Reiner Giesler

The invisible carbon: an early indication of ecosystem change!

The invisible carbon: an early indication of ecosystem change!

Project Summary

Streams are sensitive sentinels for environmental change by their integration of processes in terrestrial and aquatic systems. Upland headwater streams in the north Swedish tundra show seasonally exceptional high concentrations of uncolored dissolved organic carbon (DOC) and high CO2 concentrations. We suggest that this reflects on-going changes in the terrestrial environment responding in their delivery of carbon (C) to the recipient aquatic systems. This is a hitherto unknown effect of a changing tundra landscape that will have large implications for the positive feedback on the global climate warming because of the large quantities of C that is stored in tundra soils. Current climate change mobilizes the stored C in upland tundra soils and cause a substantial increase in headwater stream C emissions and water-borne C losses.

We are studying stream CO2 fluxes mainly across a 42-km long stream network in the Miellajokka catchment near Abisko to better understand how stream functional traits and landscape features affects CO2 emissions. We are amongst others using different isotopic approaches (13C, 15N, 87Sr/86/Sr, 34S18O4 and water isotopes) and high-resolution measurements of stream CO2 and oxygen to disentangle different sources and processes that affects stream CO2 concentrations and emissions. We are also studying spatiotemporal variations in stream DOC across different tundra streams to unravel how different landscape features and hydrological conditions affect stream DOC concentrations, its degradability and qualitative characteristics. We are particularly interested in pulses of high stream DOC concentrations that has occurred irregularly during early autumns.


Carl-Magnus Mörth, Stockholm University
Steve Lyon, Stockholm University
Ann-Kristin Bergström, Umeå University
Ryan Sponseller, Umeå University
Jan Karlsson, Umeå University
Martin Berggren, Lund University
Gerard Rocher Ros, Umeå University

Funding organizations

The Swedish Research Council (VR) 2013-5001
FORMAS 2014-970



SITES is a nationally co-ordinated infrastructure for terrestrial and limnological field research.

SITES extends throughout Sweden with different ecosystems and climatic zones, from agriculture lands, forest, cultivated forest to mires, streams, lakes and alpines.

SITES offers all scientists to use participating field research stations. Either you can be on site yourself or outsource an assignment to the technical staff at the station. You also have the opportunity to use existing data collected at the stations. There are, in a number of areas of research, extensive and long series of data. Read more about what SITES provides here.


Within SITES three new infrastructures has been initiated and is now under development: SITES WaterSITES AquaNet och SITES Spectral.


Project Description

SITES Water aims to build a long-term and well-coordinated measurement program
that will form the basis for the infrastructure where hydrological, physical, chemical and biological parameters in lakes and streams will be measured.

SITES Water builds a unique long-term measurement program where hydrological, physical, chemical, and biological parameters within lakes and streams are measured. Based on this ‘backbone’ infrastructure SITES Water will thus provide data and facilities to address a broad range of scientific questions relevant for the scientific community.

Seven of SITES nine stations participate. SITES Water is either initiated as a new facility at some stations or built upon already existing stream/lake networks at some other stations. SITES Water share and competence develop the team/crews across stations working with these structures and data to deliver a state-of-the-art measurement program.  

SITES Water data

There are several types of data collected within SITES Water divided into six layers.

Each layer are described below and there specify well what type of data that are collected and distributed. All layers are divided into base and advance level where base level apply to all stations, and advance apply to some and are usually a result of already ongoing programs and built on previous knowledge at the station.

Site in abisko

Abisko scientific station is unique and versatile modern research station located app. 200 km north of the polar circle. The station has international standard and are used by a number of different research projects addressing high tech experiments in soil and water terrain. Abisko also provides measurement programs and observations for a number of different parameters. The surrounding environment is diverging both from a topographic perspective but also regarding climate gradients.

Researches in Abisko utilize the measurement programs and observational data series along with specific experiment and modelling to address questions mainly related to environment and climate change. Addressed time perspectives of these studies range from hundreds of millions of years back in time to different future scenarios.

Each year between 500 and 600 researchers from the whole world visit Abisko. The station provides lodging, guest kitchen, laboratories, offices, library, workshops, and lecture halls, meeting rooms, green house, “attempt gardens”, storage rooms and a meteorological station.

For access of observations and data from measurement programs in Abisko please contact the station manager, explore Abisko base program of parameters and sampling plots or visit Abisko-GIS (external homepage).

Abisko is part of SITES infrastructures SITES Water and SITES Spectral.

The homepage of Abisko can be found here.

Abisko researcher 

Reiner Giesler

Effects of reindeer on plant and soil nutrient stoichiometry in Arctic tundra

Effects of reindeer on plant and soil nutrient stoichiometry in Arctic tundra

Project Summary

Herbivores directly and indirectly influence the structure and function of ecosystems throughout the world. Present conceptual models predict that herbivores have a positive effect on nutrient availability and primary productivity in nutrient rich environments and a negative one in nutrient poor environments. However, a recent meta-analysis did not support a positive relationship between plant nutrient availability and the effect of herbivores on nitrogen cycling in several grassland ecosystems. The reason for the shortcoming of present theories could be that they fail to incorporate the complex interactions regulating the release of nutrients from the soil organic matter by microbial decomposers.

In order to assess this shortcoming, a new stoichiometric explicit model of the nutrition of herbivores, plants and microbes was designed. In contrast to previous models, it includes delayed composition and stoichiometric constraints on decomposers similar to what we find in terrestrial ecosystems.

This project will focus on 1) testing predictions of the model in a reindeer-dominated tundra ecosystem and 2) further developing the model by adding key processes that operate in northern ecosystems (e.g. uptake of organic nutrients by plants, herbivore-mediated changes in plant community composition).

Funding Organizations

The Kempe Foundation


Johan Olofsson, Umeå University
Mehdi Cherif, Umeå University

Microbial use of phosphorus in soils

Microbial use of phosphorus in soils

Project Summary

Globally, phosphorus (P) together with nitrogen (N) is the most important nutrient element limiting plant growth. In boreal forest ecosystems, P limitation is found in groundwater discharge areas and recent studies also indicate that many alpine ecosystems may be P limited. In this project I will study microbial strategies to utilize phosphate and organophosphorus compounds and the effect of surface sorption. One method that will be used is measurement of microbial respiration using a respicond. This is a microbial bioassay for studying the availability of P to microorganisms.

Ongoing studies

In the first project we sampled six different South African forest soils. The soils were selected to represent a broad range of soil properties, especially concerning aluminium, iron and organic carbon content. The respiration results will be compared to the amount of P in the soil to show how much of the total P pool that microorganisms can utilise and how the microbial availability is affected by iron and aluminium concentrations in the soil. This way we can compare in detail how different soil properties interact with microbial available P determined in the bioassay.

In the second ongoing study we sampled 30 islands in Lake Hornavan and Lake Uddjaur, situated close to Arjeplog in the boreal forest of Northern Sweden. The time since the last major fire vary between the islands and the wildfires form a chronosequence which is closely correlated to island size and vegetation succession (Wardle et al. 1997). Earlier results indicate increasing phosphorus limitation over time since the last fire (Wardle et al, 2004). During this study we will compare the different P and N pools with microbial growth kinetics in relation to island size and humus depth.