Scrubbing Up: Multi-Scale Investigation of Woody Encroachment in a Southern African Savannah
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Area
2.2. Land Cover Field Survey
2.3. Classification Nomenclature
2.4. Image Analysis
2.5. Multi-Scale Comparison
2.6. Environmental Drivers of Land Cover Change
3. Results
3.1. Land Cover Change
3.2. Nkhulu Exclosure Area
3.3. Multi-Scale Comparison
3.4. Environmental Drivers of Land Cover Change
4. Discussion
4.1. Multi-Scale Monitoring of Land Cover Change
4.2. Land Management and Ecological Impacts of Land Cover Change
5. Conclusions
Supplementary Materials
Acknowledgments
Author Contributions
Conflicts of Interest
References
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General Habitat | Medium Resolution Land Cover Classes | VHR Land Cover Classes |
---|---|---|
Woodland | 1. Closed woodland (75–100% canopy cover) | 1. Trees (main trunk >7 cm diameter) |
2. Open woodland (50–75% canopy cover) | 2. Shrubs (main trunk <7 cm diameter) | |
Grassland | 3. Discontinuous grassland (25–50% canopy cover) | 3. Long grass |
4. Continuous grassland (0–25% canopy cover) | 4. Sparse grass | |
Anthropogenic classes | 5. Agriculture | 5. Agriculture |
6. Built-up | 6. Built-up | |
Bare | 7. Bare | 7. Bare |
Water | 8. Water | 8. Water |
9. Swamp | 9. Swamp |
Sensor | Image Acquisition Date | Sites | Spatial Resolution (m) | Spectral Bands | Overall Classification Accuracy (%) |
---|---|---|---|---|---|
QuickBird | 9 December 2002 | 1 | 2.8 | B, G, R, NIR | 91.0 |
IKONOS | 7 March 2002 | 2 | 4 | B, G, R, NIR | 90.6 |
IKONOS | 28 April 2001 | 3 | 4 | B, G, R, NIR | 87.7 |
WorldView-2 | 14 October 2014 | 1 | Resampled to 2.8 | CB, B, G, Y, R, RE, NIR1, NIR2 | 90.2 |
IKONOS | 27 September 2014 | 2 | 4 | B, G, R, NIR | 92.5 |
IKONOS | 27 September 2014 | 3 | 4 | B, G, R, NIR | 90.6 |
Landsat ETM+ | 18 June 2002 | 1, 2 and 3 | 30 | B, G, R, NIR, SWIR1, SWIR2 | 75.2 |
Landsat OLI | 27 June 2014 | 1, 2 and 3 | 30 | CA, B, G, R, NIR, SWIR1, SWIR2, C | 75.2 |
Class | Site 1 | Site 2 | Site 3 | Sites 1–3 Total | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | 2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | 2001 cover (Ha) | 2014 cover (Ha) | Cover change (%) | February 2001 cover (Ha) | 2014 cover (Ha) | Cover change (%) | |
Trees | 814.3 | 550.4 | −5.3 | 1801.5 | 502.6 | −17.1 | 1864.3 | 482.3 | −11.8 | 4421.8 | 1299.3 | −13.5 |
Shrubs | 1440.8 | 2238.7 | +16.1 | 1380.0 | 2652.0 | +16.7 | 1436.6 | 3609.6 | +18.6 | 4029.7 | 8222.7 | +18.1 |
Long grass | 2272.4 | 1637.4 | −12.8 | 3629.1 | 3585.0 | −0.6 | 7496.9 | 6751.2 | −6.4 | 12,738.1 | 11,556.8 | −5.1 |
Sparse grass | 164.7 | 215.1 | +1.0 | 424.7 | 466.9 | +0.6 | 400.3 | 426.2 | +0.2 | 955.9 | 1057.1 | +0.4 |
Bare | 127.3 | 174.7 | +1.0 | 170.2 | 240.8 | +0.9 | 172.2 | 221.4 | +0.4 | 440.7 | 600.0 | +0.7 |
Swamp | 29.4 | 21.7 | −0.2 | 79.9 | 19.2 | −0.8 | 142.2 | 106.5 | −0.3 | 249.2 | 148.4 | −0.4 |
Built up | 37.6 | 60.8 | +0.5 | 17.5 | 18.4 | 0.0 | 7.8 | 6.4 | 0.0 | 62.2 | 85.2 | +0.1 |
