Patterns of nitrogen and phosphorus pools in terrestrial ecosystems in China

Abstract. Recent increases in atmospheric carbon dioxide (CO2) and temperature relieve the limitation of these two on terrestrial ecosystem productivity, while nutrient availability constrains the increasing plant photosynthesis more intensively. Nitrogen (N) and phosphorus (P) are critical for plant physiological activities and consequently regulates ecosystem productivity. Here, for the first time, we mapped N and P densities of leaves, woody stems, roots, litter and soil in forest, shrubland and grassland ecosystems across China, based on an intensive investigation in 4175 sites, covering species composition, biomass, and nutrient concentrations of different tissues of living plants, litter and soil. Forest, shrubland and grassland ecosystems in China stored 7665.62 × 106 Mg N, with 7434.53 × 106 Mg (96.99 %) fixed in soil (to a depth of one metre), and 32.39 × 106 Mg (0.42 %), 59.57 × 106 Mg (0.78 %), 124.21 × 106 Mg (1.62 %) and 14.92 × 106 Mg (0.19 %) in leaves, stems, roots and litter, respectively. The forest, shrubland and grassland ecosystems in China stored 3852.66 × 106 Mg P, with 3821.64 × 106 Mg (99.19 %) fixed in soil (to a depth of one metre), and 3.36 × 106 Mg (0.09 %), 14.06 × 106 Mg (0.36 %), 11.47 × 106 Mg (0.30 %) and 2.14 × 106 Mg (0.06 %) in leaves, stems, roots and litter, respectively. Our estimation showed that N pools were low in northern China except Changbai Mountains, Mount Tianshan and Mount Alta, while relatively higher values existed in eastern Qinghai-Tibetan Plateau and Yunnan. P densities in plant organs were higher towards the south and east part of China, while soil P density was higher towards the north and west part of China. The estimated N and P density datasets, Patterns of nitrogen and phosphorus pools in terrestrial ecosystems in China (the pre-publication sharing link: https://datadryad.org/stash/share/78EBjhBqNoam2jOSoO1AXvbZtgIpCTi9eT-eGE7wyOk , are available from the Dryad Digital Repository (Zhang et al., 2020). These patterns of N and P densities could potentially improve existing earth system models and large-scale researches on ecosystem nutrients.