Plant secondary metabolites: a key driver of litter decomposition and soil nutrient cycling

Abstract

International audienceA broad and diversified group of compounds, secondary metabolites, are known to govern species interactions in ecosystems. Recent studies have shown that secondary metabolites can also play a major role in ecosystem processes, such as plant succession or in the process of litter decomposition, by governing the interplay between plant matter and soil organisms. We reviewed the ecological role of the three main classes of secondary metabolites and the methodological challenges and novel avenues for their study. We highlight emerging general patterns of the impacts of secondary metabolites on decomposer communities and litter decomposition and argue for the consideration of secondary compounds as key drivers of soil functioning and ecosystem functioning.Synthesis. Gaining a greater understanding of plant-soil organisms relationships and underlying mechanisms, including the role of secondary metabolites, could improve our ability to understand ecosystem processes. We outline some promising directions for future research that would stimulate studies aiming to understand the interactions of secondary metabolites across a range of spatio-temporal scales. Detailed mechanistic knowledge could help us to develop models for the process of litter decomposition and nutrient cycling in ecosystems and help us to predict future impacts of global changes on ecosystem functioning

Impacts of Anthropogenic Noise on Litter Chemistry and Decomposition Processes in a Semi-Arid Ecosystem

“…These data indicate that litter C/N ratio is an important predictor of litter decomposition rates, a result supported by many previous studies (e.g. Aerts, 1997;Eiland et al, 2001;Chomel et al, 2016). However, litter decomposition rates also differed between litter collected in June and September, although litter C/N ratio was similar ( Figure 6, Table 1).…”

“…This observation contradicts other studies conducted in sagebrush (Wiens et al, 1991;Karban et al, 2004;Karban et al, 2006). It may be that the Folin-Ciocalteu method for quantification of total phenolics lacked sufficient specificity to detect small differences in individual phenolic compounds between treatments (Appel et al, 2001;Chomel et al, 2016). Alternatively, we may have missed the effects of herbivory on terpene concentrations in sagebrush because folivores feed on ephemeral leaves (Takahashi and Huntly, 2010), and feeding decreases as the summer progresses (Karban et al, 2006).…”

“…We found no difference in potential litter decomposition rates between noise and control sites. This strongly suggests that total phenolic concentrations did not change, because it has been well established that increased phenolic concentrations in leaf litter reduces decomposition rates (see review Chomel et al, 2016). Thus, it appears that noise pollution does not affect plant-soil interactions in these ecosystems via its impacts on leaf litter chemistry changes.…”

“…Although Chapman et al (2006) reported increased litter quality in evergreens, others (White, 1991;Paavolainen et al, 1998) have shown evergreens induce secondary metabolite production (i.e. monoterpenes) in response to herbivory which then, in turn, decelerates decomposition (Chomel et al, 2016). These diverging responses make predicting the impacts of herbivory on sagebrush difficult.…”

“…Changes in each one of these variables have a direct impact on microbial activity, with an increase in activity as C/N ratios and phenolic concentrations decrease (Eiland et al, 2001) and a decrease in activity with an increase in C/N ratio or phenolic or monoterpene concentrations (Hättenschwiler and Vitousek, 2000;Chomel et al, 2016). Despite these predictable impacts of changes in litter chemistry on decomposition, impacts of herbivory on litter chemistry have been highly variable among plant types, leading to both acceleration and deceleration of decomposition in response to herbivory (Chapman et al, 2006;Bardgett and Wardle, 2010).…”