Nitrogen enrichment buffers phosphorus limitation by mobilizing mineral-bound soil phosphorus in grasslands

A new study published in the journal Ecology presents biogeochemical evidence to address the question of whether ecosystem nutrient limitation patterns shift from N-limitation to P-limitation under anthropogenic N enrichment. Figure: Wang, et al. Ecology, 2021

Nitrogen enrichment buffers phosphorus limitation by mobilizing mineral-bound soil phosphorus in grasslands. Phosphorus (P) limitation is expected to increase due to nitrogen (N)-induced terrestrial eutrophication, although most soils contain large P pools immobilized in minerals (Pi) and organic matter (Po).

In a new study published in the journal Ecology authors assessed whether transformations of these P pools can increase plant available pools alleviating P limitation under enhanced N availability.

The mechanisms underlying these possible transformations were explored by combining results from a 10-year field N-addition experiment and a 3700-km transect covering wide ranges in soil pH, soil N, aridity, leaching, and weathering that can affect soil P status in grasslands.

“Nitrogen addition promoted dissolution of immobile Pi (mainly Ca-bound recalcitrant P) to more available forms of Pi (including Al- and Fe-bound P fractions and Olsen P) by decreasing soil pH from 7.6 to 4.7, but did not affect Po”, explain Dr. Wang from State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China.

According to this study, soil total P declined by 10% from 385±6.8 to 346±9.5 mg kg-1, while available-P increased by 546% from 3.5±0.3 to 22.6±2.4 mg kg-1 after 10-year N addition experiment, associated with an increase in Pi mobilization, plant uptake, and leaching. Similar to the N-addition experiment, the drop in soil pH from 7.5 to 5.6 and increase in soil N concentration along the grassland transect were associated with an increased ratio between relatively mobile Pi and immobile Pi.

These results provide a new mechanistic understanding of the important role of soil Pi mobilization in maintaining plant P supply and accelerating biogeochemical P cycles under anthropogenic N enrichment. This mobilization process temporarily buffers ecosystem P-limitation or even causes P eutrophication but will extensively deplete soil P pools in the long run

“Our results also suggest that ecosystem P cycling model predictions should incorporate the interactions of N and P cycles by considering N enrichment effects on accelerating soil P cycling rates, that models can be further refined via delineating the dependence of Pi transformation on precipitation, and the ubiquitous role of soil pH in driving the biogeochemical pathways of Pi transformation”, concludes Prof. Josep Penuelas from CREAF-CSIC Barcelona.

Reference: Wang, R., Yang, J., Liu, H., Sardans, J., Zhang, Y., Wang, X., Wei, C., Lü, X., Dijkstra, F.A., Jiang, Y., Han, X., Peñuelas, J. 2021. Nitrogen enrichment buffers phosphorus limitation by mobilizing mineral-bound soil phosphorus in grasslands. Ecology, doi: 10.1002/ecy.3616

Climate and soil determine the distribution of plant traits

A new study published in Nature Ecology and Evolution presents the first global quantification of how interactions of climate and soil drive variation in plant form and function. Map shows the ecoregions (30) included in the study, the number of species per ecoregion is colour-coded (from white= few, yellow= medium to red=many measurements). Source: Joswig et al. Nat. Ecol. Evol. (2021)


An international research team succeeded in identifying global factors that explain the diversity of form and function in plants. Led by the University of Zurich, the Max Planck Institute for Biogeochemistry in Jena and the University of Leipzig, the researchers collected and analyzed plant data from around the world. For the first time, they showed for characteristics such as plant size, structure, and life span how strongly these are determined by climate and soil properties. Insights derived from this could be crucial to improving Earth system models with regard to the role of plant diversity.

