Tag Archives: ecology

Hey, Jasmine, come and meet Robert and Violet

Fied Bindweed - Convolvulus arvensis - busy doing what?

Field Bindweed – Convolvulus arvensis – busy doing what?

Common sense, ‘facts’, things taken for granted, taken as read: the history of science shows that all these can be swept aside like old toys by some confident new research. The idea of unchanging, fixed species?  Darwin saw to that.  Solid matter? Smashed by nuclear physics.  In botany? Well, Darwin and evolutionary theory are still transforming our view of how plants came to be what they are today.  However, considering that much less funding goes to botanical research than other sciences, I wonder if other surprises still await us. Yes, the way a seed germinates and grows is clever, but after that, plants just stand there alone, stupid, blind, waiting to be picked, or eaten, or trodden on, or strimmed – don’t they? Isn’t that how they’re different from animals?

I’d like to hazard a guess at what a new surprise might be: plants have a social life. Since I’ve taken more time to observe plants and read about them in the last year or so, my view of them has changed.  Here are some examples.

Plants communicate. Not in the ‘talk to your geranium’ sense, or the ‘scream when they’re cut’ sense, but more commonly with chemicals. In the book I reviewed in my last post, Weeds, Richard Mabey writes that

The air and the soil are busy with constant streams of chemical messages – plant pheromones – designed to deter predatory insects, seduce pollinators, kill off competitors, encourage companion plants and warn other plants of insect attack.

These pheromones can be volatile compounds evaporating from the leaves or soluble chemicals exuding from the roots into the water in the soil. The roots of field bindweed (Convolvulus arvensis – in photo at top) secrete something which inhibits the germination of most grain crops.  The seeds of the striking thornapple (Datura stramonium ) can release chemicals which inhibit cabbages and tomatoes.

Thornapple - Datura stramonium - the poisonous weed that looks like a garden flower

Thornapple – Datura stramonium – the poisonous weed that looks like a garden flower

The growing tip of the plant dodder, which is parasitic on tomatoes, spirals round till it senses tomato leaf chemicals and then grows straight toward their source.

Plants are interdependent. Gardeners often use the phrase ‘companion plants’ to describe plants which grow well together: my Agenda du jardinier bio (organic gardener’s diary) lists dozens under ‘Voisinage favorable’: plant garlic near tomatoes but away from artichokes, celery near beetroot but away from salads etc. Pheromones may be at work here too.

An even closer association is between plant roots and beneficial fungi – I had heard of truffle oaks of course, but I was surprised to read in a botany textbook that ‘most higher plants have an association with soil fungi’. Yes, ‘most higher plants’: estimates are as high as 95%.  A root which cohabits (‘is infected with’ seems too value-laden a term) with a symbiotic fungus is called a mycorrhiza. The fungal threads can cover a huge area and help the plant source scarce minerals such as phosphates and nitrates, as well as water.  In return the fungus receives carbohydrates from the green plant. This short clip shows how it works:

A plant that combines many of these features is Cistus monspeliensis, which I wrote about on this blog here. As well as helping absorb nutrients, the fungus on its roots secretes a toxin which stops other seeds germinating – and it’s true that each Cistus usually sits in a bare patch of ground.

To give a few more examples, they’re also particularly important in trees of northern temperate areas, such as oaks, birches and conifers; and in heathers – Erica and Arbutus. Many orchids can’t even germinate without a particular fungus, which may account for their appearance in patches, from seeds germinating within the area of ground which contains fungus.  This makes evolutionary sense: plants originated in the seas and first colonised wet areas.  Fungal help would have been invaluable in spread to drier habitats, and once the solution was found, why evolve another?

Here’s forestry specialist Professor Suzanne Simard explaining that a forest is really a community, whose members have different roles:

You can make the most of mycorrhizae in organic gardening by inoculating your seeds and plants with fungal spores: see here:

One point I came across often is that industrial-scale grain growing goes against this process: the grain-bearing species are the least likely to have mycorrhizae; they therefore need higher levels of chemical fertiliser than other crops; and application of fungicides and other processes further reduce the biological activity of the soil.  All in all, we’re getting some insights in how to live with Nature, which, as Richard Mabey has said, is bigger than us.

In the second part of this theme, I’ll look at the lifestyles of plants – and their relationship with humans. Meanwhile, what more appropriate song title for this post than Stevie Wonder’s 1979 ‘Secret life of plants’?

 

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Botany epitome no 1: juniper, rosemary and heather

I’ll start by explaining the odd title. A couple of times recently I’ve been out and looking for plants and noticed that several characteristic species of that habitat were growing close to each other, giving a typical snapshot of its ecology. Number one? Yes, there’s another one coming soon.

