Monthly Archives: September 2018

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.

Reiter2
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.

Reiter3
Sampling location on the eLTER research site near the Sde Boker campus, Israel
Reiter4
Alexander Goldberg with the field spectrometer
Reiter5
The cosmic-ray neutron probe in the field – powered by the sun
Reiter6
Me collecting soil samples on the field
Reiter7
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.

fig. 1. blog 3
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.

fid2. blog 3
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!

fig3. blog 3
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.

fig 4. blog 3
Outlining a manuscript at the café in Pentland Hills Regional Park.
fig5 blog 3
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:

fig 6 blog 3

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).

Far1

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.

far5

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:

Far0

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.

Figure1

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.

Figure2

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.

Figure3

Figure 3: One of monitoring stations for cave meteorological data

Figure4

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.

Figure5

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


About the Author:

AuthorPicture

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