Soil boring? My take on the image problem of soil science.

I am passionate about soil, especially about soil biodiversity and how soil organisms and plants interact and control C and N cycling. I have studied soils since I started my undergraduate in 1996, and I have witnessed a complete turnaround when it comes to interest in soil biodiversity and the functions it performs. When I started my PhD, no one was interested in soil organisms and how they regulate crucial ecosystem processes that also happen to be central to sustainable agriculture. Now, everyone is interested – from farmers, to policy makers, to fellow ecologists.

Well, I say everyone, but that is clearly not the case. Soil is still remarkably unsexy. I will illustrate this with a little anecdote.

Last Friday, I met the third year Zoology student who had been assigned to do a final year Science Media Education Project with me. As we walked up the stairs, I asked her what her background was, and she replied and said: “….. and you study soils, right?” in a slightly too upbeat manner. We went to my office, and after finding out that she’d like to interact with primary school children, I suggested organizing a book launch family activity or classroom activity linked to a children’s book about an earthworm that I provided scientific advice for. I explained to her what the book is about (it is about a little worm with low self-esteem, who goes on a journey and meets lots of impressive animals, but eventually finds out that worms are crucial for soil health and plant growth), that the authors are based in Manchester, and that it will come out in February. I saw her face light up as she got increasingly enthusiastic, and I said: “You probably thought, oh no, I have to do a project on soil” to which she replied that she had indeed been a bit worried. When she left, I felt happy that I had been able to excite her about the project, but sad that she had been worried about studying soil.

Sadly, I can’t really blame her.

I, too, often feel deeply bored when I read about soil.

Why is this? Continue reading

Soil Carbon Storage: The Headache of Grazing

[This is a guest post by Thomas Ross, a 3rd year Biology student at The University of Manchester – he is currently doing a Science Media Project on the effects of grazing on soil C storage, which I am supervising. This blog post is part of his portfolio, and he has to reflect on its impact in his final submission. So don’t hesitate to leave your comment!]

The carbon stored in soil amounts to double that in the atmosphere and biomass combined and soil has the potential to sequester more. As atmospheric levels of carbon dioxide have been on the rise there has been an increase in global temperatures and climate change (here, the processes involved in soil carbon storage explained in more detail). The potential of the soil carbon reservoir to sequester this carbon from the atmosphere, and potentially ease the speed of climate change, can be influenced by our actions and the way in which we manage land. One such way is through the grazing of domestic livestock.

Grazing has the potential to modify ecosystems drastically and thus affect soil carbon storage. But how much is too much? Unfortunately, I cannot give you a definitive answer as the effects of grazing on soil carbon storage vary greatly. Some studies showing increases in soil carbon due to grazing, others decreases and some no changes at all. This causes a tricky problem when deciding how to manage livestock to ensure maximum soil carbon storage and withholding the interests of all stakeholders. Continue reading

Blood, sweat, and tears: the story behind the paper

I have already hinted at it in a previous post, and I have been tweeting a lot about it during the past couple of days: our paper ‘Soil food web properties explain ecosystem services across European land use systems’ is now online on the PNAS website! The paper is about, well, soil food webs, and how important they are for ecosystem services. Of course, I already knew that, as did many others, and relationships between groups of soil organisms and ecosystem processes have been shown before. But in this paper, we show that there are strong and consistent relationships between soil food web properties and processes of carbon and nitrogen cycling on a European scale!

Anyway, this is all pretty exciting, but I don’t want to write about the actual content and message of the paper here. No. Because when you see a paper like this, nice and shiny and with a blue PNAS logo on the side, with slick figures, a list of references, online supplementary information, and a small box detailing the contribution of each author, oh, and not to forget the acknowledgements thanking the funder, the landowners, and the people who helped in the lab, you don’t think about all the blood, sweat, and tears that went into putting together such a paper. And blood, sweat, and tears went in it. Continue reading

Drought belowground

There is a heat wave in the UK, and at least in the north, where I live, not a single drop of rain has fallen for at least three weeks. I quite like it, especially since last year was basically one long, wet, windy autumn and I was craving for a real summer. But, with temperatures this high, and with this little rainfall, many plants are starting to look a bit poorly. Grass is turning brown, and forbs are hanging their heads. Especially in the north of England, where normally everything is lush and green around this time, this is an unusual sight.

I know this all too well, because I am running a drought experiment – our drought pots have been tortured to the max and we wouldn’t have needed the sturdy roofs, while we had to water our control pots.

Does this look dire? Then take a look at what's happening belowground! Pots from my on-going drought experiment.

