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• 1
Article
Language: English
In: Plant and Soil, 2013, Vol.371(1), pp.435-446
Description: Background and aims: The partitioning of below ground carbon inputs into roots and extramatrical ectomycorrhizal mycelium (ECM) is crucial for the C cycle in forest soils. Here we studied simultaneously the newly grown biomass of ECM and fine roots in a young Norway spruce stand. Methods: Ingrowth mesh bags of 16 cm diameter and 12 cm height were placed in the upper soil and left for 12 to 16 months. The 2 mm mesh size allowed the ingrowth of fungal hyphae and roots whereas a 45 mu m mesh size allowed only the ingrowth of hyphae. The mesh bags were filled with either EA horizon soil, pure quartz sand or crushed granite. Controls without any ingrowth were established for each substrate by solid tubes (2010) and by 1 mu m mesh bags (2011). The fungal biomass in the substrates was estimated by the PLFA 18:2 omega 6,9 and ECM biomass was calculated as difference between fungal biomass in mesh bags and controls. Results: The maximum ECM biomass was 438 kg ha super(-1) in October 2010 in 2 mm mesh bags with EA substrate, and the minimum was close to zero in 2011 in 45 mu m mesh bags with quartz sand. The high P content of the crushed granite did not influence the ECM biomass. Fine root biomass reached a maximum of 2,343 kg ha super(-1) in October 2010 in mesh bags with quartz sand after 16 months exposure. In quartz sand and crushed granite, ECM biomass correlated positively with fine root biomass and the number of root tips, and negatively with specific root length. Conclusion: The ratio of ECM biomass/fine root biomass in October ranged from 0.1 to 0.3 in quartz sand and crushed granite, but from 0.7 to 1.8 in the EA substrate. The results for the EA substrate suggest a large C flux to ECM under field conditions.
Keywords: Biomass ; Ectomycorrhizal mycelium ; Fine roots ; Ingrowth bags ; Substrate quality ; Norway spruce
ISSN: 0032-079X
E-ISSN: 1573-5036
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• 2
Article
Language: English
In: Plant and Soil, 2014, Vol.378(1), pp.73-82
Description: Background and aims Partitioning of soil respiration is a challenging task when resolving the C cycling in forest ecosystems. Our aim was to partition the respiration of newly grown extramatrical ectomycorrhizal mycelium (ECM) and fine roots (and their associated microorganisms) in a young Norway spruce forest. Methods Ingrowth mesh bags of 16 cm diameter and 12 cm height were placed in the upper soil and left for 12-16 months in 2010 and 2011. The 2 mm mesh size allowed the ingrowth of ECM and fine roots whereas a 45 [micro]m mesh size allowed only the ingrowth of ECM. The mesh bags were filled with either homogenized EA horizon soil, pure quartz sand (QS) or crushed granite (CG, only 2011), each with five replicates. Controls without any ingrowth were established for each substrate by solid plastic tubes (2010) and by 1 [micro]m mesh bags (2011). Fluxes of C[O.sub.2] from the mesh bags and controls were measured biweekly during the growing season by the closed chamber method. Results The contribution of ECM to soil respiration was largest in the QS treatments, reaching cumulatively 1.2 and 2.2 Mg C [ha.sup.-1] 6 [months.sup.-1] in 2010 and 2011, respectively. For EA and CG treatments, the cumulative respiration from ECM was larger than from controls, however the differences being not statistically significant. The respiration of newly grown fine roots in QS amounted to 1.0 Mg C [ha.sup.-1] in 2010, but could not be identified in 2011 since fluxes from 2 mm and 45 [micro]m mesh bags were similar. The correlation of total root length in single QS mesh bags to C[O.sub.2] fluxes was poor. The contribution of fine root respiration was also not detectable in the EA and CG treatment. No correlation was found between the autumnal biomass of newly grown ECM and its cumulative respiration. Conclusion Our results suggest a substantial contribution of newly grown ECM to soil respiration. Respiration of ECM might be larger than respiration of fine roots. Keywords Soil respiration * Carbon allocation * Ectomycorrhiza * Picea abies * Fine roots
Keywords: Soil respiration ; Carbon allocation ; Ectomycorrhiza ; Picea abies ; Fine roots
ISSN: 0032-079X
E-ISSN: 1573-5036
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• 3
