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  • 2017  (14)
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  • 2017  (14)
  • 1
    Language: English
    In: Forest Ecology and Management, 01 December 2017, Vol.405, pp.200-209
    Description: Deadwood plays a crucial role in forest ecosystems, yet its impact on soil properties and specifically soil organic matter (SOM) stabilization is hitherto not fully understood or studied. We hypothesized that downed deadwood would enhance the light, labile SOM fraction in forest topsoils, and that those changes would be enhanced by advanced decay and higher rates of soil bioturbation that would move deadwood fragments into mineral soil. To test our hypotheses, we took topsoil samples directly next to European beech ( L.) downed deadwood and samples from paired reference points at eight stands in Southwest Germany. From those samples we separated SOM into three density fractions linked to physical and chemical SOM stabilization processes: the free light fraction, the aggregate-occluded light fraction and the mineral-adsorbed heavy fraction. On silicate bedrock, deadwood increased the free light fraction by 57% ( mg g ) compared to reference points. In contrast on calcareous bedrock, deadwood decreased the free light fraction by 23% ( mg g ) compared to reference points. Deadwood with advanced decay from all sites increased the aggregate-occluded light fraction by 40% ( mg g ) as well as total soil organic carbon (SOC) stocks by 24% ( mg cm ) as compared to reference points. In summary, the light fraction of SOM was affected by deadwood depending on site conditions and the more stable, aggregate-occluded fraction eventually increased near decayed deadwood through interactions between stimulated biological activity and both particulate and dissolved organic matter. Altogether these results indicate that deadwood increases SOC stocks at sites where SOM decomposition is slow enough to enable occlusion of particulate organic matter within aggregates.
    Keywords: Coarse Woody Debris ; Forest Management ; Som Stability ; Soil Aggregate ; Density Fractionation ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 2
    Language: English
    In: Forests, 01 February 2017, Vol.8(2), p.37
    Description: More intensive removal of woody biomass for the bio-economy will disrupt litter and succession cycles. Especially at risk is the retention of fine and coarse woody debris (FWD and CWD), crucial factors in forest biodiversity and nutrient cycling. However, to what extent CWD affects soil functioning remains unknown, and is seldom considered. From 32 paired test–reference points in eight Fagus sylvatica (L.) stands throughout Southwest Germany, CWD significantly increased soil C/N ratios, base saturation, and possibly pH. CWD-induced changes in soil porosity, available water capacity, and total organic carbon depended on site and CWD characteristics. As such, CWD can be viewed as a “pedogenic hot-spot” of concentrated biogeochemical and -physical processes with outsized effects on soil functioning and development. CWD management for soil functioning should consider site and tree species specific volume thresholds, timed rotations, and spatial densities, but appropriate implementation requires further research to define best management practices. If successful, overall forest resilience as well as soil functioning and productivity can be improved.
    Keywords: Soil Management ; Silviculture ; Disturbances ; Fagus Sylvatica ; Biodiversity ; Bioeconomy ; Forestry
    E-ISSN: 1999-4907
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  • 3
    In: Wiley Interdisciplinary Reviews: Water, November 2017, Vol.4(6), pp.n/a-n/a
    Description: We review the state‐of‐the‐art of cross‐disciplinary knowledge on phosphorus (P) cycling in temperate forest ecosystems, focused at studies from hydrology, biology, biogeochemistry, soil‐, and geosciences. Changes in soil P stocks during long‐term ecosystem development are addressed briefly; the general ranges of specific P pools and P fluxes within the ecosystem and the presumed underlying processes are covered more in depth. Wherever possible, we differentiate between coniferous and deciduous forests. As the most important P pools, mineral soil, forest floor, vegetation, and microbial biomass are described in terms of pool size, molecular composition, and turnover. Litterfall, soil water seepage, atmospheric deposition, and biotic uptake as the most studied P fluxes in the forest ecosystem are discussed in detail, spotlighting biogeochemical processes relevant for mobilization and retention of P in the rooting zone. Through a meta‐analysis of available literature, we build a dataset that allows the quantification of major P‐cycle components in temperate forests in terms of range and distribution, highlighting similarities and differences between coniferous and deciduous forests. The two forest types are notably distinct in their distribution of P within compartments of the plant biomass and forest floor. The possibility to construct closed local P balances is often hindered by missing information on fluxes of dissolved and particulate P across the ecosystem boundary, be it in the atmosphere, soil, or on the surface. These fluxes are irregular in space and time and feature large overall mass fluxes but comparatively small P fluxes, making the latter one difficult to quantify. 2017, 4:e1243. doi: 10.1002/wat2.1243 This article is categorized under: A schematic respresentation of the Phosphorus cycle in temperate forests. Pools and fluxes are scaled to their average size. See the full paper for more detailed information and data sources.
