Category Archives: eLTER

Atmospheric nitrogen deposition may endanger carbon storage in peatlands – how do the fungi respond?

By Heikki Kiheri, Natural Resources Institute Finland

Approximately one third of global soil carbon is stored in northern peatlands as slowly decomposing organic material. Peat carbon is accumulated due to net imbalance of production and decomposition. This enormous amount of carbon is sequestered from the atmosphere by plants and accumulated under the waterlogged, acidic conditions in peatlands which considerably reduce the rate of decomposition. Decomposition is a complex process involving many different microorganisms, including archaea, bacteria and fungi. Any increases in the availability of nutrients by atmospheric deposition, such as nitrogen compounds produced as pollution, can increase the rate of decomposition by these microorganisms. If decomposition rates increase, the sequestered carbon within peatlands may be released as greenhouse gases, including carbon dioxide and methane, and the peatland ecosystem may fundamentally change to a net source of carbon. Peatlands have taken thousands of years to form. Therefore it is critical to understand the potential risks of pollution to peatland ecosystems or we risk further compounding the rate of global warming. This is why we have chosen to study the ecological changes at the long-term fertilization site at Whim Bog, as it is ideal for quantifying the potential effects of increasing atmospheric nitrogen deposition. Whim Bog is an LTER site managed by the Centre for Ecology and Hydrology near Edinburgh, Scotland.

Key to understanding changes in the peatland ecosystem is determining changes to the vegetation and their interactions with the microbial community. The predominant groundcover plants found in peatlands include members of the family Ericaceae, such as heather and bilberry. These Ericaceous species, or ericoids, rely on a symbiotic relationship with fungi for access to organic forms of nitrogen, which are relatively inaccessible to the plant. The fungi which associate with ericoid roots form what are called mycorrhizae, which is when fungal mycelia form a close connection between their hyphae and plant roots. In exchange for organic nutrients, ericoid plants provide sugars to the fungi.

At Whim Bog we are able to measure changes to vegetation diversity and biomass, root production, nutrient allocation by plant species and mycorrhizal colonization rates of ericoid plants. By carefully measuring these different factors across several treatments of increasing nitrogen fertilization, we aim to clarify the changes to the ecosystem. These data have the potential to increase the accuracy of global carbon cycle models which do not fully account for the carbon stored in peatlands and thus the importance of peatlands to global carbon cycling.

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Our host Netty van Dijk and Dr. Tuula Larmola surveying the dense heather-cottongrass vegetation on a warm, sunny August day. (Photo by Heikki Kiheri)
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Prof. Raija Laiho collecting root ingrowth cores for root production measurements after the growing season in November. (Photo by Tuula Larmola)

We enjoyed our visits to Whim Bog and the weather was remarkably warm for autumn, with sunshine and comfortable temperatures making our work a pleasure. The beautiful countryside provided many observations of wildlife and picturesque farmland, most especially the lovely gnats. Their occasional bites served to keep us on task and focused. Coming from Finland and working in peatlands much further north, we are accustomed to the attention of biting flies, mosquitoes and swarming gnats. Surprisingly, the Scottish gnats were quite ferocious and reminded us that we should have packed our mosquito net hats. Our visit at the end of August was a fortuitous coincidence with the Edinburgh International Festival. It was a great experience to see the city alive with all manner of arts and crafts. Working with the Centre for Ecology & Hydrology has been thoroughly excellent and we look forward to our continued cooperation.heikki-3

Heikki is a PhD researcher at the Natural Resources Institute Finland (Luke) and studies microbiology at the University of Helsinki, Finland. His research focuses on mycorrhizal fungi associated with Ericaceous plant species in boreal ecosystems and changes to their relationship due to changing environmental conditions and nutrient availability. His visit to the site, with Dr. Tuula Larmola and Prof. Raija Laiho, both from Luke, was supported by eLTER H2020 Transnational Access award and project funding from the Academy of Finland to Dr. Larmola.

