Environmental heterogeneity on landslide slopes affects the long-term recoveries of forest ecosystem components

Landslides are a common disturbance in mountainous areas of the world.
Transporting and accumulating landslide debris, i.e., disturbance
legacies, such as coarse woody debris (CWD), vegetation patches, and
surface soils, generate a heterogeneous environment along slopes (zones),
which are suggested to affect forest recovery. However, the long-term
changes in forest ecosystems after landslides remain unknown, particularly
zone-dependent change patterns. We aimed to reveal the differences in the
changes in live trees, understory vegetation, CWD, and soils among zones
by surveying forests with landslide ages (years since the landslide)
ranging from 3 to 74 years and reference stands. The increase in live tree
aboveground biomass occurred at a faster rate at the lower part of the
slopes where the disturbance legacies were rich and surface soils were
stabilized due to the smaller slope angle. Chronological patterns of
understory vegetation amounts were determined by the differences in
disturbance legacy richness and the timing of subsequent canopy closure.
The amounts and decay-class diversity of CWD were determined by the
differences in legacy richness and mortality through stand development.
These zone-dependent chronological changes influenced litter production
and determined the recovery rates of surface soil carbon and nitrogen
stocks. The increase in the dominance rates of forest herbaceous species
was faster in the lower part of the slopes due to the faster surface soil
development and canopy closure. Our results illustrate that long-term
forest ecosystem succession and recovery after landslides occurs more
rapidly at the lower parts than at the upper parts of slopes.