AUTHOR=Zhao Yonghong , Zhao Weijun , Fang Huijun 

TITLE=Influence of hydrothermal factors on a coniferous forest canopy in the semiarid alpine region of Northwest China

JOURNAL=Frontiers in Forests and Global Change

VOLUME=6

YEAR=2023

URL=https://www.frontiersin.org/journals/forests-and-global-change/articles/10.3389/ffgc.2023.1193221

DOI=10.3389/ffgc.2023.1193221

ISSN=2624-893X

ABSTRACT=<p>Analyzing the physiological response of trees to climate change in the Qilian Mountains region is key to studying the impact of global change on forest ecosystems in the semiarid alpine region of Northwest China. The leaf area index (<italic>LAI</italic>) of the canopy of a forest is an important input parameter for simulating carbon and water cycles in forest ecosystems. Studying the relationship between <italic>LAI</italic> and environmental factors can provide a scientific basis for accurately describing the structure, function, and ecohydrological processes of forest ecosystems and theoretically guide for sustainable management of water conservation in forests. Methods: In this study, the <italic>LAI</italic> of <italic>the Picea crassifolia</italic> canopy was monitored for 2 years (2015–2016) by field observations, and its dynamic changes were analyzed. The relations between <italic>LAI</italic> and air temperature (<italic>AT</italic>), precipitation (<italic>P</italic>), soil temperature (<italic>ST</italic>), and soil water content (<italic>SWC</italic>) were studied using Pearson's correlation and multiple regression analyses. The results were as follows: seasonal variations in <italic>LAI</italic> showed a single-peak curve, which first increased, reached a maximum, remained relatively stable, and then decreased. The maximum value was 4.02 and 4.18 relatively observed in mid-August 2015 and 2016. The <italic>LAI</italic> of the <italic>P. crassifolia</italic> canopy in different months was positively correlated with <italic>AT</italic> and <italic>P</italic>. It was correlated between the <italic>LAI</italic> of the canopy with <italic>ST</italic><sub>40−60</sub> in May and June (<italic>p</italic> &lt; 0.05) and was also highly positively correlated between the <italic>LAI</italic> of the canopy with <italic>ST</italic><sub>60−80</sub>, <italic>ST</italic><sub>mean</sub>, and <italic>SWC</italic><sub>60−80</sub> in July and August (<italic>p</italic> &lt; 0.01). There was a positive correlation between the <italic>LAI</italic> of the canopy with <italic>SWC</italic><sub>0−60</sub> and <italic>SWC</italic><sub>mean</sub> in July and <italic>SWC</italic><sub>0−60</sub> and <italic>SWC</italic><sub>mean</sub> in August (<italic>p</italic> &lt; 0.05). The <italic>LAI</italic> of the canopy was affected by <italic>AT</italic> and <italic>ST</italic> in May and July, <italic>AT</italic> and <italic>P</italic> in June, <italic>P</italic> in August, and <italic>P</italic> and <italic>ST</italic> in September. Our study implied that the rapid increase period of the <italic>LAI</italic> of the canopy was from late May to early July. The <italic>LAI</italic> of the canopy was more influenced by temperature and water in July and August. In addition, the <italic>LAI</italic> of the canopy has significant seasonal variation although it is evergreen coniferous tree species.</p>