Long-Term Soil Ecosystem Studies

Much of the world’s food supply is produced in intensively managed cropping systems that involve high inputs and high outputs. As our populations continue to increase while the amount of arable lands steadily shrinks, these intensive systems assume greater importance. Can they be maintained into the indefinite future? Will they continue to supply high yields of our foodstuffs? Answers can be gained solely through long-term field studies.

As an example, two or even three annual crops of irrigated lowland (paddy) rice are now the norm in favorable lands of tropical Asia, and such intensive cropping produces much of the regional rice supply. When this system became possible in the 1960s with the development of rapidly maturing, semi-dwarf rice varieties (through the “Green Revolution”), long-term field experiments were soon begun to evaluate the sustainability of grain yields and soil health under multiple annual cropping. The results for one triple-cropped field study in the Philippines are depicted in the figure as grain yield response to nitrogen (N) fertilizer input. In the early years of the field study (1970-1972, upper curve), grain yield was about 6 tons ha-1 without fertilizer N input, and with increasing fertilizer application grain yield approached the yield potential of 10 t ha-1. After 19 years of continuous triple-cropping, this yield response had declined substantially in a near parallel manner (bottom curve), creating a yield loss of about 3 t ha-1 at the highest fertilizer rate. Graphically the yield loss can be attributed to the lowered starting point of the 1989-91 curve, namely the grain yield that was supported by native soil N without fertilizer N input. The nearly equal slopes of the two curves indicate that the 1989-91 crop responded similarly to fertilizer N input as in 1970-72, so the yield decline was not caused by a change in intrinsic plant characteristics.

These long-term trends strongly suggest the cause of the yield decline as decreased supply of soil N. Yet the quantity of soil N had not changed during the 19 years of intensive cropping, so this graph became the basis for directing subsequent research at changes in the quality, or chemical nature, of soil N.

Additional evidence for the central role of N in the yield decline is shown in the dotted curve (1992-93). When the role of N in the yield decline was first hypothesized in 1991, N fertilizer was applied more frequently and at greater total rates to better synchronize fertilizer N with plant N demand. The resulting boost in fertilizer N availability compensated for the decreased availability of soil N, enabling reestablishment of the original yields from 1970-72—a reversal of the yield decline.

Careful long-term management of this field study and the recording of key agronomic and soil data enabled a process-level evaluation of system sustainability, leading to mitigation options that will maintain the high productivity of this vital cropping system into future years.

Dan Olk, USDA-ARS

Reference
Cassman K.G., S.K. De Datta, D.C. Olk, J. Alcantara, M.I. Samson, J. Descalcota, and M. Dizon. 1995. Yield decline and the nitrogen economy of long-term experiments on continuous, irrigated rice systems in the tropics. p. 181-222 In R. Lal and B.A. Stewart (eds) Soil management: Experimental basis for sustainability and environmental quality. CRC/Lewis Press, Boca Raton, FL.

I began work on long-term sites, not by wise and deliberate choice, but by fluke of serendipity: when I arrived in Lethbridge as fledgling scientist, historical plots established there in 1911 were assigned to me. So a better question might be: why do I keep on working on these sites? In pondering the question, three fragmentary responses emerge.

I work on long term sites because of scientific curiosity in the insights they keep revealing, sometimes unexpectedly – often to questions unforeseen. There is pleasure in stumbling upon an urgent new riddle, and then realizing the answer may be lurking in the samples and data of those old plots.

A second reason, more visceral, is the subtle satisfaction of being tied to something – a place and the insights attached to them – that will outlive and supersede my limited, ephemeral contribution. Like planting a tree that will outlast me, there is joy in fostering a place that will yield discoveries I cannot yet foresee.

And thirdly, I work on long-term sites, even after several decades (especially now!), because I see, more and more, the cyclical nature of ecological science – the relentless continuity of growth and decay, leading to higher resilience. As a young scientist (in a period of growth), I had the thrill of learning from the sites left me by my predecessors; now (in my decaying years), I have the joy of nourishing the ground upon which the next generation might see their growth.

If my research managers (or funding agencies) were to ask me why I keep working on those old plots, I might enumerate various concrete, scientific reasons: carbon sequestration, for example, or nitrogen use efficiency. But the real reasons are probably deeper than that. And, in the end, I suspect those deeper reasons are what keep me coming back to those old plots.

