Scale- and age-dependent climate response patterns revealed in Pinus sylvestris var. mongolica and Larix principis-rupprechtii plantations in northern China

Abstract

Inconsistent forest climate response patterns across organizational scales or stand ages are increasingly documented due to the large organismal size and the long-lived nature of forest ecosystems, complicating the prediction of forest productivity trajectories. However, studies integrating the scale- and age-dependent climate responses and accounting for species-specific functional strategies are lacking, limiting our ability to assess forest-wide productivity and resilience under increasing drought stress. In this study, we investigated the climate sensitivity of radial growth (RWI) and canopy vitality (NDVI) at different growth stages for Larix principis-rupprechtii (Prince Rupprecht’s larch) and Pinus sylvestris var. Mongolica (Mongolian pine) plantations in Saihanba, the world’s largest plantation. Through integrated analysis of dendrochronological, remote sensing, and climatic datasets from 1984 to 2020, we sought to reveal distinct scale- and age-dependent climate response mechanisms of these two species. We found that individual tree-level radial growth exhibited stronger climatic sensitivity than stand-level canopy vitality, as evidenced by more pronounced inter-annual variability with climate fluctuations and greater resilience to drought events in RWI than in NDVI. Climate response patterns shifted across ontogenetic stages, with trees at juvenile stages responding more strongly to climate variables closely associated with environmental water conditions. Post-drought density reduction caused by tree mortality alleviated the competition for water resources among trees in mature stands, promoting tree growth release in Prince Rupprecht’s larch but not in Mongolian pine. This divergence may stem from larch’s more acquisitive resource-use strategy, characterized by anisohydric behavior and deciduous leaf habit, which enhances its capacity to capitalize on resource availability increases following the drought-driven tree mortality but restricts extreme drought resilience. These findings highlight the imperative to integrate multi-scale metrics for robust assessments of forest drought resilience and advocate for age- and species-specific forest management, such as targeted thinning, to optimize adaptive silvicultural interventions under intensifying climatic stressors.