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Fr.om. januari 2020 publicerar SITES nyheter enbart på engelska

Sampling GHG chambers at Stortjärn (Svartberget). Photo: Andreas Palmén Sampling GHG chambers at Stortjärn (Svartberget). Photo: Andreas Palmén
As part of the SITES Water monitoring program, floating chambers are used to determine greenhouse gas (GHG) emissions of carbon dioxide (CO2) and methane (CH4) from lakes. The GHG program is conducted at five stations (Abisko, Asa, Erken, Skogaryd and Svartberget) and runs throughout the open water season. The sampling strategy, three transects each with four chambers spread across a depth interval, is based on the lake depth structure and is individual for the different stations. Since the lakes are spread across different climate gradients, the open water season varies, with lakes located in southern Sweden able to start the program earlier in the year.   
Chamber placed on Erssjön (Skogaryd)  Photo: Siva Natchimuthu
Chamber placed on Erssjön (Skogaryd) Photo: Siva Natchimuthu
A drone in action at Lönnstorp. Photo: Lars Eklundh. A drone in action at Lönnstorp. Photo: Lars Eklundh.
As part of SITES Spectral, the SITES stations operate drones in the form of small helicopters, equipped with RGB and multispectral cameras.

RGB cameras are useful for mapping the ground in natural colors in 3-D. Multispectral cameras record images in several wavelengths, including near-infrared, and are useful for monitoring vegetation conditions. Depending on camera type and flying conditions, data need to be calibrated to provide accurate data for quantifying vegetation amount.

Per-Ola Olsson, researcher at Lund University, and collaborators have carried out an analysis of errors related to calibration, and developed a methodology for calibration that minimizes variations related to incoming light fluctuations. The analysis shows that calibration is an important step to be carried out before quantitative analyses of multispectral data from drones.

The results and useful guidelines for how to carry out the calibration were recently published in the open access journal Remote Sensing.

Reference
Olsson, P.-O., A. Vivekar, K. Adler, V. E. Garcia Millan, A. Koc, M. Alamrani & L. Eklundh (2021) Radiometric Correction of Multispectral UAS Images: Evaluating the Accuracy of the Parrot Sequoia Camera and Sunshine Sensor. Remote Sensing, 13, 577.
The SITES AquaNet platform at Svartberget. Photo: Johannes Tiwari. The SITES AquaNet platform at Svartberget. Photo: Johannes Tiwari.
The AquaNet team, led by the programme coordinator Silke Langenheder, are proud and happy to announce that a detailed description of the SITES AquaNet infrastructure has now been published in Limnology & Oceanography Methods!


SITES AquaNet offers:

  1. openness to the scientific community
  2. the possibility to use natural lake communities for experiments
  3. the possibility to conduct and participate in modularized experiments across time and space
  4. high frequency sensor systems
  5. expert support by our technical staff and
  6. access to data from the accompanying monitoring programme SITES Water.

To test the infrastructure we conducted a modularized experiment along the latitudinal gradient offered by the five lakes included in SITES AquaNet. More specifically, we manipulated a press disturbance (light reduction) and a pulse disturbance (temporary presence of fish in the mesocosms). With this we could demonstrate the suitability of the infrastructure and autonomous sensor system to host modularized experiments and provide a good example of the power and advantages of such experiments.


Publication (open access)
Urrutia-Cordero, P., Langvall, O., Blomkvist, P., Angeler, D., Bertilsson, S., Colom Montero, W., Eklöv, P., Aagaard Jakobsen, N., Klemedtsson, L., Laudon, H., Liljebladh, B., Lundgren, M., Parkefelt, L., Kelpsiene, E., Pierson, D., Rankinen, J., Striebel, M., Tranvik, L.J., Weslien, P., Hillebrand, H. and Langenheder, S. (2021), SITES AquaNet: An open infrastructure for mesocosm experiments with high frequency sensor monitoring across lakes. Limnol Oceanogr Methods.

Svartberget field technicians Hassan Ridha and Ellika Hermansson measure the growth and overall condition of spruce trees in a previous trial. Photo: Andreas Palmén. Svartberget field technicians Hassan Ridha and Ellika Hermansson measure the growth and overall condition of spruce trees in a previous trial. Photo: Andreas Palmén.
Cooperation with landowners is vital for SITES research focused on sustainable forest management. For example, in a new silviculture project, researchers from SLU, in cooperation with Skogforsk and forest companies, will take an experimental and novel approach on the establishment of pine stands in northern Sweden. Field technicians from Svartberget Research Station will be responsible for the establishment and future monitoring of the field trials.

