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.

Persistent high temperature and low precipitation reduce peat carbon accumulation.

Abstract: Extreme climate events are predicted to become more frequent and intense. Their ecological impacts, particularly on carbon cycling, can differ in relation to ecosystem sensitivity. Peatlands, being characterized by peat accumulation under waterlogged conditions, can be particularly sensitive to climate extremes if the climate event increases soil oxygenation. However, a mechanistic understanding of peatland responses to persistent climate extremes is still lacking, particularly in terms of aboveground-belowground feedback. Here, we present the results of a transplantation experiment of peat mesocosms from high to low altitude in order to simulate, during 3years, a mean annual temperature c. 5 degrees C higher and a mean annual precipitation c. 60% lower. Specifically, we aim at understanding the intensity of changes for a set of biogeochemical processes and their feedback on carbon accumulation. In the transplanted mesocosms, plant productivity showed a species-specific response depending on plant growth forms, with a significant decrease (c. 60%) in peat moss productivity. Soil respiration almost doubled and Q(10) halved in the transplanted mesocosms in combination with an increase in activity of soil enzymes. Spectroscopic characterization of peat chemistry in the transplanted mesocosms confirmed the deepening of soil oxygenation which, in turn, stimulated microbial decomposition. After 3years, soil carbon stock increased only in the control mesocosms whereas a reduction in mean annual carbon accumulation of c. 30% was observed in the transplanted mesocosms. Based on the above information, a structural equationmodel was built to provide a mechanistic understanding of the causal connections between peat moisture, vegetation response, soil respiration and carbon accumulation. This study identifies, in the feedback between plant and microbial responses, the primary pathways explaining the reduction in carbon accumulation in response to recurring climate extremes in peat soils.

Early stage litter decomposition rates for Swiss forests

Abstract: The decomposition of belowground and aboveground tree litter was studied on five forest sites across Switzerland, ranging from 480 to 1500 m in altitude, and including calcareous and acidic soils. In addition to decomposition of local litter types (Picea abies, Fagus sylvatica, Castanea sativa), the decomposition of a standard beech litter was studied on all sites. After 2 years of decomposition, mass loss ranged from 18 to 71% across the different sites and litter types. The lowest decomposition rates were observed for beech roots, while mass loss was greatest for both spruce needles and spruce roots at the low-altitude site. Mass loss during the first winter correlated best with the content of water-soluble substances. After 1 year of incubation, mass loss of the standard litter varied less than did mass loss of local litter, but variance increased during the second year for aboveground litter. These observations indicate a smaller climatic influence on litter breakdown at the beginning of the decomposition process. Litter mass loss could be described using an exponential model with a decay constant depending on either lignin/N ratio or Mn content of the litter and annual soil temperature and throughfall precipitation as climatic variables. Modelling the observed mass loss indicated a strong influence of litter quality in the first 2 years of decomposition, confirming the field data from the standard litter experiment. The experiment will continue for some years and is expected to yield additional data on long-term decomposition.

Experimental warming interacts with soil moisture to discriminate plant responses in an ombrotrophic peatland

Abstract: Question A better understanding of the response of Sphagnum mosses and associated vascular plants to climate warming is relevant for predicting the carbon balance of peatlands in a warmer world. Open-top chambers (OTCs) have been used to investigate the effect on soil biogeochemical processes in peatlands, but little information is available on the effects of OTCs on microclimate conditions and the associated response of the plant community. We aimed to understand how simulated warming and differences in soil moisture affect plant species cover. Location A Sphagnum-dominated peatlands in French Jura. Methods We used OTCs to measure the effect of a near-ground temperature increase (+1.5 °C on average) on vegetation dynamics over five growing seasons (2008–2012) in a Sphagnum-dominated peatland, in two adjacent microhabitats with different hydrological conditions – wet and dry. Microclimatic conditions and plant species abundance were monitored at peak biomass in years 1, 2, 3 and 5 and monthly during the plant growing season in year 5. Results The response to warming differed between vascular plants and bryophytes, as well as among species within these groups, and also varied in relation to soil moisture. Andromeda polifolia abundance responded positively to warming, while Vaccinium oxycoccus responded negatively, and Eriophorum vaginatum showed a high resistance. Conclusion Depth of rooting of vascular plants appeared to control the response in plant abundance, while moss abundance depended on various other interacting factors, such as shading by the vascular plant community, precipitation and soil moisture.