Tag Archives: Winter

Marcescense a bit of a mystery?

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What is marcescense? Marcescence is the holding on to dead leaves and dead plant material during winter. This happens to particular species of Deciduous trees such as beech and oak (this is a bit peculiar as the word deciduous comes from the latin for falling off more on that later) So what should happen?

In the Autumn the leaves of deciduous trees undergo many changes. The chlorophyll is lost the leaves stop making sugars and the there is a change in plant hormone levels this a signal to the base of the leaf stalk to start to seal up. This is done with a corky like layer which protects the scar left as the leaves drop preventing infection. In marcescent trees this process is incomplete and the leaves remain attached although in some cases tenuously, these leaves are then pushed off in the spring by new growth.

Marcescence
Marcescence exhibited by Beech

So what’s going on here? One of the reasons trees lose there leaves in winter is to protect themselves from storm damage. So What are the reasons for this marcestent trait well there are some clues, the age of the tree or part of the tree seem to be important as young trees or young parts of the tree seem to exhibit increased marcescence.

although there is no clear and proven reason that explains marcescence so the answer is not sure.

Having said that there are a number of theories as to why trees might exhibit Marcescence.

Marcescence
Marcescence exhibited by Oak

It may help to protect there buds from browsing herbivores the marcescent leaf hides the new buds which are a food source for these herbivores. it has also been suggested that the herbivores may nibble and taste the dry leaves. The leaves are bitter due to certain chemicals which are present in them this may then make the animal learn to leave this plant alone.

It could be to protect the young growth form frost as having the leaves present shields the new buds, or it may enable the traping of deep snow as these trees often grow on dry sites having a little extra water from snow melt may help kickstart there growth in the spring.

Or It could nutrient related

Another reason could be a means of increasing nutrient recycling as by keeping the leaves until the spring when they do fall they can form a mulch and be broken down supplying nutrients as well as keeping the base of the trees moist as mentioned previously these trees often grow on dry sites these sites are often nutrient poor as welll, it has been shown that by holding onto the leaves there is an increase in photo degradation this is important as some marcescent species leaves do not decompose well and the extra light may make the eventual decomposition easier(aromatic compounds). it could also be that by dropping the leaves in spring with the extra warmth the decomposition process by fungi and bacteria would be quicker and it may also be useful to fungi that may then be beneficial for the growing tree.

Or it could be a mixture of all the mentioned theories or may be something else not looked at yet. As I mentioned at the beginning these trees are meant to be deciduous losing there leaves and in the main there are but both beech and oak are related and some of there other relations are not deciduous so marcescence could be an in between stage as these trees have not gone completely down the deciduous route it may be a vestigial trait.

Vestigal or not marcesent trees can provide a protective winter habitat for birds as well as having benefit for invertebrates giving them access to places to overwinter. As well as being pleasing to look at and listen to when the wind blows in the winter forest.

Trip to Corrur… not train spotting!

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Trip to Corrur… not train spotting!

Friday evening in Euston station was busy, very busy. There had been some problems with overhead wires and there were a lot of disgruntled people who weren’t impressed with two blokes with rucksacks trying to get to the concourse! So we beat a retreat to a local restaurant and returned later to board our train, which being diesel was not affected by the overhead wire issue.

We had opted for the cheap sleeper option, the reclined seats, and finally having got to sleep we were woken to change trains at Edinburgh (thinking now that we should have paid the extra to get a cabin), we got settled in the new carriage and I slept until we arrived in the Highlands. Upon waking I looked out of the window as the dawn slowly broke, enjoying the views. With our stop coming up next, I spoke to the guard and he told us where to stand to get off – a small luggage door. The train arrived at Corrour, the highest train station in Scotland (and features in the film ‘Trainspotting’). we got off with a few other people, the sky seemed to be clearing and the sun came out as we tried not to skate on the ice on the short walk to the SYHA hostel where we would be staying that evening. On arrival at the hostel the guardian meet us and said we could leave some of our equipment which we were not going to need for our upcoming walk, in the bunk room on our beds.

Having sorted and repacked our rucksacks, we set off for the day. The weather seemed to be deteriorating; the higher mountains slowly disappeared in the cloud as we began up a well made track gaining height steadily until we came to a stream crossing. We did not cross the stream, but instead started up the hill in deep wet snow.

The going was initially tough, but we made good progress and began to find firmer patches of snow as we arrived at the ridge that would lead us up to Carn Dearg. Following the broad ridge was easy, although we were in the cloud and visibility was not great, on nearing the summit we meet two people coming off the top, after a brief hello and we arrived on the top the wind had now increased. We did not linger.

Following the ridge away from the summit with the wind at our backs we again made good progress in the snow and soon arrived at Bealach, with the summit of Sgor Gaibhre somewhere above us, in the now snowy, sleety sky. A quick drink and a little food and we began the slow walk up the slope, which seemed to go on a bit, but we soon arrived. The original plan had been to continue over Sgor Choinnich and then down, but the weather was not improving and we would be getting late back to the hostel by continuing on this path. Having told the hostel warden that we would be back just before, or not long after dark, we decided to descend directly down the the col and contour around the mountain, then down and cross a river further down just above a dam.

 

The walk down was hard, the snow was soft and there was a lot of wading/ squirming/ swimming to get through it. We eventually arrived at the crossing point, but the water was too deep even with a cable across the last part, it was just to risky. We descended further and had to find a gate or a crossing in the deer fence, and had a longer walk through partially frozen bog to find a crossing. It was now getting dark, but having crossed the fence it was relatively easy to find a track through the woods down to the edge of the loch, and then the track that would take us back to the hostel. After 3.5km on the track the hostel came into view, lit up against the dark wet night. On entering it was very warm with nearly a full house, after a quick change of clothing and some food we got chatting to the two people that we had seen earlier, they had intended to complete a similar route to ours, but bailed due to the weather. We chatted for a few hours, discussing what we were planning to do the following day and then went to bed, hoping for better weather in the morning.