(Arboricultural-styled) 'Fact of the Day'

[Kveldssanger]

22/11/15. Fact #84.

 

When we transplant trees we may consider applying mycorrhizae to the soil to aid with tree growth and survivability - particularly in urban environments, where soils may more likely be poor. Of course, there are benefits to applying mycorrhizae: reduced transplanting stress, increased growth, a more optimal root:shoot ratio, reduced water stress, and ultimately a reduced risk of mortality.

 

At the same time however, one should recognise that, according to research, 'native' soil mycorrhizae soon take over from any artificial inoculum, and commercial innoculum have also been found, in an array of studies, to provide no significantly increased growth rate. This might be because, where commercial innoculants have been used and their effects studied, mycorrhizal colonisation of the roots rarely exceeded 5%.

 

Conversely, when freshly-cultured laboratory innoculum were used, colonisation was at a 74% success rate.

 

So if you are looking to use mycorrhizae, get it prepared to specification - perhaps even utilise locally native genotypes from (near to site / on site) soil samples.

 

Sources:

 

Abbey, T. & Rathier, T. (2005) Effects of mycorrhizal fungi, biostimulants and water absorbing polymers on the growth and survival of four landscape plant species. Journal of Environmental Horticulture. 23 (1). p108-111.

 

Broschat, T. & Elliott, M. (2009) Effects of fertilization and microbial inoculants applied at transplanting on the growth of Mexican fan palm and queen palm. HortTechnology. 19 (2). p324-330.

 

Corkidi, L., Allen, E., Merhaut, D., Allen, M., Downer, J., Bohn, J., & Evans, M. (2005) Effectiveness of commercial mycorrhizal inoculants on the growth of Liquidambar styraciflua in plant nursery conditions. Journal of Environmental Horticulture. 23 (2). p72-76.

 

Ferrini, F. & Nicese, F. (2002) Response of English oak (Quercus robur L.) trees to biostimulants application in the urban environment. Journal of Arboriculture. 28 (2). p70-75.

 

Fini, A., Frangi, P., Amoroso, G., Piatti, R., Faoro, M., Bellasio, C., & Ferrini, F. (2011) Effect of controlled inoculation with specific mycorrhizal fungi from the urban environment on growth and physiology of containerized shade tree species growing under different water regimes. Mycorrhiza. 21 (8). p703-719.

 

Wiseman, P., Colvin, K., & Wells, C. (2009) Performance of mycorrhizal products marketed for woody landscape plants. Journal of Environmental Horticulture. 27 (1). p41-50.

 

Watson, G. & Himelick, E. (2013) The Practical Science of Planting Trees. USA: International Society of Arboriculture.

 

Wiseman, P. & Wells, C. (2009) Arbuscular mycorrhizal inoculation affects root development of Acer and Magnolia species. Journal of Environmental Horticulture. 27 (2). p70-79.

[daltontrees]

21/11/15. Fact #83.

 

Broadly-speaking, the larger the size of the vessel within the vascular system of a tree, the greater the risk of cavitation, under freeze-thaw conditions. This is because large vessels carry more water both in total and in a cross-section, which means air bubbles borne by freezing water are potentially both more frequently-occurring and larger when they do occur. These air bubbles have less likelihood of 'dissolving' into the sap again when it thaws, and therefore are more prone to causing vascular damage.

 

Of course, larger vessels means greater efficiency at conducting, though with the trade-off of greater risk of vascular damage. We do still see large vessels, however - particularly in ring-porous trees such as elm and oak. Though, in general, vessel size decreases as we go from ring-porous to diffuse-porous deciduous hardwoods, and from there decreases further as we enter the realm of coniferous softwoods.

 

It seems that species physiology, with regards to vascular properties, may likely dictate climatic ranges - at least, in part. For example, conifers with large vessels would be hugely imparied in areas where freezing (and subsequent thawing) conditions are frequent, so it is likely that they will not frequent such areas and may instead lurk up to and at their preferable 'maximum(s)'. However, where freezing conditions are common but prolonged (thawing is not so common), or just generally infrequent, vascular anatomy may not be so important (such as at high and low latitudes) - therefore, near to the equator, or right up in the arctic where freezing is common but thawing is not, vascular properties may potentially be more varied.

 

Source: Sperry, J. (1995) Limitations on Stem Water Transport and Their Consequences. In Gartner, B. (ed.) Plant Stems: Physiology and Functional Morphology. USA: Academic Press.

 

According to Effects of ring-porous and diffuse-porous stem wood anatomy on the hydraulic parameters used in a water flow and storage model KATHY STEPPE and RAOUL LEMEUR (2006) -

 

" we analyzed the stem wood anatomy of the beech [F. sylvatica] and oak [Q. robur] trees. Calculation of stem specific hydraulic conductivity of beech and oak ... confirmed the differences in [hydraulic resistance] predicted by [a recently developed water flow and storage model].

 

"The contributions of different vessel diameter classes to the total hydraulic conductivity of the xylem were calculated. As expected, the few big vessels contributed much more to total conductivity than the many small vessels. Compared with beech, the larger vessels of oak resulted in a higher hydraulic conductivity (10.66 versus 4.90 kg m–1 s–1 MPa–1). The calculated ratio of [hydraulic conductivity] of oak to beech was 2, confirming the [hydraulic resistance] ratio obtained by model calibration."

