Mixed plantation regulates forest floor water retention and temperature sensitivity in restored ecosystems on the Loess Plateau, China

Abstract

Ongoing warming and frequent extreme rainfall are endangering hydrological functioning in reforested ecologically vulnerable areas. The forest floor plays an important role in water conservation; however, knowledge of water retention of forest floor and its temperature sensitivity under climate change remains limited particularly in restored ecosystems. Here, we investigated and sampled litter and topsoil from three monoculture plantations, two mixed plantations, and one natural grassland on the hilly and gullied Loess Plateau. We used an artificial climate incubator to simulate different climate conditions and measure the effects on litter and topsoil water retention. Generalized additive models were used to explore the relationships between temperature sensitivity of water-retention capacity and influencing factors. The results showed that mixed plantations shortened the water retention time of litter and topsoil. In addition, mixed plantations significantly improved the maximum water-holding capacity of litter, but reduced the maximum water-holding capacity of topsoil. Litter water-retention capacity temperature sensitivity (LTS) was significantly greater than that of soil (STS). Moreover, communities with strong LTS generally had weak STS. Nonetheless, mixed plantations tend to have a more stable forest floor water-retention capacity. Soil porosity, bulk density, litter mass, and canopy openness were the key factors affecting the maximum water-holding capacity and water-retention capacity of forest floors. Overall, our results indicated that mixed plantations adjusted the water retention time of the forest floor and had a more stable water-retention capacity, which was of great significance for plantation management in arid and semi-arid regions.