Remote-Sensed Monitoring of Dominant Plant Species Distribution and Dynamics at Jiuduansha Wetland in Shanghai, China
Abstract
:1. Introduction
2. Data and Methods
2.1. Study Area
2.2. Data Acquisition and Preprocessing
Sensor | Acquisition Date | Band | Resolution (m) | Tidal Level | Application |
---|---|---|---|---|---|
ZY-1 02C Satellite | 2012.05.16 | multi-spectral | 10 | low | automatic identification of vegetation type |
Panchromatic band | 5 | low | auxiliary visual interpretation | ||
ZY-3 Satellite | 2012.03.25 | multi-spectral | 5.8 | low | automatic identification of vegetation type |
Plant Species | Leaf-on Time | Leaf-off Time | Field Sample Numbers | Selected Pixels from Satellite Images | |
---|---|---|---|---|---|
2011 | 2012 | ||||
P. australis | Mid-April | November | 42 | 14 | 108 |
S. alterniflora | Mid-May | December | 32 | 21 | 124 |
Z. latifolia | Mid-April | November | 0 | 13 | 18 |
S. mariqueter | Late-April | November | 26 | 8 | 54 |
Total | 100 | 56 | 304 |
2.3. Spectral Characteristics of Different Plant Species
Plant Species | 2012-03-25 | 2012-05-16 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Image | Spectral Reflectance | NDVI | Image | Spectral Reflectance | NDVI | |||||
Green | Red | Near Infrared | Green | Red | Near Infrared | |||||
P. australis | 1041.41 | 1188.74 | 1480.74 | 0.11 | 1108.90 | 848.58 | 2473.68 | 0.49 | ||
S. alterniflora | 752.16 | 820.56 | 1108.46 | 0.15 | 1028.20 | 906.87 | 1376.87 | 0.21 | ||
Z. latifolia | 1153.06 | 1195.89 | 1316.67 | 0.05 | 1156.88 | 925.29 | 2240.35 | 0.42 | ||
S. mariqueter | 1145.07 | 1264.00 | 1438.11 | 0.06 | 1124.75 | 1003.39 | 1479.25 | 0.19 |
2.4. Schemes for Identifying Dominant Plant Species
- (1)
- Set NDVI5 as the object and assigned 0.12 as a threshold to divide NDVI5 into vegetated area (NDVI5 > 0.12) and non-vegetated area (NDVI5 ≤ 0.12).
- (2)
- Assigned −0.1 as a threshold to identify non-vegetated areas and water and assigned 0.28 as a threshold to group the vegetation areas into NDVI5-low and NDVI5-high areas.
- (3)
- According to the difference in green-up time, we identified the areas with NDVI5-low where NDVI3-S > −0.06 were S. alterniflora and the areas where NDVI3-S ≤ −0.06 were S. mariqueter. We identified the areas with NDVI5-high where NDVI3 > −0.06 was P. australis and the areas with NDVI3 ≤ −0.06 was Z. Latifolia.
3. Results and Analysis
3.1. Classification Precision Evaluation
Plant species | Reference Pixel Number | Classified Pixel Number | Correct Number | Production Precision | User Precision |
---|---|---|---|---|---|
S. mariqueter | 54 | 59 | 45 | 0.83 | 0.76 |
S. alterniflora | 124 | 130 | 112 | 0.90 | 0.86 |
P. australi | 108 | 98 | 93 | 0.86 | 0.95 |
Z. latifolia | 18 | 17 | 15 | 0.83 | 0.88 |
Total reference pixel number | 304 | 304 | 265 | ||
Overall classified precision = 87.17% | |||||
Kappa coefficient = 0.81 |
3.2. Spatial Distribution of Plant Species
Islands | P. australis | S. alterniflora | S. mariqueter | Z. latifolia | Total |
---|---|---|---|---|---|
Jiangyanansha | 12.66 | 6.93 | 109.11 | 225.22 | 353.93 |
Shangsha Island | 1089.46 | 52.47 | 303.51 | 0.00 | 1445.43 |
Zhongsha Island | 258.37 | 751.31 | 42.99 | 0.00 | 1052.67 |
Xiasha Island | 654.46 | 2491.49 | 433.22 | 0.00 | 3579.17 |
Total | 2014.95 | 3302.20 | 888.83 | 225.22 | 6431.19 |
Percentage | 31.33 | 51.35 | 13.82 | 3.50 | 100.00 |
3.3. Temporal Changes in Plant Species
Time | P. australis | S. alterniflora | S. mariqueter | |||
---|---|---|---|---|---|---|
Area (ha) | Spreading Rate (%/yr) | Area (ha) | Spreading Rate (%/yr) | Area (ha) | Spreading Rate (%/yr) | |
1997 * | 167.5 | 100 | 966.56 | |||
2004 * | 563.49 | 33.77 | 1014.39 | 130.63 | 1789.02 | 12.16 |
2012 | 2002.29 | 31.92 | 3295.26 | 28.11 | 779.72 | −7.05 |
4. Conclusions
- (1)
- Taking advantage of the different characteristics on NDVI of the four dominant plant species at different green-up phenophases, we developed a decision tree classification scheme to identify the distribution of these species. This method could effectively identify the four dominant plant species at Jiuduansha Wetland, with an overall classification accuracy of 87.17% and the Kappa Coefficient of 0.81;
- (2)
- S. alternifloras formed a large area of a single dominant salt marsh plant community which covered an area of 3302.20 ha at Jiuduansha Wetland. It had wide ecological amplitude that its upper limit of distribution can reach P. australis zone and lower limit of distribution can reach S. mariqueter zone. P. australis occupied about 2014.95 ha land area and mainly grew on high and middle tidal flats where elevation is higher than 2.9 m. Most of the S. mariqueter plant species grew on middle tidal flats where elevation is about 2–3 m. It covered an area of 888.83 ha and its community density increased with elevation;
- (3)
- The area of P. australi showed an increasing trend in from 1997 to 2004 and from 2004 to 2012, with an annual spreading rate of 33.77% and 31.92%, respectively. The area of S. mariqueter displayed an increasing trend and a decreasing trend from 1997 to 2004 and from 2004 to 2012, respectively, with an annual rate of 12.16% and −7.05%. The area of S. alterniflora showed an increasing trend in from 1997 to 2004 and from 2004 to 2012, with an annual spreading rate of 130.63% and 28.11%, respectively. Especially, S. alterniflora expanded very quickly and showed a trend of surrounding P. australi on Zhongsha Island and Xiasha Island and occupying the habitats of S. mariqueter.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Lin, W.; Chen, G.; Guo, P.; Zhu, W.; Zhang, D. Remote-Sensed Monitoring of Dominant Plant Species Distribution and Dynamics at Jiuduansha Wetland in Shanghai, China. Remote Sens. 2015, 7, 10227-10241. https://doi.org/10.3390/rs70810227
Lin W, Chen G, Guo P, Zhu W, Zhang D. Remote-Sensed Monitoring of Dominant Plant Species Distribution and Dynamics at Jiuduansha Wetland in Shanghai, China. Remote Sensing. 2015; 7(8):10227-10241. https://doi.org/10.3390/rs70810227
Chicago/Turabian StyleLin, Wenpeng, Guangsheng Chen, Pupu Guo, Wenquan Zhu, and Donghai Zhang. 2015. "Remote-Sensed Monitoring of Dominant Plant Species Distribution and Dynamics at Jiuduansha Wetland in Shanghai, China" Remote Sensing 7, no. 8: 10227-10241. https://doi.org/10.3390/rs70810227