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Restoring forests has recently received considerable attention in the context of sequestering carbon and supporting biodiversity. Although considering alien species as a tool for natural forest restoration still remains controversial, harnessing alien species when they are already present in an ecosystem might result in overall benefits for nature and society. In this study we evaluated whether the presence of an alien tree species supports or hinders the establishment of naturally regenerating forests in Shiretoko National Park, Japan. In particular, we focused on Larix kaempferi, which is widely present yet non-native to the region, and examined how this alien species affects two factors influencing the success of restoration: wind disturbance and deer herbivory. We examined the following effects of L. kaempferi plantations on natural regeneration: (1) the windbreak function for protecting native tree growth and (2) the nursery function to promote the regeneration of native tree saplings and seedlings under high herbivory pressure. We assessed tree height and regeneration, using large-scale remotely sensed data and terrestrial inventory data in five major vegetation types. We found that L. kaempferi plantations can protect native species from predominant winds. Additionally, L. kaempferi canopy cover promoted abundance and species richness in understory saplings and seedlings compared to other vegetation types such as primary and secondary forests, even under excessive browsing pressure. No regenerating L. kaempferi individuals were observed during the field census, suggesting the species is likely not invasive in our study system. The positive relationship between alien tree species and the regeneration of native tree assemblages emphasizes that existing alien species have the potential to act as nurse plants. Our findings imply that the presence of alien species can contribute to natural forest restoration by improving the local environmental conditions for native species in the short-term. Given the multiple ecological and social needs in our changing world, careful consideration is required to evaluate the long-term consequences of alien species. Especially in ecosystems in which alien species have already established, using their positive functions rather than swiftly eradicating them from the landscape might be beneficial for long-term restoration goals. We conclude that managers need to be aware of the context-dependency of alien species to make restoration more effective.

Owing to the existence of global Pleistocene refugia, the relict and ancient component of the modern endemic flora is considerable in South-Central China. Study of these relict species helps to understand past and recent ecological processes affecting species persistence, and also provides knowledge to guide human-assisted management and conservation practice. In this study, we investigated the current status of the remnant populations of Cathaya argyrophylla, one of the emblematic “living fossils”, growing in the Dalou Mountains of South-Central China. We quantified the population structure of C. argyrophylla and investigated demographic changes of seedlings over a ten year period to learn the plant’s regeneration patterns following the establishment of two national and provincial nature reserves in late 1970s. Notable “gaps” in age structure over 40 years were found, suggesting significant recruitment failures in these scattered population since the establishment of the nature reserves. Further, the number of dead individuals peaked at ages between 40 and 80 years and the seedlings showed high mortality in the past 10 years, probably due to intensified competition from the nearby broad-leaved trees and the reduction of suitable micro-habitats. These facts indicated that attention needs to be paid and follow-up measures should be taken to more effectively conserve C. argyrophylla in the future.