1
|
Huang H, Mackereth RW, Mitchell CPJ. Impacts of forest harvesting on mercury concentrations and methylmercury production in boreal forest soils and stream sediment. Environ Pollut 2024; 341:122966. [PMID: 37981183 DOI: 10.1016/j.envpol.2023.122966] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/21/2023]
Abstract
Methylmercury (MeHg) is the most neurotoxic and bioaccumulative form of mercury (Hg) present in the terrestrial and aquatic food sources of boreal ecosystems, posing potential risks to wildlife and human health. Harvesting impacts on Hg methylation and MeHg concentrations in forest soils and stream sediment are not fully understood. In this study, a field investigation was carried out in 4 harvested and 2 unharvested boreal forest watersheds, before and after harvest, to better understand impacts on Hg methylation and MeHg concentration in soils and stream sediment, including their responses to different forest management practices. Changes in total Hg (THg) and MeHg concentrations, first-order potential rate constants for Hg methylation and MeHg demethylation (Kmeth and Kdemeth) as well as total carbon content and carbon-to-nitrogen ratio post-harvest in upland, wetland and riparian soils and stream sediment were assessed and compared. Increases in MeHg production were minimal in upland, wetland or riparian soils after harvest. Sediment in streams with minor buffer protection (∼3 m), greater fractions (>75%) of harvested watershed area and more road construction had significantly increased THg and MeHg concentrations, %-MeHg, Kmeth and total carbon content post-harvest. From these patterns, we infer that inputs of carbon and inorganic Hg into harvest-impacted stream sediment are likely sourced from the harvested upland areas and stimulate in situ MeHg production in stream sediment. These findings indicate the importance of stream sediment as potential MeHg pools in harvested forest watersheds. The findings also demonstrate that forest management practices aiming to mitigate organic matter and Hg inputs to streams can effectively alleviate harvesting impacts on Hg methylation and MeHg concentrations in stream sediment.
Collapse
Affiliation(s)
- Haiyong Huang
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Robert W Mackereth
- Centre for Northern Forest Ecosystem Research, Ontario Ministry of Natural Resources and Forestry, Thunder Bay, ON, Canada
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
| |
Collapse
|
2
|
Zeidler M, Šipoš J, Banaš M, Černohorský J. Homogenization of bryophyte species after alpine grassland restoration. J Environ Manage 2022; 319:115628. [PMID: 35793573 DOI: 10.1016/j.jenvman.2022.115628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 06/10/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
The causes of decreasing plant species richness include abandonment of traditional management and the spread of invasive species, even in alpine habitats. Studies on the restoration and management of alpine habitats are predominantly focused on vascular plants, although an important part of alpine vegetation and its diversity is formed by bryophytes. We used bryophytes to indicate changes that occur after the clearcutting of nonindigenous dwarf pine (Pinus mugo Turra) and attempted to reveal the community to which the development of bryophyte species structure was directed. We compared species richness and composition between surveys to test for changes in spatial heterogeneity bryophyte communities. We also tried to reveal the main ecological drivers of the restoration process. The study was performed in the (sub)alpine area of the Eastern High Sudetes Mts. (the Czech Republic). We estimated bryophyte species cover and compared the composition of the bryophyte community in autochthonous grassland areas, areas under the dwarf pine canopy, and clearcut areas to reveal the pattern of shifts 9 years after the treatment. We also measured soil characteristics to reveal the environmental habitat conditions. Evidence of taxonomic homogenization of habitat after dwarf pine removal was found. Light conditions and attributes of litter were the driving factors of successional changes in the bryophyte communities, which led to taxonomic homogenization. This finding explains the slow restoration process due to dwarf pine legacy on the clearcut area. The succession trends were also shaped by unobserved factors, such as climate change and environmental eutrophication. We highly recommended active management and long-term monitoring.
