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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #412866
Research Project: Development of Management Strategies for Livestock Grazing, Disturbance and Climate Variation for the Northern Plains

Location: Livestock and Range Research Laboratory

Title: Experimental evidence that poor soil phosphorus (P) solubility typical of drylands due to calcium co-precipitation favors autonomous plant P acquisition over collaboration with mycorrhizal fungi

Author
item Reinhart, Kurt
item Vermeire, Lance
item Penn, Chad
item LEKBERG, YLVA - Mpg Ranch

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2024
Publication Date: 9/28/2024
Citation: Reinhart, K.O., Vermeire, L.T., Penn, C.J., Lekberg, Y. 2024. Experimental evidence that poor soil phosphorus (P) solubility typical of drylands due to calcium co-precipitation favors autonomous plant P acquisition over collaboration with mycorrhizal fungi. Soil Biology and Biochemistry. 199. Article 109605. https://doi.org/10.1016/j.soilbio.2024.109605.
DOI: https://doi.org/10.1016/j.soilbio.2024.109605

Interpretive Summary: Problem- Drylands with calcareous soils (i.e. subsoils containing carbonates) make up approximately a third of land. We have a poor understanding of phosphorus (P) limitation and P-acquisition strategies in these dryland systems. Accomplishment- Results indicate calcium carbonate in the subsoil reduced plant available phosphorus, plant P uptake, and plant biomass. In drylands with calcium-related phosphorus compounds, P-deficient plants rely more on root-mining strategies than P scavenging by mycorrhizal fungi. Relative to other plant species, the invasive weed cheatgrass (Bromus tectorum) had superior P-mobilization and P-uptake strategies and was able to resist P-deficient conditions. Our findings support that invasive plants are likely to have unique nutrient acquisition strategies and capable of invading nutrient-limited systems.

Technical Abstract: Calcareous dryland soils possessing calcium-related phosphorus (P) compounds make >30% of Earth’s land, yet the relative importance of P-acquisition strategies among plant species in these systems is not well known. No experiment has investigated potential interactions between calcium carbonate [CaCO3] and arbuscular mycorrhizal fungi (AMF) on plant performance and P-acquisition strategies which could test for potential mechanisms without the limitations (e.g. soil heterogeneity) of in-situ comparisons over natural gradients. To fill this knowledge gap, we conducted an experiment with a geochemical treatment (CaCO3 replacement series), AMF treatment, and three invasive and five native grassland plants. We hypothesized an increase in soil CaCO3 would 1) reduce soil available P (while total P was constant), 2) reduce plant biomass and P uptake, and 3) shift P-acquisition strategies toward root mining as calcium-bound P increases. The geochemical treatment reduced available P by as much as 57%. On average, large additions of CaCO3 reduced total biomass of plants by 19% and plant uptake of P by 15%. The invasive grass Bromus tectorum resisted low soluble P conditions and maintained shoot biomass over CaCO3 gradient. Results indicated shifts in the relative importance of mycorrhizal scavenging versus root mining. Plants had varying responses to AMF. In contrast to theory on nutritional mutualisms, rarely did AMF and geochemical treatments interact and affect plant biomass. When they did interact, our results mostly failed to detect an increase in mycorrhizal responsiveness with less available P (and occasionally detected the opposite) thereby suggesting i) AMF cannot easily solubilize calcium-bound P and ii) plants may derive less benefit from AMF than expected when calcium compounds limit P solubility. CaCO3 additions tended to increase a leaf trait (leaf manganese [Mn]) indicator of root exudates that mobilize calcium-bound P for plants grown without AMF, thereby suggesting some inducible root mining of P across species, especially Artemisia frigida and Poa secunda. However, plant species had varying Mn, and CaCO3 and species interacted to affect Mn. Relative to other plants, B. tectorum had the greatest leaf Mn and greatest uptake of P thereby suggesting superior P mobilization and constitutive root mining of P. In dryland soils with less soluble P, plants are likely to rely more on root mining P-acquisition strategies than mycorrhizal scavenging.