MSc Graduate, 2004
Ectomycorrhizal status and growth of interior douglas-fir on degraded reforestation sites, 2000-2002
Most conifers in the Pacific Northwest form ectomycorrhizae and the benefits of such symbiotic associations are increased nutrient and water uptake, resistance to root pathogens, and tolerance to environmental extremes. In this study, survival and growth of commercially inoculated Douglas-fir seedlings raised under current nursery conditions and outplanted on standard reforestation sites and degraded sites such as landings were evaluated. Landings were significantly more compacted and had lower levels of organic matter and mineralizable-N compared to adjacent clearcuts. Commercially available inoculants did not improve growth, yet it was found that at time of outplanting seedlings were not heavily colonized. On the same sites, the ectomycorrhizal status and growth of nonectomycorrhizal (at time of outplanting) Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) seedlings outplanted on degraded and standard reforestation sites were also assessed. Chemical analysis revealed that seedlings grown on landings had potentially toxic levels of Fe and Al in their needles. In both the field and greenhouse, Rhizopogon vinicolor-like was the most abundant ectomycorrhizal type found in landing soil. On landings ectomycorrhizal colonization was significantly higher than on adjacent clearcuts however, seedling growth and the diversity of ectomycorrhizal types were significantly lower. Before drawing conclusions concerning the potential of commercial inoculants, nurseries should modify growing conditions if they wish to favor good ectomycorrhizal formation before outplanting. This research indicates that under the harsh conditions that are found on landings Douglas-fir can readily form ectomycorrhizae but with a limited number of symbionts.