Evolution forms of land systems based on ascendency and overhead: A case study of Shaanxi Province, China

摘要

There were three basic forms of land system evolution: fluctuation, degradation and optimization. Based on the basic principles of system analysis, this study established a framework for analyzing the evolution form of land systems according to the sustainability and the relationship between ascendency and overhead, and then identified the evolution froms of land systems in Shaanxi Province. The results showed that the evolution of land systems in Shaanxi Province was in a fluctuation form and its sustainability showed a trend of increasing first and then decreasing between 1980 and 2015. The sustainability of land system evolution in Loess Plateau and Guanzhong Basin also increased first and then decreased, the changes in Loess Plateau were particularly significant and reached an optimization form during 1990-2000 and 2005-2010. The land system evolution in Guanzhong Basin in a less sustainable form of fluctuation after 2000. Land systems in Qinba Mountain were in an optimization form except for during 1980-1990 and 2005-2010. All three geographic units evolved in an optimization form between 1990 and 2000, and the sustainability of land system evolution in Shaanxi Province has increased from north to south both in 2000-2005 and 2010-2015; however, its sustainability weakened from north to south in 2005-2010. The verification of the results based on the information entropy change of the land systems showed that it was feasible and credible to distinguish the evolution form of land systems based on ascendency and overhead.