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<p>Plant photosynthetic physiology is a crucial process reflecting plant growth and productivity. The maximum rate of Rubisco carboxylation (<em>V<sub>c,max</sub></em>) and the maximum rate of electron transport (<em>J<sub>max</sub></em>) of plant leaves are the main limiting factors of photosynthetic capacity and indispensable parameters in ecosystem mechanism models. Accurate simulation of <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> is vital to improve the prediction precision of vegetation dynamics under the background of climate changes. However, using traditional CO<sub>2</sub> response curves to obtain <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> was time-consuming (about 30 to 60 minutes for each CO<sub>2</sub> response curve) and labor-intensive in the field. The rapid photosynthesis-intercellular CO<sub>2</sub> concentration (A-Ci) response technique (RACiR) provided a potential convenient way to obtain A-Ci curve in an open gas exchange system, which would greatly improve the measurement efficiency. Nevertheless, whether the RACiR detecting method verified by limited conifers and deciduous species (especially poplar trees) in previous studies could be generally used for other plant functional groups remains unclear.</p><p> </p><p>Therefore, here we selected <em>Viburnum Odoratissimum</em> as the target and used Li-cor 6800 to test the applicability of the rapid RACiR detecting method on evergreen species. As the changes of CO<sub>2</sub> ranges and rates are the most important parameters in the method, we set 10 different change ranges of reference [CO<sub>2</sub>] (i.e., 400-1500 ppm, 400-200-800 ppm, 420-20-620 ppm, 420-20-820 ppm, 420-20-1020 ppm, 420-20-1220 ppm, 420-20-1520 ppm, 420-20-1820 ppm, 450-50-650 ppm, 650-50-650 ppm) to verify the accuracy of traditional CO<sub>2</sub> response curves and RACiR and to explore suitable [CO<sub>2</sub>] change ranges for evergreen species.</p><p> </p><p>Finally, our results showed that <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> calculated by 10 rapid A-Ci response curves except <em>J<sub>max</sub></em> calculated by 650-50-650 ppm [CO<sub>2</sub>] were not significantly different from those calculated by traditional A-Ci response curves. Moreover, 400-200-800 ppm [CO<sub>2</sub>] compared with the other [CO<sub>2</sub>] ranges was suitable for <em>V. Odoratissimum</em>. Our results indicated the advantage of RACiR method for evergreen species and implied that preliminary experiments should be carried out according to specific tree species to determine the most appropriate change range of [CO<sub>2</sub>] when using RACiR to calculate <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em>.</p>

Using traditional photosynthesis-intercellular CO concentration (A-C) response (TACiR) curves to obtain the maximum rates of ribulose-1,5-bisphosphate carboxylase oxygenase carboxylation (V) and electron transport (J) is time-consuming and labor-intensive. Instead, the rapid A-C response (RACiR) technique provides a potential way with high efficiency. However, multiple parameter settings of RACiR technique for different plant life forms remain unclear. Here, we used Li-Cor 6800 to test the applicability and optimum parameter settings of RACiR curves for evergreens and herbs. We set 11 groups of [CO], i.e., R1 (400-1500 ppm), R2 (400-200-800 ppm), R3 (420-20-620 ppm), R4 (420-20-820 ppm), R5 (420-20-1020 ppm), R6 (420-20-1220 ppm), R7 (420-20-1520 ppm), R8 (420-20-1820 ppm), R9 (450-50-650 ppm), R10 (650-50 ppm) and R11 (650-50-650 ppm), and made contrasts between TACiR and RACiR curves. We found that V and J calculated by TACiR and RACiR overall showed no significant differences across 11 [CO] gradients (P<0.05). The efficiency and accuracy of R2, R3, R4, R9 and R10 showed higher superiority than others. Moreover, the accuracy of manual empty chamber correction method was higher than the automatic method. In conclusion, the RACiR technique could be generally used to obtain photosynthetic parameters with higher efficiency than traditional methods for various life forms.

