Swiss Federal Institute for Forest, Snow and Landscape Research

About: Swiss Federal Institute for Forest, Snow and Landscape Research is a facility organization based out in Birmensdorf, Switzerland. It is known for research contribution in the topics: Climate change & Soil water. The organization has 1256 authors who have published 3222 publications receiving 161639 citations. The organization is also known as: WSL.

Spatial and temporal variation in organic acid anion exudation and nutrient anion uptake in the rhizosphere of Lupinus albus L.

Abstract: We investigated in situ the temporal patterns and spatial extent of organic acid anion exudation into the rhizosphere solution of Lupinus albus, and its relation with the nutrient anions phosphate, nitrate and sulfate by means of a rhizobox micro suction cup method under P sufficient conditions. We compared the soil solution in the rhizosphere of cluster roots with that in the vicinity of normal roots, nodules and bulk soil. Compared to the other rhizosphere and soil compartments, concentrations of organic acid anions were higher in the vicinity of cluster roots during the exudative burst (citrate, oxalate) and nodules (acetate, malate), while concentrations of inorganic nutrient anions were highest in the bulk soil. Both active cluster roots and nodules were most efficient in taking up nitrate and phosphate. The intensity of citrate exudation by cluster roots was highly variable. The overall temporal patterns during the lifetime of cluster roots were overlaid by a diurnal pattern, i.e. in most cases, the exudation burst consisted of one or more peaks occurring in the afternoon. Multiple exudation peaks occurred daily or were separated by 1 or 2 days. Although citrate concentrations decreased with distance from the cluster root apex, they were still significantly higher at a distance of 6 to 10 mm than in the bulk soil. Phosphate concentrations were extremely variable in the proximity of cluster roots. While our results indicate that under P sufficient conditions cluster roots take up phosphate during their entire life time, the influence of citrate exudation on phosphate mobilization from soil could not be assessed conclusively because of the complex interactions between P uptake, organic acid anion exudation and P mobilization. However, we observed indications of P mobilization concurrent with the highest measured citrate concentrations. In conclusion, this study provides semiquantitative in situ data on the reactivity of different root segments of L. albus L. in terms of root exudation and nutrient uptake under nutrient sufficient conditions, in particular on the temporal variability during the lifetime of cluster roots.

Trophic level modulates carabid beetle responses to habitat and landscape structure: a pan‐European study

Abstract: 1. Anthropogenic pressures have produced heterogeneous landscapes expected to influence diversity differently across trophic levels and spatial scales. 2. We tested how activity density and species richness of carabid trophic groups responded to local habitat and landscape structure (forest percentage cover and habitat richness) in 48 landscape parcels (1 km2) across eight European countries. 3. Local habitat affected activity density, but not species richness, of both trophic groups. Activity densities were greater in rotational cropping compared with other habitats; phytophage densities were also greater in grassland than forest habitats. 4. Controlling for country and habitat effects we found general trophic group responses to landscape structure. Activity densities of phytophages were positively correlated, and zoophages uncorrelated, with increasing habitat richness. This differential functional group response to landscape structure was consistent across Europe, indicated by a lack of a country × habitat richness interaction. Species richness was unaffected by landscape structure. 5. Phytophage sensitivity to landscape structure may arise from relative dependency on seed from ruderal plants. This trophic adaptation, rare in Carabidae, leads to lower phytophage numbers, increasing vulnerability to demographic and stochastic processes that the greater abundance, species richness, and broader diet of the zoophage group may insure against.

Conifers depend on established roots during drought: results from a coupled model of carbon allocation and hydraulics.

Abstract: Trees may survive prolonged droughts by shifting water uptake to reliable water sources, but it is unknown if the dominant mechanism involves activating existing roots or growing new roots during drought, or some combination of the two. To gain mechanistic insights on this unknown, a dynamic root-hydraulic modeling framework was developed that set up a feedback between hydraulic controls over carbon allocation and the role of root growth on soil-plant hydraulics. The new model was tested using a 5 yr drought/heat field experiment on an established pinon-juniper stand with root access to bedrock groundwater. Owing to the high carbon cost per unit root area, modeled trees initialized without adequate bedrock groundwater access experienced potentially lethal declines in water potential, while all of the experimental trees maintained nonlethal water potentials. Simulated trees were unable to grow roots rapidly enough to mediate the hydraulic stress, particularly during warm droughts. Alternatively, modeled trees initiated with root access to bedrock groundwater matched the hydraulics of the experimental trees by increasing their water uptake from bedrock groundwater when soil layers dried out. Therefore, the modeling framework identified a critical mechanism for drought response that required trees to shift water uptake among existing roots rather than growing new roots.

Elevated atmospheric CO2 and increased N deposition effects on dissolved organic carbon—clues from δ13C signature

Abstract: In the last growing season of a 4-yr experiment, the effects of elevated atmospheric CO 2 (370 vs. 570 μmol CO 2 mol −1 ) and increased N deposition (0.7 vs. 7 g N m −2 yr −1 ) on concentrations, fluxes, and properties of dissolved organic carbon (DOC) were investigated in two different forest soils. Model ecosystems with spruce and beech were established in large open-top chambers with lysimeters containing an acidic loam and calcareous sand. The added CO 2 was depleted in 13 C and thus, the net input of new C into soil organic matter (SOM) and DOC could be quantified. The effects of elevated CO 2 and increased N deposition on concentrations and properties of DOC collected with suction cups at 5–10 cm depth were negligible. Export of DOC by drainage was reduced under elevated CO 2 in the calcareous sand (−22%), but as concentrations were unaffected this was a secondary effect of a reduced drainage. The differences in DOC between the two soils were large, indicating that soil properties had a greater influence on DOC than the CO 2 and N induced changes in above- and below-ground biomass. This was probably caused by the low input of ‘new’, less than 4-yr-old C into DOC. At 5–10 cm depth, the fraction of new C was 5±1% of total DOC in the acidic loam and 8±1% in the calcareous sand under elevated CO 2 . This indicates that potential sources of new C such as throughfall, litter leaching, and rhizodeposits made minor direct contributions to the DOC of the soil solution during the four experimental years. The fractions of new C in DOC at 5–10 cm depth were significantly smaller than those in SOM at 0–10 cm depth, which accounted for 22±2% of total SOM in the acidic loam and for 17±2% in the calcareous sand. The fractions of new C in water-soluble organic C (WSOC) of the bulk soil at 0–10 cm (25–29%) were larger than in DOC, showing that the origins of WSOC and DOC were different. The losses of new C through drainage (30 mg C m −2 yr −1 ) were small in comparison to the net input of new C into SOM (240–400 g C m −2 4 yr −1 at 0–10 cm depth). This strongly suggests that exports of DOC are not a major part of the ‘missing carbon sink’.