Impact of wildfire and clear-cutting in the boreal forest on methyl mercury in zooplankton

1999 ◽  
Vol 56 (2) ◽  
pp. 339-345 ◽  
Author(s):  
Edenise Garcia ◽  
Richard Carignan
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Dissolved Oxygen ◽  
Boreal Forest ◽  
Methyl Mercury ◽  
Dry Weight ◽  
Zooplankton Biomass ◽  
Clear Cutting ◽  
Forest Logging ◽  
Reference Lakes

We compared the effects of forest logging and wildfire on methyl mercury (MeHg) concentrations in bulk zooplankton collected in 38 oligotrophic lakes located in the boreal forest. Mean MeHg concentrations were slightly but significantly higher (P < 0.01) in zooplankton collected in lakes with recently logged watersheds (135 ng·g dry weight-1) than in lakes with recently burned (97 ng·g dry weight-1) or undisturbed watersheds (112 ng·g dry weight-1). MeHg levels in zooplankton collected in burned and reference lakes were not significantly different. Multiple regression including all the lakes showed that four variables (dissolved organic carbon, pH, dissolved oxygen, and immature zooplankton biomass) explained 43% of the variability in MeHg levels in bulk zooplankton. Regressions calculated for each group of lakes explained less (reference lakes) or more of the variability in MeHg (logged and burned lakes) than the general model did. Dissolved organic carbon was the only variable common to all models, which indicates the importance of watershed processes in the transfer of humic matter bound Hg to lakes. However, variables related to methylation rate, such as pH, sulfate concentrations, and average dissolved oxygen in lake water, also explained part of the variation in MeHg concentrations in zooplankton.

In situ dissolved organic carbon (DOC) release by submerged macrophyte–epiphyte communities in southern Quebec lakes

2009 ◽  
Vol 66 (9) ◽  
pp. 1522-1531 ◽  
Author(s):  
M. Demarty ◽  
Y. T. Prairie
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Myriophyllum Spicatum ◽  
Dry Weight ◽  
Release Rates ◽  
Doc Production ◽  
Epiphyte Communities ◽  
Benthic Chambers ◽  
Freshwater Macrophyte

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte–epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C·m–2·h–1. Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C·m–2·h–1 (standard deviation (SD), ±0.65) or 56 µg C·g dry weight–1·h–1 (SD, ±8), which we suggest can be used for extrapolations at the lake scale.

scholarly journals Are dissolved organic carbon concentrations in riparian groundwater linked to hydrological pathways in the boreal forest?

2020 ◽  
Vol 24 (4) ◽  
pp. 1709-1720 ◽  
Author(s):  
Stefan W. Ploum ◽  
Hjalmar Laudon ◽  
Andrés Peralta-Tapia ◽  
Lenka Kuglerová
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Spatial Variability ◽  
Boreal Forest ◽  
Management Practices ◽  
Groundwater Chemistry ◽  
Stream Bank ◽  
Small Streams ◽  
Lateral Distance ◽  
Topographic Depressions

Abstract. The riparian zone (RZ), or near-stream area, plays a fundamental role in the biogeochemistry of headwaters. Here, wet, carbon-rich soils can change groundwater chemistry before it enters the stream. In the boreal forest, the RZ plays an especially important role in the export of dissolved organic carbon (DOC) to streams. However, the RZ is not uniform, and spatial variability of riparian groundwater hydrology and chemistry can be large. Terrestrial topographic depressions create hydrological pathways towards focal points in the RZ, which we refer to as “discrete riparian inflow points” (DRIPs). Combining the chemical function of the RZ and the convergence of hydrological pathways, we hypothesize that DRIPs play a disproportionally large role in conveying DOC to small streams. Earlier work has demonstrated that runoff from DRIPs can make up the majority of riparian flow contributions to streams, but it is currently unknown how their groundwater chemistry differs from the rest of the RZ. Therefore, we ask the following question: are DOC concentrations in riparian groundwater linked to hydrological pathways in the boreal forest? To answer this question, we sampled riparian groundwater during six campaigns across three boreal headwater streams in Sweden. The groundwater wells were distributed into 10 DRIP and non-DRIP pairs (60 wells), following transects from the upland (20 m lateral distance from the stream bank) to the near-stream area (<5 m lateral distance from the stream bank). The variability in DOC, pH, and electrical conductivity (EC) was analyzed using linear mixed-effects models (LMMs). We explained the variability using three factors: distance from the stream, seasonality, and DRIP/non-DRIP. Our results showed that DRIPs provided DOC-rich water (34 mg L−1) with relatively low EC (36 µS cm−1). The “non-DRIP” riparian water had 40 % lower DOC concentrations (20 mg L−1) and a 45 % higher EC (52 µS cm−1) on average. Moreover, groundwater chemistry from DRIPs was spatially and temporally relatively homogeneous. In contrast, non-DRIP water transformed distinctly in the last 25 m towards the stream, and the chemical variability was also larger between seasons. We concluded that hydrological pathways and spatial variability in riparian groundwater DOC concentrations are linked, and that DRIPs can be seen as important control points in the boreal landscape. Characterizing DRIPs in headwater catchments can be useful for upscaling carbon inputs in boreal stream ecosystems and for delineating hydrologically adapted buffers for forest management practices.

