Soil Physical, Biological, Ecological, and Chemical Effects of Litter Manipulation.

Litter manipulation experiments are a useful tool to study forest nutrient and carbon dynamics but the regular addition or removal of litter also affects important soil properties, such as water content, temperature, and habitat space for decomposer organisms. I draw on data from two large-scale litter manipulation experiments in tropical forest and temperate woodland to demonstrate how we can use litter manipulation experiments to increase our understanding of soil ecology and function. During 6 years of litter manipulation in a tropical forest in Panama, we observed concerted changes in decomposition processes, root biomass distribution, soil nutrient cycling and carbon dynamics and measured substantial release of soil carbon as CO₂ via ‘priming effects’. A comparison between litter manipulation and fertilization treatments at the same forest site demonstrated the crucial importance of forest litter for nutrient retention and uptake by plants. I highlight open questions about interactions between plant growth and soil processes and present a new litter manipulation experiment comparing temperate woodland and tropical forest, which aims to answer some of these questions.