Root and leaf decomposition of four temperate species in Mt. Gariwang, Kangwon Province: associations with litter traits and microbial community

Byung Bae Park1, Julia Inacio. Carvalho1*, Ji Young An2, Ye Jin Kong1, Min Seon Cho1,3,

Lan Thi Ngoc Tran4, Mark Bryan Carayugan1

(1Department of Forest Resources, Chungnam National University,

2Division of Environmental and Forest Science, Gyeonsang National University,

3Gyeryongsan National Park Office, Korea National Park Service,

4Forest Environment and Geospacial Technology Research Institute)

Abstract: Root and leaf litter decomposition play a vital role in biogeochemical processes in forest ecosystems. Despite their importance, considerable uncertainties persist regarding the factors controlling decomposition variability. Here, we aimed to (i) investigate the decomposition rates of leaves and roots (with varying diameters), and (ii) the influence of litter traits and microbial community on decomposition processes. Four forest stands were selected, each one dominated by a different species: Quercus mongolica (QM), Pinus koraiensis (PK), Pinus densiflora (PD), and Larix kaempferi (LK). Leaf litter and root samples were collected within the plots, with roots categorized into four diameter classes: 0-0.5, 0.5-1, 1-2, and 2-5 mm. Using the litterbag method, a total of 768 root litterbags (4 species × 4 diameters × 3 plots × 4 collections × 4 replicates) and 192 leaf litterbags (4 species × 3 plots × 4 collections × 4 replicates) were set up. After 359 days of field exposure. leaf and root decomposition rates (k-values) were calculated. Initial root and leaf chemical (C, N, C:N, P, K, Mg, Ca, hemicellulose, cellulose, and lignin) and morphological traits (specific area and length) were analyzed. Additionally, mineral and organic soil were collected to analyze the microbial community and their relationships with k-values. Results revealed that root and leaf k-values ranged from 0.38-0.46 year–1 and 0.38-0.62 year-1, respectively. Root k-values varied among species and were significantly higher for PD (0-0.5 and 2-5 mm) and PK (0.5-1 and 1-2 mm). In contrast, no difference was observed in leaf k-values among species. For root decomposition, k-values of PK and LK followed the order: 0.5-1 mm > 0-0.5 and 1-2 mm > 2-5 mm, meanwhile, k-values of QM and PD did not differ among root diameters. Positive relationships were observed between root k-values with initial Mg, P, N, K, specific root length and area, and fungal Shannon index, and negative relations were observed with initial C:N ratios and C. Concerning leaf decomposition, k-values were not significantly related to any of our analyzed initial traits and microbial community properties. These results indicate that root and leaf decomposition are driven by different factors, highlighting the complexity surrounding decomposition patterns, and consequently the biogeochemical processes in forest ecosystems.

Keywords: mass loss, cool-temperate forest, decay constant, litter quality, fine root.

Acknowledgment: This study was carried out with the support of ‘R&D Program for Forest Science Technology (Project No. 2022461B10-2424-0201)’ provided by Korea Forest Service (Korea Forestry Promotion Institute).