Mapping coastal salt marshes in China using time series of Sentinel-1 SAR

Hu, Yuekai; Tian, Bo; Lin, Yu‐Ching; Li, Xiuzhen; Huang, Ying; Shi, Runhe; Jiang, Xiaoyi; Wang, Lihua; Sun, Chao

doi:10.1016/j.isprsjprs.2021.01.003

Cited by 84 publications

(43 citation statements)

References 68 publications

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“…Also, the similarity of dense P. australis and S. alterniflora stands represented in SAR data may lead to misclassification of these two species in some regions. For example, Hu et al [57] misclassified S. alterniflora as P. australis in Yueqing Bay where our results showed only S. alterniflora covered large extents as founded in our field survey. SAR data have advantages of differentiating plant species with various heights, while multispectral data contain abundant spectral information.…”

Section: A Total Extent Estimatementioning

confidence: 48%

“…In southern China, P. australis usually grows with C. malaccens and the latter is dominant in Guangxi as we found in the field survey. Hu et al [57] found no C. malaccens but only P. australis in southern China, which was due to the difficulty in distinguishing these two species by SAR. Also, the similarity of dense P. australis and S. alterniflora stands represented in SAR data may lead to misclassification of these two species in some regions.…”

Section: A Total Extent Estimatementioning

confidence: 99%

Section: A Total Extent Estimatementioning

confidence: 99%

“…Hu et al [57] mapped coastal saltmarshes in China using time series of Sentinel-1 SAR data and interpreted 127,477 ha with 4 species of saltmarshes. Our results were 7.4% lower than Hu et al [57] mainly due to the discrepancy of Suaeda. The plants of Suaeda are quite short and small, and sparsely distributed if newly transplanted, thus leading to low reflectance in multispectral Sentinel-2 data and difficulty in differentiating from tidal flats.…”

Section: A Total Extent Estimatementioning

confidence: 99%

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Areal Extent, Species Composition, and Spatial Distribution of Coastal Saltmarshes in China

Jin

Chen

et al. 2021

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Coastal saltmarshes are key ecosystems with important ecological functions. Yet, they have experienced widespread decline. Due to their importance, the conservation and restoration of saltmarshes are globally-shared objectives, including China. Despite multiple local studies, nationwide information about saltmarshes in China is scarce. Thus, we used remote sensing to delineate the spatial distribution and areal extent of saltmarshes along coastal China, and resolve their species composition. By interpreting 10 m spatial resolution Sentinel-2 images on Google Earth Engine, assisted with field survey and literature search, totally 118,010 ha of saltmarshes were delineated in coastal China in 2019. Seven typical saltmarsh species were identified, with Phragmites australis, Spartina alterniflora and Scirpus mariquater as dominant species, accounting for 95.5% of total saltmarsh extent, while Suaeda salsa, Tamarix chinensis, Cyperus malaccensis and Sesuvium portulacastrum were present in limited abundance. The P. australis and exotic species S. alterniflora grow along almost all coastal provinces, but P. australis dominates in the north while S. alterniflora dominates in the middle part of coastal China. Suaeda salsa occurs mainly in the north and has suffered large losses. Tamarix chinensis is abundant in Shandong province, S. mariquater in the Yangtze River delta, C. malaccensis in Guangdong and Guangxi provinces, and S. portulacastrum in Taiwan. The exotic species S. alterniflora expanded extensively along the coast and its expansion rate continues to increase. The results provided conform a muchneeded baseline for future monitoring efforts and the assessment of progress in the conservation and restoration projects toward recovering saltmarshes in China. Index Terms-Distribution, remote sensing, saltmarsh, Sentinel-2 I. INTRODUCTION ALTMARSHES are coastal ecosystems formed by herbaceous communities growing in saltwater or brackish mudflats that

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Section: A Total Extent Estimatementioning

confidence: 48%

Section: A Total Extent Estimatementioning

confidence: 99%

Section: A Total Extent Estimatementioning

confidence: 99%

Section: A Total Extent Estimatementioning

confidence: 99%

See 2 more Smart Citations

Areal Extent, Species Composition, and Spatial Distribution of Coastal Saltmarshes in China

Jin

Chen

et al. 2021

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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show abstract

