Evaluating stand structural and functional impacts of understory removal in forests dominated by low-nutrient specialists in South Korea

Abstract

Characterizing the impacts of understory removal, a practice regulating stand structural and functional processes through deliberate control of resource competition, is fundamental to advancing the sustainable management of open canopy forests with dense undergrowth. However, whether understory management is effective in areas dominated by conifers that are tolerant of nutrient limitation remains underexplored. This study investigates soil physicochemical properties, overstory metrics, fine root biomass and necromass by depth, and litterfall production by component in Pinus rigida forests with intact (CON) and eradicated (UR) understory strata for up to five years (2015–2020). Understory removal exerted a limited influence on most soil properties, except for available P, which decreased by 70%, and Ca²⁺, which increased by at least twofold in UR (p < 0.05). All overstory metrics remained uniform regardless of the presence or absence of the understory. Both CON and UR followed a similar negative vertical fine root biomass and necromass distribution with depth, whereas annual production of foliar, non-dominant twig, bark, seed, and miscellaneous litter was significantly greater in CON than in UR (p < 0.05). Given the minimal structural and functional gains from understory removal, it is thus more reasonable to maintain an understory layer in forests populated by low-nutrient specialists to refine overstory stem quality and continue the delivery of other forest regulating and supporting ecosystem services. Our findings contribute to the development of effective understory management strategies, providing valuable insights into the sustainable use and management of forest resources.