Response of <scp>ESV</scp> Topographic Gradient to <scp>LULC</scp> in Mountain‐River‐Sea Transitional Space Based on Markov‐<scp>PLUS</scp> Modeling: A Case Study of the Southwest Guangxi Karst‐Beibu Gulf, China

ABSTRACT The Guangxi Southwest Karst‐Beibu Gulf (GSK‐BG) is a complex mountain‐river‐sea transitional space made up of a special combination of karst mountains, river basins and coastal zones, presenting a slope zone tilted from northwest to southeast. At present, there is still a gap in identifying the characteristics of the topographic gradient response of past‐present‐future ecosystem service value (ESV) changes to land use and land cover (LULC) changes in the transitional space of mountains, rivers and seas. To that end, this study employed the Markov‐PLUS model, land use transfer matrix and land use mapping to portray the characteristics of the changes in LULC and ESV from 2000 to 2030, as well as to analyze the analyze the LULC change towards the ESV response. Then the role of LULC transformation on ESV under different terrain gradient topographic factors was further explored to fill the current research gap. The results show: (1) The highest ESV was 479,332 million yuan in 2010 and the lowest was 473,424 million yuan in the urban development scenario (UDS). The distribution of ESV in space is shown as “high in the northwest and low in the central and southeastern part of the country”, which shows a trend of increasing and then decreasing in time. (2) Forest land (FL) is the main contributor to total ESV. The improvement in ESV in the study area was mainly due to the transfer of other land uses to FL and water body (WB), and the decrease in ESV was mainly due to the conversion of FL and WB to other land uses. (3) The topographic gradient response of ESV changes to LULC changes is more pronounced for the 2030 natural development scenario (NDS), ecological protection scenario (EPS), and UDS. The types of land transfers that predominate mainly on steep slopes at lower elevations as well as in areas with steep slopes at higher elevations include grassland (GL) and FL to unutilized land, with terrain distribution index (TDI) of 5.27 and 4.02, and bare land (BL) and FL to GL, with TDI of 4.75 and 3.53. Therefore, the topographic gradient characteristics of the region should be taken into account in the development and utilization of land resources and improvement of ESV in the mountain‐river‐sea transitional complex geospatial space.