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.

Increased N deposition retards mineralization of old soil organic matter

Abstract: The aim of this study was to investigate the effects of increased N deposition on new and old pools of soil organic matter (SOM). We made use of a 4-yr experiment, where spruce and beech growing on an acidic loam and a calcareous sand were exposed to increased N deposition (7 vs. 70 kg N ha −1 yr −1 ) and to elevated atmospheric CO 2 . The added CO 2 was depleted in 13 C, which enabled us to distinguish between old and new C in SOM-pools fractionated into particle sizes. Elevated N deposition for 4 yr increased significantly the contents of total SOM in 0–10 cm depth of the acidic loam (+9%), but not in the calcareous sand. Down to 25 cm soil depth, C storage in the acidic loam was between 100 and 300 g C m −2 larger under high than under low N additions. However, this increase was small as compared with the SOM losses of 600–700 g C g C 0.25 m −1 m −2 from the calcareous sand resulting from the disturbance of soils during setting up of the experiment. The amounts of new, less than 4 yr old SOM in the sand fractions of both soils were greater under high N deposition, showing that C inputs from trees into soils increased. Root biomass in the acidic loam was larger under N additions (+25%). Contents of old, more than 4 yr old C in the clay and silt fractions of both soils were significantly greater under high than under low N deposition. Since clay- and silt-bound SOM consists of humified compounds, this indicates that N additions retarded mineralization of old and humified SOM. The retardation of C mineralization in the clay and silt fraction accounted for 60–80 g C m −2 4 yr −1 , which corresponds to about 40% of the old SOM mineralized in these fraction. As a consequence, preservation of old and humified SOM under elevated N deposition might be a process that could lead to an increased soil C storage in the long-term.

Genetic variation within and among populations of the threatened lichen Lobaria pulmonaria in Switzerland and implications for its conservation

Abstract: The foliose epiphytic lichen Lobaria pulmonaria has suffered a significant decline in European lowlands during the last decades and therefore is considered as endangered throughout Europe. An assessment of the genetic variability is necessary to formulate biologically sound conservation recommendations for this species. We investigated the genetic diversity of the fungal symbiont of L. pulmonaria using 143 specimens sampled from six populations (two small, one medium, three large) in the lowland, the Jura Mountains, the pre-Alps and the Alps of Switzerland. Among all nuclear and mitochondrial regions sequenced for this study, variability was found only in the internal transcribed spacer (ITS I), with three polymorphic sites, and in the nuclear ribosomal large subunit (nrLSU), with four polymorphic sites. The variable sites in the nrLSU are all located within a putative spliceosomal intron. We sequenced these two regions for 81 specimens and detected six genotypes. Two genotypes were common, two were found only in the more diverse populations and two were found only in one population each. There was no correlation between population size and genetic diversity. The highest genetic diversity was found in populations where the fungal symbiont is reproducing sexually. Populations with low genetic diversity included only the two same common genotypes. Our study provides evidence suggesting that L. pulmonaria is self-incompatible and heterothallic. Based on our results we give populations with sexually reproducing individuals a higher rank in terms of conservation priority than strictly asexual populations. The remaining lowland populations are so small, that one single catastrophic event such as a windthrow might destroy the entire population. Hence we suggest augmenting such populations in size and genetic diversity using small thallus fragments or vegetative diaspores collected in other populations. As we did not detect any locally adapted genotypes, these transplants can be taken from any other genetically diverse population in Switzerland.

Temperature-dependent reproduction of the spruce bark beetle Ips typographus, and analysis of the potential population growth

Abstract: The spruce bark beetle Ips typographus (L.) is one of the most important forest pests in Central Europe, but despite this the effects of temperature on life history and population growth are largely unknown. This study examines the effects of temperature on reproduction and intrinsic demographic statistics. 2. Laboratory experiments on oviposition were carried out at six temperatures in the range 12-33 ∞C, using the so-called sandwich rearing technique for bark beetles. 3. A linear relationship between oviposition rates and temperatures in the range 15-25 ∞C was used to estimate the lower temperature threshold for oviposition as 11.4 ∞C. With a nonlinear model fitted to the data across the whole range of experimental temperatures, the lower and upper limiting temperatures and optimum temperature were found to be 7.9, 33.7, and 28.9 ∞C, respectively. A model for daily oviposition rate was fitted, which describes the pattern of oviposition over the entire oviposition period. 4. The analysis of life tables, combining developmental rates, reproduction, mortality, and sex ratio, suggests maximum population growth (rm) at near 30 ∞C. 5. After generating a first brood, spruce bark beetles often re-emerge from the tree and produce other sister broods. The effects of temperature and number of sister broods on demography were evaluated using age-specific life-table analyses. It is hypothesized that sister broods play an important role in regions where I. typographus is monovoltine, but have only moderate significance where this species has more than one generation per season.

