Abstract:

Objective: This study aims to explore the the differences in the response of dominant tree radial growth of Larix principis-rupprechtii growing on different slope aspects in the semi-arid area of Liupan Mountine to meteorological and soil factors, so as to provide a scientific foundation for predicting forest growth and adaptation forestry management strategies under future climate change. Method: The research focused on L. principis-rupprechtii plantations growing in Diediegou small watershed of Liupan Mountain. Eleven sample plots were established along the different slope orientations (northwest slope-north slope-northeast slope-southeast slope). The annual average basal area increment (BAI) of individual dominant trees was determined. Pearson correlation analysis and structural equation model were used to analyze the impact of slope aspect difference on dominant tree’s BAI during 3 distinct periods: a climate-stable period (1995—2004), a rapid warming period (2005—2015) and a rapid precipitation increase period (2016—2020). Result: 1) In the period of rapid warming, drought stress resulted in a rapid decrease in BAI of older dominant trees (23–26 a) on the northwest semi shady slope and north shady slope (average rate was –57.2 mm²·a^?1, P<0.01). However, the younger dominant trees (9–14 a) were hardly influenced by rapid warming, the BAI on the northeast semi shady slope and the southeast semi sunny slope showed an obvious increase (the average rate was 125.43 mm²·a^?1, P<0.01). 2) During the climate-stable period, the temperature difference of slope aspects had a greater impact, showing a negative correlation with the northwest shady slope and a positive correlation with other slopes, but the correlation degree was different. During the rapid warming period, BAI showed a positive correlation with precipitation on the northeast semi shady slope and southeast semi sunny slope, a negative correlation with temperature on the northwest semi shady slope and north slope, and the soil thickness had a greater correlation with BAI on all slopes. During the rapid precipitation increase period, BAI in major slope aspects showed a significant positive correlation with standardized precipitation evapotranspiration index (SPEI), and the BAI on the semi shady slopes also showed a significant positive correlation with precipitation, while the BAI on the shady and southeast semi sunny slopes showed a significant negative correlation with temperature (P<0.05). 3) During the climate-stable period, temperature was the main influencing factor, with direct and indirect influence coefficients of 0.55 and –0.221, respectively. During the rapid warming period, soil factors had a greater impact on BAI growth, and there was a significant positive correlation between soil thickness and BAI, with a total influence coefficient of 0.533. During the rapid precipitation increase period, BAI was only significantly positively influenced by SPEI, with a total influence coefficient of 0.29. Conclusion: In the climate-stable period, the difference in radial growth of L. principis-rupprechtii between slope aspects is relatively small, and the different slope aspects are more affected by temperature. In the rapid warming period, there is significant difference in radial growth between slope aspects, and at this time, different slope aspects are more affected by soil thickness. After the rapid precipitation increase period, the radial growth difference between slope aspects begin to decrease, and SPEI is the main factor affecting the radial growth difference between slope aspects. These findings suggest that adjusting the stand structure can improve the power of L. principis-rupprechtii plantations in Liupan Mountain’s semi-arid region to withstand disaster stress and achieve long-term sustainable forest management.

Key words: Liupan Mountain, Larix principis-rupprechtii, radial growth, slope difference, environmental factor