Plant-soil interactions: the cycle of life

Last spring, I gave a TED talk about plant-soil interactions and their importance in the global carbon cycle at a TEDx event organised by Amsterdam University College. You can watch the video below, but for those of you who rather read (actually, I am one of those people, as I never have the patience to watch a video from beginning to end!) you can also read the full text below.

Do you ever think about soils? Do you ever think about soils, other than, when your boots are muddy, or your vegetables dirty? Well, I’m going to talk about soils.

Soils! Without soils, we would not be here. Soils sustain all life on land. And that is because all energy flows through soils, via photosynthesis and respiration.

Have soils always been here?

No!

Have you ever thought about how soils are formed? Where plants came from? And the tiny invisible microbes that live in the soil?

More than 4.5 billion years ago, there was no soil. There wasn’t even life. There were only oceans. But somewhere between 4.5 and 3.5 billion years ago, the first microorganisms appeared in the oceans. There wasn’t even free oxygen at that time! But then, photosynthesis evolved in bacteria, and cyanobacteria started producing oxygen around 2.7 billion years ago. About 1.5 billion years ago, the first fungi appeared, and much later, around 500 million years ago, the first land plants arose. Probably, photosynthesis in these plants was derived from photosynthetic bacteria inside plant cells (the endosymbiosis theory). Those first land plants – like this little liverwort – had no, or very rudimentary roots (remember, there was no soil that they could grow their root in, only rock!), and were likely helped on land by symbiotic fungi. 

And this is where soil started to form. 

An extremely dry summer in Manchester

Right at the end of the extremely dry period we had this summer I decided to do a little experiment: I started taking a photo of the patch of grass in my street in Manchester, in the North West of England, every couple of days. I study the effects of drought on ecosystems (see my previous posts about the effects of drought belowground here and here) and I thought it would be nice to show how the grass in my street would bounce back after the rain had started.

Only… it didn’t. The rain did not come as intensely as I expected, and the grass did not bounce back as quickly as I expected. The first (top left) photo was taken on the 12^thof July, the last (bottom right) on the 20^thof August. And still you can see bare soil and brown patches! This patch of grass would look a lot lusher and greener during a normal Manchester summer.

The grass in my street in Manchester this summer. 

But, more importantly, while aboveground plant growth seems mostly recovered, the composition of the community has changed (which you can’t see in these photos), and as I’ve shown in my research, this might continue to affect belowground communities and the processes they perform.

Of course, this little patch of grass in Manchester is not that important for the functioning of our ecosystems. But it is a nice illustration of the impacts of an extremely dry summer on grassland and how long it takes for these fast-growing plants to regain their biomass!

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?