Linking tree community functional change with soil carbon dynamics during secondary succession in a naturally regenerating tropical forest in Panama

Wallwork, Abby and Sayer, Emma and Banin, Lindsay and Skiba, Ute and Dent, Daisy (2021) Linking tree community functional change with soil carbon dynamics during secondary succession in a naturally regenerating tropical forest in Panama. PhD thesis, Lancaster University.

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Abstract

Naturally regenerating tropical forests are increasingly important for their role in the global carbon (C) balance, particularly due to their ability to rapidly sequester large amounts of C in aboveground biomass during forest regrowth. Over half of all C in tropical forests is stored belowground, yet in contrast to the predictable pattern aboveground, there is no clear pattern of soil C accumulation with time during forest regrowth, and we are therefore currently unable to predict and increase soil C sequestration during tropical forest regrowth. Soil C turnover and storage depends on the input of plant-derived organic matter which is likely to be affected by shifts in tree community resource-use strategy (functional group) during secondary succession from light-demanding to shade-tolerant species, and the corresponding reduction in litter quality. As tree community composition can differ between forest stands of similar ages, I hypothesised that tree community functional composition would better predict soil C dynamics during secondary tropical forest succession than stand age and specifically, that differences in litter quality between shade-tolerant and light-demanding tree species would influence rates of soil C turnover via litter decay rates and changes to the soil microbial community. The body of work presented in this thesis provides compelling evidence in support of my overarching hypothesis that soil C accumulation is more closely related to tree functional composition than forest age. My studies highlight some of the potential pathways by which tree community composition can influence soil C storage via plant-derived organic matter inputs representing substrate for the soil microbial community. Overall, the research presented in this thesis demonstrates that tree functional composition could be one of the main factors determining belowground C storage and therefore, my work represents an important first step towards using tree functional groups to predict soil C accumulation in secondary tropical forests.