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At first glance, the diversity of plant form and function seems difficult to comprehend. However, it can be described in terms of morphological, physiological, and biochemical characteristics. It has been shown previously that traits across species fall into two main categories within which each plant must maintain a balance: first, size and second, economy of metabolism. In a recent study in Nature Ecology and Evolution, a team of researchers has now confirmed for the first time, using a greatly enlarged global dataset for 17 different plant traits, that these two main categories apply to all plants studied worldwide. In the size category, plants balance height, leaf size, and seed size, among other traits. These traits are also influenced by hydraulic components of water transport in plants. The economics category describes how quickly and effectively the plant gains energy and biomass through photosynthesis, balanced against how long it survives. This category is determined by measurable characteristics such as the structure and composition of the leaves in terms of leaf area, as well as their elemental composition (nitrogen, phosphorus and carbon). The team showed that life strategies of the plant species collected worldwide in the TRY database are well explained by these two main categories.

Plant traits are influenced by a wide variety of external factors, such as climate, soil conditions, and human intervention. It has not yet been possible to determine which factors are decisive at the global level. To answer this question, the research team, led by Julia Joswig at the University of Zurich and the Max Planck Institute for Biogeochemistry in Jena, analyzed the characteristics of over 20,000 species. Information on climate and soil conditions at the location of each plant was included in the analysis.

“Our study clearly demonstrates that plant traits worldwide can be explained by joint effects of climate and soil,” Joswig said, adding, “This suggests that aspects of climate change and soil erosion, both of which occur as a result of land use change, for example, should be researched together.”

Many of the relationships described here were already known from small-scale, local studies. “But the fact that these processes could now be shown globally and their significance quantified is an important milestone,” adds Prof. Miguel Mahecha of the University of Leipzig. “Studies of this kind can guide global Earth system models to represent the complex interaction of climate, soil and biodiversity, which is an important prerequisite for future predictions,” Mahecha adds.

As expected, the study shows how the height of plant species changes along latitudes, due to differences in climate. However, the economic traits of plants do not show this gradient. Similarly, soil quality is only partially affected by climate, so there is a latitude-independent component in information about soil. Joswig and her colleagues show that this soil information is also relevant for the economic traits. Besides climate, soil-forming factors include organisms living in the soil, geology and topography, and of course time. Global change affects climate, organisms, and to some extent topography. Therefore, the study suggests that global risks to plant life should be explored especially in relation to climate change and soil erosion.

“In conclusion, our study contribute to the advance of our understanding of broad scale plant functional patterns. In particular, we highlight the combination of independent and particularly joint effects of climate and soil on trait variation, an interaction which has to date been neglected because few studies include both in a single analysis, at the global scale as we have done here”, concludes Prof. Josep Peñuelas from CREAF-CSIC.

Acknowledgments: This study used plant trait data from a collection of datasets made available in the TRY database at MPI-BGC.

Original publication:

Climatic and soil factors explain the two-dimensional spectrum of global plant trait variation

Julia S. Joswig, Christian Wirth, Meredith C. Schuman, Jens Kattge, Björn Reu, Ian J. Wright, Sebastian D. Sippel, Nadja Rüger, Ronny Richter, Michael E. Schaepman, Peter M. van Bodegom, J. H. C. Cornelissen, Sandra Díaz, Wesley N. Hattingh, Koen Kramer, Frederic Lens, Ülo Niinemets, Peter B. Reich, Markus Reichstein, Christine Römermann, Franziska Schrodt, Madhur Anand, Michael Bahn, Chaeho Byun, Giandiego Campetella, Bruno E. L. Cerabolini, Joseph M. Craine, Andres Gonzalez-Melo, Alvaro G. Gutierrez, Tianhua He, Pedro Higuchi, Herve Jactel, Nathan J. B. Kraft, Vanessa Minden, Vladimir Onipchenko, Josep Penuelas, Valerio D. Pillar, Enio Sosinski, Nadejda A. Soudzilovskaia, Evan Weiher, Miguel D. Mahecha. Nature Ecology and Evolution (2021) DOI 10.1038/s41559-021-01616-8

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