Thursday 26 February 2015

Hybridity’s contribution to Evolution

Part 3
No, not an evolutionary tree, merely the ginkgo maiden hair emblem of a Japanese district

I have argued in Part 1 and Part 2 that the most frequent occurrence of hybridisation is when closely related animals or plants breed together and that their line of issue repeatedly backcrosses within the group of one of their parents. The effect of the original cross is hugely diluted but never-the-less new genetic material will have  transferred from species to species. Such genetic information gives natural selection a greater pool of genes to work with.

I have said little about incredibly rare successful hybridisations between organisms genetically distant. Such events of varying ‘distance’ have been recorded and continue to occur. They neatly explain the mysterious appearance of completely new animals or plants in the fossil record. Such animals or plants are not so different to be completely bizarre and are consistent with reasonable deduction of the identity of their parents - albeit this is made difficult by the fact that the parents will often be extinct.

The consequence of hybridity is that the ‘tree’ of evolution is not merely a series of simple branches. Instead, from it’s very beginnings the branches and twigs are entwined and grafted together. Even the roots, not normally depicted, are finely matted.

I had intended today to use the three ‘fossil trees’, Ginkgo biloba, Taxodium distichum and  Wollemia nobilis to both further my argument and to celebrate the wonders of evolution. I now find there is so much of interest about ginkgo and its cycad ancestry that I need to write further posts after this one!

About ginkgo
A fine Ginkgo biloba in Kew Garden

Ginkgo, The Maidenhair tree is repeatedly recorded in the fossil record over a period of 270 million years. Fossils have even been found here in North Yorkshire in Scalby. I wonder if I can claim to be native? Over this time ginkgo  has remained remarkably constant although it did evolve into several now extinct species and once had worldwide distribution. Ginkgo biloba is the only species surviving. 
It must be very difficult to classify the extinct ginkgo species when, for example, the leaf shape of the modern plant has numerous variations on a single tree. There is very little difference between the present day form and the oldest of fossils. One might ask why over such time it has not made small Darwinian changes into something quite different.

Known from the fossil record, ginkgo was thought by western science to be extinct until discovered by a dutchman in Japan in the palindromic year 1691.
It had been preserved planted around ancient Chinese temples. It no doubt had traditional herbal uses as well as sacred traditions. Resistant to fire there is an old legend that a dense planting of ginkgo once protected an ancient temple from being burnt down. 
It would now seem that in China some present day ginkgo forest has survived directly in nature.
Propagation material had been taken from China to Japan about a thousand years ago where it also became sacred.

Ginkgo has survived and now continues to thrive in disturbed, rocky, wet, yet well drained soil. It is known to grow in soils as acid as pH 5 but seems fairly pH tolerant. I grew it in York at a neutral pH 7. In fact it is very easy to grow and is remarkably tolerant to pollution and susceptible to hardly any pest and disease. It makes an excellent street tree where it can survive at very low light intensities.
Beautiful yellow Autumn colour on my tree

It is reported to live up to 3000 years old and achieve heights of more than forty meters. Its longevity is aided in that it freely vegetatively propagates from basal ligno-tubers or broken attached branches that root into the ground. Ginkgoes are usually monoecious (single sex, male or female) although dioecious trees have also been recorded. Males are favoured  for public planting because females carry large seeds that smell rancid!  A possible factor in it’s decline and near extinction might be that dinosaurs were significant vectors of its stinking seed.

My young tree initially developed a tall unbranched trunk rather reminiscent of young ginkgoes competing in forest
Revered in Japan, several ginkgoes were within a kilometre of the epicentre of the Hiroshima explosion. Although charred they fully recovered and perhaps relevant to the theme of this post and ginkgo’s genetic stability over 270 million years, no mutations were reported.

