Abstract
Research Highlights: Short-term nitrogen (N) addition did not significantly alter the effects of seasonal drought on the leaf functional traits in Machilus pauhoi Kanehira seedlings in N-rich subtropical China. Background and Objectives: Seasonal drought and N deposition are major drivers of global environmental change that affect plant growth and ecosystem function in subtropical China. However, no consensus has been reached on the interactive effects of these two drivers. Materials and Methods: We conducted a full-factorial experiment to analyze the single and combined effects of seasonal drought and short-term N addition on chemical, morphological and physiological traits of M. pauhoi seedlings. Results: Seasonal drought (40% of soil field capacity) had significant negative effects on the leaf N concentrations (LNC), phosphorus (P) concentrations (LPC), leaf thickness (LT), net photosynthetic rate (A), transpiration rate (E), stomatal conductance (Gs), and predawn leaf water potential (ψPD), and significant positive effects on the carbon:N (C:N) ratio and specific leaf area (SLA). Short-term N addition (50 kg N·hm−2·year−1 and 100 kg N·hm−2·year−1) tended to decrease the C:N ratio and enhance leaf nutrient, growth, and photosynthetic performance because of increased LNC, LPC, LT, leaf area (LA), SLA, A, E, and ψPD; however, it only had significant effects on LT and Gs. No significant interactive effects on leaf traits were detected. Seasonal drought, short-term N addition, and their interactions had significant effects on soil properties. The soil total C (STC), nitrate N (NO3−-N) and soil total N (STN) concentrations were the main factors that affected the leaf traits. Conclusions: Seasonal drought had a stronger effect on M. pauhoi seedling leaf traits than short-term N deposition, indicating that the interaction between seasonal drought and short-term N deposition may have an additive effecton M. pauhoi seedling growth in N-rich subtropical China.
Highlights
Global environmental change is amongst the most crucial factors that influence the biodiversity, structure and function of forest ecosystems [1,2,3]
The second Principal Component Analysis (PCA) axis accounted for 17.89% of the total variation, with strong loadings of Ci and Water use efficiency (WUE) (Table S1, Figure 1)
leaf N concentrations (LNC), C:N ratio, and LPC were selected as chemical traits, and E, A, Gs, and ψPD were selected as physiological traits
Summary
Global environmental change is amongst the most crucial factors that influence the biodiversity, structure and function of forest ecosystems [1,2,3]. As the most important drivers of environmental change, the climate change (especially the drought stress) and atmospheric nitrogen (N) deposition seriously affect the primary productivity and stability, carbon (C) and water cycles of the forest ecosystems [3,4]. Drought can decrease the availability of soil nutrients, resulting in plant N limitation, which stunts growth and increases mortality [4,6,7]. N deposition can alter soil nutrient cycle, and increase soil acidification and cations leaching from the soil [12], resulting in plant nutrient imbalances and further stunting of growth [13,14]
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