Nitrogen dynamics in managed boreal forests: Recent advances and future research directions

Nitrogen (N) availability plays multiple roles in the boreal landscape, as a limiting nutrient to forest growth, determinant of terrestrial biodiversity, and agent of eutrophication in aquatic ecosystems. We review existing research on forest N dynamics in northern landscapes and address the effects of management and environmental change on internal cycling and export. Current research foci include resolving the nutritional importance of different N forms to trees and establishing how tree–mycorrhizal relationships influence N limitation. In addition, understanding how forest responses to external N inputs are mediated by above- and belowground ecosystem compartments remains an important challenge. Finally, forestry generates a mosaic of successional patches in managed forest landscapes, with differing levels of N input, biological demand, and hydrological loss. The balance among these processes influences the temporal patterns of stream water chemistry and the long-term viability of forest growth. Ultimately, managing forests to keep pace with increasing demands for biomass production, while minimizing environmental degradation, will require multi-scale and interdisciplinary perspectives on landscape N dynamics.     

Efficacy of Si fertilization to modulate the heavy metals absorption by barley (Hordeum vulgare L.) and pea (Pisum sativum L.)

Silicon-based fertilizers and soil amendments can have direct and indirect positive influences on cultivated plants. The solid forms of Si-based substances, the most widespread in use, are efficient only at high application rates due to their low level of solubility. Several types of Si-based substances such as fumed silica, slags from the iron and steel industry, modified slags, and a Si-rich product were tested using barley and pea as silicon accumulative and non-accumulative plants, respectively, at two application rates. The plants were grown under toxic concentrations of heavy metals in a greenhouse. Si-rich materials high in water-soluble Si had a positive effect at both the low and high application rates, and for both plant species. This type of substance can be regarded as Si fertilizer, demonstrating greater efficiency at a low application rate and lessened efficiency at a high application rate for protection of the cultivated plants against accumulation of the heavy metals.

     

Environmental perceptions of second home tourism impacts in Finland

Experiencing nature and enjoying natural amenities have long been identified as key motives for rural second home tourism. However, the more people travel and spend time in the natural environment, the more it is disturbed by their actions and activities. In this paper, we examine how people perceive the environmental impacts of rural second home tourism and how they justify their views. The study focuses on Finland where rural second homes are widespread. Analysis is based on a questionnaire survey conducted among Finns in 2012 (n?=?1189). Responses from different groups of respondents (second home owners, regular users of second homes and non-users) are quantitatively and qualitatively analysed. The results indicate that the Finnish respondents generally think that second home tourism poses some degree of harmful environmental impacts. However, it is the second home owners who are least worried about these environmental impacts. They generally justify their opinions using a “place-related” perspective, that is, by referring to their own experiences and actions at the cottage site. In contrast, the non-users see environmental impacts more often from a broader perspective by referring to the wider environmental interconnections with second home tourism. In our discussion, we introduce the notions of place-based (relative) and phenomenon-based (relational) environmental perceptions as a potential framework for future research on this topic. In mitigating the increasing environmental impacts of second home tourism, understanding the environmental perceptions and awareness of second home owners and users is crucial to be successful in mobilising sustainable options and environmental governance.     

Occurrence of PPCPs in the marine environment: a review

Little research has been conducted on the occurrence of pharmaceuticals and personal care products (PPCPs) in the marine environment despite being increasingly impacted by these contaminants. This article reviews data on the occurrence of PPCPs in seawater, sediment, and organisms in the marine environment. Data pertaining to 196 pharmaceuticals and 37 personal care products reported from more than 50 marine sites are analyzed while taking sampling strategies and analytical methods into account. Particular attention is focused on the most frequently detected substances at highest concentrations. A snapshot of the most impacted marine sites is provided by comparing the highest concentrations reported for quantified substances. The present review reveals that: (i) PPCPs are widespread in seawater, particularly at sites impacted by anthropogenic activities, and (ii) the most frequently investigated and detected molecules in seawater and sediments are antibiotics, such as erythromycin. Moreover, this review points out other PPCPs of concern, such as ultraviolet filters, and underlines the scarcity of data on those substances despite recent evidence on their occurrence in marine organisms. The exposure of marine organisms in regard to these insufficient data is discussed.     

Hydroponic root mats for wastewater treatment—a review

Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs.     

Release of PCBs from Silvretta glacier (Switzerland) investigated in lake sediments and meltwater

This study is part of our investigations about the release of persistent organic pollutants from melting Alpine glaciers and the relevance of the glaciers as secondary sources of legacy pollutants. Here, we studied the melt-related release of polychlorinated biphenyls (PCBs) in proglacial lakes and glacier streams of the catchment of the Silvretta glacier, located in the Swiss Alps. To explore a spatial and temporal distribution of chemicals in glacier melt, we combined two approaches: (1) analysing a sediment record as an archive of past remobilization and (2) passive water sampling to capture the current release of PCBs during melt period. In addition, we determined PCBs in a non-glacier-fed stream as a reference for the background pollutant level in the area. The PCBs in the sediment core from the Silvretta lake generally complied with trends of PCB emissions into the environment. Elevated concentrations during the most recent ten years, comparable in level with times of the highest atmospheric input, were attributed to accelerated melting of the glacier. This interpretation is supported by the detected PCB fractionation pattern towards heavier, less volatile congeners, and by increased activity concentrations of the radioactive tracer ¹³⁷Cs in this part of the sediment core. In contrast, PCB concentrations were not elevated in the stream water, since no significant difference between pollutant concentrations in the glacier-fed and the non-glacier-fed streams was detected. In stream water, no current decrease of the PCBs with distance from the glacier was observed. Thus, according to our data, an influence of PCBs release due to accelerated glacier melt was only detected in the proglacial lake, but not in the other compartments of the Silvretta catchment.     

Climate change,multiple stressors and human vulnerability: a systematic review

We systematically reviewed current climate change literature in order to examine how multiple processes that affect human vulnerability have been studied. Of the 125 reviewed articles, 79 % were published after 2009. There are numerous concepts that point out to stressors other than climate change that were used in reviewed studies. These different concepts were used interchangeably, and they illustrate processes that act on different scales. Most widely used concepts included non-climatic (40 % of the articles), multiple stressors (38 %) and other factors (37 %). About 75 % of the studies either acknowledged or carefully analyzed the social and environmental context in which vulnerability is experienced. One-third of the studies recognized climate change-related stressors as the most important, one-third argued that stressors other than climate are more important, and the rest of the studies did not analyze the relative importance of the different processes. Interactions between different stressors were mentioned in 76 % and analyzed explicitly in 28 % of the articles. Our review shows that there are studies that analyze the social context of vulnerability within climate change-related literature and this literature is rapidly expanding. Reviewed studies point out that there are multiple interacting stressors, whose interlinkages need to be carefully analyzed and targeted by policies, which integrate adaptation to climate change and other stressors. In conclusion, we suggest that future studies should include analytical frameworks that reflect dissimilarities between different types of stressors, methodological triangulation to identify key stressors and analysis of interactions between multiple stressors across different scales.