Henry Janzen

Check out the Google analytics report (website traffic) attached for the LTSE website. http://ltse.env.duke.edu/files/ltse/discussion/Analytics_ltse.env.duke.e...




This timeline/graph shows the resultant traffic of two events: The GSC07 workshop and a Duke news release .

This graph shows that we successfully generated ~40 referring websites that boosted traffic (temporarily) by a factor of 10.

It is yet to be seen if this will have a permanent effect on overall traffic.

Also attached is the Duke News release from Friday January 25, 2008. http://ltse.env.duke.edu/files/ltse/discussion/soilsave._print.pdf

Challenge to theCommunity: This can't possible be all the traffic this website deserves. I believe that email is our enemy to adopting community sites like this. Great conversations are being lost in email threads. If we could post the good conversations on the website, they would be saved and relearned by our students free of charge (almost).

Top 10 Countries accessing the LTSE website.

Second Post-Workshop Communication 13 January 2008
Global Soil Change and LT Soil-Ecosystem Studies

To: GSC 2007 Workshop Participants
Fr: Dan Richter & Mike Hofmockel

Thanks are still owed to each of you for active participation at our remarkable workshop!

As the second communication in response to our workshop, this is still very much an experiment. Monthly communication seems do-able in this form, at least for the immediate future; let’s approach this like any good experiment. Comments, suggestions, critiques, or new ideas are encouraged. We are strongest working together.

A. Workshop-Related Business
1. Progress on workshop summary submissions. We have “assigned” each of you to submit a workshop summary to a suggested news outlet. “Assignments!!” are found in the table below the draft workshop-summary at the url:
http://ltse.env.duke.edu/gsc07_coordination
The goal is one submission per person, and while time is passing and we should submit workshop summaries soon, this is not a difficult task. Edit the draft workshop summary to satisfy yourself, then send it to a newsletter or journal with your name as first author. Keep Mike and Dan Richter informed, so that we can send congratulations!!

2. Update on Seeds of Discovery “Homework.” The first 500-word draft has been received, this from David Powlson, who addressed the question, “Why I am working on long-term sites” which is posted at:
http://ltse.env.duke.edu/node/920
Remember “homework” essays can address “Why I am working on long-term sites?”, or “How to make long-term soil studies work harder?” or “What are key findings that can only be discovered in long-term soil studies?” If you feel inclined, you might supplement your short essay with a figure or table that demonstrate how short-term studies may be misleading compared with soil and ecosystem trajectories that become apparent only with long-term study. Our target date for drafts is 15 January.

3. How to post your own poster on LTSE website! If you presented a poster at the 2007 Workshop (Meg, Gobina, David, Mike, Jianwei, DanielM, DanR, Jason, Julie, and Arlene), convert the poster to a pdf file and post it on our LTSEs website!! This is easy, and here’s how!! Note that the following easy steps are useful for many website applications.
a. Login, click on Create Content (upper screen), select and click on Publication from list of content types.
b. In the Submit Publication window, enter the Title of your poster; enter the Publisher as “Global Soil Change workshop - Dec2007 - Duke University”;
enter Authors with first authors family name first;
enter Year as “2007”;
select “Poster” from the pull-down of Publication Types;
enter Kewords as “Global Soil Change workshop 07”;
then browse and attach your pdf file, clicking “Upload”;
and finally, click the submit button on the bottom of the form.

4. LTSEs website will highlight new projects list and workshop notes.
A list of new ideas for projects, papers, reviews, and cross-site projects will soon be posted on the website’s “Global Soil Change 07” pull-down list (left hand side of main page). Meeting notes will also be available at the same location.

5. Planning future workshops & themes. I have been re-considering the how to organize future workshops. I was impressed with our workshop dynamics that sprang directly from breadth of our deliberations. I now think that each future workshop should have a theme, for example, LTSEs and the global carbon cycle, but that each future workshop should also be about how to network LTSEs irrespective of the workshop theme. Your reactions will be appreciated.
I will be developing ideas about the second workshop in the upcoming few months. In addition to themes and locations, an important issue concerns future participants. We need to build breadth of community, so we need to invite new persons to our table. As much as I’d like to be able to invite each of you to all five workshops, we won’t be able to do this given constraints of budget.

