Multivariate path analysis of factors influencing Larix principis-rupprechtii plantation regeneration in northern China

Abstract

Forest regeneration is a critical indicator of the overall health of forest ecosystems, and is considered to be a vital process in which old and senescent trees are replaced by young ones. The seed-to-seedling transition entails seedlings’ emergence from seeds and their establishment, this phase being the most vulnerable to mortality effects from biotic and abiotic factors. Larix principis-rupprechtii is a typical tree species in northern China, where the natural regeneration of artificial forests dominated by this species is very limited. This study explored the limiting factors affecting the natural regeneration of Larix principis-rupprechtii forests via field surveys of large-scale sampling plots. Redundancy analysis and structural equation models were developed and applied to determine the relative importance of direct and indirect factors affecting the regeneration of Larix principis-rupprechtii plantations. We found a negative relationship between the regeneration index and stand structure, for which the path coefficient was –0.54, the strongest correlation. Conversely, the regeneration index was positively correlated with the herb index, soil index, and elevation, having path coefficients of 0.06, 0.07, and 0.32, respectively. The soil index was negative correlated with both elevation and herb index, with path coefficients of –0.31 and –0.53, respectively, while stand structure was negatively correlated with the herb index and positively correlated with elevation (respective path coefficients: –0.62 and 0.29). Stand density and tree height to crown base were the main factors representing stand structure and, accordingly, the most important factors influencing forest regeneration of the species. At a stand density of ca. 200 trees·hm−2, the number and quality of seedling regeneration were robust. In later stages of stand management and thinning, the proper adjustment of stand density and timely pruning interventions can promote this tree’s natural regeneration to achieve the sustainable development of forest resources.