    Keywords: Phosphorus Cycle ; Phosphorus ; Phosphorus Cycle ; Compartments ; Phosphorus ; Uptake ; Biogeochemistry ; Biomass ; Plant Biomass ; Environmental Changes ; Soil Water ; Pools ; Soil Water ; Distribution ; Composition ; Forests ; Phosphorus Cycle ; Biogeochemistry ; Biogeochemistry ; Biomass ; Biology ; Phosphorus ; Forests ; Microorganisms ; Ecosystems ; Moisture Content ; Forest Floor ; Forest Ecosystems ; Forests ; Stocks ; Hydrology ; Forests ; Rooting ; Pools ; Seepage ; Components ; Hydrology ; Deciduous Forests ; Forest Floor ; Fluxes ; Atmospheric Pollutant Deposition ; Soils ; Hydrology ; Seepage ; Biomass ; Hydrology ; Forest Biomass;
    ISSN: 2049-1948
    E-ISSN: 2049-1948
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  • 4
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2017, Vol.180(2), pp.220-230
    Description: Standard procedures to assess P availability in soils are based on batch experiments with various extractants. However, in most soils P nutrition is less limited by bulk stocks but by strong adsorption and transport limitation. The basic principle of root‐phosphate uptake is to strip phosphate locally from the solid phase by forming a radial depletion zone in the soil solution, optionally enhanced by release of mobilizing substances. Microdialysis (MD), a well‐established method in pharmacokinetics, is capable to mimic important characteristics of P root uptake. The sampling is by diffusional exchange through a semipermeable membrane covering the probes with their sub‐mm tubular structure. Additionally, the direct environment of the probe can be chemically modified by adding, ., carboxylates to the perfusate. This study is the first approach to test the applicability of MD in assessing plant available phosphate in soils and to develop a framework for its appropriate use.We used MD in stirred solutions to quantify the effect of pumping rate, concomitant ions, and pH value on phosphate recovery. Furthermore, we measured phosphate yield of top‐soil material from a beech forest, a non‐fertilized grassland, and from a fertilized corn field. Three perfusates have been used based on a 1 mM KNO solution: pure (1), with 0.1 mM citric acid (2), and with 1 mM citric acid (3). Additionally, a radial diffusion model has been parametrized for the stirred solutions and the beech forest soil.Results from the tests in stirred solutions were in good agreement with reported observations obtained for other ionic species. This shows the principal suitability of the experimental setup for phosphate tests. We observed a significant dependency of phosphate uptake into the MD probes on dialysate pumping rate and on ionic strength of the outside solution. In the soils, we observed uptake rates of the probes between 1.5 × 10 and 6.7 × 10 mol s cm in case of no citrate addition. Surprisingly, median uptake rates were mostly independent of the bulk soil stocks, but the P‐fertilized soil revealed a strong tailing towards higher values. This indicates the occurrence of hot P spots in soils. Citrate addition increased P yields only in the higher concentration but not in the forest soil. The order of magnitude of MD uptake rates from the soil samples matched root‐length related uptake rates from other studies. The micro‐radial citrate release in MD reflects the processes controlling phosphate mobilization in the rhizosphere better than measurements based on “flooding” of soil samples with citric acid in batch experiments. Important challenges in MD with phosphate are small volumes of dialysate with extremely low concentrations and a high variability of results due to soil heterogeneity and between‐probe variability. We conclude that MD is a promising tool to complement existing P‐analytical procedures, especially when spatial aspects or the release of mobilizing substances are in focus.