So where did ginkgo come from? Although thousands of its fossils are known, there is no fossil record of its immediate parent. Botanists could not agree how to classify something that had both conifer and cycad characteristics and invented a division in plant classification to especially contain it. 
Genome studies have shown that ginkgo contains cycad genes. Gingko in common with cycads, but in common with no other tree, achieves fertilisation by means of  mobile flagellate spermatozoa.  
(Botanical note. Fertilisation is a distinct process to pollination and the pollen tube which precedes it. Motile ginkgo sperm do not have to swim very far)

So could ginkgo be a hybrid? Even today this is a heretical notion and would appear to have never even been considered. Perhaps it has been suggested and dismissed with a sneer. 
If it were a hybrid what might be the two parents? Conifers are the only tree that grew alongside the early cycads as far as I know. Perhaps ‘the other parent’ wasn’t a tree, cycads themselves are woody and very tree-like. I felt I must read about cycads!

I thought I had better check out cycads and to find out if this most ancient of plants actually hybridises.
It is very promiscuous indeed according to modern breeders. Cycad propagation text books actually advise how to avoid  hybridisation. 
Most evolutionists do not seem to consider hybrids a possibility! Interspecifically ginkgo hybridises very freely. Between distinct cycad genera a significant numbers of successful crosses have also been recorded. This is a long way from creating a ginkgo but a distant hybridisation event or a series of crosses seems no less believable than standard evolutionary theory. 
If cycads were shown to be one of the parents of a past hybridisation would it challenge neo-darwinian theory? I think not. In my next hybrid post I will write about an iconic conifer that has been shown to be an ancient hybrid. Of it having any significance to evolutionary theory there is not a whisper!

A rare slate blue cycad in Funchal botanic garden

Cycads are fascinating plants that share ginkgo's monoecious life cycle, longevity and resistance to fire. 

I was fascinated to discover the story of the cycad Encephalartos woodii. Now extinct in the wild, only one specimen was ever recovered. It is a male that produces fertile pollen. 
Plants have the advantage over most animals that they can reproduce vegetatively. E. woodii propagates very freely from suckers and grows into a six meter high vigorous 'tree'. It is now to be found worldwide in five hundred botanic gardens and many more are in private collections.

Where did it come from? We are in the realm of speculation. Had the females become extinct? A very real possibility. Was it a hybrid (between two cycad species) and a female form had never existed?

Is it possible to recreate a female encephalartos and obtain viable seed? There are various possibilities that are being tried. 
A recognised fact about cycads is that they sometimes change sex if subjected to stress. It needs a very strong will to almost kill your prize plant to actually try! 
Another approach, close to my story, is to use fertile pollen to hybridise with a close encephalartos species and to repeatedly back cross over several generations using E. woodii pollen to recreate a female version of the original plant! Note the time between germination and production of seed is a long one. It might be a long wait.

Micro propagation can be used to vegetatively propagate thousands of 'spare' plants for the breeders to play with.

I have no information what-so-ever that ginkgo did not evolve in a straight line from a single now extinct cycad. What grieves me is that no one seems to have looked at the possibility of hybridisation and without evidence just assumes the usual story.
cycad in Funchal botanic garden

Never give up on an apparently dead cycad. It can be vegetatively propagated from leaf, root or stem! I haven’t a clue about the history of this cycad in Steven’s new garden.

Neanderthals and humans 
If you condense the four billion year age of the earth to that of a day it was a single second before midnight when these two very close relatives got together. Perhaps a very good time for a fling. Being genetically close and sharing the same number of chromosomes many unions were destined for procreation.

I lay in my bed and got thinking about recent revelations that we share with neanderthals 2 to 4% of our genetic make up. I got to wondering that when, as we surely will, further analyse fossil neanderthal DNA, that a similar ratio of human DNA will grace their own genome.

I thought that 4% is quite a high number and surely represents frequent liaisons. After all, when hybrid genes are subsumed into a populations over hundreds of generations of back-cross-dilutions they will virtually vanish. Reminiscent of dubious homeopathic molecules that disappear with their repeated logarithmic dilutions!

But was I now dreaming?  Surely my hybrid posts are about how natural selection selects from a widened pool of genes made available by hybridisation. If neanderthal genes held advantages, then of course they would remain. Indeed how much better the chances of several linked genes being passed on than those of a single mutation as typified by neo-darwinian theory. 
Recall that several genes from hybridisations are often associated together and change is not always just an isolated mutation.
I wondered how many beneficial Darwinian random mutations never saw the light of day?

I then had a nightmare. What if the 4% figure was achieved after statistical binning? I awoke with a jolt and realised that as they had been looking for neanderthal genes they would not on this occasion have dumped them!

