Wednesday, 28 May 2014

The perfect lawn - more complicated than you might think.


This garden in the west of Scotland was built on a piece of moorland in the 1960s and no attempt was made to add drainage infrastructure to the ground before the building project began.

For about 20 years the owners followed the instructions of gardening gurus and treated the lawn with moss killer and weed killer and and so on. However, the ground is extremely wet, and I don't think that the manufacturers ever really intended the chemicals to have a miraculous effect on such ground. The work has been an interesting experiment to show how the population of plants responded to the treatment.

As it happened, the owners treated only part of the lawn, while another part was untreated. Strangely, in the treated region the edges were also missed, so that we can now compare the effects on the two areas. Both areas still have a great diversity of species, but the ranges of species in the two areas are very different. This difference may also be to do with other variables, as the two areas are on different sides of a house, and have different drainage. The treated lawn is surrounded by a six foot tall hedge, while the untreated lawn has a 30 foot tall woodland on one side and a steep drop on the another side.

This photo shows the edge of the treated lawn. The untreated edge has a lot of green grass and daisies, while the treated area is mostly moss and grass.


This is a close up of the untreated edge. Most of the species are broad leaved, and the majority of obvious plants are grass and daisies. 


This is a close-up of the treated area. It contains very sparse grass and a lot of moss (I like moss, so that's not a complaint). 


In the completely untreated area on the other side of the house there are also a lot of broad leaved plants, and a lot of grass. This photo below shows a common marsh orchid that has seeded from nearby.



There are a number of interesting wildflowers. I like this one, but I have not had a chance to identify it yet. 


There are a lot of buttercups. 


There are quite a number of reeds in one very damp area. I like the reeds and the general diversity of species. It gives information about the soil conditions and I like watching the soil conditions change over the years and seeing that change reflected in the population and growth of the plants on the surface. 


Returning to the treated area on the other side of the house, we can see that this area also has a great diversity of species, but here the species are mostly mosses and just a few grass plants here and there. 

It's very hard to say what the connection is between the years of lawn treatment and the presence of the moss. Was the lawn treated because there was a lot of moss (and that moss is still there in spite of the treatment)? Or is the moss there because of the effects of the lawn treatment (removing broad leaved weeds that might have removed some of the water from the soil and reduced the tendency for moss to colonize the area.) I don't really know what the reason is for the large quantity of moss. However the area is notable for its lack of daisies and I assume that that is to do with the long term application of weedkiller. 

 This is a photo of a representative section of the treated lawn.
 It has a lot of interesting mosses and not much grass. 


This is a particularly attractive moss in the treated lawn. 


There are also some lichens. 


Another lichen:



So what is the conclusion here?

To reiterate, this is about making a lawn on undrained moorland, which is a pretty interesting thing to try to do.

It seems to me that the weedkillers were very effective at getting rid of daisies, but I quite like daisies, so on balance I'd be inclined to just keep them and no bother to use weedkiller. That's a personal preference.

From the moss point of view, I suspect that it's all down to the drainage of the site. The treated lawn seems to me to be much less well drained than the untreated part of the lawn, so it's entirely possible that the moss situation seen here is purely related to drainage, and unconnected to the use of moss killer over the years.

I could be wrong about that though, and it may be that the removal of the broad leaved weeds has made the ground even wetter and that the ground has become a bit poisoned by heavy use of chemicals.  I suspect that the health of the grass has been affected by the use of lawn treatment, because the grass actually got more and more sparse with more treatment. Perhaps the nitrogen fixing weeds were lost and that made the ground less attractive to grass and more attractive to moss. Possibly in such we ground it would have been more effective to just apply a nitrogen feed to encourage the grass and help it to out-compete the other species.

What's my main conclusion though?

Well my real conclusion is that if I found that I had a mossy lawn then I would try to become interested in mosses and enjoy it. If I had a lawn full of wild flowers then I'd try to become interested in wild flowers and enjoy that. If I absolutely had to have a perfect lawn, and I lived in a very wet place, then I think I'd grow it in a pot. 



Dryopteris wallichiana

This is an unusual type of fern called Dryopteris wallichiana. It is a very striking plant with a very dark central line down the back of each frond and makes a very bold statement in a garden border. 


