Abstract
The extensive afforestation efforts on the Loess Plateau, incurring
hundreds of billions of CNY, trigger heightened vegetation cover,
depleting soil water, and imperiling ecosystem sustainability.
Widespread debate persists over the feasibility and optimal locations
for afforestation. However, what has been overlooked is the potential
presence of alternative stable states within ecosystems, a captivating
system equilibrium behavior. This study integrates remote sensing,
minimal model, and environmental data to investigate the equilibrium
behavior (quantified by tree cover) of forest ecosystems on the Loess
Plateau and its implications. The findings suggest a threshold
relationship between tree cover and annual precipitation, with a
significant increase observed up to 400 mm. Beyond this threshold,
alternative stable states emerge, characterized by high tree cover
(forest, >35%) and medium tree cover (open woodland,
7%~35%). The equilibrium behavior of the forest
ecosystem combines thresholds and alternative stable states. Increasing
spatial heterogeneity, especially the positive feedback between
vegetation and precipitation, results in advancing transition thresholds
with higher annual precipitation. Regime shifts from forest to open
woodland increase carbon stock but decrease water yield, revealing a
trade-off between carbon sequestration and water resources. This nuanced
understanding of equilibrium enhances both theoretical comprehension and
practical planning for afforestation on the Loess Plateau, promoting the
functions and services of the forest ecosystem.