In total, 19 silvicultural trials will be established over a period of two years on forestland of varying fertility. For some trials, many years have passed since the actual felling. The aim is to study the long-term effects of tree species, soil preparation, reforestation method and plant-fertilization.

Recent inventories of young stands in the interior of Norrland have revealed low stem and quality stem numbers per hectare. In particular, many young pine stands show trees severely damaged by, among other things, moose grazing and fungal infections. The so called multi-damaged pine forests means a large loss in future production. In some cases, the stands are so damaged that the best option is to start all over again. This is very costly for landowners and there is no guarantee that the same problems won’t arise again.

Thus, it is important to avoid previous mistakes in silviculture. The experiments will compare several potential establishment alternatives to improve the knowledge of producing young stands.

Two main alternatives will be tested. One based on various measures to accelerate the height growth of the pine plants which would reduce the time they are susceptible to moose grazing. Using an excavator to prepare mounds that allow for group planting is one such example.

The other alternative to be tested is the use of other tree species like Norway spruce, Silver birch, Russian larch (a.k.a. Siberian larch) and Lodgepole pine. Species comparisons in production are either rare or unfavourable. Spruce suffer less from grazing and are not sensitive to the fungal damages that affect pine. To avoid the low production of spruce compared to pine seen on many locations in the interior of Norrland, plant fertilization of spruce will be tested. Birch is relatively untested in the area, while stands with Russian larch often have shown good results in growth but comparisons are lacking. Experimental results and experience regarding site selection and silvicultural methods are very limited for both. Lodgepole pine is relatively common in the area and avoided by game for grazing.

There are extensive trials where the higher long-term production of Lodgepole pine compared to Scots pine is evident, but the wood quality and stability of planted Lodgepole pine on fertile soil may be questionable. Mixed sowing of pine and Lodgepole pine can therefore be a way to increase the probability of having a high production stock with a sufficiently high number of undamaged stem.
Location of the deployed pressure gauge south of Bolmsö island.  The pressure gauge was installed at a water depth of approximate 1 m. Photo: Clemens Klante. Location of the deployed pressure gauge south of Bolmsö island. The pressure gauge was installed at a water depth of approximate 1 m. Photo: Clemens Klante.
In a new project, the wave climate at Lake Bolmen will be investigated to gain new insights about the hydrodynamics of the lake and the waves’ effect on water quality. Recent measurements of water pressure will be used to help to calibrate and validate wave models, which will be a helpful asset for analysis of current and future conditions.

Lake Bolmen is Skåne’s most important drinking water resource. The lake’s ecology and chemical status has changed during the last decades and some of these changes could negatively affect water quality. One of the most noticeable changes is the effect of brownification, resulting in yellow to brown colored water due to the increase of humic substances and iron leachate from the catchment. One aim of the Bolmen Research station is to create knowledge that helps to sustain Bolmen as reliable water resource, ecosystem and place for recreation. Therefore, further insight into changes to water quality is important.
The pressure gauge (the tube) before deployment. The gauge is strapped to a stone (ca.25kg) that ensures that it does not change in position, neither in height nor place. Photo: Clemens Klante. The pressure gauge (the tube) before deployment. The gauge is strapped to a stone (ca.25kg) that ensures that it does not change in position, neither in height nor place. Photo: Clemens Klante.
One factor influencing water quality is the hydrodynamics and the wave climate (see fact box below) of the lake. This is because waves mainly determine transport and mixing conditions through the whole lake and within the water column. Due to Lake Bolmen's relatively large size (183 km2), waves induced by wind are likely to occur, but specific knowledge about them is limited. With the application of a wave model, that later will be combined with a general hydrodynamic model, a better understanding of Lake Bolmen’s hydrodynamics will be gained.

Recently conducted measurements of water pressure will help to calibrate and validate this model. Even though measurements have only been recorded on a single side of the lake, the contribution is rather large as this is the first real measurement of this kind. In addition to the simulation of the present wave climate at Lake Bolmen, analysis of future conditions due to changes in climate and ice cover will be conducted.

In the future the wave measurements will be extended and additional water quality measurements at different locations within the lake will be conducted. This will allow a more detailed combined analysis of water quality changes and interactions with hydrodynamics and the wave climate present at Lake Bolmen.
 
Text: Clemens Klante, Sweden Water Research and Lund University.

Wave climate
Wave climate is defined as the distribution of wave height, period, and direction averaged over a period of time for a particular location.

Source: Herbich J.B., Walters T. (1987) Wave climate. In: Climatology. Encyclopedia of Earth Science. Springer, Boston, MA. https://doi.org/10.1007/0-387-30749-4_195

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