Category Archives: eLTER

HOW TO MEASURE SOIL MOISTURE IN THE DESERT WITH COSMIC-RAY NEUTRONS?

Author: Stephanie Reiter

eLTER TA site: Negev

Research stay dates:      09/16 to 01/17  

The water bound in our soils, in particular soil moisture, influences plant growth, water infiltration, flood regulation and even climate patterns. Although on a global scale the overall quantity of soil moisture is small (<0.05%), it influences ecological, hydrological and meteorological processes.

Soil moisture content is an essential variable for eco-hydrological modelling or irrigation management as it provides the main water storage for plant uptake. Although the precise prediction of soil moisture over various scales is of high interest, its measurement and quantification is still challenging. Satellite remote sensing techniques are able to depict soil moisture patterns over large areas but a major drawback of these measurements is a shallow penetration depth of only a few centimeters of topsoil. Point measurement techniques using in-situ measurements can be interpolated to bigger areas but the spatial variability of soil moisture may complicate the upscaling; the vertical measurement depth of commonly used soil moisture in-situ probes is restricted to the topsoil layer as well.

Cosmic-ray neutron sensing (CRNS) is able to close the gap between large scale satellite remote sensing and point measurements, allowing soil moisture to be quantified non-invasively at the intermediate scale, e.g. for a small watershed or field site. The method uses measurements of cosmic-ray neutrons in a cosmic-ray neutron probes footprint, its horizontal (circular) and vertical measurement area. The cosmic-ray neutron particles are mainly absorbed and moderated by hydrogen. As a result, these neutrons are highly sensitive to the concentration of water in soil. This means under wet soil conditions the probe will detect less neutrons than under dry soil conditions. Especially in arid and semi-arid regions where water is scarce, it is critical to better understand soil moisture dynamics. That is why we set up a research project in a dryland region on the European Long-Term Ecosystem Research (eLTER) site in the Negev Desert, Israel.

In September 2016, I traveled from Berlin to Tel Aviv with a 32 kg heavy metal box containing a cosmic-ray neutron probe, a massive soil driller and an extra-large hammer. For normal people these things seem to be peculiar to travel with, but not so for a Geoecologist.

Not speaking any Hebrew, I had to figure out how to get from Tel Aviv to the Midreshed Sde Boker, an educational center in the middle of the Negev Desert, where I independently conducted the research on soil moisture measurements for my Master thesis. Fortunately, Israelis are extremely helpful. Several young soldiers helped me getting to Sde Boker with the neutron detector. And wow, what a place. A green oasis overviewing the Martian-like desert landscape of the Sde Zin valley, home to a small but flourishing community of about 1800 people, many of them students and researchers of the Ben-Gurion University of the Negev and its affiliated institutes there.

Desert research in the arid environment of the Negev has a long history, starting in the late 1950s with the establishment of the close-by first experimental farm near Avdat, where Michael Evenari and his colleagues were keen to investigate ancient and innovative practices to meet the challenges of Israeli agriculture. The story of Evenaris farm for runoff and desert ecology research is described in his personal and scientific narrative The Negev: The challenge of a desert, giving an idea of historical environmental research before satellite remote sensing, computer models or neutron probes were invented. When I visited the farm, dust and sand covered books in the library and piles of hand-drawn maps were scattered here and there. The old measurement instruments on the roof of the now abandoned building were fascinating to me, raising my spirits to be a desert researcher.

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At the Evenari desert farm in Avdat, Israel

Basically, what I wanted to do was measure soil water in the desert with cosmic-ray neutrons. My research aimed at quantifying soil moisture over tens of hectares using a combined approach that comprised the novel physical science based CRNS and hyperspectral remote sensing of vegetation. I installed the cosmic-ray neutron probe on the eLTER field site next to the Sde Boker campus and started measuring shortly after my arrival towards the end of the dry season in mid-September.

My daily routine would include walking through the heat to the field site to check the probe and transfer data to a computer. In order to convert the neutron intensity into soil moisture, I needed to conduct three calibration campaigns that consisted of the collection of soil samples in the CRNS probes’ circular footprint area. It turned out that taking soil samples up to a depth of 40 cm is a real challenge in the concrete like, dry desert soil. Although I had helping hands from my colleagues Kristina and Haijun, and from the lab technician Alexander Goldberg, we were not able to use the special soil driller that I brought from Germany to extract the samples. We adjusted the sampling method to the field conditions and used a spade to dig holes and extract the samples by hand for the laboratory analysis.