B. The Larger LT Soil Research Base Project

1. Exciting cross-site fellowship opportunities for PhD students and post-docs. Although not massive, we have about $10,000 set aside in years two to five for travel and research support for students and post-docs who aim conduct research on a question at several LTSEs. In the coming months, I will write a short Request for Short Proposals statement(RFSP), have the RFSP reviewed by some of you, set a submission date, and then convene three or four of us to review cross-site research proposals, and award funds. We can invite awardees to future workshops. Suggestions about any of this are welcome.

2. I’m writing a content paper, that will be co-authored by us all, aimed at Nature, Science, or BioScience, journals with broad readership that allows us to expand the base of persons who value LTSEs. I’ve corresponded with BioScience Editor who has expressed great interest. I plan to finish a first draft then post it on the website for review by us all.

3. Recruitment of popular science writers. I have contacted Mike Tennessen and Monte Basgall and other popular science writers about our project. The workshop PowerPoint presentations, posters, and Seeds of Discovery essays and will be introductory materials we can provide these writers.

6. Ouch!! Still Lost: A Duke Univ library book, Gene Likens’ Long Term Ecological Research is checked out to Richter and traveled to CEFS in Goldsboro. It is a small dark green hardback, so kplease return if the book walked home with you.

NEWS FOR Third Post-Workshop Communiqué
On-going Business
1. Seeds of Discovery essays
2. Cross-site fellowship opportunities for PhD students and post-docs
3. Progress with popular science writer
4. Future workshops & themes
5. Linkage of LTSEs project with IUSS working group
6. Content paper, co-authored by us all

New Business
1. Project Ceres! (something brand new!).

My opinion that many preferences of LTEs can be assessed in a network study and we are lucky to use such network principles from the very beginning of LTEs foundation in the former USSR since mid 30s last century in agronomic research. This approach was realized in a series of publications which define the unified system of indicators, sampling protocols and analytical methods. As a result, already in the mid of 60s last century zonal features of average fertilizers rates efficiency were specified, in which role of soil factor was estimated at the level of the Reference Soil Groups in modern World Reference Base for Soil Resources. Geographical principles in generalization of experimental data were used in construction of statistical models for the specific agro-ecological zones (AEZ) or soil types. These models provided possibility for numerical experiments 20-30 years ago, when we had no possibility to use dynamic modeling. One example can be linking LT field experimental results with weather data series in agrometeorological publications in 70s last century for long-term forecasts of fertilizers efficiency. Updating these results based on modern climate tendencies allows to estimates effects of climate dynamics on fertilizers efficiency change. This demonstrates how modern science provides insights relevant to tomorrow’s questions, as Henry Janzen put it in one of his publications: “The insights from one generation of scientists can often be applied to the questions of the next… Though our data may be aimed at today’s queries, the understanding that emerges, if it is deep enough, can offer clues to tomorrow’s questions still unseen”.

It seems that LTEs provide an excellent example of such continuity in Earth’s studies when an importance of really long experiment becomes more substantial with time. It becomes more substantial than the views of a researcher who initiated the experiment or even an institution which supervises LTE continuation as it can be interested only in one field of interest.

A shift in approaches from plot to landscape was very important in 1990s with an attempt to use more than 150 LTEs in the former USSR for agroecosystem research with widening system of indicators, mainly physical, microbiological and physiological ones; assessment of climate factor; application of dynamic models for forecast purposes in integrated assessment of sustainability. Alas, this attempt was not fully realized, but allowed to reveal limitations for agronomic LTEs use in agroecosystem study, one of them connected with necessity of multi-disciplinary research through cooperation with other scientists in a wide range of other disciplines. Perhaps, here a “snowball” effect works – the more data are available for the specific site as a result of interest of such multi-disciplinary team, the more interest of other scientists to use the it for their own research. My own experience of Ph.D. work at one of LT experimental site with growing forest belts in semi desert was demonstrated such preference of initiation research in a place where joint information was available for crop, native plants and tree growth, trends of soil moisture and groundwater dynamics, biodiversity study and weather data for long-term … Seems to me an ideal for which we need to approach but it’s impossible without joint interest, so promotion of existing LT sites is a very important question. Plots of land with a known and well documented historical data require not less attention than nature reservations, especially taking in mind their practical importance for increasing crop yields and price we need to pay for obtain the desired yields.

