Local root status: a neglected bio-factor that regulates the home-field advantage of leaf litter decomposition

The ‘home-field advantage (HFA) hypothesis’ predicts a litter-field affinity effect on litter decomposition. In terrestrial ecosystems, plant roots have comprehensive roles in regulating litter-decomposer interactions, yet their potential influences on HFA remain unsolved. To fill this gap, we conducted a litter transplant experiment in a subtropical forest, and tested whether roots affect litter-field affinity via interactions with soil microbial functions. Leaf litters of Quercus variabilis and Pinus massoniana were incubated at their conspecific-dominated and heterospecific-dominated forests. Root-specific incubation microcosms were manipulated by using a series of root ingrowth cores to control the access of living fine roots. Entire exclusion of roots led to a significant suppression of HFA, and the affinity effect was amplified under a medium root constraint treatment (by 0.5 mm mesh). Incubation field (‘home’ vs. ‘away’) generally had a positive effect on litter mineralization when roots were present, and roots became more influential after 9 months than 3 months of incubation. Although microbial enzymatic functions and their impact on litter N loss depended on root status, they were not associated with incubation field. Our findings advocate that a moderate amount of local roots is essential for HFA in leaf litter decomposition, and taking account of root-mediated species-specific bio-interactions will advance our understanding of native litter- home field affinity.