Challenges of utilizing municipal compost as an amendment in boreal forest reclamation subsoil material

Erika Rovena Valek
Forest reclamation sites are often located in areas not suited for agriculture and therefore have poor soil conditions. To assist in the rehabilitation of forests on these types of sites, organic amendments can be used. Close to large urban centers, compost derived from municipal organic waste can be utilized to enhance soil suitability for plant growth by increasing organic matter and nutrient availability. When organic amendments are incorporated into the soil surface, however, improved
more » ... l conditions are often accompanied by an increase in cover of disturbance adapted ruderal species that compete with planted tree seedlings. The primary objective of this thesis was to examine a novel site preparation technique that explores the impact of inverting a 25 cm organic layer (here compost) beneath a 20 cm mineral soil cap. We hypothesized that the buried compost layer would provide a deep, nutrient rich rooting environment for tree seedlings while the cover of mineral soil would limit interspecific competition from weedy species during the vulnerable initial years following planting. This method was compared to the more conventional treatment of applying materials at the soil surface including salvaged topsoil material and compost. All soil treatments containing compost had poor seedling survival after the first growing season, with no seedling survival in the surface applied compost. Soil treatments with a mineral soil cap over compost initially had high mortality (70%); however, growth for the remaining tree seedlings was better in the second growing season relative to other soil treatments. This poor survival was clearly influenced by the chemical composition of the compost and our failure to incorporate the material deep enough into the mineral subsoil. During the composting process at the waste plant, biosolids had been added, which significantly increased the salinity of the Firstly, I would like to thank my supervisor Dr. Simon Landhäusser for supporting and guiding me along this journey. It was Simon's enthusiasm for research and confidence in my abilities that challenged me and held me to a very high standard. Without this, I would not have gained the breadth of knowledge I now have from this experience and will carry with me for the rest of my life. The past three years have been very challenging, but overall rewarding and I am thankful for his patience and thoroughness. Additionally, I would like to thank Dr. Brad Pinno and Dr. Guillermo Hernandez Ramirez for serving on my committee, taking the time to read my thesis, and providing insightful comments. The Landhäusser Research Group made this experience very enjoyable and I feel fortunate to call the individuals in this group colleagues and friends. I would especially like to thank
doi:10.7939/r3vt1h58k fatcat:a5xnbms3jvewpeaglotpeysbxi