The attached table contains not only answer on the question of the text title (third column) but also short description of methods necessary to achieve expected results (methodology column), limitations at the moment for that as well as detected future tasks. While the first subject, naimly networking in agronomic studies, may be more relevant for us based on existing experience of LTEs network maintenance, all others seems more general for all our participants. That’s why I suppose the table can be improved and updated by all of us.

David Powlson, Rothamsted Research, UK

• I started my career in soil science working at Rothamsted Research, UK. This is the site of several long-running experimental field sites, the oldest being the Broadbalk Wheat experiment started in 1843. It was originally designed to compare crops yields achievable from (the then newly developed) chemical fertilizers with those from animal manure. In its first few decades the experiment laid the foundations for our current understanding of plant nutrition.
• My first research was not directly concerned with long-term sites but rather with the development of a method to measure the quantity of organic carbon held in the cells of living organisms in soil (the soil microbial biomass). However some of the soils I used came from the long-term sites so I have always appreciated the immense values of these sites as resources for other research.
• One of the great strengths of long-term sites is that they are a source of material, and background knowledge, that is of value in research projects quite different from those for which they were originally designed – and often for work that could never have been envisaged by the initiators of the experiments. Thus, if I wish to conduct process level research or test hypotheses using soils that differ in only factor only I can easily obtain them. For example, I can sample soils with high or low organic matter content, high or low content of specific nutrients or different pH but having the same texture and mineral content. I do not have to spend years getting soils into the required contrasting states - what a benefit!
• Although types of work, and must, be done using soils from non-experimental farms or forests, the advantage of long-term experimental sites is that they normally have their history well recorded. So research requiring a contrast in properties can be conducted with confidence that there are a minimal number of confounding factors.
• Climate change caused by enhanced emissions of carbon dioxide and other greenhouse gases is probably the biggest challenge facing humanity and the planet on which we depend for our survival. The amount of carbon held in the organic matter in the world’s soils is very large – about twice the amount held in the carbon dioxide in the atmosphere. Thus changes in land use that cause a change in soil organic matter content, if reproduced over large areas, can influence the global carbon cycle – either slowing climate change if additional carbon is locked up (sequestered) or making it worse if soil organic carbon declines and is released as carbon dioxide. However changes in soil carbon content occur slowly, over periods of years or decades (depending on climate and other factoras) so generally cannot be reliably measured over short periods. Long-term experiments (or networks of space-for-time sites or long-term monitoring efforts) are the only ways of obtaining information on soil carbon changes and thus assessing the likely climate change impacts of different changes in land use and management practices. I have been involved in efforts to use results from long-term experiments for this purpose. Initially we simply extrapolated results from contrasting treatments in several long-term experiments in Europe to estimate changes in soil carbon stocks for the land area of Europe for a range of possible land-use scenarios. A more satisfactory way of assessing future trends is to use models of soil carbon dynamics. But before doing this it is essential to check that the models correctly simulate changes in soil carbon content for the environments concerned. This can only be done by comparing model simulations with changes actually measured in the past – long-term experiments are the ideal source of such data. I was involved in a major international effort to assemble information from over 100 long-term experiments worldwide and use data from some of them to evaluate several models. The initiative was called SOMNET – Soil Organic Matter Network. I think this was a significant service to soil science, and to humanity, through the increased confidence with which we can now predict the impact of land use changes on soil carbon stocks in the context of climate change. And it could not have been achieved if earlier generations of scientists had not had the foresight to initiate long-term experiments – and others that followed had not had the vision and persistence to continue them.
• Producing sufficient food for the world’s population (probably about 9 billion later this century) is another major challenge. Long-term experiments are one important source of information on the crop yields that are achievable with different levels of input and the impacts on soil and the wider environment of a range of management practices.

Vladimir had another one of his invaluable: "one other idea not to forget"!!

If I understand, Vladimir suggested that we consider splitting the website's metadata in two tiers.
One tier or first set of menu items about LTSEs would total about a dozen key questions. They could be answered quickly and efficiently, even in passing;
the other set of menu items would be more lengthy, still not cumbersome, but more like the current metadata menu of items.