Plants and Nitrogen – a love & hate relationship

Author: Melanie Batista of Universidade de Lisboa

Hi there!

I want to tell you about my visit to the LTER site at Whim Bog, Edinburgh, Scotland. The Centre for Ecology & Hydrology, based on the Natural Environment Research Council, manages a LTER site with facilities to study the effects of dry and wet nitrogen deposition. Nitrogen is an essential element for plant growth, however, like everything in life, too much is just too much. Wet deposition occurs when nitrogen enters the system in the form of precipitation, and dry deposition refers to forms of nitrogen dissolved in the atmosphere. Excess of nitrogen can lead to severe changes in ecosystems, especially if they are oligotrophic – meaning that they are adapted to low nutrient conditions. Studying these changes is exactly what this LTER site is about. The site is a peatland ecosystem, dominated by the shrub Calluna vulgaris and the  sedge Eriophorum vaginatum.

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During my visit I studied the effects of dry deposition of nitrogen in the plant community – I assessed plant diversity and structure, using a set of transects along a gradient of ammonia (NH3). This gradient is imposed to the plant community by an automated free air release facility that releases gaseous ammonia. The  system fumigates only when wind speed and direction are within determined values, creating an ammonia gradient covering about 60 m in extend, with ammonia values ranging between ambient (c. 0.5 NH3 µg m-3) and 100 µg NH3 m-3 (annual averages).

One last thing about the Scottish experience. You ever heard about midges? Before my trip to Edinburgh I never heard about them. And, until my last day of my field work, when I was starting to think the midges were little more than a myth, they appeared in full force. It seems that until then there were never the perfect conditions. But, on that last afternoon, the sun shone brightly after a light rain, the wind had stopped blowing, and from one second to another, millions of little flying dots appeared from under the shrubs to land on our hands, faces, ears… everywhere. So I learned what midges are.

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Melanie is a fellowship researcher at the Centre for Ecology, Evolution and Environmental Changes, Universidade de Lisboa. She studies plant functional diversity, mainly of the Mediterranean vegetation in Portugal, in response to different environmental changes, such as desertification and grazing.

Contact: mkobatista@fc.ul.pt

 

URL: http://ce3c.ciencias.ulisboa.pt/member/melanie-koumlbel

In the realm of blueberries and moss… radiometry measurements at Kindla Integrated Monitoring site, Sweden

By Jan Pisek, Senior Research Fellow, Tartu Observatory, Estonia

The BRACE project (Background Reflectance ACross Europe) is one of 23 small projects supported by the eLTER H2020 project’s Transnational Access scheme (which is funded by the European Union). The objective of the project is to collect in situ measured background/understory reflectance data across diverse ecosystem research sites in Europe. The results should be particularly useful for validating remotely sensed data and for producing Northern hemisphere maps of seasonal forest dynamics, enabling analysis of understory variability, one of main contributors to uncertainty in present estimates of spring leaf emergence and fall senescence. Our data can also be used as an input for improved retrieval of biophysical parameters and for modelling local carbon and energy fluxes.

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Our equipment for making understory spectra measurements at Kindla (from right to left): portable spectrometer; controlling unit (laptop); measuring tape and forest flags for laying out and marking transects; white Spectralon reference panel.

First stop was the Kindla Integrated Monitoring site in Sweden, which my colleague, Krista Alikas, and I visited in July 2016.  Kindla is one of the most inaccessible and wild areas in Örebro county, and it is also a large nature reserve (over 900 hectares).  To get good quality data, we have to collect our measurements in overcast, diffuse light conditions. You cannot do much when the sky is blue and the sun is shining, and during such moments we explored our surroundings and gorged on huge quantities of ever-present blueberries.

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Our first 100 m long transect is laid out and ready to be measured in the forests of Kindla, Sweden (orange flags mark every 4 m along the transect). Notice the blueberry bushes (Vaccinium myrtillus) all around.

