Monitoring vegetation dynamics in Zhongwei, an arid city of Northwest China
| dc.contributor.author | Wang, Haitao | en |
| dc.contributor.committeechair | Kennedy, Lisa M. | en |
| dc.contributor.committeemember | Juran, Luke | en |
| dc.contributor.committeemember | Shao, Yang | en |
| dc.contributor.committeemember | Thomas, Valerie A. | en |
| dc.contributor.department | Geography | en |
| dc.date.accessioned | 2014-06-11T08:00:55Z | en |
| dc.date.available | 2014-06-11T08:00:55Z | en |
| dc.date.issued | 2014-06-10 | en |
| dc.description.abstract | This case study used Zhongwei City in northwest China to quantify the urbanization and revegetation processes (1990-2011) through a unified sub-pixel measure of vegetation cover. Research strategies included: (1) Conduct sub-pixel vegetation mapping (1990, 1996, 2004, and 2011) with Random Forest (RF) algorithm by integrating high (OrbView-3) and medium spatial resolution (Landsat TM) data; (2) Examine simple Dark Object Subtraction (DOS) atmospheric correction method to support temporal generalization of sub-pixel mapping algorithm; (3) And characterize patterns of vegetation cover dynamics based on change detection analysis. We found the RF algorithm, combined with simple DOS, showed good generalization capability for sub-pixel vegetation mapping. Predicted sub-pixel vegetation proportions were consistent for "pseudo-invariant" pixels. Vegetation change analysis suggested persistent urban development within the city boundary, accompanied by a continuous expansion of revegetated area at the city fringe. Urban development occurred at both the suburban and urban core areas, and was mainly shaped by transportation networks. A transition in revegetation practices was documented: the large-scale governmental revegetation programs were replaced by the commercial afforestation conducted by industries. This study showed a slight increase in vegetation cover over the time period, balanced by losses to urban expansion, and a likely severe degradation of vegetation cover due to conversion of arable land to desert vegetation. The loss of arable land and the growth of artificial desert vegetation have yielded a dynamic equilibrium in terms of overall vegetation cover during 1990 to 2011, but in the long run vegetation quality is certainly reduced. | en |
| dc.description.degree | Master of Science | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:3160 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/48893 | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Urbanization | en |
| dc.subject | Vegetation dynamics | en |
| dc.subject | Dark Object Subtraction (DOS) | en |
| dc.subject | Random Forest | en |
| dc.subject | Sub-pixel mapping | en |
| dc.title | Monitoring vegetation dynamics in Zhongwei, an arid city of Northwest China | en |
| dc.type | Thesis | en |
| thesis.degree.discipline | Geography | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |
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