414 research outputs found
Fine-root turnover rates of European forests revisited: an analysis of data from sequential coring and ingrowth cores
Background and Aims: Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values. Methods: We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature. Results: Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86yrâ1 for Fagus sylvatica and 0.88yrâ1 for Picea abies when maximum biomass data were used for the calculation, and 1.11yrâ1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30% higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula. Conclusions: We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reportin
The abundance of arbuscular mycorrhiza in soils is linked to the total length of roots colonized at ecosystem level
Arbuscular mycorrhizal fungi (AMF) strongly affect ecosystem functioning. To understand and quantify the mechanisms of this control, knowledge about the relationship between the actual abundance and community composition of AMF in the soil and in plant roots is needed. We collected soil and root samples in a natural dune grassland to test whether, across a plant community, the abundance of AMF in host roots (measured as the total length of roots colonized) is related to soil AMF abundance (using the neutral lipid fatty acids (NLFA) 16:1Ï5 as proxy). Next-generation sequencing was used to explore the role of community composition in abundance patterns. We found a strong positive relationship between the total length of roots colonized by AMF and the amount of NLFA 16:1Ï5 in the soil. We provide the first field-based evidence of proportional biomass allocation between intra-and extraradical AMF mycelium, at ecosystem level. We suggest that this phenomenon is made possible by compensatory colonization strategies of individual fungal species. Finally, our findings open the possibility of using AMF total root colonization as a proxy for soil AMF abundances, aiding further exploration of the AMF impacts on ecosystems functioning.Environmental Biolog
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Fine-root turnover rates of European forests revisited: an analysis of data from sequential coring and ingrowth cores
Background and Aims
Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values.
Methods
We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature.
Results
Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yrâ1 for Fagus sylvatica and 0.88 yrâ1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yrâ1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30 % higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula.
Conclusions
We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting
Estimating fine-root production by tree species and understorey functional groups in two contrasting peatland forests
Background and aims Estimation of root-mediated carbon fluxes in forested peatlands is needed for understanding ecosystem functioning and supporting greenhouse gas inventories. Here, we aim to determine the optimal methodology for utilizing ingrowth cores in estimating annual fine-root production (FRP) and its vertical distribution in trees, shrubs and herbs. Methods We used 3-year data obtained with modified ingrowth core method and tested two calculation methods: 'ingrowth-dividing' and `ingrowth-subtracting'. Results The ingrowth-dividing method combined with a 2-year incubation of ingrowth cores can be used for the 'best estimate' of FRP. The FRP in the nutrient-rich fen forest (561 g m(-2)) was more than twice that in the nutrient-poor bog forest (244 g m(-2)). Most FRP occurred in the top 20-cm layer (76-82 %). Tree FRP accounted for 71 % of total FRP in the bog and 94 % in the fen forests, respectively, following the aboveground vegetation patterns; however, in fen forest the proportions of spruce and birch in FRP were higher than their proportions in stand basal area. Conclusions Our methodology may be used to study peatland FRP patterns more widely and will reduce the volume of labour-intensive work, but will benefit from verification with other methods, as is the case in all in situ FRP studies.Peer reviewe
The Wellesley News (12-01-1966)
https://repository.wellesley.edu/wcnews/1090/thumbnail.jp
Experimental and Theoretical Thermodynamic Study of Distillable Ionic Liquid 1,5-Diazabicyclo[4.3.0]non-5-enium Acetate
© 2016 American Chemical Society.A thermochemical study of the protic ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]), a prospective cellulose solvent considered for the Ioncell-F process, was carried out. The heat capacities of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and [DBNH][OAc] were measured by differential scanning calorimetry (DSC) at 223-323 and 273-373 K temperature ranges, respectively. The enthalpies of fusion and synthesis reaction of [DBNH][OAc] were measured by DSC and reaction calorimetry, respectively. The gas-, liquid-, and solid-phase enthalpies of formation of [DBNH][OAc] and DBN were determined using calorimetric and computational methods. The enthalpy of vaporization of [DBNH][OAc] was estimated from the formation enthalpies. The activity coefficients at infinite dilution of 17 and the enthalpies of solution at infinite dilution of 25 organic solutes in [DBNH][OAc] were measured by gas chromatography and solution calorimetry methods, respectively. The obtained data will be used in the design and optimization of the Ioncell-F process
Formation of the in Two-Photon Collisions at LEP
The two-photon width of the meson has been
measured with the L3 detector at LEP. The is studied in the decay
modes , KK, KK,
KK, , , and
using an integrated luminosity of 140 pb at GeV and
of 52 pb at GeV. The result is
(BR) keV. The dependence of the cross section is studied for
GeV. It is found to be better described by a Vector Meson
Dominance model form factor with a J-pole than with a -pole. In addition,
a signal of events is observed at the mass. Upper limits
for the two-photon widths of the , , and are also
given
Measurement of Mass and Width of the W Boson at LEP
We report on measurements of the mass and total decay width of the W boson
with the L3 detector at LEP. W-pair events produced in
interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in
a data sample corresponding to a total luminosity of 76.7 pb. Combining
all final states in W-pair production, the mass and total decay width of the W
boson are determined to be GeV and
GeV, respectively
Search for Heavy Neutral and Charged Leptons in ee Annihilation at = 183 and 189 GeV
A search for unstable neutral and charged heavy leptons as well as for stable
charged heavy leptons is performed at center-of-mass energies = 183
and 189 GeV with the L3 detector at LEP. No evidence for their existence is
found. We exclude neutral heavy leptons which couple to the electron, muon or
tau family, of the Dirac type for masses below 92.4, 93.3 and 83.3 GeV, and of
the Majorana type for masses below 81.8, 84.1 and 73.5 GeV, respectively. We
exclude unstable charged heavy leptons for masses below 93.9 GeV for a wide
range of the associated neutral heavy lepton mass. If the unstable charged
heavy lepton decays to a light neutrino, we exclude masses below 92.4 GeV. The
production of stable charged heavy leptons with mass less than 93.5 GeV is also
excluded
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