I believe Vladimir might more efficient progress in pulling the many Russian LTEs together into our LTSEs metadata base, should he be able to make use of an abbreviated set of a dozen questions.

Discussion anyone? Did I understand you properly Vladimir?
Dan Richter

Let this be a place to collect suggestions on ways to promote LTSEs.
One effort already under way is the "Workshop Summary Submission Coordination".

Vladimir Romanenkov has suggested -
One more idea not to forgot concerning LTEs promotion. I think it can be a 12-leaf calendar with pictures of the longest or the best known experiments from all the continents. It can include a new and also a quite old small image of the same place. The idea that it can be circulated in different scientific circles and can last longer that any poster of this sort.

Please add more ideas by posting comments to this discussion.

First Post-Workshop Communication 19 December 2007
Global Soil Change and LT Soil-Ecosystem Studies

We will not soon forget last week’s warm Carolina-December days. Many thanks to each of you, especially for your active participation! A workshop participant list with contact information will be emailed within a few minutes of this being posted.

As we are a sample of a much larger community, our science is obviously vital and composed of enthusiastic researchers at all stages of scientific life. This is a very good sign, given the scientific challenges we face in decades ahead.

This communication is a first response to all of our incredible interactions. I foresee several subsequent communications in coming weeks. Here, there are four items plus an appendix. Subsequent communications will be in about a week, the 25th December (see item #1 below) and on 1 January (see preview at the end of this text, prior to appendix). Please, as we all move ahead, if you have comments, suggestions, critiques, or ideas, feel free to share these; we are strongest as a growing community, working together. Share your perspectives and experience in reviewing any aspect of our project, including the following!

1. Announcement that a short workshop summary will be circulated for your review by 25 December, next Tuesday. This summary can be used for short reports that each of us will send to news outlets starting early in the New Year (can each of us submit just one?). We need suggestions of additional news outlets in the soils and environmental sciences, also internationally, and land and water management magazines and newsletters.
Our list of outlets for the workshop summaries needs expanding: EOS, Frontiers in Ecology, CSA News, IUSS Bulletin, Elements, Trends in Ecology, Forestry Source, New Scientist, and websites of IUSS, CZEN, LTER, ILTER, LTSE.
Please suggest other outlets to Michael and Dan Richter. Authorship of these summaries will be flexible, generous, and fair. I suggest that whoever submits a workshop summary should list their name as first author and add “and 2007 Global Soil Change Workshop Participants.”
The summary I will send by 25 December, will cover:
a. Locations and funding support.
b. Attendees, some of their roles, and quotable quotes (eg. Amapu’s “making LTSEs work harder,” “LTSEs contribute uniquely to soil and environmental science,” “Rice LTSEs in Asia measure the heartbeat of the agro-ecosystem that supports between two to three billion persons,” “We can really understand soils and the ecosystems they support by long-term observation and analysis.”).
c. Workshop charge and accomplishments: The workshop reviewed new scientific findings from long-term studies, and initiated long-term planning to upgrade the world’s long-term soils research base, all to better address the many ways the Earth’s soils will be key to meeting the world's burgeoning economic and environmental demands. Not only did we establish a long-term soil-observatory network, we have accomplished this with a remarkable website that allows us all to build this network in coming years.
d. Future workshops and themes: I will suggest we hold our second workshop in the Carolinas, taking advantage of two other LTSEs nearby, but that the following three workshops be held in proximity to contrasting but productive LTSEs around the world. We will need to work on this carefully but I am confident we can do this. Potential themes for future workshops include how the long-term soils research base is critical for improving the sustainability of food, fiber, and fuel production systems; managing soils and ecosystems and their interactions with the global carbon cycle; and improving soil-processing of nutrients, organic wastes, toxics, and other contaminants.

2. Press release with short announcement of workshop results:
I am working on a brief press release coming out of Duke. Ideas are welcome. Any of your organizations can do this, and I think we should encourage you all to do so. I’ll be happy to review any of your drafts to check facts, etc.

