Positive interactions in shaping neighborhood diversity during secondary forests recovery: Revisiting the classical paradigm

Abstract

Secondary forests recovery, following disturbances, plays a pivotal role in ecosystem dynamics and biodiversity recovery. Given the rising frequency and intensity of anthropogenic disturbances within forest ecosystems, understanding the mechanisms underlying secondary succession is vital for the effective restoration and conservation of compromised ecosystems. In the classical secondary succession paradigm, early-arriving species are gradually replaced by their later-arriving counterparts. However, over time, valuable historical insights into the involvement of pioneer species become obscured and challenging to discern, particularly in community-scale studies. Consequently, this obscurity has predominantly directed contemporary research predominantly towards examining the consequences of species replacement by later-arriving counterparts during secondary succession. Concurrently, the mechanisms by which pioneer species facilitate or impede the establishment of diversity among later-arriving species remain insufficiently clarified. In this study, we established a 6-ha dynamic forest plot within a secondary forest that has undergone nearly four decades of restoration. Specifically, we utilized the individual species-area relationship (ISAR) framework to evaluate the neighborhood diversity structure of 49 evergreen and 20 deciduous species identified within our evergreen broad-leaved forest plot. Our findings indicate that deciduous tree species undergo a transition from diversity accumulator to repeller in diversity structuring as they progress through different life history stages. On the other hand, evergreen trees either engage in diversity accumulator or neutral. Through repeated plot surveys, we established a comprehensive dataset encompassing the mortality and regeneration of evergreen and deciduous tree species from 2014 to 2020. Spatial covariance models were employed to quantify the distinct effects of density dependence on deciduous and evergreen tree species. The results demonstrate significant negative density dependence mortality and self-thinning in deciduous species at all life history stages. Conversely, adult evergreen tree species facilitate the survival of their seedlings and saplings. In contrast to the classical paradigm that primarily focuses on the replacement of pioneer species by successor species, our findings reveal: (i) self-inhibition mechanisms that shape the neighborhood diversity spatial patterns among deciduous tree species, (ii) self-promotion or neutral mechanisms that influence the diversity spatial patterns of evergreen tree species, and (iii) early-arriving tree species that play a role in facilitating the establishment and diversity of late-arriving counterparts. These results not only signify the significant role of late-arriving species in the natural recovery of secondary forests but also propose that integrating the mechanisms of facilitation, inhibition, and neutral interactions into the classic forest succession paradigm could reshape our interpretation of interactions within plant communities across historical, current, and future timeframes. Such comprehension holds implications for forest management policies and conservation practices.