On seven of the days during my research stay, we conducted hyperspectral measurements of soil and vegetation on the site using a heavy field spectroradiometer. The field work in the heat of the day with temperatures rising up to 40 degrees Celsius and no shade was hard but I always enjoyed the rides to the site in the electric golf cart, when we could get it.

My research at the eLTER site in Israel showed that CRNS is a reliable technique to measure soil moisture content (even in minute amounts) in a natural dryland environment with shrub vegetation. Area average soil moisture values could be derived up to a penetration depth of 46 centimeters over an area of about 28 hectares reliably. The approach to combine CRNS data with remotely sensed vegetation parameters in order to obtain comparable values of soil water content needs to be tested in further (desert) studies. By the end of my research, the vegetation grew only sporadically on the field and I was not able to detect a clear signal of vegetation in the hyperspectral data. Ideally, spectral data can provide vegetation indices such as the Normalized Difference Infrared Index (NDII), a proxy to assess root zone soil moisture which is able to visualize the natural interaction between precipitation events, soil moisture and leaf water content.

I enjoyed my research stay in Sde Boker, learned a lot about Israeli culture and hummus, and met wonderful people from all over the world. In the evenings, I would leave my air conditioned student apartment, and take a five-minute walk to the cliff where the wide view over the Zin Valley never ceased to amaze me, and where the night sky was so clear that I could see the far-far away galaxies sending out continuous streams of cosmic ultra-high-energy particles. My thoughts would drift through space and time like the cosmic-ray neutrons that hit my neutron probe.

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Sampling location on the eLTER research site near the Sde Boker campus, Israel
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Alexander Goldberg with the field spectrometer
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The cosmic-ray neutron probe in the field – powered by the sun
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Me collecting soil samples on the field
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The Sde Zin valley, Israel

About the Author:

Reiter1Stephanie (26) is a graduate student with a MSc. in Geoecology. She is passionate about the importance of soils within our ecosystems. During her research at the eLTER site in Israel, she studied how to measure water in desert soils non-invasively using a novel method called cosmic-ray neutron sensing. Her research stay was supported by the eLTER H2020 Transnational Access grant. When not digging in soils or dealing with extragalactic particles, she enjoys long-distance hiking, gardening and organic food.

E-Mail: stereite@gmail.com

Light and conversation advance the work of the Cairngorms LTSER

Author: Jen Holzer

Cairngorms LTSER

Israeli musicians Ehud Banai and the Refugees muse in the 1987 song, “Magic of the Galil”:

 

“…I imagined Scotland as Tavor Mountain

one dark night when I froze from cold

a guitar helped me

the fire helped me

the morning of renewing light helped me….”

 

While longing for landscapes of the Holy Land throughout the ages is incomparable, nostalgia of Israeli pop songs longing for landscapes abroad is also a noteworthy modern theme. As an Israeli researcher on my first trip to Scotland — in December 2016 – I was inspired by the bucolic and rugged landscapes of Cairngorms National Park, but I was also unduly influenced by the brief daylight, and cold and grey of solstice in the Highlands. To the contrary, when I returned this June 2018 at peak daylength, sunny days seeming to brighten every interaction.

In December 2016, Dr. Jan Dick, a Scottish scientist based at the Center for Ecology and Hydrology, helped to coordinate an interview tour of Edinburgh, Aberdeen, Perth, and the Cairngorms National Park that would comprise a case study of the Cairngorms LTSER, part of a cross-platform study that also includes LTSER platforms in Romania and Spain. During that first visit, we conducted 23 in-depth stakeholder interviews in nine days.

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Cairngorms LTSER stakeholders interviewed in December 2016.

This June, I returned to present our findings, based on those interviews, about how the Cairngorms Long-Term Socio-Ecological Research (LTSER) platform is measuring up to its goals, as well as by comparing it to other LTSER platforms I had visited in Romania and Spain. Days were long and sunny, with Scots seeming to revel in the specialness of these bright but short-lived weeks on the calendar. While I had noticed the Scotch sociability and penchant for storytelling on my last visit, on this visit nearly everyone we met seemed to be taking the opportunity of our meeting to visit a special natural spot or go for a lunchtime jog on the grounds of a nearby estate.

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Presenting interview findings to geologist ‘Ness Kirkbride, on the grounds of Scottish Natural Heritage’s Battleby Conference Centre campus.

