Physicochemical Surface-soil Properties after Litter-removal Manipulation in a Cambodian Lowland Dry Evergreen Forest

Litter plays key roles in forest ecosystems, and forest degradation is likely to spur a further decline in leaf litterfall inputs to forest soils. However, the effects on physicochemical surface-soil properties remain largely unknown, especially in seasonal tropical forest ecosystems. We initiated a litterremoval manipulation experiment in a Cambodian lowland evergreen forest undergoing intensive selective logging. Litter removal performed for 2 and 4.4 years respectively triggered an increase in bulk density and decrease in surface-soil carbon (C) and nitrogen (N) contents to 67 and 73% of the original levels, respectively. After only 2 years of treatment, bulk density rose to very high value (>1.40 Mg m) likely preventing further soil compaction, while the C and N reduction effects lasted over 2 years. Greater soil compaction occurs in stands with a smaller initial bulk density. However, C (N)-rich soils did not necessarily lose a greater relative proportion of C (N) than C (N)-poor soils. Although N remained above C following the litter removal, conservative trends in the C:N ratio suggested a limited capacity for N retention. Together, our data suggest that shifts in leaf litter inputs in response to localized human disturbances may have rapid and lasting consequences on physicochemical surface-soil properties; possibly accelerated by a tropical climate. Moreover, a speedy recovery to an adequate litter supply, at least before reaching the upper soil compaction limit, is essential to conserve forest ecosystems. Discipline: Soils, fertilizers and plant nutrition Additional key words: bulk density, carbon, forest degradation, nitrogen, soil compaction