Effect of biofuel waste, urea, deer browsing and vegetation control on Pinus banksiana seedling growth on a dry upland site in central Canada

Ash from biofuels and nitrogen fertilizer are increasingly being used as soil amendments. While this can increase tree growth, it can also increase mammalian grazing and competition with vegetation. We applied moderate amounts (1.5 t ha^-1 y^-1) of ash and 74 kg N ha^-1 y^-1 of urea in each of two years to a well-drained site in southeastern Manitoba, planted with <i>Pinus banksiana</i>. Subplots received deer browsing and/or vegetation control. The ash resulted in an increase in pH in the upper 15m of mineral soil from ca. 5.7 to 6.6, and the urea created short-term spikes in soil inorganic N (NH₄ and NO₃) levels. Urea combined with ash significantly increased seedling relative growth rates in the first two years, with seedlings being largest with urea, with or without ash. However, by the fourth year seedling growth and size did not differ between the amendments. Urea application increased browsing damage to 91 %, but only when vegetation was mowed. Browsing guards resulted in seedlings having 1.6 times greater shoot mass by the end of the fourth growing season. These results suggest that on sandy soils in the dry region of central Canada, <i>P. banksiana</i> may get little benefit from ash applications.

Ecological Effects of Wolves in Anthropogenic Landscapes: The Potential for Trophic Cascades Is Context-Dependent

In recent years, large predators have made a comeback across large parts of Europe. However, little is known about the impact that recolonizing predators may have on ecosystems with high degrees of anthropogenic influence. In Scandinavia, wolves (Canis lupus) now inhabit areas affected by intense forestry practices and their main prey, moose (Alces alces), are exposed to significant human hunting pressure. We used long-term datasets to investigate whether the return of wolves has affected moose distribution (i.e., presence and abundance) as well as browsing damage (i.e., presence and intensity) by moose on Scots pine (Pinus sylvestris). We found that the probability of moose presence and abundance increased with time since wolf territory establishment and was higher inside wolf territories than outside. Additionally, the probability of browsing damage was also higher inside wolf territories compared to outside, but wolf occurrence had no effect on browsing damage intensity. We suggest two possible underlying mechanisms behind these results: (1) wolves might select to establish territories in areas with higher moose abundance, increasing their probability of encounters, and/or (2) hunters within wolf territories reduce the number of harvested moose to compensate for wolf predation. This study highlights that the return of large predators to landscapes with strong anthropogenic influence may result in alternative effects than those described in studies on trophic cascades located in protected areas.