“…Subsequently, the invasion and control of exotic species have become a hot topic and drawn wide attention from ecoenvironmental community all over the world [11]. Information on the spatial distribution, areal extent, and species composition of salt marshes across a wide range of time is of critical importance to governmental agencies, science communities, and citizens, whereas despite national and international concerns, few data of salt marshes in China have been publicly available at national scale [12,13].…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Mapping of Salt Marshes in the Intertidal Zone of China during 1985–2019

Chen

Jin

et al. 2022

J Remote Sens

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This study mapped the areal extent, identified the species composition, and analyzed the changes of salt marshes in the intertidal zone of China during the period 1985–2019. With the aid of the cloud platform of the Google Earth Engine, we selected Landsat 5/8 and Sentinel-2 images and used the support vector machine classification method to extract salt marsh information for the years of 1985, 1990, 1995, 2000, 2005, 2010, 2015, and 2019. Seven major species of salt marshes: Phragmites australis, Suaeda spp., Spartina alterniflora, Scirpus mariqueter, Tamarix chinensis, Cyperus malaccensis, and Sesuvium portulacastrum were identified. Our results showed that salt marshes are mainly distributed in Liaoning, Shandong, Jiangsu, Shanghai, and Zhejiang, with varying patterns of shrinking, expansion, or wavering in different places. The distribution of salt marshes has declined considerably from 151,324 ha in 1985 to 115,397 ha in 2019, a drop of 23.7%. During the same period, the area of native species has dropped 95.4% from 77,741 ha to 3,563 ha for Suaeda spp. and 45.1% from 60,511 ha to 33,193 ha for P. australis; on the contrary, the area of exotic species, S. alterniflora, has exhibited a sharp rise from just 99 ha to 67,527 ha. For the past 35 years, the driving factors causing salt marsh changes are mainly land reclamation, variations in water and sand fluxes, and interspecific competition and succession of salt marsh vegetation. These results provide fundamental reference information and could form the scientific basis for formulating policies for the conservation and utilization of salt marsh resources in China.

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Leaf litter decomposition and its drivers differ between an invasive and a native plant: Management implications

Cheng

Liu

Zhang

et al. 2022

Ecological Applications

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Litter decomposition is a key process of the carbon cycle in terrestrial and aquatic ecosystems. The dominant conceptual model of litter decomposition assumes that environmental conditions, litter traits, and decomposer composition control litter decomposition in a decreasing order, yet whether this hierarchical model applies to both invasive and native plant species is unknown. Here, by comparing a widespread invasive plant and its native counterpart in Chinese coastal saltmarshes, we aimed to examine whether the hierarchy of factors controlling litter decomposition varies with plant species in the face of plant invasions. Leaf litter of invasive Spartina alterniflora and native Phragmites australis was collected across an 18° latitudinal range to capture wide variation in litter traits. These leaf litter samples were transported to three saltmarsh sites of different latitudes and were incubated in litterbags varying in mesh size (0.1, 2, and 5 mm) to manipulate decomposer composition. After 90‐day incubation, we found a parallel latitudinal pattern in leaf litter decomposition rate (k) between S. alterniflora and P. australis regardless of saltmarsh site and mesh size. Nonetheless, the k value of S. alterniflora was 2.2‐fold higher than that of P. australis. Moreover, there was a shift in the hierarchy of factors controlling k values between S. alterniflora and P. australis: environmental conditions (climate and soil) dominated other factors in P. australis, whereas litter traits contributed more than environmental conditions in S. alterniflora. Overall, our findings show that leaf litter decomposition and its dominant controlling factors across broad geographical ranges can vary with plant invasions, having important implications for managing invasive plants in the context of conserving coastal blue carbon.

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Mapping coastal salt marshes in China using time series of Sentinel-1 SAR

Cited by 84 publications

References 68 publications

Areal Extent, Species Composition, and Spatial Distribution of Coastal Saltmarshes in China

Areal Extent, Species Composition, and Spatial Distribution of Coastal Saltmarshes in China

Spatiotemporal Mapping of Salt Marshes in the Intertidal Zone of China during 1985–2019

Leaf litter decomposition and its drivers differ between an invasive and a native plant: Management implications

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