Besides the long days and beautiful weather, another particularly special aspect of my experience was the nature of the trip itself. I will explain. My host, Dr. Jan Dick, often refers to her leadership of the EU-sponsored OPENness project by saying something like: “It’s the most fantastic thing. I got paid to take the results of our research back to the stakeholders and ask them if they thought it was useful – or to tell us that it’s rubbish. I don’t care if they do think it’s rubbish – I just want to know whether it was useful!” This was also the mandate of my second trip to Scotland. My PhD research is an evaluation of LTSER platforms in Europe; in particular, the following questions:

 

  • Are social questions being integrated into ecological science?
  • Is it stakeholder-driven science?
  • Is there evidence of impacts?
  • Is there added value to this approach?
  • What are the challenges?

 

One of the novel aspects of this project is that it evaluates research that aims to be transdisciplinary, which means that it attempts to integrate different disciplines, diverse researchers and practitioners, and their varied types of knowledge, and then to make that research directly applicable to the policy and practice of environmental management. So, as outlined in our evaluation approach (Holzer et al. 2018), we believe an essential part of evaluating transdisciplinary research (or research that aims to be transdisciplinary) is to take the evaluation results back to the potential end-users of that knowledge (before publishing) and getting their validation and/or criticism, and to incorporate that into the final results.

 

For the most part, the co-directors of the Cairngorms LTSER did validate our findings, which was affirming in that it meant that our interviewees had corroborated perceptions of local experts, and that on the whole, we had synthesized the interview material to accurately represent the big picture. However, what was perhaps more interesting came up when Dr. Jan Dick turned to me on the way to the LTSER co-directors’ meeting and said, “I’m using you as a boundary object!” A boundary object is any tangible thing – usually a map, graphic, or document — that a group of people, especially people with varied backgrounds and interests, can use as a focal point for their meeting, and to help keep the conversation constructive despite different points of view and reasons for being at the meeting. I realized that while I had been focused on getting feedback on my results, if another important goal was to contribute something to the platform itself, then my visit did inherently give something back in that it provided a clear focus – and perhaps even inspiration — at the LTSER co-directors’ meeting, which was convened because of my visit. To put it bluntly, bringing a visitor from abroad may create an excuse for doing certain things!

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My trip provided an opportunity for Dr. Jan Dick to catch up with her Environmental Change Network colleague ‘Ness Kirkbride.

I have read many accounts of scientists and creatives getting their best ideas while walking, swimming, or sleeping. On this trip, ideas really came together for the paper we hope to co-author with LTSER co-directors when we brought a laptop along to an outdoor café for lunch. If I had to be honest, I would tell you that I’m an introvert, and spending many of my hours manning the helm of my computer is a perk of doing a PhD. But I will also be the first to say that while good ideas may start with a solitary stroll or laps in the pool, they get developed in conversation, all the better if that conversation can take place somewhere beautiful.

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Outlining a manuscript at the café in Pentland Hills Regional Park.
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A morning jog on the Muir Way near Holyrood Park in Edinburgh.

It was a productive and engaging trip, with perks like staying minutes from Edinburgh’s Holyrood Park, getting to work outdoors, and opportunities to socialize with scientists – like at the ESCom Conference  where I had the opportunity to present a flash talk. Now that I’m back in Israel, I’m ready to write the great next pop song longing for another summer in Scotland.


About the Author:

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Jen is a PhD candidate in the Technion Socio-Ecological Research Group in Haifa, Israel. Her research evaluates impacts of the transition in ecological research toward transdisciplinary socio-ecological research. Her trip to Scotland was funded by an eLTER Transnational Access research exchange grant. She is happy to receive your comments, questions, and feedback at jholzer@technion.ac.il.

If you would like to be interviewed by Jen’s colleague Yael Teff-Seker, who will be conducting walking interviews in the Cairngorms National Park in July 2018, please be in touch.

Adventures in the stoichiometry of Braila Island, Research Center in Systems Ecology and Sustainability

Author: Shabnam G.Farahani

Braila eLTER

My scientific trip to Romania started on September 2nd, 2017. On the following day, I visited the Faculty of Biology, of the University of Bucharest where I met  the intimate staff of Biogeochemical Circuits laboratory.

On Monday morning after meeting the team from the Research Center in Systems Ecology and Sustainability, we headed to the Braila Research Station. The Research Centre in Systems Ecology and Sustainability (RCSES) of the University of Bucharest was established in 1999. RCSES coordinates the national Long Term Ecological Research Network and contributes to large scale and long-term research in Europe (e.g. LTER Europe, ILTER, LifeWatch Europe).

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During the three days of my stay in Braila, I was accompanied by a friendly and well organized team who assisted with the sampling and field experiments for my research.

