Post-disturbance erosion impacts carbon fluxes and plant succession on recent tropical landslides

Tropical landslides are suitable locations to study short-term carbon (C) fluxes because of the rapid changes that occur for the first few years following initial disruption of the slope. Because of the high heterogeneity among landslide soils and plant re-colonization patterns, we measured C fluxes from 30 landslides in the Luquillo Experimental Forest in northeastern Puerto Rico from 8-13 months after landslide formation. Post-landslide erosion resulted in significantly higher soil output on dioritic than on volcaniclastic soils, with no temporal decline in soil output during the study. Much more C was found in landslide soils than in plant biomass, and we estimate that 6-24% of the soil C standing stock would erode from our plots within 1 year. Even the relatively small amount of C in plant matter was in flux, with four to five times plant C standing stock deposited into the plots as plant litter and two times standing stock leaving our plots in 1 year. This rapid turnover of C is indicative of highly unstable substrates that likely stabilize over successional time. We combined our short-term study with past chronosequence studies to project long-term carbon movement in landslides. We suggest that landslides in Puerto Rico represent a net down slope movement of C despite deposition from surrounding forest soils, litter from the surrounding landscape and in situ successional re-growth.