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  • 1
    Language: English
    In: Soil Biology and Biochemistry, 2010, Vol.42(8), pp.1347-1354
    Description: How the mixture of tree species modifies short-term decomposition has been well documented using litterbag studies. However, how litter of different tree species interact in the long-term is obscured by our inability to visually recognize the species identity of residual decomposition products in the two most decomposed layers of the forest floor (i.e. the Oe and Oa layers respectively). To overcome this problem, we used Near Infrared Reflectance Spectroscopy (NIRS) to determine indirectly the species composition of forest floor layers. For this purpose, controlled mixtures of increasing complexity comprising beech and spruce foliage materials at various stages of decomposition from sites differing in soil acid–base status were created. In addition to the controlled mixtures, natural mixtures of litterfall from mixed stands were used to develop prediction models. Following a calibration/validation procedure, the best regression models to predict the actual species proportion from spectral properties were selected for each tree species based on the highest coefficient of determination ( ) and the lowest root mean square error of prediction (RMSEP). For the validation, the (predictions versus true proportions) were 0.95 and 0.94 for both beech and spruce components in mixtures of materials at all stages of decomposition from the gradient of sites. The decreased only marginally by 0.04 when models were tested on independent samples of similar composition. The best models were used to predict the beech-spruce proportion in Oe and Oa layers of unknown composition. They provided in most cases plausible predictions when compared to the composition of the canopy above the sampling points. Thus, tedious and potentially erroneous hand sorting of forest floor layers may be replaced by the use of NIRS models to determine species composition, even at late stages of decomposition.
    Keywords: Forest Floor ; Mixed-Species Forests ; Beech ; Spruce ; NIRS ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, 2003, Vol.35(1), pp.177-186
    Description: This study compared field and laboratory decomposition rates of coarse woody debris (CWD) (〉10 cm diameter) from three tree species: Pinus radiata , Eucalyptus regnans , and Eucalyptus maculata . For this purpose, the density loss of logs on the ground sampled from chronosequences of sites following harvesting was determined using the water replacement technique. P. radiata logs were sampled 1, 2.5, 6, and 9 years following harvesting, and logs of E. regnans and E. maculata were collected from sites that were harvested 1, 3.5, 6.5, and 12 and 1.5, 6.5, and 11.5 years ago, respectively. In addition, the C/N ratio of wood was determined and current respiration rates of logs from these different age classes were measured through laboratory incubation. The times for loss of 95% of material ( t 0.95 ) determined from density loss for these species were 24 years for P. radiata , 43 years for E. regnans , and 62 years for E. maculata . The decomposition rates of CWD derived from laboratory respiration were 6.1, 5.9 and 11.9 times higher than the decay rates from density loss in P. radiata , E. regnans , and E. maculata , respectively. This points to severe constraints of decomposition through adverse conditions in the field. The changes in respiration rates and C/N ratio with age of decaying logs indicated that the single component, negative exponential decay model could be applied satisfactorily only to P. radiata . In the case of the eucalypt species, substrate quality (expressed through respiration rates) declined in the oldest samples. This may be explained by the loss of rapidly decomposing sapwood and the retention of more decay-resistant heartwood. In these cases, a two-component model will be more suitable to describe the density loss of decaying wood.
    Keywords: Coarse Woody Debris ; Wood Density ; Wood Respiration ; Decomposition ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 3
    Language: English
    In: Soil Biology and Biochemistry, April 2019, Vol.131, pp.9-18
    Description: Functionally, ectomycorrhizal (ECM) and saprotrophic (SAP) fungi belong to different guilds, and they play contrasting roles in forest ecosystem C-cycling. SAP fungi acquire C by degrading the soil organic material, which precipitates massive CO release, whereas, as plant symbionts, ECM fungi receive C from plants representing a channel of recently assimilated C to the soil. In this study, we aim to measure the amounts and identify the drivers of ECM and SAP fungal biomass in temperate forest topsoil. To this end, we measured ECM and SAP fungal biomass in mineral topsoils (0–12 cm depth) of different forest types (pure European beech, pure conifers, and mixed European beech with other broadleaf trees or conifers) in a range of about 800 km across Germany; moreover, we conducted multi-model inference analyses using variables for forest and vegetation, nutritive resources from soil and roots, and soil conditions as potential drivers of fungal biomass. Total fungal biomass ranged from 2.4 ± 0.3 mg g (soil dry weight) in pure European beech to 5.2 ± 0.8 mg g in pure conifer forests. Forest type, particularly the conifer presence, had a strong effect on SAP biomass, which ranged from a mean value of 1.5 ± 0.1 mg g in broadleaf to 3.3 ± 0.6 mg g in conifer forests. The European beech forests had the lowest ECM fungal biomass (1.1 ± 0.3 mg g ), but in mixtures with other broadleaf species, ECM biomass had the highest value (2.3 ± 0.2 mg g ) among other forest types. Resources from soil and roots such as N and C concentrations or C:N ratios were the most influential variables for both SAP and ECM biomass. Furthermore, SAP biomass were driven by factors related to forest structure and vegetation, whereas ECM biomass was mainly influenced by factors related to soil conditions, such as soil temperature, moisture, and pH. Our results show that we need to consider a complex of factors differentially affecting biomass of soil fungal functional groups and highlight the potential of forest management to control forest C-storage and the consequences of changes in soil fungal biomass.
    Keywords: Ergosterol ; Pure and Mixed Forest Stands ; Soil Fungi ; Soil Carbon Pools ; Topsoil ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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