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  • Dissolved Organic Nitrogen
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  • 1
    Language: English
    In: Biogeochemistry, 2003, Vol.66(3), pp.265-286
    Description: Although dissolved organic matter (DOM) released from the forest floor plays a crucial role in transporting carbon and major nutrients through the soil profile, its formation and responses to changing litter inputs are only partially understood. To gain insights into the controlling mechanisms of DOM release from the forest floor, we investigated responses of the concentrations and fluxes of dissolved organic carbon (DOC) and nitrogen (DON) in forest floor leachates to manipulations of throughfall (TF) flow and aboveground litter inputs (litter removal, litter addition, and glucose addition) at a hardwood stand in Bavaria, Germany. Over the two-year study period, litter manipulations resulted in significant changes in C and N stocks of the uppermost organic horizon (Oi). DOC and DON losses via forest floor leaching represented 8 and 11% of annual litterfall C and N inputs at the control, respectively. The exclusion of aboveground litter inputs caused a slight decrease in DOC release from the Oi horizon but no change in the overall leaching losses of DOC and DON in forest floor leachates. In contrast, the addition of litter or glucose increased the release of DOC and DON either from the Oi or from the lower horizons (Oe + Oa). Net releases of DOC from the Oe + Oa horizons over the entire manipulation period were not related to changes in microbial activity (measured as rates of basal and substrate-induced respiration) but to the original forest floor depths prior to manipulation, pointing to the flux control by the size of source pools rather than a straightforward relationship between microbial activity and DOM production. In response to doubled TF fluxes, net increases in DOM fluxes occurred in the lower forest floor, indicating the presence of substantial pools of potentially soluble organic matter in the Oe + Oa horizons. In contrast to the general assumption of DOM as a leaching product from recent litter, our results suggest that DOM in forest floor leachates is derived from both newly added litter and older organic horizons through complex interactions between microbial production and consumption and hydrologic transport.
    Keywords: Dissolved organic carbon ; Dissolved organic matter ; Dissolved organic nitrogen ; Forest floor ; Litter manipulation ; Resource availability ; Water flux
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, 2011, Vol.43(8), pp.1742-1745
    Description: Dissolved organic nitrogen (DON) plays a key role in the N cycle of many ecosystems, as DON availability and biodegradation are important for plant growth, microbial metabolism and N transport in soils. However, biodegradation of DON (defined as the sum of mineralization and microbial immobilization) is only poorly understood. In laboratory incubations, biodegradation of DON and dissolved organic carbon (DOC) from Oi and Oa horizons of spruce, beech and cypress forests ranged from 6 to 72%. Biodegradation of DON and DOC was similar in most samples, and mineralization of DON was more important than microbial immobilization. Nitrate additions (0–10 mg N L ) never influenced either DON immobilization by microorganisms or mineralization. We conclude that soil microorganisms do not necessarily prefer mineral N over DON for meeting their N demand, and that biodegradation of DON seems to be driven by the microbial demand for C rather than N. Quantifying the dynamics of DON in soils should include consideration of both C and N demands by microbes. ► Biodegradation of dissolved organic nitrogen (DON) and carbon (DOC) was similar. ► Mineralization of DON was more important than microbial immobilization. ► Nitrate additions never influenced either DON immobilization or mineralization. ► DOC and DON they should be considered as a single pool of dissolved organic matter.
    Keywords: Dissolved Organic Nitrogen ; Dissolved Organic Carbon ; Nitrate ; Biodegradation ; Mineralization ; Microbial Immobilization ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 3
    Language: English
    In: Environmental pollution (Barking, Essex : 1987), September 2006, Vol.143(1), pp.178-85
    Description: The role of detrital quantity and quality in forest floor N leaching was investigated in a litter manipulation experiment at a deciduous forest under chronic N deposition. Dissolved inorganic nitrogen (DIN) comprised the bulk of nitrogen leaching from the control except a short period following autumn litterfall. The dominance of DIN was strengthened by litter exclusion, whereas the addition of glucose or fresh litter led to a small increase in dissolved organic nitrogen (DON) and either a temporary or gradual reduction in NO(3)(-) release, respectively. Changes in soluble organic C and microbial C in the forest floor implied that increased availability of C sources might have enhanced microbial immobilization of DIN, either temporarily following glucose application or over the longer term following litter addition. The results suggest that detrital quantity and quality can play a crucial role in determining the balance between DIN and DON in N-enriched forest soils.