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Braila city is located in the flat plain of Baragan.  On the east side there is the Danube, which forms an island – The Great Braila Island surrounded by the Macin channel, Cremenea channel and Valciu channel. On the northern side there is the Siret river and on the north-western side there is the Buzau River.

Braila took  me back in time as a lively and amazing city. I was genuinely impressed by the city’s past and how it became a cosmopolitan economical center of the previous century, it is really worth seeing for those who want to admire the sights of the Danube and Braila Island. In my PhD thesis at National Academy of Science of Belarus, I am examining the elemental composition of zooplankton and seston communities as it varies seasonally in the littoral and pelagic zones of temperate lakes. As such during my field trip in Braila Island, I focused on spatial differences in seston community as a limiting factor for food quality of freshwater consumers and their C:N ratios in 7 different stations along the Danube river.

After finishing the field trip, we visited the Pontoon of the Small Braila Island Natural Park administration and got acquainted with its staff.

On September 7th, we made a farewell to the beautiful city of Braila and departed for Bucharest in order to carry on the elemental analysis, at the University.

“ KUFTEH “in a foil

Kufteh is a Persian, also middle eastern yummy food which is a kind of herb meat ball in tomato plum sauce which was so similar to what I did in sample preparation for CN machine at Bucharest University . I divided each filter into four pieces, roll them as a ball and packed them in foil, then weighed them by micro scale to place them in machine.

To tell the truth, this trip was a unique opportunity for me not only for learning new things in stoichiometry at the LTSER  site, but also for having so much fun, going with the boat on the Danube, sightseeing in Braila City, cooking steak for the team by my own recipe and 3 nights living in pontoon on beautiful Danube river.

This project would have been really impossible without the support of all my colleagues from the Faculty of Biology.

I am using this opportunity to express them my gratitude for providing the facilities of such exciting exploratory trip.


About the Author:

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Shabnam is a PhD student at Belarus National Academy of Science

CaveGIS – bringing location analysis to the underground

Author: Vojkan Gavojić

eLTER TA site: Postojna Planina Cave System (PPSC)

Postojna-Planina cave systems’ consists of more than 30 km long passages of Postojnska and Planinska jama caves. Their passages collect and conduct surface and underground waters from Pivka and Cerknica and release them to Planinsko polje. It also represents the most biologically diverse cave in the world with more known species of stygobionts (obligate, permanent resident of aquatic subterranean habitats) than any other subterranean site in the world. Such complex system allows researchers to conduct long-term interdisciplinary karstological research that combines knowledge from chemistry, hydrology, physics, geology, geomorphology, meteorology, ecology, zoology etc.  Large amount of different data have been collected through years and decades, often with redundancy, which resulted in multiple data collections for same phenomenon at the same time window and in same space. Intention of this research is to consolidate such data so they can be presented through geographic information system (GIS) within same time-space window, providing all the researchers unified basis for further research. Such basis would consist of spatial, numerical and spatio-temporal data, which all together will allow location analysis in such complex systems such caves are.

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Figure 1: Fixed cave survey point – the basis for determination of location

But, first things first! Where do data come from? And when? Usually, researchers focus on space and time frame that is proposed by their research objectives. The phenomenon that they are tracking is located in space. Corridor type spaces that caves are represented by are plotted on survey maps by speleologists using different methods and tools. Postojnska jama cave, for example, has fixed cave survey points that have been used to determine exact location of points where data about different phenomenon are being collected by automatic monitoring stations or by manual collections.

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Figure 2: Postojnska jama cave corridors with locations of monitoring stations

Data acquisition is dependent on time frame defined by researcher. Intervals can vary from seconds to days within defined time frame. There is variety of phenomenon that can be monitored: cave meteorological data (temperature, humidity, air flow, gases…), hydrological data (pH, water flow, conductivity …), chemical data (presence of metallic elements or solutions), cave species, rock movements, speleothem formation, limestone dissolution etc. So, it is variety of data that can be changes over time.

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Figure 3: One of monitoring stations for cave meteorological data

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Figure 4: Stalagmite formation in Postojnska jama cave

When we determine location of monitoring stations we can present such data in spatio-temporal visualization. For example, using space-time cubes we can visualize the space-time frame of collected data, and determine whether they can be used for our own research. By providing such data from one central place, e.g. GIS database, we can ease researchers in process of data acquisition, and enable them to perform spatio-temporal and location analysis within their frame or research.

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Figure 5: Space-time cube visualization of conductivity values (left) and species number (right) on locations in time


About the Author:

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Vojkan is PhD student of Karstology at University of Nova Gorica, whose research focuses on using GIS and Remote Sensing in Karstology researches.

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.