Article
Language: English
In: Biogeochemistry, 2011, Vol.106(3), pp.461-473
Description: Dissolved organic carbon (DOC) is an important component of the C cycle in forest ecosystems, but dynamics and origin of DOC in throughfall and soil solution are yet poorly understood. In a 2-year study, we analyzed the radiocarbon signature of DOC in throughfall and soil solution beneath the Oa horizon and at 90 cm depth in a Norway spruce forest on a Podzol soil. A two-pool mixing model revealed that throughfall DOC comprised mainly biogenic C, i.e. recently fixed C, from canopy leaching and possibly other sources. The contribution of fossil DOC from atmospheric deposition to throughfall DOC was on average 6% with maxima of 8–11% during the dormant season. In soil solution from the Oa horizon, DO 14 C signature was highly dynamic (range from −8‰ to +103‰), but not correlated with DOC concentration. Radiocarbon signatures suggest that DOC beneath the Oa horizon originated mainly from occluded and mineral associated organic matter fractions of the Oa horizon rather than from the Oi or Oe horizon. Relatively old C was released in the rewetting phase following a drought period in the late summer of 2006. In contrast, the DO 14 C signature indicated the release of younger C throughout the humid year 2007. In soil solutions from 90 cm depth, DO 14 C signatures were also highly dynamic (−127‰ to +3‰) despite constantly low DOC concentrations. Similar to the Oa horizon, the lowest DO 14 C signature at 90 cm depth was found after the rewetting phase in the late summer of 2006. Because of the variation in the DO 14 C signatures at this depth, we conclude that DOC was not equilibrated with the surrounding soil, but also originated from overlaying soil horizons. The dynamics of DO 14 C in throughfall and soil solution suggest that the sources of DOC are highly variable in time. Extended drought periods likely have a strong influence on release and translocation of DOC from relatively old and possibly stabilized soil organic matter fractions. Temporal variations as well as the input of fossil DOC needs to be considered when calibrating DOC models based on DO 14 C signatures.
Keywords: Dissolved organic carbon ; Forest soils ; Norway spruce ; Throughfall ; Radiocarbon ; C
ISSN: 0168-2563
E-ISSN: 1573-515X
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• 4
Article
Language: English
In: Wetlands, 2012, Vol.32(3), pp.579-587
Description: Changes of water table level and oxygen supply affect the nitrogen (N) and carbon (C) mineralization of fen soils with potential consequences for the N and C sink and sources function of fens. Here we studied the response of gross N mineralization and CO 2 emissions to water table fluctuations in an acidic minerotrophic fen. In a laboratory study lasting 117 days, undisturbed soil cores were either a) permanently flooded or b) subject to flooding, water table drawdown and reflooding. In the permanently flooded cores the CO 2 emissions were constantly low, but gross ammonification and immobilization of NH 4 + increased after a lag phase of about 30 and 70 days, respectively. In the fluctuated cores, gross ammonification and NH 4 + immobilization first remained constant but then increased after water table drawdown of 30 days. Emission of CO 2 peaked immediately after water table drawdown, followed by a decrease and a second maximum after about 30 days. Following re-flooding, gross ammonification and immobilization of NH 4 + first decreased but recovered after about 30 days to the level of the permanently flooded cores. In contrast, the CO 2 emissions decreased immediately and permanently after re-flooding. The cumulative gross ammonification was larger in the permanently flooded cores than in the fluctuated cores. Rates of gross nitrification and immobilization of NO 3 − were generally low and did not respond to the treatments. The ratios of CO 2 emission/gross ammonification were in the range of 1 to 4 under anoxic condition which seems to be caused by fast N turnover in the microbial biomass pool and low rates of C-mineralization of soil organic matter. Our results indicate that water table fluctuations in fen soils affect N and C mineralization differently. Changes of water table of a few days likely have a bigger effect on C-mineralization than on gross N mineralization.
