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.

Microwave L-band emission of freezing soil

Abstract: We report on field-measured microwave emission in a period of frost penetration into a grassland soil. The measurements were recorded with a high temporal resolution using an L-band radiometer mounted on a 7-m high tower. The observation period (December 2002 to March 2003) included two cycles of soil freezing and thawing with maximum frost depth of 25 cm. In situ soil temperature and liquid water content were measured at five depths down to 45 cm. Soil moisture profiles were calculated using the COUP numerical soil water and heat model in combination with measured soil properties and meteorological data monitored at the site. The L-band radiation data clearly showed the penetration and thawing of seasonal soil frost. We calculated soil reflectivities based on in situ measured and modeled soil moisture profiles by applying a coherent radiative transfer model. The calculated reflectivities were compared with the radiometrically determined soil reflectivities. It was demonstrated that the quantitative consistency between these reflectivities was significantly improved by applying an impedance matching approach accounting for surface effects. In this particular case, the dielectric structure of the uppermost soil horizon was largely influenced by soil roughness, vegetation, and snow cover. The radiometrically measured soil reflectivities were fitted using a radiative transfer model in combination with a roughness model assuming a soil surface roughness of 25 mm. The analysis during a period of frost penetration shows coherent behavior of the soil reflectivity. Temporal oscillation of the measured L-band radiation appears to be a coherent effect. This effect has the potential to be used for estimating the frost penetration velocity.

Trait differentiation and adaptation of plants along elevation gradients

Abstract: Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta-analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.

Carbon and Nitrogen Dynamics in Preferential Flow Paths and Matrix of a Forest Soil

Abstract: Natural abundance (δ) of the stable isotopes 13 C and 15 N has gained acceptance for studying C and N cycling in forests. In most studies, bulk soil samples are collected to determine isotope abundance. Such sampling overlooks the potential impact of preferential flow on isolope distribution. The objective of this study was to investigate the effects of preferential flow on the distribution of soil organic carbon (SOC), total N, δ 13 C, and δ 15 N in a forest soil in Central Switzerland. Preferential flow paths in the soil were identified with a dye tracer, Brilliant Blue (Pluss-Staufer AG, Oftringen, Switzerland), that was homogeneously applied to the soil surface. In the stained preferential flow paths, concentrations of SOC and total N were 15 to 75% higher than in the soil matrix. The total increase of SOC in preferential flow paths ranged from 740 to 960 g C m -2 in four individual soil plots. Values of δ 13 C and δ 15 N were lowest in tree leaves and in the forest floor, and inereased with soil depth, thus with the degree of decomposition of SOC. In the mineral soil, preferential flow paths were significantly depleted in 13 C by 0.15 to 0.4‰ as compared with the soil matrix. The δ 15 N values increased with soil depth from 0.9 to 4.7‰ in the preferential flow paths and from 0.5 to 6‰ in the soil matrix. Adding a highly enriched 15 N-tracer homogeneously to the soil surface showed a higher recovery of 15 N in the soil and in the fine roots sampled from preferential flow paths than in those sampled from the soil matrix. Our results suggest that in preferential flow paths, SOC is younger and N cycling is more rapid than in the soil matrix.