Intra-annual stem radial growth of Qinghai spruce and its environmental drivers in the Qilian Mountains, northwestern China

Unraveling the individual and interactive effects of climate and competition on branch growth dynamics in Pinus koraiensis in Northeast China

Introduction

The quantitative modeling of dynamic branch growth in Korean pine (Pinus koraiensis) and the analysis of the factors influencing branch growth are essential prerequisites for making scientifically sound management decisions in Korean pine plantations. To date, the effects of competition, climate and their interactions on branch growth have been insufficiently investigated. Additionally, limited knowledge exists regarding whether these impacts vary depending on the social status of trees. In the face of the current challenges posed by climate change, accurate information to inform forest management and policy-making is urgently needed.

Methods

We collected 745 branches from 54 sampled trees of Korean pine and, we employed a mixed-effects model to assess the effects of tree variables, competition, climate, and their interactions on branch growth. Furthermore, we simulated branch growth under different combinations of competition and climatic conditions to provide practical and targeted recommendations for Korean pine plantation management.

Results

Our results demonstrate that (1) in addition to branch age, size, and tree height growth, competition, climate, and their interactions significantly improved the branch growth model, with the effects of interactions surpassing the individual effects of climate, which highlights the importance of considering interactive effects; (2) the effects of climate and competition varied depending on the social status of the trees, with dominant and intermediate individuals showing greater sensitivity to competition and climate than suppressed individuals, suggesting that, for future research in this direction, prioritizing sampling of dominant and intermediate individuals would be a cost-effective approach; and (3) owing to the presence of interactions, the influence of climate on branch growth was modulated by competition, suggesting that adjusting competition levels in response to climate stress could lead to desirable branch growth outcomes.

Discussion

Our study underscores the importance of understanding the different sources of variation in branch growth is crucial for advancing our understanding of tree growth and crown dynamics, as well as for formulating sustainable management policies amidst the uncertainties of climate change.

Nutrient allocation patterns of Picea crassifolia on the eastern margin of the Qinghai-Tibet Plateau

It can provide a basis for decision making for the conservation and sustainable use of forest ecosystems in mountains to understand the stoichiometric properties and nutrient allocation strategies of major tree species. However, the plant nutrient allocation strategies under different environmental gradients in forest systems of arid and semi-arid mountains are not fully understand. Therefore, three typical regions in the Qilian Mountains on the eastern edge of the Qinghai-Tibet Plateau were selected based on precipitation and temperature gradients, and the stoichiometric characteristics and nutrient allocation strategies of Qinghai spruce (Picea crassifolia) of the dominant tree species under different environmental gradients were investigated. The results showed that (1) the stoichiometric characteristics of plant tissues were different in the three regions. (2) The importance of each tissue in the plant nutrient allocation varied in different regions, showing that the plant roots are more important in the warm-wet region, while the plant leaves, branches and trunks are more important in the transition and hot-dry regions. (3) The influencing factors affecting plant nutrient allocation strategies were inconsistent across regions, which showed that plant nutrient allocation strategies in the warm-wet and transition region were mainly influenced by soil factors, while they were more influenced by climatic factors in the hot-dry region. The patterns of plant nutrient allocation strategies and drivers under different environmental gradients could help us better understand the ecological adaptation mechanism and physiological adjustment mechanism of forest ecosystem in mountains.