Keywords: Gross ammonification ; C mineralization ; Wetland ; Fen soil ; Water table
ISSN: 0277-5212
E-ISSN: 1943-6246
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• 5
Article
Language: English
In: Plant and Soil, 2007, Vol.292(1), pp.79-93
Description: Fine root systems may respond to soil chemical conditions, but contrasting results have been obtained from field studies in non-manipulated forests with distinct soil chemical properties. We investigated biomass, necromass, live/dead ratios, morphology and nutrient concentrations of fine roots (〈2 mm) in four mature Norway spruce ( Picea abies [L.] Karst.) stands of south-east Germany, encompassing variations in soil chemical properties and climate. All stands were established on acidic soils (pH (CaCl 2 ) range 2.8–3.8 in the humus layer), two of the four stands had molar ratios in soil solution below 1 and one of the four stands had received a liming treatment 22 years before the study. Soil cores down to 40 cm mineral soil depth were taken in autumn and separated into four fractions: humus layer, 0–10 cm, 10–20 cm and 20–40 cm. We found no indications of negative effects of N availability on fine root properties despite large variations in inorganic N seepage fluxes (4–34 kg N ha −1  yr −1 ), suggesting that the variation in N deposition between 17 and 26 kg N ha −1  yr −1 does not affect the fine root system of Norway spruce. Fine root biomass was largest in the humus layer and increased with the amount of organic matter stored in the humus layer, indicating that the vertical pattern of fine roots is largely affected by the thickness of this horizon. Only two stands showed significant differences in fine root biomass of the mineral soil which can be explained by differences in soil chemical conditions. The stand with the lowest total biomass had the lowest Ca/Al ratio of 0.1 in seepage, however, Al, Ca, Mg and K concentrations of fine roots were not different among the stands. The Ca/Al ratio in seepage might be a less reliable stress parameter because another stand also had Ca/Al ratios in seepage far below the critical value of 1.0 without any signs of fine root damages. Large differences in the live/dead ratio were positively correlated with the Mn concentration of live fine roots from the mineral soil. This relationship was attributed to faster decay of dead fine roots because Mn is known as an essential element of lignin degrading enzymes. It is questionable if the live/dead ratio can be used as a vitality parameter of fine roots since both longevity of fine roots and decay of root litter may affect this parameter. Morphological properties were different in the humus layer of one stand that was limed in 1983, indicating that a single lime dose of 3–4 Mg ha −1 has a long-lasting effect on fine root architecture of Norway spruce. Almost no differences were found in morphological properties in the mineral soil among the stands, but vertical patterns were apparently different. Two stands with high base saturation in the subsoil showed a vertical decrease in specific root length and specific root tip density whereas the other two stands showed an opposite pattern or no effect. Our results suggest that proliferation of fine roots increased with decreasing base saturation in the subsoil of Norway spruce stands.
