Short-Term Nitrogen Addition Does Not Significantly Alter the Effects of Seasonal Drought on Leaf Functional Traits in Machilus pauhoi Kanehira Seedlings

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.

Effects of Increased N Deposition on Leaf Functional Traits of Four Contrasting Tree Species in Northeast China

“…Correlations were more consistent in gymnosperms, likely because evergreens such as P. koraiensis often hold more mechanical tissues which could help avoiding damage as result of frost or drought [ 59 ]. In previous studies LD of woody species was furthermore found negatively related to the fractions of epidermis and mesophyll but positively related to the fraction of sclerified tissues [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. In partial contrast to our second hypothesis we did not find correlations of LD (and LT) with epidermis and mesophyll thicknesses in the studied gymnosperms; variable cell sizes and number [ 19 , 60 ] and air spaces may thus explain differences in LD (and LT) beside changes in structural tissue fractions [ 14 , 46 ].…”

“…While some previous studies indicated that greater N deposition rates may reduce the growth and/or decrease the leaf area due to a toxic effect of ammonium on certain tree species, incl. F. mandshurica [ 43 , 44 ], this was not the case for the studied species under given experimental conditions—indicating that observed effects on leaf traits are indeed based on a varied N availability.…”

Direct and indirect effects of precipitation change and nutrients addition on desert steppe productivity in Inner Mongolia, northern China

“…N addition mediates the effect of drought on soil water content reduction. The response of arid grassland to drought is stronger (Dziedek et al 2016), and N addition could decrease plants' drought resistance (Yu et al 2019). However, the carbon and nitrogen content and bulk density of soil did not respond signi cantly to such short-term habitat changes.…”

Contrasting effects of plant inter- and intraspecific variation on community trait responses to nitrogen addition and drought in typical and meadow steppes

“…In this study, we uncovered changes in CWMs for most of the traits, and the contribution of inter- and intraspecific variation. N addition increased LNC and decreased C: N at both species- and community-level in the two steppes, indicating that N addition enhanced the availability of N nutrients and in turn reflected a shift towards a rapid resource absorption and growth strategy [ 43 ], and a decrease in the C:N is results from elevated LNC and a relatively stable carbon level under N addition [ 44 ]. Moreover, drought caused an increase in LNC of the meadow steppe, supporting the finding that suggested increased LNC with increasing drought [ 45 ].…”