And news of potential hybrid ancestry millions of years before modern humans and neanderthals emerged

From the December 20/27  2014 issue of the New Scientist
According to the New Scientist, the science community are eagerly awaiting results from findings in the Rising Star cave in South Africa from where several skeletons have been taken for analysis. They would appear to be between 2 and 3 million years old, the time when Homo was splitting from Australopithecus.
I loosely quote the New Scientist. “instead of a neat family tree it looks like a number of ape like creatures existing a few million years back interbred to produce a messy collection of species, from which we eventually emerged”

Wednesday 18 February 2015

Soil Carbon Capture

Nature’s glue and superglue: humus and glomalin 


Most of the gardening press portrays bulky organic matter as humus. Wrong. It is not. Humus is a small and very distinct component of soil organic matter. Most organic matter whether added by grower or nature is destined to quickly decay. Not necessarily a bad thing as valuable nutrients are released when the carbonaceous component returns to carbon dioxide and water.
Generally humus is much more long lasting. Sometimes for hundreds of years when intimately mixed with soil particles, particularly clay, it binds particles together in what we hope are ‘water stable crumbs’.
Even science is fairly ambivalent as to what humus actually is and in different circumstances the term has different meanings. You might remember from your geography books, forms of humus that occur in nature called mull, moder and mor. Yes, it bored me too!  
Mull is formed when plant residues mix evenly into the surface profile - rather similar to a gardener’s soil without the dubious benefit of cultivation but with the benefit of worms. Mor is accumulated partially decayed organic debris that builds up on the surface, is usually acid, relatively stable and any breakdown is dominated by fungal action.

Even the humus I refer to today, in terms of  definition, is something of a ‘mish mash’. Perhaps that is because it is a bit of a mash up in chemical terms! 
Scientists used to say they could not properly define humus because its extraction destroyed its true nature. They talked about humic and fulvic acids. They still talk about its colloidal nature.
Fresh plant and animal organic remains undergo a process of gradual decay. I think of it as a journey taken with poor navigation. Numerous organisms and processes are involved. They might include those in the gut of a vertebrate such as a horse, to those of the  smallest soil-living bacteria. Invertebrates, bacteria and fungi will all join the party. It is not just breakdown, it is synthesis too, when organic matter is food for an organism and becomes part of its substance, not to mention it’s faeces with all that enzyme action. The process might start by being rasped by a snail’s radula or the decay caused by grey mould. It ends with black humified material usually destined to quickly oxidise completely away to simple inorganic chemicals.

The mystery is why humus, as shown by radio carbon dating, can benefit the soil for hundreds of years. The reason is not completely clear. One factor might be that this mangled organic debris has no regular structure. Unlike fresh organic material where molecules join together in a series of regular patterns, these are no longer a feature of humus. Bacterial enzymes which are capable of organic matter breakdown usually work on ‘lock and key principles’. No regular structure means no easy way in.
Another factor is the very small size of some organic materials. Not only can they intimately mix in with and glue together clay particles, soluble humates might even penetrate within the lattice structure of clay where the spaces are too small for bacteria to enter.
Some ‘particulate’ humus is merely tough and hard organic material derived, for example, from woody material.
Sorry to be vague but soil organic matter does have that reputation of ‘muck and magic’.

Mycorrhiza are the source of glomalin

That a third of the world’s stored soil carbon weighing thousands of millions of tons was unknown until barely twenty years ago is truly amazing!  It is a constituent of every soil examined in what is now worldwide investigation. It is a tough glycoprotein and is a superglue that sticks sand, silt and clay together into wind and water resistant highly fertile  crumbs. It is a product of the tough linings of hyphae and spores of dead mycorrhizal fungi. Known as the arbuscular fungi of the genus glomales, all rely on symbiosis with plants to derive their carbohydrate content. Glomalin is a rich store of iron and nitrogen and is very stable with a life of as much as forty years. Its iron content is thought to be significant in a plant’s ability to fight pest and disease.
Although the amount of glomalin in a soil is highly variable it’s not unreasonable to estimate an average soil content at least five times that of humus. Humus content is partially protected by glomalin.
Needless to say no-till methods of farming that are now starting to proliferate worldwide  - although not in the UK - hugely enhance glomalin formation. 
Not only does minimum cultivation encourage glomalin production that hugely improves soil fertility and plant yield, it sequesters a lot of carbon.

