Abstract
Research Highlights: Understanding of the spatial variation of root exudation on a regional scale can help understand the response of plant physiological activities to environmental changes. Background and Objectives: Although root exudation has become an important topic in belowground ecology, its relationship with root traits and environmental factors is poorly understood. Our objective was to explore how root traits and environmental factors influence root exudation. Materials and Methods: We used a multi-factorial design consisting of three tree species spanning across sites located at three latitudes to assess root exudation dynamics, which was measured using a syringe-basis incubation system. Results: The strongest and clearest effect observed in our study was a decrease in root exudation rates of Korean pine (Pinus koraiensis Sieb. et Zucc.) and larch (Larix gmelinii (Rupr.) Kuze.) at sites located in higher latitudes. Root exudation rates were positively related to mean annual temperature, mean annual precipitation, and negatively related to soil total organic carbon. Conclusions: Root exudation in coniferous species decreased at sites located in higher latitudes. Despite differences in root exudation rate among sites located at different latitudes and species with suitable variation in root morphological traits and environmental factors, we could not identify consistent influencing factors on root exudation rates.
Highlights
In addition to transferring carbon (C) and nutrients to the soil through the turnover of fine roots, plants release labile carbon compounds from roots into the rhizosphere, a process referred to as root exudation [1]
Despite differences in root exudation rate among sites located at different latitudes and species with suitable variation in root morphological traits and environmental factors, we could not identify consistent influencing factors on root exudation rates
Root exudation rates ranged from 2.88 to 6.85 mg C m−2 h−1 across sites and species included in our study
Summary
In addition to transferring carbon (C) and nutrients to the soil through the turnover of fine roots, plants release labile carbon compounds from roots into the rhizosphere, a process referred to as root exudation [1]. Root exudates can comprise 5%–21% of assimilated carbon that trees allocate to roots [2]. Due to the magnitude and ubiquity of root exudation in forests, it is considered a key process responsible for shaping the rhizosphere environment [5]. Root exudation is a key mediator in plant–microbe–soil interactions and functions, thereby influencing soil organic matter (SOM) decomposition [6], nutrient cycling [7], microbial community assemblages [8], and soil enzyme activity [9]. Despite the magnitude of carbon allocated to root exudation on an annual basis and its importance on ecosystem process, relatively little is known regarding the relative importance of root and environmental factors on root exudation. Our objective was to explore how root traits and environmental factors influence root exudation.
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