The Cirque de Mourèze with the village in the background (photo Wikipedia)

 The first place is near the Cirque de  Mourèze, an area of dolomitic pillars and weird shapes sculpted by erosion, about 20 km north of where I live. Dolomite – a mineral named after the French geologist Déodat Gratet de Dolomieu (1750–1801) – is formed by the combination of magnesium and limestone, and resists erosion so that patches of it protect the limestone beneath while the surrounding stone is eroded by acidic water.

L to R: juniper, rosemary and heather

Just north of Mourèze the narrow road goes through a few hectares of a unique landscape known to Chaiselongue and me as ‘the Libyan bit’ or ‘the road to Apollonia’, not for a Hope/Crosby film but since it reminds her of a landscape she knew as a child in North Africa. It’s a very dry sandy area between hills of limestone outcrops, protected in a small pass.  It’s the only area I’ve seen near here which has a lot of heather growing in it, and in the patch I saw, that was associated with juniper and rosemary.  All three plants have adopted the same dense bushy shrubby habit, and small linear leaves, for the same reason: to reduce water loss. All three are often found near the sea, adding to the coastal feel of ‘the Libyan bit’. Spot the odd one out? Yes, juniper is a conifer, so it has cones rather than flowers like the other two.

The juniper is Juniperus oxycedrus, prickly juniper. The leaves are typically arranged in threes on the stem, and this species is distinguished from the other common juniper species, J. communis (common juniper), by having two white stripes on the top of the spiky leaf, while J. communis  has only one on a softer leaf.  The former species is native to and most common in the area of the Mediterranean basin where it often colonises burnt or neglected ground; it also has brownish cones ripening to red-purple in the second year. The latter species is native to Britain and in my area tends to be found at higher altitudes; it has green cones ripening to black and it’s these which give an oil used for making gin. The wood of prickly juniper, known as cade in French, produces an oil which has disinfectant properties and is used in the treatment of psoriasis. The wood of both is valued for its durability – I have a lovely pocketknife with a juniper handle.

Then there’s rosemary (Rosmarinus officinalis), too well known to say a lot about except that its English name has nothing to do with roses or Mary, coming from the Latin ros marinus meaning ‘dew of the sea’.  The Roman Pliny explained that it grew ‘in dewy places’ – well, maybe, but dew is rare where I found it. The two prongs rising from the flower are the two stamens. Glands on the leaves produce the oil which gives the plant its aroma, and which is supposed to improve blood circulation. I love using rosemary with all sorts of meat, and roast or fried potatoes (my son’s idea), though famously Elizabeth David wouldn’t have it in the kitchen except as decoration in a vase.

Erica multiflora

The heather is Erica multiflora, which I don’t think has an English name, probably since it’s native to the area between Spain, North Africa and Italy. The stamens protruding from the bell are a characteristic feature, as are the long stems, which bear the flowers near the tips.

For this trio of plants I thought I’d find some trio music. If someone says ‘jazz trio’ what usually comes to mind is a piano/bass/drums unit, such as the famous Bill Evans or Brad Mehldau outfits.  To mark the North African connection I’m suggesting something different which is a favourite of mine : the Anouar Brahem Trio with the Tunisians Brahem on oud and Lassad Hosni on percussion, and Barbaros Erköse (from Turkey) on clarinet. Here’s the title song from their album Astrakhan Café (2000).

NB – if you like this, look on youtube and you can find the whole album – better still of course, buy any Brahem album and you won’t be disappointed.

Coming up next: number two in the series.

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Appearances can be deceptive: Eryngium campestre (field eryngo)

 

So this is another thistle in the garrigue, right? Wrong. It’s not a member of the thistle family at all – they’re with daisies, cornflowers and chicory in the family Asteraceae (used to be called Compositae), and Eryngium is, like fennel,  in the family Apiaceae (used to be Umbelliferae).  One clue is in the repeated branching of the stem into umbels (stalks or rays branching off from one point), and  another is in the stamens, which are not fused together as in thistles, if you look closely.

 

One name for this in French is the ‘herbe aux cent têtes’, due to the umbels, another is  chardon roulant, rolling thistle, and the similar l’èrba rotla means the same in Occitan.  Why? Because although the plant is a perennial, the stem can break off when it dries and blow in the wind to scatter seeds elsewhere.  But normally, the hooked seeds are dispersed by furry animals – it relies on mammals to spread.  Another characteristic is its long root system of up to 5 metres, which, like its leathery and spiny leaves ,is an adaptation to dry conditions. The root is also often  parasitised by a fungus, Pleurotus eryngii, which produces edible mushrooms, or by the parasitic flower Orobanche.   So it’s not just a solitary thistle in the wilderness, but a whole ecosystem.