Water | 68.6 | 56.4 | −0.3 | 77.3 | 41.5 | −0.5 | 153.0 | 69.6 | −0.7 | 287.0 | 160.0 | −0.5 |
Agriculture | - | - | - | 29.1 | 84.3 | +0.7 | - | - | - | 29.1 | 84.3 | +0.2 |
Class | Site 1 | Site 2 | Site 3 | Sites 1–3 Total | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | 2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | 2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | 2002 cover (Ha) | 2014 cover (Ha) | Cover change (%) | |
Closed woodland | 370.3 | 1250.7 | +13.6 | 300.1 | 918.0 | +4.9 | 114.2 | 979.6 | +7.0 | 730.4 | 2960.9 | +7.4 |
Open woodland | 2713.0 | 2477.4 | −3.6 | 2446.2 | 2605.5 | +1.3 | 3107.2 | 3684.3 | +4.6 | 7820.4 | 8301.7 | +1.6 |
Discontinuous grassland | 2065.8 | 1696.4 | −5.7 | 4331.7 | 4275.2 | −0.4 | 5249.2 | 3961.8 | −10.4 | 11,106.5 | 9390.9 | −5.7 |
Continuous grassland | 1044.2 | 651.5 | −6.0 | 4794.9 | 4327.7 | −3.7 | 3299.2 | 3335.2 | +0.3 | 8720.6 | 8074.2 | −2.1 |
Bare | 107.6 | 154.0 | +0.7 | 390.1 | 273.8 | −0.9 | 244.3 | 216.3 | −0.2 | 705.2 | 608.7 | −0.3 |
Swamp | 56.8 | 99.8 | +0.7 | 86.8 | 72.1 | −0.1 | 328.6 | 142.0 | −1.5 | 466.6 | 292.5 | −0.6 |
Built up | 50.2 | 78.3 | 0.4 | 10.7 | 21.8 | +0.1 | 0.1 | 1.1 | 0.0 | 61.1 | 101.3 | +0.1 |
Water | 85.0 | 84.3 | 0.0 | 67.5 | 67.6 | 0.0 | 85.9 | 108.3 | +0.2 | 226.3 | 245.9 | +0.1 |
Agriculture | - | - | - | 228.2 | 94.3 | −1.1 | - | - | - | 234.5 | 95.0 | −0.5 |
Class | Nkhulu Exclosure | Site 3 Excluding Nkhulu Exclosure | ||||
---|---|---|---|---|---|---|
2001 Cover (Ha) | 2014 Cover (Ha) | Cover Change (%) | 2001 Cover (Ha) | 2014 Cover (Ha) | Cover Change (%) | |
Trees | 21.6 | 24.8 | +2.8 | 1839.7 | 465.4 | −11.9 |
Shrubs | 16.7 | 48.2 | +27.4 | 1420.3 | 3552.7 | +18.4 |
Long grass | 61.1 | 36.7 | −21.2 | 7438.2 | 6715.1 | −6.3 |
Sparse grass | 10.5 | 4.4 | −5.3 | 389.9 | 421.9 | +0.3 |
Bare | 3.0 | 0.6 | −2.2 | 169.2 | 220.8 | +0.4 |
Swamp | 1.5 | 0.0 | −1.3 | 140.7 | 106.5 | −0.3 |
Built up | 0.0 | 0.0 | 0.0 | 7.8 | 6.4 | 0.0 |
Water | 0.3 | 0.0 | −0.3 | 152.7 | 69.6 | −0.7 |
© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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Marston, C.G.; Aplin, P.; Wilkinson, D.M.; Field, R.; O’Regan, H.J. Scrubbing Up: Multi-Scale Investigation of Woody Encroachment in a Southern African Savannah. Remote Sens. 2017, 9, 419. https://doi.org/10.3390/rs9050419
Marston CG, Aplin P, Wilkinson DM, Field R, O’Regan HJ. Scrubbing Up: Multi-Scale Investigation of Woody Encroachment in a Southern African Savannah. Remote Sensing. 2017; 9(5):419. https://doi.org/10.3390/rs9050419
Chicago/Turabian StyleMarston, Christopher G., Paul Aplin, David M. Wilkinson, Richard Field, and Hannah J. O’Regan. 2017. "Scrubbing Up: Multi-Scale Investigation of Woody Encroachment in a Southern African Savannah" Remote Sensing 9, no. 5: 419. https://doi.org/10.3390/rs9050419
APA StyleMarston, C. G., Aplin, P., Wilkinson, D. M., Field, R., & O’Regan, H. J. (2017). Scrubbing Up: Multi-Scale Investigation of Woody Encroachment in a Southern African Savannah. Remote Sensing, 9(5), 419. https://doi.org/10.3390/rs9050419