Keywords: Ca/Al ratio ; Fine roots ; Fine root biomass ; Fine root morphology ; Liming ; Mn concentration ; Nitrogen deposition ; Norway spruce
ISSN: 0032-079X
E-ISSN: 1573-5036
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• 6
Article
Language: English
In: Biogeochemistry, 2011, Vol.103(1), pp.59-70
Description: The input of heavy metals by atmospheric deposition to forested watersheds substantially decreased during the last decades in many areas. The goal of our study was to identify the present sinks and sources of metals and factors influencing metal mobility at the catchment and soil profile scale. We determined concentrations and fluxes of Cd, Zn, Cu, Cr and Ni in precipitation, litterfall, soil solutions (Oi, Oe, Oa horizon percolates, 20 and 90 cm soil depth) and runoff in a forest ecosystem in NE-Bavaria, Germany for 1 year. The metal concentrations in solutions were mostly 〈10 μg l −1 beside Zn (〈1200 μg l −1 ). The present total deposition was estimated at 1.0, 560, 30, 1.2 and 10.4 g ha −1  year −1 for Cd, Zn, Cu, Cr and Ni, respectively. The mass balance (total deposition minus runoff) at the catchment scale indicated actual retention of Zn, Cu and Ni, but an almost balanced budget for Cr and Cd. Considering the soil profile scale, the Oi horizon still acted as a sink, whereas the Oe and Oa horizons were presently sources for all metals. The solid–solution partitioning coefficients indicated higher mobility of Cd and Zn than of Cu, Cr and Ni in forest soils. In the mineral soil horizons, K d values derived from field measurements were substantially larger than those predicted with empirical regression equations from Sauvé et al. (Environ Sci Technol 34:1125–1131, 2000; Environ Sci Technol 37:5191–5196, 2003). The mineral soil acted as a sink for all metals beside Cd. Dissolved organic C and pH influenced the metal mobility, as indicated by significant correlations to metal concentrations in Oa percolates and runoff. The solid–solution partitioning coefficients indicated higher mobility of Cd and Zn than of Cu, Cr and Ni in forest soils. Overall, the decreased deposition rates have obviously induced a source function of the Oe and Oa horizon for metals. Consequently, mobilization of metals from forest floor during heavy rain events and near surface flow conditions may lead to elevated concentrations in runoff.
Keywords: Heavy metals ; Biogeochemistry ; Forest soils ; Catchment ; Sink and source function
ISSN: 0168-2563
E-ISSN: 1573-515X
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• 7
Article
Language: English
In: Biology and Fertility of Soils, 2018, Vol.54(6), pp.761-768
Description: Drying and rewetting (D/W) of soils often leads to a pulse of total dissolved phosphorus (TDP) by lysis of sensitive microorganisms. The relevance of D/W on the P cycle in ecosystems depends on the duration of the TDP release. In forest soils, the forest floor represents a hotspot of microbial activity and is often prone to D/W. Here, we investigated the dynamics of TDP, the microbial P pool (Pmic), and the composition of microbial communities after D/W. Samples were taken from Oi and Oe layers of a European beech and a Norway spruce site and desiccated up to − 100 MPa (pF 6) at 20 °C, while controls were kept moist. TDP and Pmic were measured 0, 1, 3, 7, and 14 days after rewetting and the composition of microbial communities was analyzed by automated ribosomal intergenic spacer analysis after 14 days. After D/W, the largest TDP net release (D/W-control) was from Oe layers with 40–50 mg P kg −1 and inorganic P as the dominant fraction. The TDP concentrations decreased strongly in Oi layers within 1 (beech) to 4 (spruce) days, while remaining stable in Oe layers. The TDP dynamics were linked to the decrease and recovery of Pmic after D/W. Pmic dynamics differed between layers and stand types, suggesting the influence of microbial communities with different D/W sensitivities. The composition of microbial communities varied strongly among sites and layers, while D/W only affected the composition of bacterial and fungal communities in the spruce Oe layer. D/W of forest floors increases the plant available P and affects the P cycle in forest ecosystems.