Response of Dissolved Organic Carbon following Forest Harvesting in a Boreal Forest

AMBIO ◽  
2009 ◽  
Vol 38 (7) ◽  
pp. 381-386 ◽  
Author(s):  
Hjalmar Laudon ◽  
Johannes Hedtjärn ◽  
Jakob Schelker ◽  
Kevin Bishop ◽  
Rasmus Sørensen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Boreal Forest ◽  
Forest Harvesting

Scaling of increased dissolved organic carbon inputs by forest clear-cutting – What arrives downstream?

2014 ◽  
Vol 508 ◽  
pp. 299-306 ◽  
Author(s):  
Jakob Schelker ◽  
Karin Öhman ◽  
Stefan Löfgren ◽  
Hjalmar Laudon
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Clear Cutting

Characteristics of Sediment and Organic Carbon Export from Pristine Boreal Forest Watersheds

1982 ◽  
Vol 39 (12) ◽  
pp. 1699-1718 ◽  
Author(s):  
Robert J. Naiman
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Boreal Forest ◽  
Particulate Organic Matter ◽  
Terrestrial Ecosystems ◽  
Dry Weight ◽  
Carbon Export ◽  
Watershed Area ◽  
First Choice ◽  
Spring Freshet

Estimates of the amount of material moving annually from terrestrial ecosystems to the ocean are largely based on an incomplete understanding of events occurring throughout the hydrologic year, and only a vague comprehension of in-stream processes controlling that export. Discharge, suspended sediment, particulate organic matter (POM; > 0.5 μm), dissolved organic carbon (DOC; <0.5 μm diameter), and the percentage of organic matter were measured from 1979 to 1981 in five pristine Quebec streams: First Choice Creek (1st order; watershed area: 0.25 km2), Beaver Creek (2nd order; 1.83 km2), Muskrat River (5th order; 204 km2), Matamek River (6th order; 673 km2), and the Moisie River (9th order; 19 871 km2). All streams, with the exception of First Choice Creek, have a strong spring freshet when 43–55% of the annual discharge occurs. By describing sediment and organic carbon export throughout the annual hydrologic cycle, 1 showed that during the 2-mo spring freshet 71–92% of the annual sediment load is exported but only 59–65% of the annual POM load, and only 47–51% of the annual DOC load. Sediment yield is relatively constant between watersheds (1.5–7.6 g∙m−2∙yr−1), as is POM export (1.0–6.7 g ash-free dry-weight [AFDW]∙m−2∙yr−1); however, export DOC varies from 3.1 g C∙m−2∙yr−1 in First Choice Creek to 48.4 g C∙m−2∙yr−1 in Beaver Creek. There appears to be rapid loading of carbon between 1st- and 2nd-order streams in boreal forests, followed by biological and physical processing as watershed area increases. Thus, for the Moisie River watershed, export of total organic carbon (TOC) is reduced to only 4.7 g C∙m−2∙yr−1. Export of coarse particulate organic matter (> 1 mm) is negligible (normally < 0.1 mg∙L−1), as is oxidation of the suspended load (< 0.5%∙d−1). Effects of summer storms, natural diel variations, and depth of sample from the water column are shown to have a minimal influence on concentrations. Rating curves (kg∙d−1 vs. discharge) are developed to estimate the annual yield of sediment, POM, and DOC, and to evaluate long-term variations. From the results I suggest that in-stream processing and retention devices exert considerable control over the quantity and nature of suspended organic material. Physical processes such as the discharge regime and stream power are relatively less important in determining organic concentrations, but more important in determining sediment concentrations.Key words: seston, carbon, sediment, boreal forest, watershed, river, stream, export

scholarly journals Content and changes in dissolved organic matter in meadow and arable soils over time

2019 ◽  
Vol 52 (2) ◽  
pp. 183
Author(s):  
Bożena Dębska
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Dissolved Organic Carbon ◽  
Seasonal Changes ◽  
Dry Weight ◽  
Arable Soils ◽  
Successive Sampling ◽  
Climate Conditions ◽  
Weight Content

<p>Considering the discrepancies in the reports on seasonal changes in the content of  dissolved organic carbon, this paper concerns the research which aimed at defining the content and seasonal changes in dissolved organic matter (DOM) in arable and meadow soils in moderate climate conditions. The research has involved the soils sampled in the kujawsko-pomorskie province (Poland). Gleic Phaeozems (meadow soils), Brunic Arenosols and Eutric Cambisols were sampled from the depth of 0-30 cm, 30-60 cm and 60-100 cm, November 2011 through September 2013. The soil samples were analyzed for dry weight content, pH, content of total organic carbon and total nitrogen. DOM was extracted with 0.004 mol·dm<sup>-3</sup> CaCl<sub>2</sub>, in the extracts the content of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) were assayed. The share of DOC was determined by the soil management. The analysis of variance did not show significant differences in the content of TOC and Nt across the soil sampling dates. Were recorded changes in DOC and DNt between successive sampling dates; for topsoil for DOC – from -12.06% to 13.34% (meadow soils) and for DNt  -40.84% to 47.44% (arable soils).</p><p><strong> </strong></p>

Sign in / Sign up

Export Citation Format

Share Document