Does this look dire? Then take a look at what’s happening belowground! Pots from my on-going drought experiment.

So, plants are having a hard time, and I can imagine farmers are becoming worried. Because summer droughts are expected to increase in the UK, and when crops are stressed to their limit, this will lead to yield reductions. Modern agricultural crops have evolved to be adapted to high-resource, low risk environments, and have very different properties than their wild ancestors (read this great paper by García-Palacios et al.) – properties that are not much good for resisting drought conditions.

However, if you think that carnage is going on aboveground, then take a look belowground. Continue reading

To observe or to extract? Different methods for studying soil organisms

Interest in characterising soil communities is booming, fuelled by the growing recognition that soil biota govern processes of carbon (C) and nitrogen (N) cycling – processes that underpin the delivery of soil-based ecosystem services such as climate mitigation and sustainable food production. Soils capture carbon, which can exacerbate climate change when released to the atmosphere, and they provide nitrogen and other nutrients for growing crops and feeding livestock – when these nutrients are lost from soils, they can pollute ground and surface water and cause a loss of biodiversity. Because soil microbes decompose organic matter, thereby releasing N for plant growth, and respiring C, they determine the balance between the release and retention of C and N in soils.

In my work, I have a particular interest in the role of soil fungi and bacteria in these processes. Moreover, I want to find out how land use change and climate change affect the relative abundance of fungi and bacteria, and the chain of soil fauna that feed on them (the fungal and the bacterial energy channel, respectively), and how these changes in turn affect processes of C and N cycling. For example, some of my recent work shows that fungal-dominated microbial communities of extensively managed grassland retain N better and have lower N leaching losses, about which you can read more in this old blog post. Also, I have shown that fungal-based soil food webs and the processes of C and N cycling that they carry out are less affected by drought, which is expected to increase with climate change, than bacterial-based soil food webs.

An example of a soil food web, with the fungal decomposition pathway (dashed arrows) and the bacterial decomposition pathway (solid arrows). Both fungi and bacteria are consumed by a chain of soil fauna, that consists of protozoa, nematodes, collembola, and mites.

An example of a soil food web, with the fungal decomposition pathway (dashed arrows) and the bacterial decomposition pathway (solid arrows). Both fungi and bacteria are consumed by a chain of soil fauna, that consists of protozoa, nematodes, collembola, and mites.

To do this type of work, obviously, you have to measure the composition of soil microbial communities, or even of entire soil food webs. This is not an easy task, as most of these organisms are not, or barely, visible for the naked eye. For decades, direct microscopy was the only possibility to quantify and characterise the composition of soil microbial and soil faunal communities. For microbial communities, this involves transferring a soil suspension onto a microscopic slide, staining the fungi and bacteria, and then counting their hyphae or cells using a microscope. I used this method during my PhD and spent weeks, if not months, looking through a microscope. Although still frequently used, in recent years, direct microscopy has been increasingly replaced by the measurement of phospholipid fatty acids (PLFAs), a component of the cell membranes of fungi and bacteria. Because different microbes have different PLFAs in their cell membranes, the PLFA composition of a soil sample can be used as a ‘fingerprint’ of the soil microbial community. In other words, it doesn’t only tell you about the relative abundance of fungi and bacteria, but also about the composition of the bacterial community. Continue reading

The diversity beneath our feet

Yesterday, Georgina Mace gave a seminar in the Faculty of Life Sciences at the University of Manchester. Of course, I was at the front row (well, almost), as I have only just started at Manchester and I was employed to reinforce ecology and environmental sciences in the Faculty. I have seen Georgina Mace speak before, and today she spoke about biodiversity, and specifically, the decline of it.

In her talk, she highlighted trends in the decline of plants, birds, mammals, reptiles, fish, and amphibians, mainly as a result of habitat destruction. She spoke about mechanisms of these organisms to cope with disturbances; some species just cope with changing circumstances, some move away to new habitats, and some (or, rather a lot, as evidenced by the graphs in her presentation) go extinct. At the end of her talk, she spoke about why biodiversity is important for humans. First of all, humans value biodiversity because of its intrinsic value – we simply want to know that there are elephants in Africa, or panda bears in China (although personally, I couldn’t care less about panda bears).  Second, we want to conserve species because we want to preserve the genetic library of life, and all the information about its evolution that is locked up in genes. And finally, we want to conserve biodiversity because it provides ecosystem services that are directly beneficial for humans, although the science underpinning this relationship is still thin on the ground. Continue reading