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  • 1
    Language: English
    In: Forest Ecology and Management, 15 November 2015, Vol.356, pp.136-143
    Description: Phosphorus is an essential yet scarce macronutrient, and as such forest nutrition often relies on cycling of P between biomass and soils through litterfall and roots. For technical and soil protection reasons, modern harvesting systems create thick brash mats on skid trails by depositing residues, thus concentrating P there. What portion of this redistributed P is immobilized, lost, or recycled could be significant to forest nutrition and management. However, open questions exist regarding the quantity and fate of P deposited on skid trials. The aim of this study was to determine how much P is redistributed to skid trails and what happens to that P. We modeled the amount of P deposited on a skid trail during a whole-tree thinning of an Mill. stand, and quantified P stocks in the forest floor and mineral soil five years after the operation. An estimated 60% of harvested P from the encatchment was deposited on the skid trail. Five years after the harvest, forest floor P stocks in the skid trail dropped from an extrapolated 8.9 to 4.4 g m . The difference of 4.5 g m of P was not evident in mineral soil stocks, and loss through runoff or leaching would be minimal. With the greatest concentration of roots in the forest floor on the middle of the skid trail, mineralization and uptake of the missing P was the most likely explanation. This suggests that accumulated P on skid trails can be recycled through uptake by trees. Further testing in other stands and on which vegetation takes up accumulated P is still needed.
    Keywords: Nutrient Cycling ; Plant Uptake ; Whole-Tree Harvesting ; Brash Mats ; Allometric Modeling ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Language: English
    In: Forests, 01 June 2017, Vol.8(6), p.193
    Description: While differences in greenhouse gas (GHG) fluxes between ecosystems can be explained to a certain degree, variability of the same at the plot scale is still challenging. We investigated the spatial variability in soil-atmosphere fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) to find out what drives spatial variability on the plot scale. Measurements were carried out in a Scots pine (Pinus sylvestris L.) forest in a former floodplain on a 250 m2 plot, divided in homogenous strata of vegetation and soil texture. Soil gas fluxes were measured consecutively at 60 points along transects to cover the spatial variability. One permanent chamber was measured repeatedly to monitor temporal changes to soil gas fluxes. The observed patterns at this control chamber were used to standardize the gas fluxes to disentangle temporal variability from the spatial variability of measured GHG fluxes. Concurrent measurements of soil gas diffusivity allowed deriving in situ methanotrophic activity from the CH4 flux measurements. The soil emitted CO2 and consumed CH4 and N2O. Significantly different fluxes of CH4 and CO2 were found for the different soil-vegetation strata, but not for N2O. Soil CH4 consumption increased with soil gas diffusivity within similar strata supporting the hypothesis that CH4 consumption by soils is limited by the supply with atmospheric CH4. Methane consumption in the vegetation strata with dominant silty texture was higher at a given soil gas diffusivity than in the strata with sandy texture. The same pattern was observed for methanotrophic activity, indicating better habitats for methantrophs in silt. Methane consumption increased with soil respiration in all strata. Similarly, methanotrophic activity increased with soil respiration when the individual measurement locations were categorized into silt and sand based on the dominant soil texture, irrespective of the vegetation stratum. Thus, we suggest the rhizosphere and decomposing organic litter might represent or facilitate a preferred habitat for methanotrophic microbes, since rhizosphere and decomposing organic are the source of most of the soil respiration.
    Keywords: Methane ; Carbon Dioxide ; Nitrous Oxide ; Soil Gases ; Methanotrophy ; Soil Texture ; Forestry
    E-ISSN: 1999-4907
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  • 6
    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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