Ecosystem services in the typical black soil region of Northeastern China: implications for the optimal land use pattern

Determining the ideal future land use pattern with the purpose of enhancing ecosystem services (ESs), weakening the trade-off, and strengthening the synergy between them is of major important for the sustainable use of black soil. Water retention (WR), water purification (WP), soil retention (SR), carbon storage (CS), habitat quality (HQ) were chosen to analyze the spatio-temporal change of ESs, as well as trade-offs and synergies amongst ESs from 2005 to 2020 in the the typical black soil region of northeastern China (TBSN). We used the cropland quality level as a limitation to identify the foremost sensible ecological redline area. By comparing the spatio-temporal change of ESs and their relationships from 2020 to 2035 below extraordinary scenarios representing natural development, cropland development, and ecological redline policies, we decided the ultimate land use pattern of TBSN. The results indicated that: (1) The conversion of cropland (+ 997.3 km²), grassland (-3527.82 km²), and built-up land (+ 2303.19 km²) was dramatic, and the landscape pattern become fragmented, notably in Songnen typical black soil subzone. (2) The ESs showed a noticeable downward trend, and the strength of trade-off increased in areas with large-scale conversions between land use types and increasing level of landscape fragmentation. (3) 10% was the optimal redline threshold for the main indicator. The ecological redline scenario was the optimal solution that maximized the improvement of ESs (WR + 51.93%, NE-6.30%, PE-5.50%, SR + 21.27%, CS + 6.68%, HQ + 0.73%), minimized trade-offs and maximized synergies in the coordinated development of cropland and ecological land. The findings can serve as a scientific foundation for ecosystems management and land resources allocation in black soil regions.