Forest age and precipitation magnitude affected the contribution rate of rainfall to soil water

Soil water dynamics and its response to precipitation are affected by soil properties and vegetation characteristics. Changes in forest age will significantly affect soil properties and vegetation characteristics. Therefore, exploring the contribution of rainfall to soil water (CRSW) in forests with different ages is helpful to understand the recharge mechanism of precipitation to soil water in forests with different ages.

We calculated the CRSW by using stable hydrogen isotope combined with binary linear mixed model. Furthermore, we used structural equation modeling (SEM) to quantify the relative importance of vegetation factors (leaf area index, litter and fine root biomass) and soil properties (bulk density, porosity and field capacity, pre-rain soil water content) to CRSW.

Following small rainfall events (7.4 mm, 19.6 mm), there was no difference in CRSW among forests with different ages, while the CRSW of rainfall events above 20 mm (23.3 mm, 30.1 mm, 47.3 mm) was significantly different among them. When heavy rainfall events (30.1 and 47.3 mm) occurred, the CRSW of the old-growth forest (> 150 years) was the largest. SEM analysis showed that plant factors significantly affected CRSW after 23.3 mm and 30.1 mm rainfall events. After the 47.3 mm rainfall event, soil properties were the most important factors affecting CRSW.

Under the background of frequent extreme precipitation events, old-growth forests (> 150 years) exhibit stronger storage capacity for large-scale rainfall events. Therefore, the effects of forest age on soil water interception and storage should be fully considered in the forest management and protection.