3. Homework for us all!! The Thursday 13 December Notes from a most vigorous discussion clearly state that each of us has a homework writing assignment, all under the banner of “Seeds of Discovery.” The Thursday Notes suggest short 500-word essays be drafted by us all by 15 January. These could be directed at questions such as, “How to make long-term soil studies work harder?”, “Why I work at LTSEs?”, “What are key findings that can only be discovered in LTSEs?” You might supplement your short essay with a figure or table (Sharon Billings’ great idea!) that demonstrate how soil-ecosystem observations over a few years may be misleading compared with long term trajectories that will only become apparent with long-term study. These drafts need not be especially polished, but do try to submit a good draft. We will collect these on the website, and review them in the future.

4. Lost and Found:
Found: Arlene Tugel’s poster tube, which has already been mailed.
Lost: Duke Univ library book, Gene Likens’ Long Term Ecological Research, a small dark green hardback checked out to Richter. Please return asap.

ISSUES FOR 1 January Post-Workshop Communiqué
1. Workshop notes, specifically outputs of our discussions.
2. Content paper draft, co-authored by us all aimed at Nature, Science, BioScience, etc.
3. Details on cross-site fellowship opportunities for PhD students and post-docs.
4. Website posting of presentations and posters.
5. Popular science writer.
6. More on future workshops & themes.
7. Linkage of LTSEs project with IUSS working group (Dr. Mermut)
7. Project Ceres! (something new!).

Appendix: Vladimir requested these two lists of new ideas and projects that was discussed, Wednesday, 12 December 2007, shortly after lunch.

New projects: papers, reviews or even new cross-site studies

1) LT management impacts on :
. mineralogy and mineral surfaces
. organic matter functions, composition
being altered in a variety of unexpected ways
. macro and so called micro-nutrient cycling, bioavailability, fractions
. subsoil dynamics
. soil water and gas phases
. changing plant-response functions with time
. soil food webs and the biological “excitement”
. POPs (persistent organic pollutants)
. Next generalization rice studies
. Techniques for cross-ecosystem comparison (e.g. forest vs pasture) when you aren’t comparing the same horizons.
. Review of differences of organic and inorganic amendments of N (particularly to the atmosphere, ie Zak, Harvard Forest)
. Comparisons of farmyard manure and NPK. Quantity versus timing issues.
. Soil-borne pathogens and weeds, invasive organisms, pharmaceuticals
. Off-site changes (occurring outside the plots themselves)
. Looking at the spatial heterogeneity of our systems and the effects on properties
. Soil physical properties (e.g. aggregation, effects of SOM, conductivity)
. Economics? Develop economic treatments up front (include in planning)
. Organo-minero-microbial interactions. Mechanisms at the molecular level.
. What are the dynamic characteristics of soil that we can measure? (e.g. conversion of inorg. C to org. C, or the formation of salts)
. Change from results-oriented to dynamics oriented studies (including time as a factor)
. Plant-microibal interactions (e.g. symbiotic interactions, the rhizosphere
. Social, historical and cultural soil interactions
. What is the threshold value? Indicators of change for management.
. Hypothesis testing across two or more sites
. Cross-disciplinary writing (of experiments, proposals)
. Extrapolation and predictions

We need to look at all of these things on the list in regard to long term experiments.

It is important to prioritize (which might be different from experiment to experiment).

We are seeing much different responses between organic and inorganic nitrogen amendments

When you are applying organic manure every year, this builds up and gradually releases nutrients and other compounds. This changes the background soil conditions and might well have implications for farm growth.

We also need to consider the changes that happen to the landscapes around our plots- these elements are also changing.

Economics is really important and we aren’t positive how to address it. It is “coming”. There are a number of experiments when economists have been brought in to crunch the numbers after the fact. We should consider treatments that are economic to give them data. For example- organic transition. We try degrees of treatments and think about costs. Start with the economists in the planning.
We need to understand the mechanisms of organo-mineral-microbial interactions (at the molecular level)

2) Related papers & new projects (that don’t neatly fit the LT management effects model)

Linking LTESs and how they have contributed to our conceptual models and quantification of soil change

Generic lessons from LT studies in transition (all LTSEs go through transitions)

Sampling considerations

Spatial-temporal considerations: especially as we continue to be forced from quadrat-plot approaches to larger soil- and land-scapes

Popular scientific accounts of soil change, especially those linking to global scale

Changes over the duration of LTSEs in climate-management interactions

Land-application and cycling of wastes

Treasure and burdens.