    Keywords: Air Pollutants ; Biodegradation, Environmental ; Ecosystem ; Nitrogen ; Plant Leaves ; Trees
    ISSN: 0269-7491
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  • 4
    Language: English
    In: Environmental Pollution, 2006, Vol.143(1), pp.178-185
    Description: The role of detrital quantity and quality in forest floor N leaching was investigated in a litter manipulation experiment at a deciduous forest under chronic N deposition. Dissolved inorganic nitrogen (DIN) comprised the bulk of nitrogen leaching from the control except a short period following autumn litterfall. The dominance of DIN was strengthened by litter exclusion, whereas the addition of glucose or fresh litter led to a small increase in dissolved organic nitrogen (DON) and either a temporary or gradual reduction in NO release, respectively. Changes in soluble organic C and microbial C in the forest floor implied that increased availability of C sources might have enhanced microbial immobilization of DIN, either temporarily following glucose application or over the longer term following litter addition. The results suggest that detrital quantity and quality can play a crucial role in determining the balance between DIN and DON in N-enriched forest soils. Detrital quantity and quality play a crucial role in regulating the release of DON and DIN from the forest floor under chronic N deposition.
    Keywords: C Limitation ; Dissolved Inorganic Nitrogen ; Dissolved Organic Nitrogen ; Forest Floor ; N Saturation ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
    Source: ScienceDirect Journals (Elsevier)
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  • 5
    Language: English
    In: Biogeochemistry, 2010, Vol.101(1), pp.243-256
    Description: Fluxes of dissolved organic carbon (DOC) and nitrogen (DON) may play an important role for losses of C and N from the soils of forest ecosystems, especially under conditions of high precipitation. We studied DOC and DON fluxes and concentrations in relation to precipitation intensity in a subtropical montane Chamaecyparis obtusa var. formosana forest in Taiwan. Our objective was, to quantify DOC and DON fluxes and to understand the role of high precipitation for DOC and DON export in this ecosystem. From 2005 to 2008 we sampled bulk precipitation, throughfall, forest floor percolates and seepage (60 cm) and analyzed DOC, DON and mineral N concentrations. Average DOC fluxes in the soil were extremely high (962 and 478 kg C ha −1  year −1 in forest floor percolates and seepage, respectively) while DON fluxes were similar to other (sub)tropical ecosystems (16 and 8 kg N ha −1 year −1 , respectively). Total N fluxes in the soil were dominated by DON. Dissolved organic C and N concentrations in forest floor percolates were independent of the water flux. No dilution effect was visible. Instead, the pool size of potentially soluble DOC and DON was variable as indicated by different DOC and DON concentrations in forest floor percolates at similar precipitation amounts. Therefore, we hypothesized, that these pools are not likely to be depleted in the long term. The relationship between water fluxes in bulk precipitation and DOC and DON fluxes in forest floor percolates was positive (DOC r  = 0.908, DON r  = 0.842, respectively, Spearman rank correlation). We concluded, that precipitation is an important driver for DOC and DON losses from this subtropical montane forest and that these DOC losses play an important role in the soil C cycle of this ecosystem. Moreover, we found that the linear relationship between bulk precipitation and DOC and DON fluxes in forest floor percolates of temperate ecosystems does not hold when incorporating additional data on these fluxes from (subtropical) ecosystems.
    Keywords: Dissolved organic nitrogen ; Dissolved organic carbon ; Precipitation ; Fluxes ; Forest floor ; Subtropical montane forest
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 6
    Language: English
    In: Soil Biology and Biochemistry, June 2002, Vol.34(6), pp.813-822
    Description: The forest floor in temperate forests has become recognized for its importance in the retention of elevated inputs of dissolved inorganic nitrogen (DIN) and as a source of dissolved organic matter (DOM). A laboratory leaching experiment was conducted over the period of 98 d to examine the origin of dissolved organic carbon (DOC) and nitrogen (DON) in a deciduous forest floor, and the effect of resource availability and microbial activity on the production mechanisms involved. The experiment was composed of different types of treatments: exclusion of specific forest floor layers (no Oi, no Oe) and addition of carbon sources (glucose, cellulose, leaf, wood) and NH sub(4)NO sub(3) (nitrogen). The cumulative amount of CO sub(2) evolution was positively related to the availability of C sources at each treatment: glucose 〉 leaf = wood = cellulose 〉 control = no Oe = nitrogen 〉 no Oi. DOC release was related to the amount of C sources but showed no clear correlation with CO sub(2) evolution. An increase in C availability generally led to a reduction in the release of DON as well as DIN. In contrast, the amendment of NH sub(4)NO sub(3) reduced the cumulative DOC release but enhanced the release of both DON and DIN. Fresh leaf litter was a more important DOC source than labile substrates (glucose and cellulose) as well as more stable substrates (forest floor materials and wood). Among forest floor layers, more humified horizons (Oe and Oa) were the primary source of DIN and made a similar contribution to DOM release as the Oi layer. The changes in DOM composition detected by a humification index of the leachates, in combination with a shift in the final microbial biomass C, suggested that DOM released from the soluble pools of added litter or the Oi layer contained a substantial amount of microbially processed organic matter. Our study demonstrated the importance of C availability in regulating microbial activity and immobilization of dissolved N in an N-enriched forest floor. However, the discrepancy between substrate lability and DOC production, in combination with a rapid microbial processing of DOC released from labile C pools, illustrated the complicated nature of microbial production and consumption of DOC in the forest floor.