For most of my life I did not realise that soils sometime contain significant amounts of pure carbon, the long lasting remains of historic fire. When vegetation is burnt most of the carbon is released in the form of carbon dioxide. But not all when char falls to the ground. Sugar cane soil for example is often very fertile as a consequence of annual burning.(A process unfortunately not free from atmospheric pollution). 

I have written previously about ancient, fabulously fertile, very deep, Amazonian black earth soils which are known as terra preta. They were created by bygone farmers who over numerous generations added charcoal to their soil.
Science has never quite accepted the claim of modern South American farmers who sometime sell a thin layer of their soil to garden centres for compost(!) and claim that it grows back. This is not so silly as it sounds because charcoal with it’s vast porous internal spaces is an ideal substrate for arbuscular mycorrhizal fungi. If the rate of glomalin production is speedier than its decay the volume of the soil’s carbon grows!

My own interpretation of some recent research

There is now considerable interest in adding ‘biochar’ to agricultural soil. Made by pyrolysis from unwanted woody and vegetative remains it has the potential to create soil fertility and at the same time to sequester carbon.

Much research is taking place. The result of a recent trial at Southampton University worries me. Please indulge me for exploiting my platform of ‘writing a blog’ to make a suggestion!
The Southampton work is a very fine piece of research that has had much recent publicity. Done by geneticists using lettuce and thale cress, that darling of researchers, it showed that biochar/soil mixes gave healthy growth as a result of favourable genetic stimulation. Unfortunately they also found  a suite of genes that switch on a plants ability to fight pathogens to be completely inactive. The fear that char might make a plant vulnerable to pest and disease would be the death nell to this nascent technology being adopted. The research gave no indication that the plants actually suffered from any infection. 

I think they have drawn the wrong conclusion  

It has been my understanding that a plant’s defences are switched on when pest and disease threatens. We keep reading about how plants signal the presence of predators to mobilise their fighting resources. Every phyto-chemical synthesised to fight a pathogen comes at ‘a cost’. If a plant is healthy and unthreatened it does not need these genes to be working!  My own interpretation is that biochar encourages healthy growth but the trial control of less fertile agricultural soil causes stresses that alert the plant’s defences.

Even if as is likely, I have got it all wrong, we should not jump to conclusions. It is my understanding that field studies generally support the notion that plants grown in biochar are healthy. It is thought to be one of the huge benefits of terra preta soil!

I do think researchers have a problem with biochar in that the fresh material of this porous and strongly absorptive material has very different properties to older samples that have weathered, become charged with nutrients and teem biological life.
As an ingredient of a growing compost it seems in my own experience that fresh unprepared charcoal is pretty useless. But when I scoop up a spadeful from my charcoal enriched soil it gives superb results in a pot!

Making my own ‘charcoal’

I have reported before that I go out on a limb in how I prepare what I claim to be char. I do not let my bonfires burn through. I immediately extinguish the final burning embers by dousing with water. What a thrill to to see the immediate transformation to jet black shiny flaky remains.

Peter and I have recently had a project in Cathi’s garden. Her sixty meter long hedge had been uncut for all of ten years! Peter worked all day with his chain saw whilst with the ‘help’ of my son I dragged the wood away to create a thirty meter long pile. 
Last week it was dry enough to burn. 
We created a really hot firm blazing compact base and together spent ten man-hours continuously dragging branches to the hot blazing pyre. Peter later retreated and left me with at least a cubic meter of ember. I spent a very happy half hour with the hose pipe. Never before have I had a fire big enough to give me twelve piled barrow loads of lovely black gold! My normal fires produce a barrow of bounty and only take a couple of cans of water to extinguish. Not this one!

