C3–C4 Plant Dynamics, Soil Microbiome Shifts, and the Vicious Cycle of Farmland Abandonment

This study examines the ecological and socioeconomic feedback mechanisms that drive farmland abandonment. We analyze two interconnected processes: (1) the competition between C3 and C4 plants and its impact on soil microbiome composition, and (2) the accelerated spread of perennial grasses in abandoned fields. C4 species, favored by warmer and drier climates, alter root carbon exudation patterns and gradually shift soil bacterial communities toward a simplified grassland-type structure. At the same time, abandoned lands become seed reservoirs for invasive grasses, which proliferate through wind dispersal and extensive rhizome networks. Their expansion significantly increases weed management costs, discouraging aging farmers from continuing cultivation. This dynamic creates a vicious cycle where abandonment fuels further abandonment. By linking plant ecology, soil microbiology, and rural socioeconomic dynamics, the paper highlights the urgent need for integrated strategies to break this cycle and sustain agricultural landscapes.