    Keywords: Dissolved Organic Matter ; Dissolved Organic Carbon ; Dissolved Organic Nitrogen ; Dissolved Inorganic Nitrogen ; Forest Floor ; C and N Availability ; Soil Microbial Activity ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 7
    Language: English
    In: Biogeochemistry, 2009, Vol.93(3), pp.291-296
    Description: The Ferrous Wheel Hypothesis (Davidson et al. 2003) postulates the abiotic formation of dissolved organic N (DON) in forest floors, by the fast reaction of NO 2 − with dissolved organic C (DOC). We investigated the abiotic reaction of NO 2 − with dissolved organic matter extracted from six different forest floors under oxic conditions. Solutions differed in DOC concentrations (15–60 mg L −1 ), NO 2 − concentrations (0, 2, 20 mg NO 2 − -N L −1 ) and DOC/DON ratio (13.4–25.4). Concentrations of added NO 2 − never decreased within 60 min, therefore, no DON formation from added NO 2 − took place in any of the samples. Our results suggest that the reaction of NO 2 − with natural DOC in forest floors is rather unlikely.
    Keywords: Abiotic nitrite immobilization ; Dissolved organic carbon ; Dissolved organic nitrogen ; Ferrous Wheel Hypothesis
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 8
    Language: English
    Description: Variability in runoff fluxes of dissolved and particulate carbon and nitrogen from two watersheds of different tree species during intense storm events...
    Keywords: Dissolved Organic Carbon ; Dissolved Organic Nitrogen ; Particulate Organic Carbon ; Particulate Organic Nitrogen ; Monsoon Storm ; Forested Watershed
    Source: DataCite
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  • 9
    Language: English
    In: Biogeochemistry, 2001, Vol.55(3), pp.327-349
    Description: Despite growing attention concerning therole of dissolved organic matter (DOM) inelement cycling of forest ecosystems, thecontrols of concentrations and fluxes of bothdissolved organic carbon (DOC) and nitrogen(DON) under field conditions in forest soilsremain only poorly understood. The goal ofthis project is to measure the concentrations and fluxes of DON, NH 4 + , NO 3 − and DOC in bulkprecipitation, throughfall, forest floorleachates and soil solutions of a deciduousstand in the Steigerwald region (northernBavaria, Germany). The DOC and DONconcentrations and fluxes were highest inleachates originating from the Oa layer of theforest floor (73 mg C L −1 , 2.3 mg NL −1 and about 200–350 kg C, 8–10 kg Nha −1 yr −1 ). They were observed to behighly variable over time and decreased in themineral topsoil (17 mg C L −1 , 0.6 mg NL −1 and about 50–90 kg C, 2.0 to 2.4 kg Nha −1 yr −1 ). The annual variability ofDOC and DON concentrations and subsequentialDOC/DON ratios was substantial in allsolutions. The DOC and DON concentrations inthroughfall were positively correlated withtemperature. The DOC and DON concentrationsdid not show seasonality in the forest floorand mineral soil. Concentrations were notrelated to litterfall dynamics but didcorrespond in part to the input of DOC and DONfrom throughfall. The throughfall contributionto the overall element fluxes was higher forDON than for DOC. Concentrations and fluxes ofDON were significantly correlated to DOC inthroughfall and the Oi layer. However, thecorrelation was weak in Oa leachates. Inaddition, seasonal and annual variation ofDOC/DON ratios indicated different mechanismsand release rates from the forest floor forboth components. The concentrations of DOC andDON in forest floor leachates were in mostcases dependent neither on the pH value orionic strength of the solution, nor on thewater flux or temperature changes. As aconsequence, the DOC and DON fluxes from theforest floor into the mineral soil werelargely dependent on the water flux if annualand biweekly time scales are considered.
