What is the major cause of Pinus taeda chlorosis in southern Brazil?

Authors: RODRIGUES, VALDECIO - Universidade Federal Do Parana; MOTTA, ANTONIO - Universidade Federal Do Parana; GOMES, JOAO BOSCO - Brazilian Agricultural Research Corporation (EMBRAPA); BOGNOLA, ITAMAR - Brazilian Agricultural Research Corporation (EMBRAPA); MAGRI, EDERLAN - Universidade Federal Do Parana; Prior, Stephen; SILVA, SERGIO - Brazilian Agricultural Research Corporation (EMBRAPA); AUER, CELSO - Brazilian Agricultural Research Corporation (EMBRAPA); MAEDA, SHIZUO - Brazilian Agricultural Research Corporation (EMBRAPA); JUNIOR, MAURO - Association Of Forest Companies (ACR)

Submitted to: Journal of Soil Science and Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2024
Publication Date: 12/17/2024
Citation: Rodrigues, V., Motta, A., Gomes, J., Bognola, I.A., Magri, E., Prior, S.A., Silva, S.R., Auer, C., Maeda, S., Junior, M.M. 2024. What is the major cause of Pinus taeda chlorosis in southern Brazil?. Journal of Soil Science and Plant Nutrition. 25(1):934-947. https://doi.org/10.1007/s42729-024-02176-z.
DOI: https://doi.org/10.1007/s42729-024-02176-z

Interpretive Summary: Pine forests exhibiting needle chlorosis (yellowing) and tree death have been reported by the Brazilian forest industry in recent years. The goal of this study was to evaluate chlorotic sites exhibiting decline since this is similar to what has been seen in some agroforestry systems in the Southeastern US. This work suggests a possible relationship between soil slope and lack of an A horizon, as well as nutritional imbalance/nutrient deficiency in some areas. Findings indicated that chloroses in southern Brazil may be associated with two distinct problems. The first was associated with some similar characteristics for decline in igneous derived soils (i.e., excess of Mn, deficiency of Fe). The second indicates a nutritional deficiency of Mg and Ca in sedimentary derived soils. The association of biotic and abiotic characteristics of specific locations requires further investigation to better understand factors influencing decline in pine systems. The present work provides the first formal report on the association between decline and soil fertility/pine nutrition in southern Brazil.

Technical Abstract: Pine (Pinus taeda) forests exhibiting foliar chlorosis and tree death following abrupt climatic events have been reported by the southern Brazilian forest industry in recent years. The goal of this study was to evaluate chlorotic sites exhibiting pine chloroses symptoms noted by forest companies. Five pairs (control and chlorotic areas) of forest sites of similar age were selected for samplings and analyses of soil, root, litter, needle, and timber disc samples. Soils were developed from igneous (four sites) and sedimentary (one site) parent source materials. On igneous derived soil, chlorotic areas symptoms had higher soil fertility and plant tissues (needle, wood and bark) with higher nutrient concentrations than control areas. Plant tissue concentrations of manganese (Mn) and calcium (Ca) were higher for chlorotic areas and needle chlorosis was characterized by basal paling of needles. The lack of an A horizon was also characteristic of chlorotic areas. On sedimentary derived soil, the chlorotic areas had low soil fertility, lower tissue nutrient concentrations, particularly magnesium (Mg), and needle tip chlorosis. There was no difference in litter biomass and 100 fascicle weight between chlorotic and control areas. Findings suggest two distinct conditions promoting pine chlorosis in southern Brazil: high fertility soils may be nutritionally imbalanced due to high levels of Mn and/or Ca; and low fertility soils resulted in a deficiency of Mg.