There are 15 km of paths in the nature reserve area, allowing individual walks of 7-10 km – just perfect to fit within the windows of our (in)activity when there was no hope of sudden increased cloudiness. Kindla’s summit, 425 meters above sea level, is also one of the county’s highest points. There is an additional 11-meter viewing tower, which allows you to rise over the treetops to get a fantastic view over the green sea of surrounding forests.

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The splendid vista from the Kindla’s summit (426 meters above sea level).

We were told that you can find traces of bear, wolf, lynx and wolverine in Kindla, but the animals are clearly very shy and maybe unsurprisingly we failed to make a closer encounter with any of these animals. On the other hand, we were apparently sharing our accommodation with another typical local representative. We were staying in a nice and cosy barn-turned-into-hostel (we were the only guests all week) in the nearby tiny village of Nyberget. During nights we could often hear a strange, not entirely unpleaseant murmur coming from the base or underneath the building. Upon our departure we were told that it was most likely a badger.

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Interesting teeth bite pattern from an incognito visitor (a fellow researcher, perhaps?).

With support from the eLTER H2020 project, we are looking forward to making similar measurements from two other European LTER sites this year: Montado in Portugal and Zöbelboden, Austria.

Author: Jan Pisek

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Jan got his PhD. degree from University of Toronto, Canada. He is currently a senior research fellow at Tartu Observatory, Estonia. Jan is primarily interested in field- and space-based multi-spectral and multi-angle optical remote sensing, biophysical parameter and vegetation structure mapping. Jan would like to thank Lars Lundin and Stefan Löfgren of Swedish University of Agricultural Sciences (SLU) for providing excellent supplementary materials and introduction to the Kindla Integrated Monitoring Site.

 

Fruška gora LTER site from the perspective of hoverflies, treeclimbers and satellites

By Dušanka Krašić

If it wasn’t for this geological bump (the highest peak 549m), the northern part of Serbia would remain devoid of many ecosystem services, much of its biodiversity, life forms, oxygen, historical values and research opportunities. In simple terms, it would be quite boring area. Fruška gora is the first Serbian National park, founded and proclaimed in 1960. Once an island in the Pannonian sea, after the sea went dry it became an isolated mountain chain about 80 km long and completely surrounded by flat land. Due to its origin, the mountain treasures rich deposits of fossils in its rocks allowing us to peek into the past whenever we are feeling curious. It’s a soulful place with many stories and historical events carved in its forests and stones.

Its deciduous broadleaved forest is comprised of beech, oak, lime and hornbeam, the main edificator species. Out of 110 species of birds recorded on Fruška gora, it is certainly worth to mention the Imperial eagle, one of the most endangered species on The IUCN Red List of Threatened Species. Around 1500 of plant species grow on Fruška gora and that’s a lot of species for such a pimple. Among them more than 700 have medicinal value and many are of relict and endemic character.

Besides potential excitement after running from a wild boar there is not much adrenalin rushing nature phenomena on Fruška gora. Fruška gora lies in the temperate zone thus you will not find a hand size isopods in the area however the research we conduct can be quite alluring to scientifically inclined, not to say odd, individuals.

In addition to standard and not so charming monitoring of common soil and air parameters, we are conducting some fancy research studies here. One of them is studying syrphid flies. Syrphids are flies from the insect family Syrphidae which pretty much look like bees and wasps, though unlike these insects they hover like little helicopters and can stay motionless in the air which is why they were nicknamed hoverflies.

 

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Chrysotoxum cautum, indicator of habitat heterogeneity
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Ferdinandea cuprea, indicator of well preserved old forest

Why would anyone study this group of flies? Well besides they are really cute, they are also quite important pollinators enabling the existence of the myriad plant species. In fact, after the bees, hoverflies are the second most important group of pollinators. They are also very sensitive to habitat and climate change thus great environmental change indicators, meaning that their presence and abundance specifies the degree and the rate of environmental change. We are studying the influence of external environmental traits including climate change on the occurrence of selected hoverfly taxa.

