The Impact of Nitrogen Application on Leaf and Root Functional Traits of Davidia involucrata Saplings

Abstract

Understanding the effects of nitrogen (N) deposition on plant functional traits can provide insights into their adaptation strategies. We conducted an N application experiment (0, 5, 10, 15 g N m−2) with potted saplings of the endangered species Davidia involucrata and examined 24 functional traits of both leaves and roots. We found that N application increased the leaf morphological traits, except for a significant decrease (by 19.2%–27.0%) in specific leaf area (SLA). Compared to the control treatment, N application significantly increased the specific root surface area (SRA), specific root length (SRL), and root tissue density (RTD) by 9.2%–20.1%, 20.2%–47.9%, and 30.8%–46.4%, respectively, while root diameter was conservative and insensitive to N application. Additionally, N application had contrasting effects between leaf and root carbon, N, and phosphorus contents and their stoichiometry. SRL, SRA, and RTD were positively correlated with most leaf photosynthetic traits, but negatively correlated with SLA. Moreover, root biomass and root chemical traits were also tightly correlated with leaf photosynthetic traits and chemical traits. These results suggest that N application may trigger a resource-conservative strategy for leaves but a nutrient-acquisitive strategy for roots. Future N deposition combined with other practices, such as simultaneous P fertilizer application, can be effective for the scientific conservation of D. involucrata populations in their natural habitats.