A plant economics spectrum of litter decomposability

Summary 1. Recent evidence indicates tight control of plant resource economics over interspecific trait variation amongst species, both within and across organs, referred to as ‘plant economics spectrum’ (PES). Whether and how these coordinated whole‐plant economics strategies can influence the decomposition system and thereby impact on ecosystem carbon and nutrient cycling are yet an open question. More specifically, it is yet unknown whether plant functional traits have consistent afterlife effects across different plant organs. 2. To answer those questions, we conducted a common‐garden decomposition experiment bringing together leaves, fine stems, coarse stems, fine roots and reproductive parts from a wide range of subarctic plant types, clades and environments. We measured all plant parts for the same (green and litter) plant economics traits and identified a whole‐plant axis of carbon and nutrient economics. 3. We demonstrated that our local ‘PES’ has important afterlife effects on carbon turnover by driving coordinated decomposition rates of different organs across species. All organ decomposabilities were consistently controlled by the same structure‐related traits (lignin, C and dry matter content) whilst nutrient‐related traits (N, P, pH, phenols) had more variable influence, likely due to their contrasting functions across organs. Nevertheless, consistent shifts in elevation of parallel trait–decomposition relationships between organs indicate that other variables, potentially related to organ dimensions, configuration or chemical contents, codetermine litter decomposition rates. 4. Whilst the coordinated litter decomposabilities across species organs imply a coordinated impact of plant above‐ground and below‐ground litters on plant–soil feedbacks, the contrasting decomposabilities between plant parts suggest a major role for the relative inputs of organ litter as driver of soil properties and ecosystem biogeochemistry. These relationships, underpinning the afterlife effects of the PES on whole‐plant litter decomposability, will provide comprehensive input of vegetation composition feedback to soil carbon turnover.