This is a close-up of one of the opening fronds, taken in May in a warmer than average spring in the West of Central Scotland. 


Pellea ovata

This plant is a very unusual kind of fern called Pellaea ovata.


The photographs below show how unusually regular and geometric the leaves and stems are. 






This is a young frond uncurling in the centre of the plant.



The Wollemi Pine


This tree is a Wollemi Pine. The Wollemi Pine is a very old and rare plant, and its history can be found at the Wollemi Pine website. This specimen is privately owned and is kept in a conservatory in the West of Scotland. In the warmth of the conservatory it is growing very fast, and the new growth at the end of each branch can be seen clearly. The new light green section at the end of each branch shows in stark contrast to the darker green of the older branch section. The tree is about 4 feet tall. 


This photo show the branch in close-up so that the new light green and older dark green growth can be seen clearly. 


In very new growth the leaves are curled up, but the straighten out as they mature, so that the whole structure ends up flat. 


Over winter the apical meristem produced a clear covering which seemed to protect it from above. This also appeared on the end of each branch. 


When the branches began to grow in spring the clear covering was broken through and the remains of it can still be seen at the junction between the old and new growth. 


Friday, 23 May 2014

How does the internet work?

Who is this text for?


This text is intended as a help for primary teachers who are to begin teaching computer science in the coming academic year. It is specifically written for the level of understanding of a primary school pupil in order to be an aid for teachers. If you are in this position and have other computing questions I would be pleased to hear them. This text was written by Jennifer Deegan, using technical information contributed by Tim Deegan.

What is a computer network?


A computer network is a set of two or more computers, linked to one another using electric cable, radio waves, or beams of light in fibre optic cable. If more than two computers are linked, then there must be a computer at every junction in the network. Messages are passed like chinese whispers (or like a bucket chain), so they go from computer to computer to computer, through the network until they reach their destination.

What constitutes a "computer"


When we say a “computer” we do not just mean a laptop, desktop or tablet computer. We also include many other devices that contain internet linked computers. For example: a mobile phone, a central heating boiler that can be turned on from a mobile phone, a house burglar alarm which could send a message to the owners phone or PC, VoIP phones, set top boxes for watching TV,  satellites, and lots of other things.

The internet is a huge computer network


There are many millions of computers connected together across the world now. The total network is known as the  internet, and strictly speaking, it is a big network made up of many smaller networks. A lot of the computers are only there to pass information on from one part of the network to another. An example of such a computer would be the internet routers that we have in our houses to connect the internet outside the house to the laptops, desktops and tablet PCs inside.

The World Wide Web (www) runs on top the internet, and it is the set of services that people have developed to run on these networked computers.(Many people now use the terms "internet" and "www" interchangeably, and that's okay in most situations.) There are millions (or billions perhaps) of pages of information in the www, and they are all easily accessible to us. We can learn from them, just as if they were a giant encyclopedia. There are also shops and games and videos, and all sort of other interesting things. But how does our computer get hold of these pages and display them on our computer screen?

How does the internet actually work in detail?

How does a computer ask for and receive a web page?


Just as each house has a street address (e.g. 25 Primrose Lane) each computer has its own address IP address (Internet Protocol address). An IP address looks like this:  “172.16.254.1”.

When we type a website address or “url” (uniform resource locator) into the bar at the top of a browser window, the computer sends a message asking for that web page to be loaded into the browser window. The computer sends the computer name from the url (e.g. www.bbc.co.uk) to a special computer on the internet called a DNS server (Domain Name System Server). The DNS server may have to pass the message around a bit to get the full answer, but when the passing around has been done, then the DNS server will send back the ip address of the computer on which the website lives. Our computer can then send a message to that computer, asking for a copy of the webpage. Our browser will then load the new copy of the web page that we have requested into our browser window.

Sometimes we might wish to load the same webpage quite frequently, day after day, or week after week. In this case our computer would store a copy of the webpage in a place called the “cache”, so that the page can be reloaded again later. This means that the page can be reloaded from the cache without the computer having to request a new copy from the far away computer that holds the original copy.

What happens when we click on a link in a web page?


The DNS section above explained how the computer summons a web page originally from across the internet, but what happens when we click on a link within a webpage? For example, what happens when we click on the link “http://www.bbc.co.uk/iplayer/cbeebies/2014-05-12” from within the page “http://www.bbc.co.uk/cbeebies/games/”?


