(Arboricultural-styled) 'Fact of the Day'

[Kveldssanger]

21/10/15. Fact #62.

 

Irrigation is usually reserved for newly-transplanted trees, though the practice does still work for established trees during periods of drought - it simply needs scaling-up.

 

During a drought period in California between 1988-1992, it was concluded that the many ~125 year old Quercus lobata that were situated on shallow clay loam - and received summer irrigation outside the root crown area but within the rooting environment - fared significantly better than those that were not irrigated.

 

Ater five weeks of irrigation, 11/12 individuals were observed to have initiated new growth, compared to only 1/12 that were not being irrigated. Extrapolated out over the course of the four years, 10/12 irrigated individuals had improved growth, whereas only 2/12 that were not irrigated had improved growth (2 and 11 individuals had, respectively, declined or undergone no change).

 

Source: Hickman, G. (1993) Summer irrigation of established oak trees. Journal of Arboriculture. 19 (1). p35–37.

[Kveldssanger]

23/10/15. Fact #63.

 

Much like the climate impacts upon trees, it also impacts upon fungi - though generally to a lesser extent. Straight away, therefore, we can observe how the climatedrives fungal presence. The climate infuences constituent species of trees, so therefore fungi 'follow' their suitable tree hosts. An indirect influence, if you will.

 

On a more direct basis however, both rainfall and temperature will have an influence upon fungal presence and activity. As a pre-cursor, normally fungi can be found from June through to Deceber, with their activity 'peaking' during October.

 

Within a woodland setting, fungi found growing on leaf litter can only manifest when leaf litter moisture content is over 50% and the average surface temperature is no lower than 4 degrees Celsius (the upper limit is a 'softer' cap than the lower limit, which is far less flexible). Therefore, when rainfall is lacking, or temperature is very low, fungi may cease to function - we may see this drop is activity during very dry periods of summer, with regards to rainfall (and one must remember temperatures in woodlands are much cooler, given the shafing effect of the canopy).

 

As a general rule of thumb, the larger the sporophore the longer the lag period is between weather change and fungi activity. Smaller sporophores will appear first, and much larger ones later - larger sporopohores may in fact only be produced if such favourable conditions persist for long periods.

 

Interestingly, one is more likely to find fungi operating within woodland settings than open grasslands (or other open settings). The canopy cover of the woodland modifies local micro-climate, and extends the period of time in which fungi can function by keeping temperatures cooler and humidity levels higher - both are favourable for fungal activity, as desiccation is essentially less of a risk. This applies for leaf litter fungi and wood-decay fungi.

 

Source: Hudson, H. (1972) Fungal Saprophytism. UK: Edward Arnold.

[Kveldssanger]

Back to normal tomorrow, for those of you that care.

[Gary Prentice]

About time you pulled your finger out:biggrin:

[David Humphries]

Back to normal tomorrow, for those of you that care.

 

+ 13 thousand views suggests that people are interested in the thread Chris.

 

The diversity of topic your sourcing is what makes it compelling, keep it up

 

 

 

.

[Steve Bullman]

Back to normal tomorrow, for those of you that care.

 

 

Speaking for myself, I'm not intelligent enough to understand half of it and therefore don't comment, but enjoy reading it all the same, keep it up

[Kveldssanger]

Good stuff.

 

This one was spurred-on by a colleague in another department at work asking whether you can make a deciduous tree not lose its leaves during the autumn and winter months.

 

Do pardon all the brackets!

 

 

26/10/15. Fact #64.

 

Can a deciduous tree that loses its leaves during winter (we'll say an individual Quercus robur, for illustrative purposes) be made to not lose its leaves, by artificially controlling conditions so that the individual receives enough sunlight and is not subject to undesirable ambient temperatures?

 

In short, probably not.

 

Whilst the principal controlling stimulus behind winter bud set is the shortening day length (do not confuse this with the 'amount of light' a tree gets - shaded individuals are still, by-and-large, able to ascertain overall length of the day), particular species (such as for our Quercus robur) lay down their winter buds long before days even begin to shorten (so during periods where conditions are still 'optimal'). Therefore, there will come a point where it just is not possible for our oak to not lose its leaves, as those winter buds will require the winter conditions to aid with bud break again in spring (that 'over-wintering', so to speak), and as existing leaves cannot persist indefinitely (most cannot survive more than 2-3 years, even in coniferous species*) there will be a point where existing leaves are shed and new ones cannot form.

 

Moving off at a tangent, it is also worth noting that the metabolism of our oak does not necessarily slow down as the days shorten and leaves are shed. Whilst both day length and temperature can impact upon its metabolic rate, this impact may at times increase metabolic rate - it is simply a case of cell division taking place in ways that do not see markedly increased growth; metabolism may raise to create organ(elles) used (in part) for both the onset of dormancy (and to survive the winter) and also for that all-important spring growth. Only when these processes have been completed will metabolism drop - it will only then raise again following the crucial wintering period, where the buds are exposed to cold temperatures.

 

To wrap up, our oak will have also 'developed' an early-warning system (or systems) that provide it with ample time to fully prepare for dormancy. The system the oak will use, and was mentioned earlier, is day length. Measuring day length is more accurate than measuring temperature, as temperature will fluctuate far more significantly than day length - it will not give the oak as much of an accurate picture, and an accurate picture is critical for survival!

 

Source: Villiers, T. (1975) Dormancy and the Survival of Plants. UK: Edward Arnold.

 

* This is not from the source quoted, but from another book - unfortunately, I cannot recall which book.

[Gary Prentice]

"most (leaves) cannot survive more than 2-3 years, even in coniferous species"

 

In something I read recently, a certain species of Eucalyptus was shown to retain leaves for, I think, over ten years. Someone researching this painted dates on leaves which were still present after a decade. I'll find the book and confirm this later.

 

It was one particular Eucalyptus species, the tallest ones in their native environment, and there was no mention of other species at all.

[Kveldssanger]

Interesting! I imagine the book I read was talking about on average (I presume!).

[JaySmith]

Back to normal tomorrow, for those of you that care.

 

 

I find your posts very informative and a lot of the topics you post about relate to my tech cert studies so please continue!