I make no apologies for having a fire. We live in the country and there are no legal restrictions. All our neighbours have domestic fires. Peter and I were always going to burn the wood. It would have cost a thousand pounds to have it recycled at the local composting plant. We see lorries burning diesel bringing all manor of wood many miles for disposal at the cost of hundreds of pounds a load! 
I do not of course have a pyrolyser which is the proper way that regular char is prepared. Pyrolyzing is of course non polluting and retains fuel residue. It is not an option for me. You might decry my methods but at least I have sequestered a lot of carbon rather than generated even more carbon dioxide. My char will sequester in the ground many years after all that wood would have rotted away to carbon dioxide and water.
I have amended my methods with the char that I generate. Not only do I now mix it with compost materials such as the copious herbaceous litter that my garden produces and the organic debris when I clean my ponds, I speed the breakdown of the soft vegetation and ‘charge up’ the charcoal with generous use of a high nitrogen general fertilizer.

I used to be rather apologetic that my ‘shiny black’ was probably inferior to that made in the normal way. I wonder. I suppose those ancient South American natives prepared their charcoal from wood - not having the technology to prepare soft vegetation into the equivalent of modern biochar. Local Amazonian practices suggest even now, that soft organic vegetation and animal droppings were stored in urine rich middens. I imagine it all got together with the charcoal before being spread on the fields.

Boys form the black stuff!

It was dark by the time I extinguished the fire
Half of the prunings
We got a good blaze
It was a bit of a competition

 We kept a small fire going for several barrow loads of woody clearings the next day

It just might be better to crush the charcoal to a powder
It would have been better to mix it in

It won’t blow away but I won’t take any chances
My previously enriched soil. I won’t pretend this is a vertical profile! (yet)

Mulched two years ago from my previous compost/char heap

The creators of terra preta mixed pottery shards into the soil. It is merely incidental that my bricks are contributing!
It was a very hard day
Making char is just ‘my cup of tea’
(‘char’ is Yorkshire dialect for tea)

I have written a new post about the use of 'my char' in potting compost
USDA link about glomalin

Friday 13 February 2015

Sudden leaf fall on evergreens

Clean sweep, it’s just completely  normal

Evergreen leaves on shrubs and trees do not last forever. They are destined to die and often there will be an annual leaf fall. A classic example is the holly when suddenly you have a carpet of brown leaves on your lawn. In most cases of evergreen leaf fall, only a proportion of the leaves drop on a single occasion. There is nothing to worry about. It’s just old age and is called senescence. Now in my dotage, I too sometimes feel senile. 
Usually leaf  fall is accompanied and followed by a flush of fresh new growth. Wish the same worked for me.

No doubt that my cedar is thriving, it has grown an extra five metres in ten years.

A fairly extreme example of evergreen Spring leaf fall is my Cedrus atlantica glauca. In April it suddenly looks somewhat sick and most of the leaves become yellow and brown and fall to the ground. If I were a beginner I would be extremely concerned. Within just a few days it starts a strong soft green transformation.

Leaves failing to fall on deciduous trees
Leaves on deciduous trees usually fall to the ground in Autumn. Not all, juvenile beech holds its leaves overwinter and becomes very untidy when leaves fall in Spring.
I feature today Hamamelis ‘Arnold Promise’  to which Autumn leaves stick like glue right through Winter and if not manually removed ruin the flowers

Beautiful Autumn colour after several weeks turns brown and without physical removal will hide the best of the flowers

I remembered to pluck all of 200 dead leaves last Autumn. Fortunately for blog illustration I missed these! 
nb ‘Arnold Promise’ is the only common variety to suffer.

Thats better!
Leaf fall on my calomondin orange

As I have previously reported our calomondin orange which has held its fruit through most of the Summer is brought in from outside into our warm light conservatory around the beginning of December.
Its leaves are looking rather tired after a hard working life. Many of the leaves start to yellow. After just a few weeks in the warmth of our conservatory the first of the flowers that will give next years fruit are starting to appear and new leaf growth is awakening. The yellowing leaves are destined to fall, usually gradually and need to be swept up over a protracted period.
I  had a lucky ‘accident’ this January when I inadvertently allowed the pot to become too dry. By the time I had noticed and given the plant a thorough soaking, the yellow leaves with the help of a shake cascaded down. Eureka, the plant shouted hurrah, and accelerated into new healthy growth. I have never seen my plant looking healthier! I suspect I will have another accident next year.

