Evolving soil water replenishment and plant water-use strategies with degradation of restoration materials in vertical greenery systems

Abstract

The ecological restoration of steep destroyed surfaces creates major challenges in ecologically fragile high-altitude regions because of the unknown ecohydrological patterns and restoration mechanisms. In this study, we investigated soil water replenishment and plant water uptake during dew and rain events in the early growth season in two vertical greenery systems restored by organic polymer materials for two and four years. Both restoration sites exhibited a relatively low contribution of dew to soil water, while direct foliar uptake from dew provided 22–25% of plant water during dew events. Compared to dew, rainfall contributed much more to soil water, while plant used only 6–21% of total water from recent rain. These two sites also exhibited some ecohydrological differences over time. In the two-year restoration site, rainwater was retained in the 0–20 cm layer because of interception by organic polymer materials, whereas in the four-year restoration site, rainwater infiltrated deeper (20–40 cm), forming preferential flow pathways and efficient water storage. During rainfall events, plants in the four-year restoration site did not immediately use infiltrated deep rainwater but adopted a more efficient water-use strategy to enhance long-term sustainability. These findings highlight the evolving plant water-use strategies as restoration materials degrade and different hydrological utilization patterns form in dew and rain events in vertical greening systems. Our study provides a theoretical support for the maintenance and irrigation of vertical greenery systems commonly exist in cold plateau areas.