution.

Owing to the powerful ability of spreading and competition of S. alterniflora species, the coastal wetland has formed the pattern of "Salsa-Spartina marsh". In the artificial area and the natural area, during 2000-2006, 15.24% and 2.11% of salsa marsh was transferred into the S. alterniflora marsh; from 2006 to 2011, 30.07% and 20.77% of salsa marsh was replaced by the S. alterniflora marsh. At the same time, the trend of the salsa marsh was quite apparent as a result of S. alterniflora marsh expanding.

Salsa marsh is mainly developed in salt marsh environment. It is the original landscape type in the coastal wetlands and plays an important role in maintaining landscape diversity. However, human activities and invasion of S. alterniflora have decreased the area of Salsa marsh and even made it disappear, having a negative impact on regional biodiversity. Therefore, starting from protecting native species of S. salsa and maintaining landscape diversity, we identified temporal spatial evolution characteristics and response mechanism of salsa marsh in the coastal wetlands under different drivers, which was of positive significance to managing and using the coastal wetlands scientifically.

系统在获得数据分片后，对分片进行哈希计算，得到每个分片的哈希值后，与之前原数据存储在智能合约中的哈希值进行比对、验证。如果哈希值相同，则系统返回数据未被改动；反之，则提醒用户数据已经被篡改。另外，考虑到分布式存储的容错性，如果出现部分分片丢失，只要丢失的分片数量小于系统数据冗余分片数量，系统仍然能够还原数据源文件，具体如图8所示。

准确切取并称取5份相同的厚度和相同质量的紫菜置于相同玻璃器皿中，控制室内温度为常温，设定微波功率分别为100，200，300，400，500 W，微波干燥9 min，测定其水分含量和感官特征。

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