To understand that we need to understand three simple concepts: IP, TCP and HTTP:

1) IP (Internet Protocol)


Each computer has an IP address like “172.16.254.1”. When a computer sends a message to another computer using the IP system, the message goes from computer to computer to computer, across the internet. This is like playing chinese whispers with a lot of children. Imagine that one child (Katie) writes a message on a piece of paper and passes it, child to child to child, across the network of children, in the hope that it will eventually reach the right person (William). The mechanism is not totally reliable; it might work, but there is a chance that it won’t. IP is a simple system by which computer send messages across the internet, but it is not totally reliable.

2) TCP (Transmission Control Protocol)


TCP is another mechanism for sending messages from computer to computer across the internet. TCP is built using IP, so it is still like chinese whispers, but there are a lot of rules included to check that messages have been received. For example, a return message is always sent confirming that the message arrived; if this does not happen, then the original messages will be sent again. Also if several messages are sent, and they arrive out of order, then the TCP mechanism ensures that they will be put in the correct order at the destination. So TCP and IP are rather similar, but TCP is much more reliable.

3) HTTP (Hypertext transfer protocol)


You will have seen the abbreviation “http” a lot as it is at the beginning of every url. HTTP is not another mechanism for sending a message, but is a structured language in which the messages should be sent. Imagine that a class were talking to each other over walkie talkies. Katie might say “The ball is in the box, over” and William might reply “10-4, Katie” which means “message received”. On walkie talkies we use a very structured language for clarity. In the same way, computers use a very structured language when they send a message over TCP to ask for a webpage. The structured language is called “http”.

So what happens when we click on the link within a web page?


We might see a link like this “http://www.bbc.co.uk/iplayer/cbeebies/2014-05-12” within the main page  “http://www.bbc.co.uk/cbeebies/games/”. We can then click on this link. When we do this, the computer sends a message using http language, through its TCP connection, to the computer that holds the original copy of the website. The message asks the computer for the part of the website that corresponds to the sub-section of the website “/iplayer/cbeebies/2014-05-12”. That page will be sent back and quickly displayed in our browser window.

What can we use the internet for?


There are many useful facilities offered by the internet. The network makes it very easy for people to communicate in writing, by voice or video message. A person in the UK can have a video phone call with several other people in several countries all at the same time, to solve a complex problem. This is now a daily activity for business people, scientists, politicians, families and many others.


Big companies and charities offer many other services via the www. Google books is making online copies available of all (out of copyright) books. People can send instructions to their banks or companies like Paypal through secure systems via the www and so organise their money online. There are special shops that operate only online (e.g. Amazon and Play.com). We can write to newspapers or to our MPs and MEPs through the internet. Friends and organisations communicate through social networks such as facebook and twitter, and very serious work is sometimes done through such media - such as organising how to get safely to work in a place that is in the grip of a civil war.


There is also a lot of crime on the www and the government and the police are still working out how to establish laws to control this crime, and how detect and punish it. We have to be very careful when using the www to avoid being duped by criminals, and to avoid handing over our personal information to the wrong people.







Thursday, 22 May 2014

Pheasants

This is a male common pheasant (Phasianus colchicus). He is a wild pheasant but is fed daily by a family, whose garden he visits. The garden is in a housing estate, but backs onto a large expanse of moorland, and is also visited by roe deer. The pheasant is about two feet long. 



His feathers are very bright and decorative. The family who care for him have recently started giving medicine to stop infection by ticks. I understand that this really helps the health of the pheasant, and causes the red wattle on his head to develop well. The well developed wattle is a sign to the females that the pheasant is in good health, and shortly after the tick treatment started, the pheasant appeared with a family (a female pheasant and three babies). The female and babies have disappeared just now, and it is likely that they are sitting on eggs. 



This is a close up view of the feathers, which are very decorative. 




This pheasant is an extremely gentle passive bird, quite unlike a cockerel, and frequently is chased away from his food by other smaller garden birds. He seems to do very well in life though, and comes every day to tap on his family's windows to ask for seed.

The photograph was taken using a 1:1 macro lens from a distance of about 8 feet with a 1/200th second exposure.