Evaluation of digital soil mapping approaches with large sets of environmental covariates

Abstract: . The spatial assessment of soil functions requires maps of basic soil properties. Unfortunately, these are either missing for many regions or are not available at the desired spatial resolution or down to the required soil depth. The field-based generation of large soil datasets and conventional soil maps remains costly. Meanwhile, legacy soil data and comprehensive sets of spatial environmental data are available for many regions. Digital soil mapping (DSM) approaches relating soil data (responses) to environmental data (covariates) face the challenge of building statistical models from large sets of covariates originating, for example, from airborne imaging spectroscopy or multi-scale terrain analysis. We evaluated six approaches for DSM in three study regions in Switzerland (Berne, Greifensee, ZH forest) by mapping the effective soil depth available to plants (SD), pH, soil organic matter (SOM), effective cation exchange capacity (ECEC), clay, silt, gravel content and fine fraction bulk density for four soil depths (totalling 48 responses). Models were built from 300–500 environmental covariates by selecting linear models through (1) grouped lasso and (2) an ad hoc stepwise procedure for robust external-drift kriging (georob). For (3) geoadditive models we selected penalized smoothing spline terms by component-wise gradient boosting (geoGAM). We further used two tree-based methods: (4) boosted regression trees (BRTs) and (5) random forest (RF). Lastly, we computed (6) weighted model averages (MAs) from the predictions obtained from methods 1–5. Lasso, georob and geoGAM successfully selected strongly reduced sets of covariates (subsets of 3–6 % of all covariates). Differences in predictive performance, tested on independent validation data, were mostly small and did not reveal a single best method for 48 responses. Nevertheless, RF was often the best among methods 1–5 (28 of 48 responses), but was outcompeted by MA for 14 of these 28 responses. RF tended to over-fit the data. The performance of BRT was slightly worse than RF. GeoGAM performed poorly on some responses and was the best only for 7 of 48 responses. The prediction accuracy of lasso was intermediate. All models generally had small bias. Only the computationally very efficient lasso had slightly larger bias because it tended to under-fit the data. Summarizing, although differences were small, the frequencies of the best and worst performance clearly favoured RF if a single method is applied and MA if multiple prediction models can be developed.

Mapping snow depth in alpine terrain with unmanned aerial systems (UASs): potential and limitations

Abstract: . Detailed information on the spatiotemporal snow depth distribution is a crucial input for numerous applications in hydrology, climatology, ecology and avalanche research. Today, snow depth distribution is usually estimated by combining point measurements from weather stations or observers in the field with spatial interpolation algorithms. However, even a dense measurement network like the one in Switzerland, with more than one measurement station per 10 km2 on average, is not able to capture the large spatial variability of snow depth present in alpine terrain. Remote sensing methods, such as laser scanning or digital photogrammetry, have recently been successfully applied to map snow depth variability at local and regional scales. However, in most countries such data acquisition is costly if manned airplanes are involved. The effectiveness of ground-based measurements on the other hand is often hindered by occlusions, due to the complex terrain or acute viewing angles. In this paper, we investigate the application of unmanned aerial systems (UASs), in combination with structure-from-motion photogrammetry, to map snow depth distribution. Compared to manual measurements, such systems are relatively cost-effective and can be applied very flexibly to cover terrain not accessible from the ground. In this study, we map snow depth at two different locations: (a) a sheltered location at the bottom of the Fluela valley (1900 m a.s.l.) and (b) an exposed location on a peak (2500 m a.s.l.) in the ski resort Jakobshorn, both in the vicinity of Davos, Switzerland. At the first test site, we monitor the ablation on three different dates. We validate the photogrammetric snow depth maps using simultaneously acquired manual snow depth measurements. The resulting snow depth values have a root mean square error (RMSE) of less than 0.07 to 0.15 m on meadows and rocks and a RMSE of less than 0.30 m on sections covered by bushes or tall grass, compared to manual probe measurements. This new measurement technology opens the door for efficient, flexible, repeatable and cost-effective snow depth monitoring over areas of several hectares for various applications, if the national and regional regulations permit the application of UASs.