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Method development for d18O analysis of phloem content.

PI: Zsofia Reka Stangl

The isotope ratio of the sugars in the phloem sap of a tree directly represent the fractionation during photosynthesis (Anet) and stomatal conductance (gs) and integrate the signal from the whole canopy. d13C of phloem content has been repeatedly used to estimate canopy water-use efficiency, i.e. Anet/gs. The simultaneous analysis of d18O and d13C would enable us to evaluate if differences in d13C are due to changes in photosynthetic capacity or in stomatal conductance (gs). This method has the potential to be used as an indicator of growth and survival under various environmental conditions, for example in response to changes in ambient temperature and water availability. Such a diagnostic tool could be useful in predictions of forest growth, changes in species composition under future climates or to screen for more resilient genotypes in forestry species. However, the analysis of d18O in phloem sugars is problematic. If sucrose breaks down during the extraction, the molecules exchange oxygen with the extraction medium, altering so the d18O of the sugars. In this project I propose to develop an optimised method for sampling and extraction of phloem content for oxygen isotope analysis, considering a set of extraction conditions, extraction time, sample preparation methods and sampling position along the stem. I will use phloem samples from mature Scots pine trees during the optimisation of the extraction method and finally compare Scots pine, Norway spruce and Silver birch when assessing the importance of the vertical sampling position along the stem. The method development will be executed in close collaboration with Jonas Lundholm at the SLU Stable Isotope Laboratory, who is an expert in analytical chemistry and oxygen isotope analysis. The field work will be done with the assistance from the staff at the Svartberget field station.

isotopic compositionstem profileisotope ratio

Soil CO2 concentration

PI: Marie Spohn

While fluxes of CO2 from the soil to the atmosphere have been studied intensively, relatively little is known about the CO2 concentration in soils. The CO2 concentration in soils is typically much higher than in the atmosphere and it might strongly affect several soil chemical and biological processes. The aim of this project is therefore to better understand how the CO2 concentration in soils changes over time and the biotic and abiotic factors that cause these changes. For this purpose, the CO2 concentration is monitored at high frequency in soils in different ecosystems, located along a climate gradient from North to South Sweden.

Soil CO2 concentrationCO2 sensorsclimate gradient

Rethinking recovery rates from mercury (Hg) pollution by reconciling evasion of legacy Hg pollution from peatlands with historical records of Hg accumulation and isotope signatures in peat profiles

PI: Chuxian Li

Anthropogenic mercury (Hg) emissions to the atmosphere have increased the concentration of this potent neurotoxin in terrestrial and aquatic ecosystems. Efforts to control this pollution have reduced atmospheric concentrations of gaseous elemental mercury (GEM) over Fennoscandia by 50% in the past 30 years. The first annual Hg mass-balance for a boreal peatland that measured peat-atmosphere exchange revealed so much evasion of the Hg pollution legacy from the peat back to the atmosphere that the mire will have recovered in decades, rather than in centuries as previously assumed. Producing this mass balance was a methodological challenge, but explaining it presents a scientific challenge. We propose that the long history of atmospheric Hg pollution, followed by sharp reductions in atmospheric Hg concentrations, switched the peatland from being a net accumulator of atmospheric Hg for millennia to suddenly becoming a net GEM emitter to the surrounding environment. We propose to test whether a recent reversal in the direction of Hg exchange between peatlands and atmosphere can be modeled by changing GEM concentrations. This model will be constrained by historical peat archives of Hg concentration and isotopic composition, as well as novel measurements of pore atmosphere Hg isotopes. This will provide information on the effectiveness of Hg emission controls for reducing Hg contamination in freshwater fish where peatlands influence aquatic Hg bioaccumulation.

Hg isotopespeatevasionmercuryisotopes

Reference climate monitoring at the Experimental Forests

PI: Ola Langvall

Reference climate monitoring takes place at all experimental forests (only during the summer in Ätnarova). It got its common design in 1989 and started routinely in January 1990. The basic measurement comprise air and ground temperatures, humidity, global radiation and precipitation. Measurement data is automatically processed for forestry applications. Climate data from the reference stations is stored and available at the respective experimental park and at Vindelns experimental parks.

climateweathertemperaturetimeserieslong timeseriesmonitoring

Undersvik

PI: Hjalmar Laudon

Forest fertilisation and nutrient leakage

Fertilizationnutrient leakageSveaskog

Vertical and horizontal patterns of pine root water and nitrogen uptake

PI: John Marshall

This project uses isotopic labels to describe the depth and breadth of root activity. The work involves adding the label to plots, monitoring the passage of the water label through the stems, monitoring the accumulation of nitrogen in the canopy, and measuring the deuterium labelling of stem wood in the trees around the plots. The understory vegetation and any mushrooms will also be described, as will patterns of soil water isotopic labelling.

Rootverticalhorizontal

Estimating GPP from stable isotopes and sapflux

PI: John Marshall

Working with Niles, Natalia, Jose, and Kersti, we have measured sapflux and the stable isotope composition of phloem sap around the tall tower at Svartberget. We will use these data to estimate GPP and compare these estimates to those from eddy flux and from Kersti's model. For precise work, this method requires knowledge of the isotopic composition of CO2 in the tree canopy. We aim to set up this measurement on the tall tower by attaching a Picarro CO2 isotope analyzer to the tower inlets.

GPPsap fluxisotopes

Trollberget regular stream sampling

PI: Eliza Maher Hasselquist

Monitoring of water chemistry in several streams. Sampling twice per week with increased frequency during the spring flood.

stream waterchemistrycatchment

Degerö regular stream sampling

PI: Mats Nilsson

Monitoring of water chemistry in several streams. Sampling twice per week with increased frequency during the spring flood.

stream waterchemistrycatchment

The Umeå Aspen (UmAsp) Collection

PI: Stefan Jansson

The Umeå Aspen (UmAsp) collection is a population of aspen trees (Populus tremula) from around the Umeå kommun, collected and cloned into two contrasting common gardens: one site closer to the coast at Skogforsk in Sävar and one at the inland, higher elevation site at Kulbäcksliden near Vindeln. Aspen is a model species for forest tree genetics and has high value in forest ecosystems. The purpose of the collection is to study natural genetic variation in traits including physiology, phenology, growth and biotic interactions. We have DNA sequencing data for all UmAsp individuals to enable population genetics studies, and together with phenotype data we are conducting genome-wide association mapping to identify and genetic variants associated with each phenotype. The two gardens facilitate validation of our findings in different environments and examination of genotype-by-environment interactions of the phenotypes studied. Principal Investigator: Stefan Jansson. Field trials manager: Kathryn Robinson.

aspengeneticspopulation

Isotope-informed hydrological modeling

PI: Kevin Bishop

Dr. Ali Ameli, Univ of British Columbia, is using the rainfall, runoff, PET and hydrological isotope data that the Krycklan/Svartberget monitoring programs have collected over the years. The project seeks to better constrain the modelling of runoff processes using the isotopes of water

equifinalityhydrological modelingstable isotopes of water