Commercial production of tree seedlings often includes various biocidal soil treatments for disease control. Such treatments can be effective in eliminating or reducing disease organisms in the soil, but may also eliminate non-targeted beneficial soil organisms, such as mycorrhizal fungi, that improve seedling performance, both in the nursery as well as the outplanted environment. The arbuscular mycorrhizal fungal (AMF) relationship has been verified for some important western coniferous species such as Calocedrus decurrens (Torr.) Florin (incense cedar), Sequoia sempervirens, (D.Don) Endl(coastal redwood) and Thuja plicata J. Donne ex D. Don (western red cedar).
This study was designed to determine the response of Calocedrus decurrens after soil fumigation with and without the addition of phosphorous fertilizer and a commercial mycorrhizal inoculant containing Glomus intraradices. Calocedrus seedling performance was monitored in both the nursery and outplanted environments.
At the nursery, non mycorrhizal seedlings had significantly less foliar phosphorous levels and uneven growth even when phosphorous fertilizers were applied. Mycorrhizal inoculation at the nursery significantly improved height growth and improved seedling uniformity on treated plots. Seedlings from the nursery beds were then outplanted on two reforestation sites. Mycorrhizal inoculation at the nursery improved survival and growth of seedlings at the outplanted site.