Soil moisture mediates the effect of plant belowground carbon allocation on the decomposition of root litter in a subtropical forest

Trees allocate carbon belowground to fuel the functioning of roots and mycorrhizal fungi, which affect litter decomposition, but the direction and magnitude of this effect are variable. While tree mycorrhizal type is often suggested to mediate this aboveground-belowground linkage, previous studies yield mixed results. In this study we investigated how absorptive root traits, soil conditions and litter type influence the response of litter decomposition to altered belowground carbon allocation, both within and across mycorrhizal types. We girdled transport roots of seven subtropical tree species to eliminate carbon allocation to distal absorptive roots. We monitored leaf and root litter decomposition surrounding girdled and un-girdled root branches. We found that girdling generally slowed leaf litter decomposition. However, the effect of girdling on root litter decomposition depended on soil moisture, stimulating decomposition in dry soil but suppressing it in moist soil. Absorptive root..., We conducted our study in a subtropical forest at Tianmu Mountain (30°18′ N, 119°26′ E). We selected 5 AM tree species (Aphananthe aspera, Phoebe chekiangensis, Cunninghamia lanceolata, Cryptomeria japonica var. sinensis Miquel, and Torreya grandis) and 2 EM tree species (Cyclobalanopsis gilva, Pseudolarix amabilis) . Three individuals of each species were randomly selected, with about 100m elevational distance between two adjacent replicates. We used leaf and root litter homogenized from a variety of local tree species, including but not limited to the selected ones. Leaf litter was collected from litter traps (1 m × 1 m) near the selected trees from November 2020 to January 2021. Root material was excavated from soil monoliths (1 m × 1 m, 10 cm depth) near the litter traps. After field sampling, leaf and root litter were prepared in the laboratory. The twigs and seeds were excluded from the collected leaf litter. Leaf litter was air-dried at room temperature. The water content of the ..., , # Soil Moisture Mediates the Effect of Plant Belowground Carbon Allocation on the Decomposition of Root Litter in a Subtropical Forest

We have submitted our raw data (**Data_ALL.xlsx**)

### *Descriptions*

### Species abbreviation: 

Apas = *Aphananthe aspera*, Phch =* Phoebe chekiangensis*, Cula = *Cunninghamia lanceolata*, Crja = *Cryptomeria japonica, *Togr* *=* Torreya grandis,* Cygi =* Cyclobalanopsis gilva*, Psam = *Pseudolarix amabilis*.

### Datasets included:

**[Species and plot information]**

species names and abbreviations; sample plot (S1,S2,S3); tree ID (S1-xx); mycorrhizal type (AM = arbuscular mycorrhizas, EM = ectomycorrhizas); root pocket ID (Dxx, the number has no ecological meaning)

**[Litter information]**

litter type (root vs. leaf); treatment (girdling vs. control); months of decomposition (0, 2, 4, 6 months); Recovery_Mass (dry weight of initial or remaining litter, unit =gram); Fraction_of_Litter_Remaining (ranging from 0 to 1); root and leaf litter k value...