 

Pleurotus eryngii

It’s that kind of shift in view which characterises the work of one of my favourite writers on natural history, Stephen Jay Gould (1941-2002). A New Yorker who became Professor of Geology and Zoology at Harvard, he is best known for his long series of monthly essays which appeared under the heading ‘This view of life’ in Natural  History magazine, and which he collected in many books. He wrote little on botany but his overall approach to the history of life on earth offers much to those seeking to understand plants, and to those who appreciate good  prose style.  At their best his essays are at the same time intricate and clear, profound and entertaining, personal and research-based.  In his collection Bully for Brontosaurus he distinguishes two sorts of nature writing: the Franciscan (after the saint) which produces a kind of nature poetry, and the Galilean which takes a ‘delight in nature’s intellectual problems’. He put himself firmly in the latter group.

 

Stephen Jay Gould

His relevance to botany? His consistent desire to understand how evolution works, rather than being satisfied with the formula ‘If it exists, it must be adaptive’. With the biologist  Richard Lewontin, he coined the term ‘spandrel’ in evolutionary theory, after the triangular gaps between arches he noticed in St Mark’s Cathedral in Venice: a feature which might have no function or evolutionary advantage, but might arise as a consequence of other structures (arches and a dome, in the case of St Mark’s).  Male nipples might be one example, existing only as a developmental relic of the necessary female equivalent, as he explained in his essay ‘Male nipples and clitoral ripples’. A botanical parallel might be some colours in flowers which are not visible to the insects the flowers attract (insects detect more ultraviolet than we do).

He appreciated just how plain weird many living things are, often resulting more from contingency or ‘happenstance’ than adaptation or design. Why else does the fern Ophioglossum reticulatum need 630 pairs of chromosomes (that’s right, 1,260 per cell)? As he explained in the essay ‘The ant and the plant’, some polyploidy or doubling of chromosomes can encourage variation, but in this fern the mechanism has gone beserk.

 

Ophioglossum reticulatum – Adder’s tongue fern

He realised that evolution was not a gradual process of accumulating small variations as Darwin had proposed, but sometimes ran very fast,  producing radical changes, while at other times there were long periods of stasis: the theory known as ‘punctuated equilibrium’ (proposed by Gould and Niles Eldredge in 1972). This remains a major explanatory hypothesis for animal evolution, though it may play a smaller, if still significant, part in the evolution of plants.  To illustrate his style, when objectors called his theory ‘evolution by jerks’, he replied that gradualism was ‘evolution by creeps’.

I also admire Gould for the breadth of his interests and for his awareness of the social context of science. He understood how religious beliefs had hindered the interpretation of fossils, for example, and this is a major theme of his fascinating book Wonderful Life. He was a committed campaigner against creationism and its attempted inroads into American education. He knew that science cannot be ‘value-free’ and his book The Mismeasure of Man is a passionate but also scientific explanation of why the concept of IQ testing is flawed and inherently racist. Does this apply to plants? Of course. Just as the word ‘intelligent’ can be a useful adjective, but can also parade as an objective phenomenon to be studied and measured scientifically, so too a plant can seem a biological organism to be described and understood as an individual, though it never exists on its own. To the farmer, Eryngium campestre is an invasive weed, to the mushroom hunter it’s just the food source for what he wants to collect, to an animal it’s an annoying burr, to the botanist a good example of a xerophyte adapted to dry conditions.  And plant, fungus, animal, climate and soil (maybe even botanist) are all developing together in an evolving ecosystem. In another example of putting genetics in context, Gould’s colleague Lewontin campaigned against genetically modified crops, seeing them as an advantage to agribusiness rather than to the farmer or consumer.

Gould and Lewontin were both members of what was known as the ‘radical science movement’, together with the American psychologist Leon Kamin and the British biologist Steven Rose.  There’ll be more of their radicalism to come in future posts, including reference to their 1984 manifesto Not in our genes, and Rose’s stimulating book Lifelines.

On to some music, and the radical poet and musician Gil Scott-Heron with one of his earliest and most influential songs, The revolution will not be televised, from his first album, Small talk at 125th and Lenox. Yes, radicals, revolution and rolling thistle – you were there before me.  But there’s another parallel. The song gets its power from the two ways of looking: our familiar and comfortable trappings of life suddenly seem ridiculous when the streets erupt.