    Keywords: Plant Availability ; Diffusion Limitation ; Spatial Heterogeneity ; Carboxylates
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 5
    Language: English
    In: Sci Rep, 2017, Vol.7(1), pp.13243-13243
    Description: Naturally produced by microbial processes in soil, nitrous oxide (NO) is an important greenhouse gas contributing to climate change. Accordingly, there is a need to accurately quantify the capability of forest ecosystems to exchange NO with the atmosphere. While NO emissions from soils have been well studied, trees have so far been overlooked in NO inventories. Here, we show that stems of mature beech trees (Fagus sylvatica) may act as a substantial sink of NO from the atmosphere under conditions of soils consuming NO. Consistent consumption of NO by all stems investigated (ranging between −2.4 and −3.8 µg m h) is a novel finding in contrast to current studies presenting trees as NO emitters. To understand these fluxes, NO exchange of photoautotrophic organisms associated with beech bark (lichens, mosses and algae) was quantified under laboratory conditions. All these organisms were net NO sinks at full rehydration and temperature of 25 °C. The consumption rates were comparable to stem consumption rates measured under field conditions. Cryptogamic stem covers could be a relevant sink of NO in European beech forests.
    Keywords: Article;
    ISSN: 2045-2322
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  • 6
    Language: English
    In: Geoderma, 01 July 2017, Vol.297, pp.61-69
    Description: The use of heavy machinery for timber harvesting causes soil damage, which may restrict forest soil functions over decades. Numerous studies have demonstrated the negative impact of soil compaction on soil physical properties, but the effects of compaction of forest soils on soil chemical and biological processes like the phosphorus availability are largely unknown. Aim of our study was to analyze the effect of skidding activity on the P dynamics on skid trails and the soil recovery ability after skidding. Furthermore, we wanted to assess if acid phosphatase activity is an appropriate indicator of soil structure damage after compaction. We investigated the phosphorus availability, acid phosphatase activity, TOC, pH value, and fine root density of soil samples from skid trails and from control plots without any skidding effect. We conducted our studies at three sites (Göttingen: Cambisols on limestone, Heide: Podzol on glacial drift and sand, and Solling: Cambisols at loess-covered sandstone) in Lower Saxony, Germany 10 to 40 years after last traffic impact in a space-for-time substitution. We observed mainly higher P concentrations and higher pH values at the wheel tracks than in the control. TOC was predominantly higher at the wheel tracks, but lower TOC at the wheel tracks was also found. In the acidic loams of the Solling region, the amount of mineralized phosphate was much higher in the tracks compared to the control areas 10 to 30 years after last traffic impact. This suggests a decoupling of P mineralization from P uptake in the wheel tracks for several decades. Furthermore, higher as well as lower phosphatase activity at the wheel tracks compared to the untrafficked control was found, but higher phosphatase activities at the wheel tracks were predominant. Acid phosphatase activity was strongly correlated with TOC, but did not correlate with the time since last traffic impact and the gas diffusivity of the soil. Therefore, our results did not confirm that acid phosphatase activity is an appropriate soil biological indicator of soil compaction and structural recovery.
    Keywords: Acid Phosphatase Activity ; P Availability ; Soil Compaction ; Soil Structure Recovery ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 7
    Language: English
    In: Geoderma, 15 February 2017, Vol.288, pp.204-212
    Description: Deadwood is a key factor in forest ecosystems, yet how it influences forest soil properties is uncertain. We hypothesized that changes in soil properties induced by deadwood mainly depend on the amount of released phenolic matter. Consequently we expected softwood- and hardwood-related deadwood effects on soil to be explained by unequal enrichment of phenolic substances. We measured differences in the quantity and composition of soil organic matter (SOM), pH, nutrient concentrations, and enzymatic activity between paired control and treatment points influenced by deadwood of silver fir ( Mill.) and European beech ( L.), and checked for correlations with total C and phenolic matter; the latter was quantified as aromaticity of water-extractable organic C through specific UV absorbance at 280 nm. Near fir deadwood, aromaticity and effective cation exchange capacity (CEC) increased while pH decreased. In comparison, concentrations of water-extractable organic C, effective CEC, exchangeable Ca and Mg , base saturation, and available molybdenum-reactive P increased near beech deadwood while exchangeable Al decreased. For fir deadwood, soil properties strongly correlated almost exclusively with total C. For beech deadwood, numerous strong correlations with aromaticity indicated that extractable phenolics influenced soil properties. These differences in correlations imply that deadwood affects soil through the composition of added phenolic matter, which would stem from differing decay processes and organisms. Decayed, particulate lignin from brown-rot in fir deadwood as opposed to oxidized, dissolved lignin from white-rot in beech deadwood would account for our observations.
