Global meta-analysis shows pervasive phosphorus limitation of aboveground plant production in natural terrestrial ecosystems

Abstract

Phosphorus (P) limitation of aboveground plant production is usually assumed to occur in tropical regions but rarely elsewhere. Here we report that such P limitation is more widespread and much stronger than previously estimated. In our global meta-analysis, almost half (46.2%) of 652 P-addition field experiments reveal a significant P limitation on aboveground plant production. Globally, P additions increase aboveground plant production by 34.9% in natural terrestrial ecosystems, which is 7.0-15.9% higher than previously suggested. In croplands, by contrast, P additions increase aboveground plant production by only 13.9%, probably because of historical fertilizations. The magnitude of P limitation also differs among climate zones and regions, and is driven by climate, ecosystem properties, and fertilization regimes. In addition to confirming that P limitation is widespread in tropical regions, our study demonstrates that P limitation often occurs in other regions. This suggests that previous studies have underestimated the importance of altered P supply on aboveground plant production in natural terrestrial ecosystems.

Fig. 1. Locations of the 652 experiments in which the effect of P addition on aboveground plant production was assessed.

a Natural terrestrial ecosystems. b Croplands. Experiments were determined to have significant P limitation based on the Ln(Response Ratio). If the Ln(Response Ratio) was higher than a threshold value (0.23 for natural terrestrial ecosystems and 0.09 for croplands), it was considered a significant case (Z test, P < 0.05) of P limitation. Determination of the threshold values is described in the “Methods” section and is supported by the Supplementary Fig. 3. Numbers in brackets are the number of experiments in the indicated group. Source data are provided as a Source Data file.

Fig. 2. Consistent occurrence of significant P limitation in all types of ecosystems.

a Significant P limitation occurred in the natural terrestrial ecosystems at almost all latitudes. The magnitude of P limitation decreased with latitude in wetlands (meta-regression, R² = 0.35, P < 0.05, N = 85) but not in any other type of natural terrestrial ecosystem (meta-regression, P > 0.05). b Significant P limitation occurred in all types of natural terrestrial ecosystems. Values in the brackets indicate the percentage of significant P limitation cases in the total sample size in each type of natural terrestrial ecosystem. c Significant P limitation occurred in croplands at all explored latitudes (absolute latitude between 0.1^° and 56.5^°), and the magnitude of P limitation decreased with absolute latitude (meta-regression, R² = 0.16, P < 0.05, N = 216). d Significant P limitation was found in 48.6% of the P-fertilization experiments in the croplands. As in Fig. 1, statistical significance of P limitation was assessed based on the Ln(Response Ratio). Dashed lines in all plots (0.23 in (a) and (b), 0.09 in (c) and (d)) indicate where the magnitude of P limitation approximates a 0.05 significance level (Z test). In (a) and (c), the size of each point is proportional to the weight used for meta-regression analysis. Source data are provided as a Source Data file.

Fig. 3. P limitation was significant in all regions and major types of ecosystems and under various fertilization regimes.

Exceptions are the non-significant P limitation in two groups of experiments in the croplands that had a small sample size (N = 8). Natural terrestrial ecosystems are shown in green (total N = 436), and croplands are shown in yellow (total N = 216). Values represent effect sizes ± 95% confidence intervals. The size of each point is proportional to the sample size (sample sizes are listed in Supplementary Table 3). The dashed lines indicate the no-fertilization effect. SSP is single superphosphate, and TSP is triple superphosphate. Source data are provided as a Source Data file.

Fig. 4. Relative influence of climate, fertilization regimes, and ecosystem properties on the magnitude of P limitation.

a Natural terrestrial ecosystems. b Croplands. The number above each bar indicates the percentage of the total explained variation accounted for by the variable. Fertilization regimes are in pink, climate factors are in blue, soil properties are in gray, and vegetation properties are in green. Source data are provided as a Source Data file.