Keywords: Drying–rewetting ; Inorganic dissolved phosphorus ; Soil microbial biomass ; Soil microbial communities ; Total dissolved phosphorus
ISSN: 0178-2762
E-ISSN: 1432-0789
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• 8
Article
Language: English
In: Plant and Soil, 2000, Vol.222(1), pp.149-161
Description: Active tree roots influence the soil chemistry in their immediate vicinity, the rhizosphere. For the first time, the extent and stability of in situ concentration gradients of major cations and anions in the soil solution around tree roots were studied in the field. Micro suction cups were installed in an acidic forest soil using a root window in a 145-year-old Norway spruce stand. Samples were collected once a week during the growing season from the rhizosphere and from the bulk soil of a non-mycorrhizal long root and of a mycorrhizal root net. For comparison, micro suction cups were installed proximal and distal to a long root in a rhizotron under controlled conditions (homogenised soil, constant water potential, nutrient solution) at the same site. Small volumes of soil solutions were analysed for NH 4 + , K + , Na + , Ca 2+ , Mg 2+ , Al 3+ , NO 3 - , Cl - and SO 4 2- by capillary electrophoresis. Total-Al was measured with ICP-AES micro injection, complexed-Al was calculated as the difference between total-Al and Al 3+ . pH values were determined with an ion-sensitive field effect transistor (ISFET) sensor. In both set-ups a significant increase of the K + concentrations was observed in the rhizosphere as compared to the bulk soil solutions of the non-mycorrhizal long roots. The concentrations of Al 3+ , H + and NH 4 + were lower in the rhizosphere. No gradients were observed for Mg 2+ and Ca 2+ at the root window. A significant depletion of these ions was found in the rhizosphere of the long root only in the rhizotron. In the case of the mycorrhizal roots, contrasting results were found with significantly higher concentrations of Al 3+ , Mg 2+ , H + , SO 4 2- and Cl - , and significantly lower K + concentrations in the rhizosphere. The extension of the gradients was estimated at about 2.5 to 5 mm for the long roots and 1 mm for the mycorrhizal roots. The observed gradients varied strongly with time. In conclusion, for Norway spruce, the effect of non-mycorrhizal long roots on the rhizosphere chemistry differs from that of mycorrhizal roots. Evaluating nutrient availability and the risk of Al 3+ toxicity to tree roots from bulk soil analysis can be misleading.
Keywords: aluminium complexation ; bulk soil ; Norway spruce ; nutrient concentration ; rhizosphere ; soil solution chemistry
ISSN: 0032-079X
E-ISSN: 1573-5036
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• 9
Article
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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• 10
Article
Language: English
In: Plant and Soil, 2007, Vol.300(1), pp.21-34
Description: Forest soils are frequently subjected to dry–wet cycles, but little is known about the effects of repeated drying and wetting and wetting intensity on fluxes of $${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$$ , $${\text{NO}}^{ - }_{3}$$ and DOC. Here, undisturbed soil columns consisting of organic horizons (O columns) and organic horizons plus mineral soil (O + M columns) from a mature Norway spruce stand at the Fichtelgebirge; Germany, were repeatedly desiccated and subsequently wetted by applying different amounts of water (8, 20 and 50 mm day −1 ) during the initial wetting phase. The constantly moist controls were not desiccated and received 4 mm day −1 during the entire wetting periods. Cumulative inorganic N fluxes of the control were 12.4 g N m −2 (O columns) and 11.4 g N m −2 (O + M columns) over 225 days. Repeated drying and wetting reduced cumulative $${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$$ and $${\text{NO}}^{ - }_{3}$$ fluxes of the O columns by 47–60 and 76–85%, respectively. Increasing $${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$$ (0.6–1.1 g N m −2 ) and decreasing $${\text{NO}}^{ - }_{3}$$ fluxes (7.6–9.6 g N m −2 ) indicate a reduction in net nitrification in the O + M columns. The negative effect of dry–wet cycles was attributed to reduced net N mineralisation during both the desiccation and wetting periods. The soils subjected to dry–wet cycles were considerably drier at the final wetting period, suggesting that hydrophobicity of soil organic matter may persist for weeks or even months. Based on results from this study and from the literature we hypothesise that N mineralisation is mostly constrained by hydrophobicity in spruce forests during the growing season. Wetting intensity did mostly not alter N and DOC concentrations and fluxes. Mean DOC concentrations increased by the treatment from 45 mg l −1 to 61–77 mg l −1 in the O tlsbba columns and from 12 mg l −1 to 21–25 mg l −1 in the O + M columns. Spectroscopic properties of DOC from the O columns markedly differed within each wetting period, pointing to enhanced release of rather easily decomposable substrates in the initial wetting phases and the release of more hardly decomposable substrates in the final wetting phases. Our results suggest a small additional DOC input from organic horizons to the mineral soil owing to drying and wetting.
Keywords: Dissolved organic carbon ; DOC properties ; Dry–wet cycles ; Forest soil ; Inorganic nitrogen ; Soil solution
ISSN: 0032-079X
E-ISSN: 1573-5036
Source: Springer Science & Business Media B.V.
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