Forested reclamation of oil sands mines in northern Alberta often use peat salvaged from lowland organic soils as a coversoil during soil reconstruction of man-made landforms. Previous studies suggest that planted tree seedlings may be limited in part by low phosphorus (P) and potassium (K) availability in peat. Fertilization is commonly used to treat nutrient limitations on reclamation sites; however, broad spectrum applications can induce strong competition from colonizing vegetation. This study explores the ability of a targeted application of individual macronutrients to 1) reduce nutrient deficiencies in peat coversoils and improve tree growth, while 2) minimizing the colonizing competition. Liquid fertilizer was applied to six-year-old aspen, pine, and spruce trees in the field using five nutrient combinations: Control (no fertilizer), NPK, PK, P, and K. Tree growth, foliar nutrient concentrations, vegetation cover, and environmental parameters were monitored over two growing seasons. Aspen responded the strongest to fertilization, particularly in the P treatment, while pine and spruce marginally responded to NPK. Competing vegetation increased in the NPK but did not respond to the P and K treatments, indicating targeted fertilization can reduce colonizing competition. Additional analyses of the soil conditions of the site suggest that other factors were potentially more limiting to the trees during the study. Targeted fertilization of forest reclamation sites at a later stand age can be an option to improve efficacy and cost savings; however, response will also depend on other site (e.g., soil pH, precipitation, soil water content) and management factors (e.g., fertilizer application rate).

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Dry forests are important sources of biodiversity where lianas are highly abundant given their ability to grow during times of drought and as a result of secondary growth processes. Lianas provide food and shelter for fauna such as birds, but there are no studies assessing the influence of liana abundance on birds in dry forests. Here we evaluate the influence of liana abundance on the avian acoustic community in the dry forests of Costa Rica at Santa Rosa National Park. We selected forest sites with different levels of liana abundance and set up automated sound recorders for data collection, analysis and estimation of the avian acoustic community. When the number of lianas increases, the avian acoustic community becomes more complex. Lianas could provide important direct and indirect resources for birds such as structure for shelter, protection, nesting and roosting, and food. The positive relationship that lianas have with birds is particularly important in dry forests where lianas are becoming highly abundant due to the level of forest disturbance and climate change, especially for some bird species that are restricted to this ecosystem. By validating the number of bird species detected in the recordings with the acoustic complexity index, we found that a higher acoustic complexity means higher species richness.

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