Ecological Quality Evolution and Its Driving Factors in Yunnan Karst Rocky Desertification Areas

Abstract

Rocky desertification is a key element affecting regional ecological quality. Rocky desertification in Southwest China directly affects the ecological security of the Yangtze River and Pearl River basins and also restricts regional economic and social development. In order to clarify the evolution laws and key influencing factors of ecological quality in Yunnan karst rocky desertification areas, a quantitative analysis based on the remote sensing-based ecological index (RSEI) model was conducted to explore the overall evolution characteristics and change laws of ecological quality in Yunnan karst rocky desertification areas in the past 30 years. The correlation between RSEI, rock outcrop rate (Fr), and driving factors was determined by redundancy analysis. The results showed the following: (1) RSEI in Yunnan karst rocky desertification areas generally showed a decreasing trend, with a fluctuation in the mid-term, followed by a tendency to recover. It fell into three stages: decline, trough, and recovery, with fitting coefficients of -0.121, -0.057, and 0.157, respectively. In contrast, Fr showed an opposite tendency, illustrating the inverse relationship between RSEI and Fr, and the rate of sequential succession was much faster than that of the reverse succession under human measures of intervention. (2) The mean value of RSEI of Yunnan karst rocky desertification areas was generally lower than that of the total Yunnan Province land areas and Yunnan non-karst rocky desertification areas, but the mean value of Fr was generally more than that of both the above-mentioned areas. In addition, the RSEI and Fr of Yunnan karst rocky desertification areas both showed lower stability values than those of both the above-mentioned areas. This generally suggested a low ecological quality and a high degree of desertification under a low stability in Yunnan karst rocky desertification areas. (3) The correlation of RSEI and Fr with driving factors followed the order of topographic factors, soil factors > water factors > anthropogenic factors. Anthropogenic factors were the driving force changing the state of rocky desertification, geological factors such as topography and soil to a larger extent determined the original macroscopic ecological relationship of rocky desertification, and water factors lay between the above two. The findings of this research will provide theoretical support and a basis for the improvement of ecological quality and comprehensive control of karst rocky desertification in Yunnan Province.

Keywords: Yunnan karst rocky desertification areas; analysis of driving mechanisms; ecological quality evolution; karst rocky desertification.

Figure 1

Location of the study area and the area division.

Figure 2

Steps for the extraction of ecological quality information (RSEI).

Figure 3

Dynamic evolution characteristics of RSEI in Yunnan karst rocky desertification areas (1990–2020).

Figure 4

Statistics of changes in RSEI mean value in Yunnan Province (1990–2020).

Figure 5

Dynamic evolution characteristics of Fr in Yunnan karst rocky desertification areas (1990–2020).

Figure 6

Statistical changes in the mean of Fr in Yunnan Province (1990–2020).

Figure 7

Correlation of RSEI and Fr with modeling factors. Note: RSEI, Fr, NDVI, WET, IBI, SI, and LST respectively represent remote sensing-based ecological index, rock outcrop rate, normalized vegetation index, wetness component, index-based built-up index, bare soil index, and land surface temperature; RSEI and Fr are response variables and the rest are interpretation variables.

Figure 8

Correlation of RSEI and Fr with soil and topographic factors. Note: RSEI, Fr, dem, slope, aspect, pH_{_0}, BD_{_0,} AWC_{_0}, SOC_{_0}, Se, Reg, SL, and Sed respectively represent remote sensing-based ecological index, rock outcrop rate, elevation, slope gradient, slope aspect, soil pH value, soil bulk density, soil available water content, soil organic carbon in soil surface, soil erosion, regolith thickness, soil layer thickness, and sedimentary layer thickness; RSEI and Fr are response variables and the rest are interpretation variables.

Figure 9

Correlation of RSEI and Fr with water factors. Note: RSEI, Fr, Ae, Ap, Wa, and Wsd respectively represent remote sensing-based ecological index, rock outcrop rate, annual actual evapotranspiration, annual precipitation, water body area, and water surface density; RSEI and Fr are response variables and the rest are interpretation variables.

Figure 10

Correlation of RSEI and Fr with anthropogenic factors. Note: RSEI, Fr, pop, GDP, Rl, Rsd, Ia, and Isd respectively represent remote sensing-based ecological index, rock outcrop rate, population spatial distribution, GDP spatial distribution, road length, road surface density, impervious surface area, and impervious surface density; RSEI and Fr are response variables and the rest are interpretation variables.