    Keywords: dissolved organic nitrogen ; L. ; forest floor ; litter layer ; throughfall ; water fluxes
    ISSN: 0168-2563
    E-ISSN: 1573-515X
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  • 10
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 1999, Vol.162(6), pp.645-652
    Description: Dissolved organic carbon (DOC) and nitrogen (DON) are important components of the carbon and nitrogen turnover in soils. Little is known about the controls on the release of DOC and DON from forest floors, especially about the influence of solid phase properties. We investigated the spatial variation of the release of DOC and DON from Oe and Oa forest floor samples at a regional scale. Samples were taken from 12 different Norway spruce sites with varying solid phase properties, including C/N ratio, pH, different fractions of extractable carbon and exchangeable cations. Most of these solid phase properties are available for large forested areas of Europe in high spatial resolution. The samples were incubated at water holding capacity for eight weeks at 15°C and then extracted with an artificial throughfall solution to measure DOC and DON release. The rates of soil respiration and N‐mineralization were determined to estimate soil microbial activity. The release of DOC and DON from Oe samples was two‐ to threefold higher than from Oa samples. The amounts released differed by one order of magnitude among the sites. The DOC/DON ratios in the percolates of the Oa samples were much higher as compared to the solid phase C/N, indicating different release rates of DOC and DON. In contrast, the DOC/DON ratios of the Oe percolates were in the range of the C/N ratios of the solid phase. The release of DOC and DON from Oe samples was not statistically correlated to any of the measured solid phase parameters, but to N‐mineralization. The DOC and DON release from the Oa samples was positively related only to pH and soil respiration. Overall it was not possible to explain the large spatial variation of DOC and DON release by the measured solid phase properties with satisfying accuracy. Einfluß von Festphaseneigenschaften, N‐Mineralisation und Respiration auf die Freisetzung von gelöstem organischen Kohlenstoff und Stickstoff aus Humusauflagen Gelöster organischer Kohlenstoff (DOC) und Stickstoff (DON) haben einen signifikanten Einfluß auf den Umsatz dieser Elemente in Böden. Bisher ist wenig über die Kontrollfaktoren der Freisetzung von DOC und DON aus Humusauflagen bekannt, insbesondere über den Einfluß von Festphaseneigenschaften. Wir untersuchten die räumliche Variation der Freisetzung von DOC und DON aus Of‐ und Oh‐Proben auf regionaler Skala. Die Proben wurden an 12 Fichtenstandorten gewonnen und unterschieden sich in C/N‐Verhältnis, pH, extrahierbarem C und austauschbaren Kationen. Viele dieser Parameter sind für europäische Wälder in hoher räumlicher Auflösung verfügbar. Die Proben wurden über 8 Wochen bei Feldkapazität und 15°C inkubiert und anschließend mit künstlicher Kronentraufe extrahiert. Die Extrakte wurden auf DOC und DON untersucht. Ferner erfolgte eine Bestimmung der Raten der N‐Mineralisation und der Respiration zur Charakterisierung der mikrobiellen Aktivität. Die Freisetzung von DOC und DON aus den Of‐Proben war 2—3 mal größer als aus den Oh‐Proben. Die Unterschiede der Freisetzungsraten zwischen den Standorten betrugen bis zu einer Größenordnung. Die DOC/DON‐Verhältnisse in den Perkolaten aus den Oh‐Proben waren deutlich höher als die C/N‐Verhältnisse der jeweiligen Festphasen, was auf unterschiedliche Freisetzungsraten von DOC und DON hindeutet. Im Gegensatz dazu waren die DOC/DON‐Verhältnisse in den Perkolaten aus den Of‐Proben ähnlich den Festphasen‐C/N‐Verhältnissen. Die Freisetzung von DOC und DON aus den Of‐Proben war nicht signifikant zu den gemessenen Festphaseneigenschaften korreliert, hingegen positiv zur N‐Mineralisation. Die Freisetzung aus den Oh‐Proben zeigte im Gegensatz dazu eine positive Korrelation zum pH und zur Bodenatmung. Insgesamt war es nicht möglich, die große räumliche Variation der Freisetzung von DOC und DON aus den verschiedenen Proben mit den gemessenen Festphaseneigenschaften mit hinreichender Genauigkeit zu erklären.
    Keywords: Dissolved Organic Carbon ; Dissolved Organic Nitrogen ; Forest Floor ; Karst ; N‐Mineralization ; Respiration
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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