Calcium and silicon precipitation in Pinus taeda needles in response to soil application of cellulosic residue

Authors: BARBOSA, JULIERME - Federal University Of Minas Gerais; MENDES, E - Federal University Of Parana Polytechnic Center; SASS, ANNE - Federal University Of Parana Polytechnic Center; MAGRI, EDERLAN - Federal University Of Parana Polytechnic Center; ARAUJO, ELOA - Federal University Of Parana Polytechnic Center; Prior, Stephen; MOTTA, ANTONIO - Federal University Of Parana Polytechnic Center; SHIZUO, MAEDA - Embrapa

Submitted to: Floresta e Ambiente (Forest and Environment)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2025
Publication Date: 9/22/2025
Citation: Barbosa, J.Z., Mendes, E.J., Sass, A.L., Magri, E., Araujo, E.M., Prior, S.A., Motta, A.C., Shizuo, M. 2025. Calcium and silicon precipitation in Pinus taeda needles in response to soil application of cellulosic residue. Floresta e Ambiente (Forest and Environment). 32(3):e20240048. https://doi.org/10.1590/2179-8087-FLORAM-2024-0048.
DOI: https://doi.org/10.1590/2179-8087-FLORAM-2024-0048

Interpretive Summary: The majority of commercial Pinus taeda production occurs in southern Brazil on acidic soils of low natural fertility, which can be similar to conditions in southern USA. This study evaluated the impact of applying composted residue (generated by the paper industry) on element distributions in P. taeda needles. Use of this material could promote sustainability practices and reduce landfilling expenses. Scanning electron microscopy combined with energy-dispersive spectroscopy microanalysis showed different elemental accumulation patterns that may have possible physiological and ecological roles in P. taeda. Calcium and Si precipitation occurred in needles of P. taeda, with Ca accumulating in the phloem, while Si accumulated in epidermal cells. Low application rates had no impact, but the application of 60 Mg ha-1 showed that Ca crystals tended to formed in phloem, and Si crystals numbers decreased in needle epidermal tissue. Analysis of crystal composition did not indicate significant changes in concentrations of Ca and Si.

Technical Abstract: The use of biosolids as a sustainable alternative in the management of planted Pinus taeda forests affects availability of nutrients and beneficial elements. Calcium (Ca) and Silicon (Si) play important roles in plant regulatory and protective systems; therefore, our objective was to use scanning electron microscopy combined with energy-dispersive spectroscopy (SEM – EDS) to analyze the accumulation of elements in P. taeda needles grown in soil that received 0 to 60 Mg ha-1 applications of cellulosic waste. Microanalyses of needle sections were performed using a SEM with elemental detection by EDS. The mapping mode allowed for detection and analysis of Ca, Si, and C distributions in needle sections. In point analysis mode, C, O, Ca, Si, S, and Al were assessed. Calcium and Si precipitation occurred in P. taeda needles, with Ca being accumulated in the phloem while Si accumulated in epidermal cells. Application of 60 Mg ha-1 changed the availability and accumulation of elements, which resulted in more Ca crystals and fewer Si crystals in comparison to other treatments.