A Study of the Initial Mulching Effect in a Sapling Planting Area: Focusing on Sapling Growth Rate and Weed Occurrence Characteristics

Background and objective: In ecological restoration sites, the use of saplings is essential for ensuring rapid adaptation and growth in the target environments. However, planting efforts have often focused on medium- to large-diameter trees due to challenges such as weed competition and management issues. To address these problems, this study aimed to investigate the effects of varying mulching thickness on weed emergence and cover, as well as survival and growth rates of planted trees in the experimental plots where saplings were planted. The findings are expected to serve as foundational data for proposing proper planting and management strategies utilizing saplings.Methods: To examine the dynamics of tree growth and weed emergence, Quercus acutissima saplings with a root collar diameter (RCD) categorized as R2 were planted at a high density of two saplings per square meter and managed with conventional weeding twice a year. Woodchip mulch was applied at three different thicknesses: 0 cm, 5 cm, and 10 cm. Changes in tree growth and weed emergence were monitored over a 30-month period. The study was divided into two key aspects: tree growth assessment and weed vegetation analysis. Tree growth was evaluated based on survival rate, growth rate, and canopy projection. Weed vegetation analysis included the number of emergent herbaceous species, presence and proportion of naturalized plants, and vegetation cover.Results: The survival rate in the mulched plots was 1.75 times higher than in the control plot with 0 cm mulch. As mulch thickness increased and the canopy projection expanded, the number of weed species decreased, effectively controlling the invasion of tall herbaceous plants competing with planted trees, as well as limiting the establishment of naturalized species. Once the canopy layer was established, all mulched plots exhibited significantly lower weed cover after weeding compared to the 0 cm mulch control. As canopy vegetation cover increased, the composition of weed species changed before and after canopy closure. In the early stages of the experiment, prior to canopy formation, high canopy openness created a light environment similar to that of agricultural fields. This condition favored the dominances of crop-associated weeds, tall herbaceous plants, and naturalized species. However, following canopy establishment, the number of emergent weed species decreased, with herbaceous vine species becoming dominant.Conclusion: Applying mulch at a thickness of 5-10 cm combined with biannual weeding can support the growth and development of saplings compared to untreated conditions. Additionally, for successful vegetation restoration using saplings, intensive management of tall herbaceous plants that suppress sapling growth is necessary before canopy formation. After canopy closure, management strategies are required to address the emerging dominance of herbaceous vine species.