Collapse
Affiliation(s)
- Miroslav Zeidler
- Department of Ecology and Environmental Science, Faculty of Science, Palacky University, Šlechtitelů 27, 78371, Olomouc, Czech Republic.
| | - Jan Šipoš
- Department of Zoology, Fisheries, Hydrobiology and Apiculture, Mendel University in Brno, Brno, Czech Republic; Department of Vegetation Ecology, Institute of Botany of the Czech Academy of Sciences, Brno, Czech Republic
| | - Marek Banaš
- Department of Ecology and Environmental Science, Faculty of Science, Palacky University, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Jan Černohorský
- Department of Ecology and Environmental Science, Faculty of Science, Palacky University, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| |
Collapse
|
3
|
Wam HK, Stolter C, Nybakken L. Compositional Changes in Foliage Phenolics with Plant Age, a Natural Experiment in Boreal Forests. J Chem Ecol 2017; 43:920-928. [PMID: 28852911 PMCID: PMC5636854 DOI: 10.1007/s10886-017-0881-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 08/04/2017] [Accepted: 08/14/2017] [Indexed: 11/24/2022]
Abstract
The composition of plant secondary metabolites (PSMs) extensively impacts ecosystem functioning. It is vital that we understand temporal patterns in the plants' allocation of resources to PSMs, particularly those influenced by human activity. Existing data are insufficient in the long-term perspective of perennial plants (age or ontogeny). We analysed phenolic concentrations in foliage from birch (Betula pubescens Ehr.) considered to be undamaged and growing on 5, 10 and 15 years old clear-cuts in two boreal forest landscapes in Norway, sampled at the peak of the growing season. In sum, low molecular weight phenolic concentrations decreased with age. Apart from one apigenin glycoside, the low molecular weight phenolics co-varied similarly at all ages, suggesting a lack of temporal compound-specific prioritisation of this group. In contrast, the concentration of MeOH-soluble condensed tannins increased with age. The compositional shift fits well with several hypotheses that may provide proximate explanations for age patterns in PSM allocations, including both resource constraints and external pressures. Regardless of these explanations, our study adds an important perennial perspective (plant age) to temporal PSM patterns already well-known in boreal plant phenology (foliage age).
Collapse
Affiliation(s)
- Hilde Karine Wam
- Division of Forest and Forest Resources, Norwegian Institute of Bioeconomy Research (NIBIO), 1431, Ås, Norway.
| | - Caroline Stolter
- Department of Animal Ecology and Conservation, University of Hamburg, 20146, Hamburg, Germany
| | - Line Nybakken
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, 1432, Ås, Norway
| |
Collapse
|
4
|
Nicholson BA, Jones MD. Early-successional ectomycorrhizal fungi effectively support extracellular enzyme activities and seedling nitrogen accumulation in mature forests. Mycorrhiza 2017; 27:247-260. [PMID: 27900594 DOI: 10.1007/s00572-016-0747-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/17/2016] [Indexed: 06/06/2023]
Abstract
After stand-replacing disturbance, regenerating conifer seedlings become colonized by different ectomycorrhizal fungi (EMF) than the locally adapted EMF communities present on seedlings in mature forests. We studied whether EMF species that colonized subalpine fir (Abies lasiocarpa) seedlings in clearcuts differed from those that colonized seedlings in adjacent mature forests with respect to mycorrhizoplane extracellular enzyme activities (EEAs) and N status of the seedlings. We tested two alternate hypotheses: (1) that EEAs would differ between the two EMF communities, with higher activities associated with forest-origin communities, and (2) that acclimation to soil environment was considerable enough that EEAs would be determined primarily by the soil type in which the ectomycorrhizas were growing. Naturally colonized fir seedlings were reciprocally transplanted between clearcuts and forests, carrying different EMF communities with them. EEAs were influenced more by destination environment than by EMF community. EEAs were as high in early-successional as in late-successional communities in both destination environments. Buds of clearcut-origin seedlings had the same or higher N contents as forest seedlings after a growing season in either environment. These results indicate that (i) symbiotic EMF and/or their associated microbial communities demonstrate substantial ability to acclimate to new field environments; (ii) the ability to produce organic matter-degrading enzymes is not a trait that necessarily distinguishes early- and late-successional EMF communities in symbiosis; (iii) early-successional EMF are as capable of supporting seedling N accumulation in forest soils as late-successional EMF; and (iv) disturbed ecosystems where early-successional EMF are present should have high resilience for organic matter degradation.
