Effects of different land-use types on soil microbial metabolic limitation and carbon use efficiency in the Yellow River floodplain

At each site, three distinct land-use types were selected: first floodplain , grassland, and farmland. Within each land-use type, three replicate plots were randomly established, yielding a total of 27 plots (3 sites × 3 land-use types × 3 replicates).

In each plot, five soil cores (0–20 cm depth) were collected using a soil auger (3.6 cm inner diameter) and composited to form one representative soil sample. A total of 54 composite samples were collected across both sampling seasons. After removing visible roots and stones, fresh soil samples were sieved through a 2 mm mesh and divided into two subsamples: one stored at -20 °C for extracellular enzyme activity analysis (completed within one month), and the other air-dried for subsequent physicochemical property measurements.