 

 

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The Blues: Centaurea cyanus – Cornflower, and jachère fleurie

Thanks to herbicides, the cornflower has disappeared from the corn – together with other plants which were probably more toxic. Disappeared along with the word ‘corn’ – until the 18th  century, all grain was called ‘corn’, and after that the term was gradually applied exclusively to Indian corn or maize (Zea mays). But thanks to the European Union policy of ‘set aside’, where farmers can be paid to leave fields fallow (jachère in French) rather than grow crops for which there is already a surplus, the idea of  sowing with an annual flower mix which won’t persist into the next year (jachère fleurie)  and which almost always includes cornflowers,  has taken off.  I’ve seen it a lot in central France, and local authorities are encouraged to sow flower mix on any empty ground they own, but this is not widespread in the Midi, where vines are predominant –  if they are grubbed up, winter wheat or maize are often sown.

So I was very pleased and intrigued when a neighbour sowed this lovely jachère fleurie in his small field on the way up to our garden. When I asked him about it, he said he just wanted to use the land for something, and that he’d got the seed mix from the chasseurs – the village hunting association.  He explained that they sow this mix, and also pea plants, in wild spots where they want to attract game. You can get ‘tall mix’ (1m), ‘short’ (0.5m), and ‘new wave’ – this is a mix of sizes which provides good cover for game and increases the insects and other invertebrates on which partridges feed. I know this neighbour also keeps bees, and I asked him if the seed mix was a special honey-assisting one (mélange mellifère). He said no, though all flowers will help the bees.  He keeps bees partly I think because he also has a lot of peach and nectarine trees he wants to have pollinated.

Research has also shown that the flower mix increases the number of true wild flowers, since the fields are untreated with chemicals and undisturbed all year. It made me think how all the activities of a village are connected, so that hunting is tied in by many links to other crops and products, to biodiversity and sustainablility. In fact I found that the Departmental Federations of Hunters are the main bodies giving advice and distributing seed.

You don’t have to drive to France to see it – you can get screensavers of jachère fleurie here (Télécharger = download), and the photos give a good idea of the effect.

On the other hand of course, if you leave land fallow, it will soon be colonised by herbs, then perennials and shrubs, and finally by trees, and eventually the biodiversity will be even greater. Fifty species per square metre is possible for old hay meadows in northern Europe, which are cut every year and hence avoid the shrub/tree succession (as opposed to four or five species in jachère fleurie).  There remains only one per cent of  the meadows which existed in 1940 (more here).

However, this recolonisation takes many years, and may not be realistic for former agricultural land with a depleted seed bank, while the jachère fleurie is an instant, artificial solution, and presumably brings the partridges in that much quicker for the hunters.   All this reminds me to have a close look at the flora in some abandoned vineyards, and at  the succession of plants here which is not the same as in northern Europe.

Time for Etta James and Burn down the cornfield (originally by Randy Newman) – an incitement to passion, or a protest against monoculture? You decide. There’s some debate whether the slide guitar is by Lowell George or Ry Cooder – for anyone with ears, it’s definitely George.

Etta James died in January.  I can’t imagine her resting in peace now – burn on, Etta.

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Viola tricolor, Darwin and ecology

Viola tricolor

This tiny, beautiful little plant appears each year in unexpected places in our garden, germinating from seed scattered from who knows where. It is also known as heartsease, a lovely name perhaps due to its pleasant perfume, or maybe to the arrangement of petals, described by William Turner in 1848 as  ‘Two faces in a hoode’, which led to the flower being seen as a symbol of love.

In French the name for any flower in this family is pensée (from which comes the English pansy), meaning thought, since it is an emblem of  remembering.   This enables me to make a connection to a giant of nineteenth-century thought.  I wanted to start with this plant because of its link to the name I’ve chosen for this blog and to Charles Darwin.  In The origin of species Darwin writes:

I have, also, reason to believe that humble-bees are indispensable to the fertilisation of the heartsease (Viola tricolor), for other bees do not visit this flower….Hence I have very little doubt, that if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare or wholly disappear.  The number of humble-bees in any district depends in a great degree on the number of field-mice, which destroy their combs and nests….Now the number of mice is largely dependent, as everyone knows, on the number of cats….Hence it is quite credible that the presence of a feline animal in large numbers might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!

He goes on just a few lines later to say:

In some cases it can be shown that widely-different checks act on the same species in different districts.  When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this!

Darwin’s great work was published in 1859, before the word ‘ecology’ even existed: it was coined in 1866 by one of Darwin’s greatest fans, the dashing German biologist Ernst Haeckel. Clearly, however, Darwin’s vast knowledge as a naturalist gave him an awareness of the interdependence of all living things, plants and animals, and of their environments.  There’s an interesting series of radio programmes on Darwin, originally broadcast to celebrate his bicentenary in 2009, available for listening here for anyone who wants an alternative to reading his magnum opus.

Note: From noise to aeronautics: for more on how Darwin’s term  ’humblebee’ was replaced by today’s word ‘bumblebee’  see here.

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