Monthly Archives: November 2016

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.

The Small Island of Braila

By Jen Holzer, Technion Socio-Ecological Research Group

After three days in and around Tulcea, we journeyed by car to the City of Braila, a city of about 200,000, famous as a node for the textile, shipbuilding, and shipping trades, and a surprisingly underdeveloped tourism industry. When our hosts told us this was not a travel destination, we were incredulous and inquired with the hotel reception. But the hotel proprietor confirmed that most hotel patrons are businessmen, mostly people from the Netherlands and England involved in the textile and shipping trades; they advised us to vacation in Brașov, the mountainous, “most beautiful part of Romania”7

After a tour of the University of Bucharest’s beautifully refurbished laboratory facilities in the city, we toured the Faculty’s pontoon on the Danube, complete with laboratories and sleeping quarters, and sat with local environmental managers and scientists for interviews and discussions.8

The next day, we drove to Stăncuţa to meet with the mayor of this communa, a collection of local villages bordering the protected Small Island of Braila, a LTSER platform. Interviewing the mayor and his colleagues at the Town Hall was illuminating for understanding the interplay of stakeholder interests – from EU funding requirements and opportunities to the situation of the veterinary technician who moved back to the hometown of his grandparents but was struggling to make ends meet, to wide local opposition to limits on grazing in the protected area on the Small Island of Braila.9

We were generously hosted for a fantastic lunch by the Mayor at a new research facility on the shores of the Danube, and set out on a short boat tour of Braila Island.

Coming from Israel, I am no stranger to a dynamic and fraught history of political conflict and transition, nor to a reality of contested natural resources. While the purpose of our trip was to understand the progress and barriers made by socio-ecological research in Romania, I was hardly expecting the depth of cultural exchange that took place on every level. I want to express my gratitude to our hosts, not only for their thoughtful hospitality down to the last detail, but also for their incredible patience in answering our questions – from the role of macrophytes in the Danube Delta ecosystem to the residual effects of the Communist period on environmental management to the role of ecologists as educators. As social ecologists, the social context of science is always relevant, on every level, including the personal.

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Jen is a PhD student in the Technion Socio-Ecological Research Group in Haifa, Israel and is affiliated with the Israeli LTSER network, with whom she is currently writing an article about applying transdisciplinary action research at the Negev Desert platform. Her research evaluates impacts of the transition in ecological research toward transdisciplinary socio-ecological research in Europe. Her trip to Romania was funded by an eLTER Transnational Access research exchange grant. She is happy to receive your comments, feedback, and suggestions for trivia questions about Romania at jholzer@technion.ac.il.