All in one go?

The other conservatory plants are not quite so cooperative. Can you identify the debris?

Most of the senescent yellow leaves have gone and new leaf growth is strong.
nb the plant had a 60gm top dressing of YaraMila fertiliser in December

Thursday 5 February 2015

Book review: ‘One day the shadow passed’ by Jonathan Reggio

A work of fiction dedicated to Masanobu Fukuoka

Masanobu Fukuoka’s influence on my own gardening philosophy
I was given a book in 1963 - I can date it precisely - written by a strange Japanese rice farmer. I now know he was to achieve worldwide renown as a great prophet of natural farming, organic horticulture and minimum cultivation. In later years he would travel the globe participating in tree establishment projects in arid places and sharing his knowledge and wisdom.
My book disappeared and I was unable to retrace it. Masanobu’s classic description of his work and his philosophy is ‘The One Straw Revolution’ first published in English in 1978.  Despite much effort I cannot find any reference whatsoever to my much earlier book of inspiration.

I do have very clear memory of some of his insights. Not least, not disturbing the ground by harmful cultivation! Strangely, I remember his ways with rice! He did not grow it in traditional flooded paddy fields but in better aerated, very wet but drainable soil. He did occasionally flood the fields to kill the weeds. He duel cropped his land with Winter barley and Summer rice. One crop could be sown before harvesting the other. He scattered his seed in tiny capsules of natural clay. He called it ‘do nothing farming’.
His vegetable garden, in light shade under fruit and nut trees, was home to his hens. He grew a wide range of traditional vegetables in a glorious but intimately managed jumble.
On the hillside his citrus trees were minimally pruned. I vividly remember his description of how the drainage in the rocky terrain was improved by burying woody debris.
He refused to use any chemicals whatsoever, he never sprayed and completely relied on natural control. He had no need for fertilisers as everything was recycled. It took several years to achieve but his rice yields were the highest in his district.

You might not recognise me, a dedicated glyphosate sprayer in much of the above. You might be surprised that with regard to my gardening philosophy Fukuoka has been a huge inspiration!

Now I ‘do’ Cathi’s garden, I share with the hens

I sometimes bury wood and last year I blogged about starting my hugelkultur raised bed

My own vegetable jumble (jungle?)

Some Bolton Percy residents regard this as my ‘do nothing’ garden.
Others think I do nothing at all!

In my cemetery gardens I use no manures, fertilisers, insecticides, fungicides or slug killer and of course I never dig. But I do use glyphosate!

An uplifting book

Jonathan Reggio’s book claims to be a work of fiction. Only thinly veiled, the main character Takeshi Fumimoto is Masanobu Fukuoka. He is so accurately and lovingly described that I think the author must have himself been one of his disciples and have personally known him.
The theme of the book is a young man, James, who feeling he is losing life’s direction goes walking on Shikoku island in Japan. He follows the trail of an ancient forty day pilgrimage, gets lost on the way and stumbles upon Takeshi’s farm. Written in the first person, the delicate understanding of the local culture, intimate descriptions of plants in the countryside and love of the people strongly suggest that James was actually Jonathan. So much for it being a work of fiction!
James leaves Japan with a new sense of life’s direction, but troubled that Takeshi is having lots of problems with his methods and is failing to achieve local acceptance.
He vows to return and seven years later goes back, not sure that the unorthodox farmer will still be there. I won’t reveal what he finds but I assure you, you won’t be disappointed.

Cathi bought me this short uplifting book just before Christmas. I had read it by the next day. Warm and sensitive it brought tears to my eyes.
Jonathan Reggio now lives with his family in the Lake District
Thank you Jonathan for your story and revelations about the life of my hero.

Masanobu Fukuoka died aged 95 in 2008. A few years earlier Masanobu had returned a grant of $10,000 to the Rockefeller brother’s fund as he felt he was too old to need it.

A beautiful and life changing story of one man’s refusal to go along with the madness of the modern world. By turns poetic, wise and entertaining... it will leave even the busiest reader with the itch to slow down, to plant something, to go on a long journey and to raise their eyes to the horizon. (Chris Cleave).

To find my previous book reviews put 'book' in the search box at the bottom of the scroll.
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