Historical evolution of gully erosion and its response to land use change during 1968–2018 in the Mollisol region of Northeast China

Gully erosion is one of the most severe types of land degradation, hindering food production and sustainable agricultural development. However, the historical evolution process and the impact of land use change on gully erosion remain unclear. To address this issue, we conducted a field investigation on gully erosion in 2018 and interpreted land use and gullies using historical remote sensing images in 1968 and 1978 over an area of 84.48 km². The study found that from 1968 to 1978 to 2018, all gully morphological parameters including gully length density and gully areal density increased significantly. The main origin of gully erosion found was from dry farmland. The annual soil loss rate induced by gully erosion was 1.46 mm during 1968–2018. Gully erosion rates were higher during 1968–1978 than during 1978–2018. Furthermore, the length, areal and volumetric erosion rates in gullies formed by multiple gullies merging was greater than that of newly formed gullies (NFG) and gullies developing continuously from a single pre-existing gully, while the widening rate of NFG was highest. The susceptibility of land use types to gully erosion was in the order of woodland < dry farmland < degraded land. The annual average increase in gully area was 871.09 m² km^-2 year^-1 for parcels that were converted from woodland to dry farmland, which was 5.56 times and 1.78 times greater than that of woodland and dry farmland maintenance, respectively. Therefore, urgent implementation of ecological land use plans and gully erosion control practices is suggested for this region.