The influence of soil frost on the quality of dissolved organic carbon in a boreal forest soil: combining field and laboratory experiments

Haei, Mahsa; Öquist, Mats; Ilstedt, Ulrik; Laudon, Hjalmar

doi:10.1007/s10533-010-9534-2

Cited by 38 publications

(34 citation statements)

References 62 publications

(65 reference statements)

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“…Based on these values, it appears probable that direct frost damage is responsible for the observed shifts in species occurrences. Besides the direct lethal eVects of frost, the sub-lethal eVects of freezing could also be of high ecological importance, and the period of freezing, the number of freeze thaw cycles and the rate of freezing can all increase the size of the eVect for a given freezing intensity (Vestgarden and Austnes 2009;Haei et al 2011). Furthermore, the role of biotic (e.g., mycorrhizal interactions) as well as abiotic interactions (e.g., soil moisture at the point of freezing determining the importance of physical stress on plant roots) deserves further investigation (Kreyling 2010).…”

Section: Discussionmentioning

confidence: 99%

Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

2011

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Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature -5.5 vs. -2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (-82%) and the most abundant mosses Pleurozium schreberi (-74%) and Dicranum scoparium (-60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (-50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.

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Section: Discussionmentioning

confidence: 99%

Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

2011

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“…The elevated export of a protein-like fraction, i.e., easily biodegradable DOM (Fellman et al, 2009), can be explained by less biotic demand and a domination of shallow flow paths during snowmelt bypassing large, strongly modified and aromatic DOM pools in the subsurface (Fellman et al, 2009). Also, near-surface freeze-thaw cycles during winter provide fresh DOM from microbial cell lysis and root mortality, which is not utilized due to the low productivity (Haei et al, 2012;Fellman et al, 2009). Differences between the two sites were more evident in other PARAFAC components.…”

Section: Snowmeltmentioning

confidence: 99%

Changes in dissolved organic matter quality in a peatland and forest headwater stream as a function of seasonality and hydrologic conditions

Broder

Knorr

Biester

2017

Hydrol. Earth Syst. Sci.

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Abstract. Peatlands and peaty riparian zones are major sources of dissolved organic matter (DOM), but are poorly understood in terms of export dynamics and controls thereof. Thereby quality of DOM affects function and behavior of DOM in aquatic ecosystems, but DOM quality can also help to track DOM sources and their export dynamics under specific hydrologic preconditions. The objective of this study was to elucidate controls on temporal variability in DOM concentration and quality in stream water draining a bog and a forested peaty riparian zone, particularly considering drought and storm flow events. DOM quality was monitored using spectrofluorometric indices for aromaticity (SUVA 254 ), apparent molecular size (S R ) and precursor organic material (FI), as well as PARAFAC modeling of excitation emission matrices (EEMs).Indices for DOM quality exhibited major changes due to different hydrologic conditions, but patterns were also dependent on season. Stream water at the forested site with mineral, peaty soils generally exhibited higher variability in DOM concentrations and quality compared to the outflow of an ombrotrophic bog, where DOM was less susceptible to changes in hydrologic conditions. During snowmelt and spring events, near-surface protein-like DOM pools were exported. A microbial DOM fraction originating from groundwater and deep peat layers was increasing during drought, while a strongly microbially altered DOM fraction was also exported by discharge events with dry preconditions at the forested site. This might be due to accelerated microbial activity in the peaty riparian zone of the forested site under these preconditions. Our study demonstrated that DOM export dynamics are not only a passive mixing of different hydrological sources, but monitoring studies have to consider that DOM quality depends on hydrologic preconditions and season. Moreover, the forested peaty riparian zone generated the most variability in headwater DOM quantity and quality, as could be tracked by the used spectrofluorometric indices.

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“…The low winter temperatures can be a driver for winter preservation of organic matter in the catchment, through lowering of metabolic rates during cold winter months and lower flow rates on rivers and through soils. Additionally, Haei et al (2012) showed that bioavailability of DOM increased with increasing soil frost conditions in winter (i.e. lower winter temperatures lead to more labile DOM release from soils); this was attributed not directly to lowered metabolism during the winter but rather frost-induced destruction of fine root structures and cell lysis releasing labile organic matter upon thawing.…”

Section: Differences In Reactivity Between Rivers and Over Seasonsmentioning

confidence: 99%

“…Warmer mean winter temperatures, and reduced frost depth and duration (Haei et al, 2012) will lessen the preservation effect that is currently seen in the north. As the mean annual temperatures rise and become more like the southern catchments, it is likely that the overall reactivity of organic matter from the catchment will be lowered as well.…”

Section: Climate and Future Loadingsmentioning

confidence: 99%

Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments

2014

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Abstract. To examine the potential influence of terrestrially derived DOM on the Baltic Sea, a year-long study of dissolved organic matter (DOM) was performed in three river catchments in Sweden. One catchment drains into the Bothnian Sea, while two southern catchments drain into the Baltic proper. Dissolved organic carbon (DOC) concentrations were positively correlated with discharge from forested catchments over the year. While the overall concentrations of DOC were several times higher in the southern two catchments, higher discharge in the northern catchment resulted in the annual loadings of DOC being on the same order of magnitude for all three catchments. Biological oxygen demand (BOD) was used as a proxy for the lability of carbon in the system. The range of BOD values was similar for all three catchments, however, the ratio of BOD to DOC (an indication of the labile fraction) in Ume river was four times higher than in the southern two catchments. Total annual BOD loading to the Baltic Sea was twice as high in the northern catchment than in the two southern catchments. Lower winter temperatures and preservation of organic matter in the northern catchment combined with an intense spring flood help to explain the higher concentrations of labile carbon in the northern catchment. Lower lability of DOM as well as higher colour in the southern catchments suggest that wetlands (i.e. peat bogs) may be the dominant source of DOM in these catchments, particularly in periods of low flow. With climate change expected to increase precipitation events and temperatures across the region, the supply and quality of DOM delivered to the Baltic Sea can also be expected to change. Our results indicate that DOM supply to the Baltic Sea from boreal rivers will be more stable throughout the year, and potentially have a lower bioavailability.

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The influence of soil frost on the quality of dissolved organic carbon in a boreal forest soil: combining field and laboratory experiments

Cited by 38 publications

References 62 publications

Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

Changes in dissolved organic matter quality in a peatland and forest headwater stream as a function of seasonality and hydrologic conditions

Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments

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