Collapse
Affiliation(s)
- Bailey A Nicholson
- Biology Department, University of British Columbia, Okanagan campus, Sci 385 - 1177 Research Road, Kelowna, BC, V1V 1V7, Canada
| | - Melanie D Jones
- Biology Department, University of British Columbia, Okanagan campus, Sci 385 - 1177 Research Road, Kelowna, BC, V1V 1V7, Canada.
| |
Collapse
|
5
|
Mazur M, Mitchell CPJ, Eckley CS, Eggert SL, Kolka RK, Sebestyen SD, Swain EB. Gaseous mercury fluxes from forest soils in response to forest harvesting intensity: a field manipulation experiment. Sci Total Environ 2014; 496:678-687. [PMID: 24993512 DOI: 10.1016/j.scitotenv.2014.06.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 06/13/2014] [Accepted: 06/13/2014] [Indexed: 06/03/2023]
Abstract
Forest harvesting leads to changes in soil moisture, temperature and incident solar radiation, all strong environmental drivers of soil-air mercury (Hg) fluxes. Whether different forest harvesting practices significantly alter Hg fluxes from forest soils is unknown. We conducted a field-scale experiment in a northern Minnesota deciduous forest wherein gaseous Hg emissions from the forest floor were monitored after two forest harvesting prescriptions, a traditional clear-cut and a clearcut followed by biomass harvest, and compared to an un-harvested reference plot. Gaseous Hg emissions were measured in quadruplicate at four different times between March and November 2012 using Teflon dynamic flux chambers. We also applied enriched Hg isotope tracers and separately monitored their emission in triplicate at the same times as ambient measurements. Clearcut followed by biomass harvesting increased ambient Hg emissions the most. While significant intra-site spatial variability was observed, Hg emissions from the biomass harvested plot (180 ± 170 ng m(-2)d(-1)) were significantly greater than both the traditional clearcut plot (-40 ± 60 ng m(-2)d(-1)) and the un-harvested reference plot (-180 ± 115 ng m(-2)d(-1)) during July. This difference was likely a result of enhanced Hg(2+) photoreduction due to canopy removal and less shading from downed woody debris in the biomass harvested plot. Gaseous Hg emissions from more recently deposited Hg, as presumably representative of isotope tracer measurements, were not significantly influenced by harvesting. Most of the Hg tracer applied to the forest floor became sequestered within the ground vegetation and debris, leaf litter, and soil. We observed a dramatic lessening of tracer Hg emissions to near detection levels within 6 months. As post-clearcutting residues are increasingly used as a fuel or fiber resource, our observations suggest that gaseous Hg emissions from forest soils will increase, although it is not yet clear for how long such an effect will persist.
Collapse
Affiliation(s)
- M Mazur
- University of Toronto Scarborough, Department of Physical and Environmental Sciences, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
| | - C P J Mitchell
- University of Toronto Scarborough, Department of Physical and Environmental Sciences, 1265 Military Trail, Toronto, ON M1C 1A4, Canada.
| | - C S Eckley
- Meteorological Service of Canada, Environment Canada, 4905 Dufferein Street, Toronto, ON M3H 5T4, Canada
| | - S L Eggert
- Northern Research Station, USDA Forest Service, 1831 Hwy 169 E, Grand Rapids, MN 55744, United States
| | - R K Kolka
- Northern Research Station, USDA Forest Service, 1831 Hwy 169 E, Grand Rapids, MN 55744, United States
| | - S D Sebestyen
- Northern Research Station, USDA Forest Service, 1831 Hwy 169 E, Grand Rapids, MN 55744, United States
| | - E B Swain
- Minnesota Pollution Control Agency, St. Paul, MN 55155, United States
| |
Collapse
|