Influencing factors on regeneration and seedling survival prediction in Larix principis-rupprechtii plantations in northern China

The natural regeneration of forest ecosystems is crucial for their sustainability, but uncertainties have impeded the regeneration of some tree species. Identifying influencing factors and effective strategies to enhance seedling survival and growth is essential. We investigated factors affecting the natural regeneration of Larix principis-rupprechtii and provided insights into seedling survival and growth. Eighteen artificial L. principis-rupprechtii forest plots were established and monitored for 3 years. A logistic regression analysis and generalized linear models were used to investigate the influence of stand age, diameter at ground level, height, and other microhabitat factors on seedling regeneration. The microhabitat factors significantly influenced the overall L. principis-rupprechtii regeneration density, as well as the density and growth of regenerated trees in different height classes. The area under the curve values for total nitrogen (0.796), total phosphorus (0.726), soil moisture (0.759), and litter thickness (0.633) were the highest, indicating a significant impact on the survival rate and mortality of the seedlings. Among these values, total nitrogen sensitivity (0.857) and specificity (0.810) were the highest, and the optimal threshold was 0.940. The survival rate decreased with increasing forest age, and the stands aged 4–7 years with a height of 1–2.5 m and a diameter at the ground level of approximately 2 cm constituted a relatively vulnerable and critical set of conditions for the survival of L. principis-rupprechtii seedlings. The model showed that at 12 years old, L. principis-rupprechtii trees were no longer vulnerable to mortality. The Kaplan–Meier model predicted future seedling survival through the construction of the comprehensive influence value and the measured seedling survival number. The model can be used to evaluate the survival rate for the final regeneration of a species, and targeted artificial seeding or replanting can improve the proportion of seedlings that survive. Our findings contribute to elucidating the factors affecting the natural regeneration of forest species and provide valuable insights for the development of effective regeneration strategies.