Effect of variable retention harvesting and stand type on soil nitrogen availability in boreal mixedwood forests

Clear-cut harvesting has been shown to increase the nitrification rate and lead to elevated levels of soil nitrate in some forests. This change in nitrogen (N) cycling and availability could negatively affect regeneration, future site productivity as well as surrounding ecosystems. Variable-retention (VR) harvesting has been proposed as a more environmentally acceptable alternative to clearcutting. VR harvesting retains a portion of live trees in the cutblocks and it is assumed that this will create conditions more similar to uncut forests and mitigate the negative effects of clearcutting on the N cycle. In boreal mixedwood forests, maintenance of a deciduous component and management of mixed stands is currently encouraged, partly based on the assumption that deciduous trees facilitate faster N cycling and higher N availability. The evidence of this phenomenon is, however, equivocal. In boreal mixedwood forests in northern Alberta, I assessed whether the uncut deciduous-dominated forests had higher N availability and faster N cycling than coniferous-dominated forests, and whether N availability was related to the proportion of deciduous trees. I also assessed the effects of clearcutting and VR harvesting on soil N availability in boreal mixedwood forests and characterized pathways and rates of nitrification. Uncut stands of deciduous forests had higher availability of ammonium but did not have faster N cycling and higher nitrate levels as hypothesized. Clearcutting had little effect on soil N availability in all forest types. Net and gross rates of N mineralization and nitrification were not altered and N availability was not elevated by clearcutting. VR-harvested sites did not differ either from clearcuts or uncut stands. Despite very low soil nitrate concentrations, nitrification was an active process at all sites, even in uncut coniferous stands. Nitrification was carried out mainly by heterotrophs and both nitrate production and consumption increased with labile C addition. Clearcutting in these boreal forests did not create a soil environment dominated by nitrate at any site. VR harvesting of western boreal mixedwood forests may not be justified based on nutritional concerns as the effects of clearcutting on N availability were minimal.Forestry, Faculty ofGraduat

Ecosystem services provided by bromeliads

A systematic review of ecosystem services provided by bromeliad plants following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The file shows the research studies and review articles published between January 1981 and June 2017. For each paper, the title, authors, year of publication, and ecosystem services are presented

Modelling of climate conditions in forest vegetation zones as a support tool for forest management strategy in European beech dominated forests

The regional effects of climate change on forest ecosystems in the temperate climate zone of Europe can be modelled as shifts of forest vegetation zones in the landscape, northward and to higher elevations. This study applies a biogeographical model of climate conditions in the forest vegetation zones of the Central European landscape, in order to predict the impact of future climate change on the most widespread tree species in European deciduous forests—the European beech (Fagus sylvatica L.). The biogeographical model is supported by a suite of software applications in the GIS environment. The model outputs are defined as a set of conditions - climate scenario A1B by the Special Report on Emission Scenarios (SRES) for a forecast period, for a specified geographical area and with ecological conditions appropriate for the European beech, which provide regional scenarios for predicted future climatic conditions in the context of the European beech’s environmental requirements. These predicted changes can be graphically visualized. The results of the model scenarios for regional climate change show that in the Czech Republic from 2070 onwards, optimal growing conditions for the European beech will only exist in some parts of those areas where it currently occurs naturally. Based on these results, it is highly recommended that the national strategy for sustainable forest management in the Czech Republic be partly re-evaluated. Thus, the presented biogeographical model of climate conditions in forest vegetation zones can be applied, not only to generate regional scenarios of climate change in the landscape, but also as a support tool for the development of a sustainable forest management strategy