How do we study hoverflies?

Using sweep netting at chosen sites along transect lines followed by species identification, either by observing morphological characters or using DNA barcodes.

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Sweep netting method to collect hoverflies

Climbing 30 m high trees to get the data

Besides practicing tree climbing, a fascinating and a hell of a fun activity, we are collecting leaves from the highest branches which we later analyze for leaf traits such as N and P concentrations, leaf dry matter content, specific leaf area and leaf size.

Why?

Plant species react to the environment they live in, their physiological processes such as photosynthesis and transpiration are heavily dependent on their surrounding.

By collecting the leaves in the areas differently affected by human activities (mainly by logging) and measuring chosen set of leave functional traits, we are tracking plant responses to these disturbances. Different species may respond differently to habitat change i.e. different disturbance level.

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Climbing trees to get leave samples; we collect mature, sun-lit leaves from parts most exposed to direct sunlight i.e. outer canopy leaves

To us it is interesting to investigate whether lime (Tilia argentea Desf. ex DC), which became heavily dominant after years of logging suppressing the oak and beech, has the same level of physiological excellence as the species which were formerly much more abundant.

Using satellite images to observe forest cover change

By using satellite images we are detecting changes in forest cover such as deforestation and fragmentation in order to quantify change patterns, ascertain the nature, extent and rate of forest cover change over time and space. We are using these results to analyze changes in spatio-temporal framework, upgrade the management of timber resources and update forest cover maps.

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Areas detected with forest gain 1969
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Areas detected with forest gain since 1969

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Dušanka Krašić is a researcher at the Biosense Institute in Serbia, Novi Sad and a fourth year PhD candidate at University of Novi Sad, Department of Biology and Ecology.

(Don’t) judge an aquifer by its covering

By Laura Busato, Siptenfelde and TERENO observatory Harz/Central German Lowland

My second time in Germany starts on a hot and sunny summer day. After a short meeting with researchers and technicians from the Helmholtz-Centre for Environmental Research in Leipzig, and some instrumentation checking, me and the other group member are ready to reach the TERENO field site near the Selke River, in Saxony-Anhalt. But why are we here? Let’s take a step back!

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Here comes the sun (at our field site)

A layer of water-bearing permeable rock or soil from which water can be extracted is called “aquifer” and its characterization is important for many reasons, especially for human use. From a wider point of view, aquifers belong to the so called Earth’s Critical Zone, the thin outer layer of our planet where interactions between soil, water, rock, air, and living organisms take place. Each aquifer has its own characteristics (some are shallow and some are deep, some are confined and some are unconfined…) but all of them can be characterized using the same methods, which are actually a lot. So that’s why we are here: to study a shallow fresh water unconfined aquifer!

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An audience gathers as we take our measurements.

This aquifer in the Central German Lowland is already well known from the UFZ group in Leipzig, as many data are already available, but when it comes to aquifer characterization (or any other thing in any other science field) data are never enough! Furthermore, this case study is a good example of the combination of the two main types of field information: direct and punctual vs. indirect and extensive. But what does this mean?

 

The first type of information (direct and punctual) comes from the typical approach to aquifer characterization, based on observation wells. They are drilled from the surface into the aquifer and are equipped with many types of probes, which automatically measure several parameters like electrical conductivity, temperature, and so on. In our field site we took advantage of the direct push-system, which pushes tools and sensors into the ground to create a borehole and, simultaneously, creates a log measuring several parameters at different depths. On the other hand, the second type of information (indirect and extensive) consists in measuring quantities that are related to the ones we are actually interested in, since determining them directly would be too difficult or too expensive. A good example is electrical resistivity, a physical parameter that depends on many factors (e.g. water content, salinity, temperature, etc.)

