**3. Results**

### *3.1. Nutrient Resorption Patterns in Planted Forests*

Globally, mean values of NRE and PRE in the planted forests were 58.98% ± 0.53% and 60.21% ± 0.77%, respectively, with no significant differences between them (*p* > 0.05, Figure 2). Generally, variations in both NRE and PRE showed remarkable differences among different climate zones and tree functional groups. While NRE significantly increased with increasing latitude (*p* < 0.05, Table 1, Figure 3a), PRE did not differ among climate zones (*p* > 0.05, Table 1, Figure 3b). Additionally, NRE did not differ between conifer and broadleaf trees (*p* > 0.05, Table 1, Figure 4a) and the PRE of conifer trees was higher than that of broadleaf trees (*p* < 0.05, Table 1, Figure 4b). Though NRE did not differ between deciduous and evergreen trees (*p* > 0.05, Table 1, Figure 4a), PRE was significantly higher in evergreen than deciduous trees (*p* < 0.001, Table 1, Figure 4b). The NRE of N-fixing trees was much lower than that of non-N-fixing trees (*p* < 0.001, Table 1, Figure 4a) and the PRE of N-fixing trees was much higher than that of non-N-fixing trees (*p* < 0.05, Table 1, Figure 4b).

**Figure 2.** N and P resorption efficiency (%, NRE and PRE) in planted forests (mean ± SE). Values in the bars represent the number of observations. Different lowercase letters represent statistical differences at *p* = 0.05 between NRE and PRE.

**Table 1.**

(%, NRE and PRE). \*: <0.05, \*\*\*: <0.001.

ANOVA table of the linear


mixed-effects

 models for N and P resorption  efficiency

**Figure 3.** N and P resorption efficiency (%, NRE (**a**) and PRE (**b**)) among different climate zones in planted forests (mean ± SE). Values in the bars represent the number of observations. Different lowercase letters represent statistical differences at *p* = 0.05 among the climate zones.

**Figure 4.** N and P resorption efficiency (%, NRE (**a**) and PRE (**b**)) between broadleaf (B) vs. conifer (C), deciduous (D) vs. evergreen (E), and non-N-fixing (N) vs. N-fixing (F) tree groups in planted forests (mean ± SE). Values in the bars represent the number of observations. Different lowercase letters represent statistical differences at *p* = 0.05 between the different functional types.

### *3.2. Controls of Nutrient Resorption in Planted Forests*

Variations in NRE and PRE at the global scale were not controlled by the same explanatory variables. Our multivariate regression analyses showed that NRE was regulated negatively by MAP and positively by green leaf P concentration (Pgreen) and latitude (LAT) (*p* < 0.001, Table 2). For PRE, green leaf N concentration (Ngreen) and Pgreen had positively and negatively impacted on it, respectively (*p* < 0.001, Table 2). The stand ages of forests had little impact on both NRE and PRE.

**Table 2.** Stepwise regressions of N and P resorption efficiency (%, NRE and PRE) with stand age (year, Age), absolute latitude (◦, LAT), mean annual precipitation (mm, MAP), and green leaf N and P concentrations (mg g<sup>−</sup>1, Ngreen and Pgreen, respectively) in planted forests. \*\*\*: <0.001.

