## Results  
### Description of Fertilization Effects on Fluxes, Optical Data, and Vegetation Characteristics  
The effect of the fertilization treatment on GPP, LUE\({}_{\rm p}\), F\({}_{\rm 760}\), LUE\({}_{\rm f}\) and Fesc\({}_{\rm fw}\) is shown in Figure 2. All these variables show a wide variation in time (campaign) and with treatment. GPP is higher in the N and NP treatments in 2014 and more substantially in 2015 during Campaigns 5 (\(F_{3,18}\)= 15.6, \(p\) < 0.01) and 6 (\(F_{3,26}\)= 13.1, \(p\) < 0.01). LUE\({}_{\rm p}\) in the N treatment is significantly different from the C treatment only during Campaign 6 (\(F_{3,26}\)= 2.7, \(p\) < 0.05). F\({}_{\rm 760}\) shows a significant increase during Campaign 2 for the NP treatment (\(F_{3,11}\)= 5.9, \(p\) < 0.05) and during Campaigns 5 (for N and NP) (\(F_{3,18}\) = 13.2, \(p\) < 0.01) and 6 (for N,NP, and P) (\(F_{3,26}\) = 19.7,\(p<0.01\)) of 2015. LUE\({}_{\text{f}}\) is significantly higher for the NP treatment during Campaign 4 of 2014 (\(F_{3,12}=4.59,p<0.05\)), while Fesc shows significant increases for the N and NP treatment of Campaigns 5 (\(F_{3,18}=11.32,p<0.05\) and \(p<0.05\), respectively ) and 6 (\(F_{3,26}=15.91,p<0.05\) and \(p<0.01\), respectively) of 2015. Figure 2: Bar graphs representing differences among treatments (control treatment, C; nitrogen treatment, N; nitrogen and phosphorus treatment, NP; and control treatment, C) of Gross Primary Production (GPP) in 2014 (**a**) and 2015 (**b**); light use efficiency of photosynthesis (LUE\({}_{\text{p}}\)) in 2014 (**c**) and 2015 (**d**); Fluorescence at 760 nm (F\({}_{760}\)) in 2014 (**e**) and 2015 (**f**); light use efficiency of fluorescence emission at 760 nm (LUE\({}_{\text{f}}\)) in 2014 (**g**) and 2015 (**h**); and fraction of F\({}_{760}\) that escapes the canopy (Fesc\({}_{\text{fw}}\)) in 2014 (**i**) and 2015 (**l**). Data are divided among campaigns. Bar graphs represent means and error bars represent 1 standard error. Group differences in (**a**–**h**) were analyzed with ANOVA test and individual differences among groups were evaluated with Tukey HSD post hoc test. Group differences in (**i,l**) were analyzed with ANOVA with the Welch correction and individual differences among groups were evaluated with the Games–Howell post hoc test. “**” refers to a significant difference from the control treatment with \(p\) value \(<0.05\) and “**” refers to a significant difference from the control treatment with \(p\) value \(<0.01\). Figure 3 displays changes in N%, APAR, Albedo\({}_{400-900}\), Ts and plant community (%graminoids) with the fertilization treatment. N% shows a quite consistent increase in the N and NP treatment in 2014 in comparison with the C treatment for Campaigns 2 (\(F_{3,11}=26.8\), \(p<0.01\)), 3 (\(F_{3,12}=14.2\), \(p<0.01\)) and 4 (\(F_{3,11}=14.2\), \(p<0.01\)) and in 2015 in Campaigns 5 (\(F_{3,18}=56.2\), \(p<0.01\)) and 6 (\(F_{3,26}=18.5\), \(p<0.01\)). APAR presents significant differences for the N and NP treatment of Campaign 2 (\(F_{3,11}=24.98\), \(p<0.01\)) of 2014 and Campaigns 5 and 6 of 2015 (\(F_{3,18}=7.37\), \(p<0.01\) and \(F_{3,26}=38.5\), \(p<0.01\), respectively). Figure 3: Bar graph representing differences among treatments (control treatment, C; nitrogen treatment, N; nitrogen and phosphorus treatment, NP; and control treatment, C) of Canopy nitrogen content (N%) in 2014 **(a)** and 2015 **(b)**; absorbed photosynthetic active radiation (APAR) in 2014 **(c)** and 2015 **(d)**; Albedo\({}_{400-900}\) in 2014 **(e)** and 2015 **(f)**; Surface Temperature (Ts) in 2014 **(g)** and 2015 **(h)**; and graminoids relative abundance (%graminoids) in 2014 **(i)** and 2015 **(l)**. Data are divided among campaigns. Bar graphs represent means and error bars represent 1 standard error. Group differences in **(e–h)** were analyzed with ANOVA test and individual differences among groups were evaluated with Tukey HSD post hoc test.