&lt;p&gt;As important components of leaf economic spectrum&amp;#160;(LES), specific leaf area (SLA), chlorophyll (Chl) content, and foliar nutrient content&amp;#160;are crucial plant functional traits (PFT) and essential parameters in most earth system models. Among those, SLA, Chl, foliar carbon (C), nitrogen (N), phosphorus (P) content&amp;#160;and their stoichiometry are key indicators&amp;#160;which are frequently focused on due to their application in predicting vegetation dynamics and ecosystem productivity in response to anthropogenic perturbations, especially atmospheric N deposition increase. With the hotspot of global N deposition transferred to subtropical and tropical regions, how forest ecosystem changes in these ecoregions response to N deposition has attracted great attention during the past decades. Hence, we established a network of nutrient enrichment experiments in eastern China's forests (NEECF) for exploring the effects of N deposition in 2010.&lt;/p&gt;&lt;p&gt;To evaluate the effect of long-term N&amp;#160;addition&amp;#160;on foliar&amp;#160;traits, we conducted field sampling of the dominant tree species (i.e., &lt;em&gt;Castanopsis eyrie &lt;/em&gt;and&lt;em&gt;&amp;#160;Castanopsis sclerophylla&lt;/em&gt;) in two subtropical forests on the platform of NEECF in August, 2020. 100 kg N ha&lt;sup&gt;-1&lt;/sup&gt;&amp;#160;yr&lt;sup&gt;-1&lt;/sup&gt;&amp;#160;were&lt;sup&gt;&amp;#160;&lt;/sup&gt;applied in each forest with 3 replications of plots, respectively.&amp;#160;The adults and seedlings of the two dominant species were sampled to make a contrast. Through the subsequent detection and analysis, we found that: (1)&amp;#160;leaf-trait syndrome of the dominant&amp;#160;species in two subtropical forests&amp;#160;followed the predictions of global LES, and the growth strategy of the old-aged&lt;em&gt;&amp;#160;C&lt;/em&gt;&lt;em&gt;.&lt;/em&gt;&lt;em&gt;eyrie&lt;/em&gt;&amp;#160;forest was&amp;#160;more conservative than the middle-aged C.&lt;em&gt;sclerophylla&lt;/em&gt;&lt;em&gt;&amp;#160;&lt;/em&gt;forest; (2) N addition had no significant effect on leaf N contents&amp;#160;and C:N ratios of both species, but significantly reduced SLA and Chl content of &lt;em&gt;C. eyrie&lt;/em&gt;&amp;#160;adults and increased C content of &lt;em&gt;C. sclerophylla&lt;/em&gt;&amp;#160;seedlings.&amp;#160;Moreover,&amp;#160;both species showed a more consistent trend of decreasing P content and a corresponding increase&amp;#160;of C:P and N:P ratios. (3) N addition shifted the&amp;#160;C~P scaling relationship of both species and SLA~P scaling relationship of &lt;em&gt;C. sclerophylla&lt;/em&gt;.&lt;/p&gt;&lt;p&gt;Our results verified&amp;#160;the existence of LES patterns among closely related species at the local scale. Moreover, we found that N addition showed&amp;#160;varied effects&amp;#160;on different leaf traits and trait-pairs relationship of subtropical evergreen plants. 10 years&amp;#8217; N addition of high dosage significantly aggravated P limitation in subtropical evergreen forests, which led to a more conservative growth strategy, especially in middle-aged C.&lt;em&gt;sclerophylla&lt;/em&gt;&amp;#160;forest. Our&amp;#160;work&amp;#160;through&amp;#160;site-level case study provided data support&amp;#160;for connecting foliar&amp;#160;functional traits with earth system&amp;#160;models, which will&amp;#160;contribute to enhance&amp;#160;the predictions of ecosystem function and vegetation dynamics&amp;#160;in the context of increasing global N deposition.&lt;/p&gt;