    Keywords: Coarse Woody Debris ; Soil Chemistry ; Lignin ; Brown-Rot Fungi ; White-Rot Fungi ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 8
    Language: English
    In: Forests, 01 September 2017, Vol.8(10), p.358
    Description: Forest harvesting removes and redistributes nutrients through felling and forwarding. Substantial quantities of nutrients can accumulate in brash mats on permanent skid trails, but their availability and uptake after multiple thinnings on soils susceptible to leaching are unknown. In this study, we modeled the deposition of base cations and phosphorus on a permanent skid trail after five thinnings of a Picea abies (L.) Karst. stand, and measured the resulting nutrient stocks in both the forest floor and mineral soil. An estimated 35%, 44%, 41%, and 61% of harvested Ca, K, Mg, and P, respectively, were redistributed to the skid trail. Of those deposited stocks, 32–65% of nutrients remained in decomposed brash material on the skid trail. Mineral soil stocks for Ca, K, and P were significantly higher in the skid trail than in the stand, which included minor increases in bioavailable pools. Skid trail root densities were not lower than the stand while bulk densities were only partially higher. Both would not limit nutrient uptake. There were no significant relations between needle nutrient concentrations and distance to the skid trail. Altogether, these results indicate that nutrient uptake from the skid trail was minimal despite their accumulation, chemical availability, and physical accessibility. This suggests that other factors such as liming and frequent thinning disturbances can repress uptake of available nutrients on skid trails.
    Keywords: Soil Management ; Picea Abies ; Brash Mats ; Needle Nutrition ; Whole-Tree Harvesting ; Liming ; Forestry
    E-ISSN: 1999-4907
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  • 9
    Language: English
    In: 2D profiles of CO2, CH4, N2O and gas diffusivity in a well aerated soil: measurement and Finite Element Modeling. Agricultural and Forest Meteorology, 247., NetherlandsElsevier. (2017).
    Description: Peer reviewed
    Keywords: Life Sciences :: Environmental Sciences & Ecology ; Sciences Du Vivant :: Sciences De L'Environnement & Écologie
    Source: ORBi (Open Repository and Bibliography), University of Liège
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  • 10
    Language: English
    In: Blood, 21 December 2017, Vol.130(25), pp.2774-2785
    Description: Platelets, anucleated megakaryocyte (MK)-derived cells, play a major role in hemostasis and arterial thrombosis. Although protein kinase casein kinase 2 (CK2) is readily detected in MKs and platelets, the impact of CK2-dependent signaling on MK/platelet (patho-)physiology has remained elusive. The present study explored the impact of the CK2 regulatory β-subunit on platelet biogenesis and activation. MK/platelet-specific genetic deletion of CK2β ( ) in mice resulted in a significant macrothrombocytopenia and an increased extramedullar megakaryopoiesis with an enhanced proportion of premature platelets. Although platelet life span was only mildly affected, MK displayed an abnormal microtubule structure with a drastically increased fragmentation within bone marrow and a significantly reduced proplatelet formation in vivo. In platelets, tubulin polymerization was disrupted, resulting in an impaired thrombopoiesis and an abrogated inositol 1,4,5-triphosphate receptor-dependent intracellular calcium (Ca) release. Presumably due to a blunted increase in the concentration of cytosolic Ca, activation-dependent increases of α and dense-granule secretion and integrin αβ activation, and aggregation were abrogated in platelets. Accordingly, thrombus formation and stabilization under high arterial shear rates were significantly diminished, and thrombotic vascular occlusion in vivo was significantly blunted in mice, accompanied by a slight prolongation of bleeding time. Following transient middle cerebral artery occlusion, mice displayed significantly reduced cerebral infarct volumes, developed significantly less neurological deficits, and showed significantly better outcomes after ischemic stroke than mice. The present observations reveal CK2β as a novel powerful regulator of thrombopoiesis, Ca-dependent platelet activation, and arterial thrombosis in vivo.
    Keywords: Platelet Activation ; Thrombopoiesis ; Casein Kinase II -- Physiology ; Peptide Fragments -- Physiology ; Thrombosis -- Pathology
    ISSN: 00064971
    E-ISSN: 1528-0020
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