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Here’s a borehole equipped with several different probes

So the point is: which approach is the best? The choice depends on the characteristics of the area, on the amount of money at our disposal, and, most of all, on the questions that need to be answered. But probably the best solution is to combine the two of them, and this is exactly what we chose for our field site.

 

The first thing we do is measuring the depth of the water table, i.e. the upper boundary of our unconfined aquifer (or, in other words, the surface separating the water-saturated soil – below – from the unsaturated soil – above). Water table depth varies over time depending on many factors and gives us information regarding the direction of groundwater flow. These direct measurements rely on the number of observation wells available, which are usually a few, as they may be too expensive and/or may modify the actual aquifer properties. Therefore, these punctual values are then properly combined to infer information also on the area between these wells, thus leading to a so-called “isophreatic map” (i.e. a map showing how the water table depth varies in the space, like a topographic map shows altitude variations)

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The “Geoprobe” direct push system drilling one of the boreholes for the ERT measurements

The second thing we do is a tracer test, to gather indirect and extensive information. Tracer tests consist in injecting a substance that can be easily detected (why appropriate tools) into the aquifer, to monitor how it changes the properties of the investigated domain. In our case, this consists in injecting a certain amount of water with a known electrical conductivity (i.e. the inverse of electrical resistivity) and to monitor how electrical resistivity and electric potential difference vary consequently over time.

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Mixing of water from Selke River with salt (NaCl, sodium chloride) to obtain the tracer with known electrical conductivity for the tracer test

To measure these physical quantities, we decided to combine two different methodologies, named electrical resistivity tomography (ERT) and mise-à-la-mass (MALM) respectively. Even if their names seem complicated, their application is rather simple. The former consists in injecting electrical current into the subsoil and measuring the generated corresponding voltage, using several metallic elements called “electrodes”. We put these electrodes directly into the aquifer thanks to four new boreholes. The voltage values are then turned into the corresponding electrical resistivity, which is finally represented into images known as resistivity cross-sections. These pictures show the resistivity pattern at the measurement time, as if we were cutting a vertical slice in the soil (perpendicular to the ground surface) among the boreholes. These resistivity values can be related to the direct information obtained from the observation wells, so as to extract only the information we are actually interested in.

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a) Surface stainless steel electrode for MALM measurements and b) plastic pipe with ten borehole electrodes (each one indicated by a yellow arrow). Each electrode is wrapped around the pipe, which is the inserted into one of the boreholes. Each of the four boreholes for ERT acquisitions is equipped with a plastic pipe with ten electrodes like this.

The latter methodology is based on the same principle, i.e. injecting electrical current and measuring the corresponding voltage. In this case our electrodes are placed on the ground surface, creating a sort of grid covering the area over which the tracer should move: here, the aim is obtaining a voltage map, which represents how voltage varies in the space of the investigated area. The main idea is that the tracer varies the measured voltage (and therefore also resistivity) over time, according to its movement, which depends on the aquifer properties. Thus, the detection of these variations should provide insights regarding the investigated domain, such as direction and flow velocity.

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Field site in the Harz/Central German Lowland. The red boxes allow the connection between the boreholes and the automated instrument carrying out the ERT acquisitions, while the red and white poles indicate the position of some of the surface electrodes for the MALM measurements.

Even if the data analysis will require some time, as combining all this information together is not so simple, the preliminary results are definitely promising. Our goal is to assess the same direction and flow velocity both from surface (i.e. MALM) and borehole (i.e. ERT) acquisitions. Thus we will be able to say that, yes, sometimes one can judge an aquifer only from the surface!

bio_picture_1Laura Busato is a PhD student at the University of Padova (Italy). She combines non-invasive geophysical methods and hydrological models to characterize the movement of water in the Earth’s Critical Zone (i.e. the thin, outer layer of our planet, where the interactions between air, soil, water, rock, and living organisms take place). She really likes listening to rock music and baking cakes.