Neighborhood analysis of underplanted Korean pine demography in larch plantations: Implications for uneven-aged management in northeast China

Abstract

Quantifying the growth and survival of underplanted Korean pine (Pinus koraiensis Sieb. et Zucc.) in existing plantations provides a critical step toward developing an uneven-aged management system in northeast China. We conducted neighborhood analysis to quantify the effect of individual-level competition on the growth and survival of underplanted Korean pines in larch plantations (Larix olgensis A. Henry and Larix kaempferi [Lamb.] Carr.). The growth rate depended significantly on target tree size and the strength of competition from neighboring trees, whereas survival depended solely on tree size. The survival rate increased sharply with increasing tree size, and trees that had reached ca. 3cm in diameter at a height of 0.3m rarely died, even under strong competition. The effect of competition from neighbors on growth was determined by the neighboring tree’s size and its spatial relationship with the target tree. Neighbors located near and southwest of the target tree produced stronger competition than trees at greater distances and different azimuths. Our simulation in which Korean pines were underplanted in strip openings showed that their growth rates increased with increasing strip width. The growth rate was also related to the strip’s azimuth and the underplanting position within the opening. The results indicate that planting Korean pines in northwest to southeast strips would create a more heterogeneous size structure than planting in northeast to southwest strips. Our results suggest that spatial factors such as strip width, strip direction, and planting position strongly influence the development and productivity of uneven-aged Korean pine–larch stands.