 

Thus ring porous trees might, if this model and ratio was found to hold true for other tree species, have about twice the vessel area of diffuse porous. So why wouldn't all trees do this, and why haven't the less conductive trees been wiped out by evolutionary pressures?

 

I think the cavitation idea is a useful way to look at it but there's also a clue in the word 'diffuse'. Diffuse porous trees are lmost certailnly compensating for lower vessel size by using more rings. It is well known that ring porous trees are very dependent on the newly created wood of the spring period to conduct the vast quantities of water that they need for their mode of existence, and do not rely on the last year's (and older) vessels to a great extent.

 

I suppose I am just speculating that in support of the 'fact' you have presented there may not only be good reasons why the ring porous model does not work in freeze-prone environments but there is a good reason why the diffuse porous model does. Narrower but more deeply distributed vessels may make up the same conductivity as a few superficial but large ring porous vessels, and there may also be an insulation factor for the deeper vessels. It seems inevitable that the insulating properties of corkier bark will be a factor too for bigger trees, although the pioneers like birch and alder are diffuse porous but have famously thin bark.

[Kveldssanger]

Some really good points there - thanks.

[Kveldssanger]

24/11/15. Fact #85.

 

There are several drivers behind stem elongation in young trees under (relatively closed) woodland canopies. These drivers include changes in air humidity, mechanical disturbances, total solar irradiation (sunlight), and light quality. The latter two are discussed below.

 

The optical qualities of leaves create a light environment beneath that has low levels of UV and visible wavelengths, and a low red:far red ratio. All of these conditions are known to drive stem elongation. For example, a reduction in the fluence (light energy received per unit area) of 320-800mm wavelengths stimulates stem elongation. Of course, this does not apply for all plants, but for many.

 

The red:far red ratio is a good measure of a plant ascertaining whether it needs to elongate. As canopies lower the ratio, the lower the ratio the more foliage above, and thus the poorer the quality of light, and thus the need for stem elongation to reach better light conditions. For shade-intolerant plants, the ratio hit a threshold by where elongation was triggered at 10% of full light.

 

Interestingly, and supported more recently by Karban in Plant Sensing & Communication, the illumination history of a plant will also determine how it responds to light levels. The author here outlines that the promotive effects of shading on elongation diminish after a period of time, and thus it can be suggested that shaded plants can either no longer elongate rapidly (due to a lack of resources, or otherwise) or alternatively change their modus operandi as they 'recognise' (hormonally) that they are in perpetual shade. I would be interested to see if there are any studies on Fagus sylvatica and red:far red light ratios, and the long-term response to differing ratios, given the species adopts a 'biding time' strategy in heavy canopy cover.

 

Source: Ballare, C. (1994) Light gaps: sensing the light opportunities in highly dynamic canopy environments. In Cladwell, M. & Pearcy, R. (eds.) Exploitation of environmental heterogeneity by plants. USA: Academic Press.

[Kveldssanger]

26/11/15. Fact #86.

 

Plants that have adaptations of growth / modifications to cope with very dry conditions are called xerophytes. Such xerophytic adaptions may include very extensive root systems, increased cell lignification surrounding particular tissues and organs, small leaves (such as needles in conifers), thick protective hairs on leaves to trap moisture and increase local humidity levels to thereby reduce moisture loss, high levels of oils, terpenes and resins within leaves, and thick waxy cuticles. The end result of any adaptation is the same - improved water efficiency.

 

Source: Watson, B. (2006) Trees: their use, management, cultivation, and biology. India: The Crowood Press.

[Kveldssanger]

27/11/15. Fact #87.

 

Connectivity between different spatial environments, such as across urban or sub-urban areas, is strongly supported by tree presence, given trees act as go-betweens for species which must travel between larger resource patches; particularly birds, bats, and moths. Further to this, connectivity provided by trees supports dioecious tree species themselves, by providing conditions (vectors) for successful pollination (and subsequent seed propagation) to reduce genetic drift as a result of the isolation of tree groups.

 

Sources:

 

Aguilar, R., Ashworth, L., Calviño, A., & Quesada, M. (2012) What is left after sex in fragmented habitats? Assessing the quantity and quality of progeny in the endemic tree Prosopis caldenia (Fabaceae). Biological Conservation. 152 (1). p81-89.

 

Gil-Tena, A., Nabucet, J., Mony, C., Abadie, J., Saura, S., Butet, A., Burel, F., & Ernoult, A. (2014) Woodland bird response to landscape connectivity in an agriculture-dominated landscape: a functional community approach. Community Ecology. 15 (2). p256-268.

 

Hale, J., Fairbrass, A., Matthews, T., Davies, G., & Sadler, J. (2015) The ecological impact of city lighting scenarios: Exploring gap crossing thresholds for urban bats. Global Change Biology. 21 (7). p2467-2478.

 

Oprea, M., Mendes, P., Vieira, T., & Ditchfield, A. (2009) Do wooded streets provide connectivity for bats in an urban landscape?. Biodiversity and Conservation. 18 (9). p2361-2371.

 

Shanahan, D., Miller, C., Possingham, H., & Fuller, R. (2011) The influence of patch area and connectivity on avian communities in urban revegetation. Biological Conservation. 144 (2). p722-729.

 

Slade, E., Merckx, T., Riutta, T., Bebber, D., Redhead, D., Riordan, P., & Macdonald, D. (2013) Life-history traits and landscape characteristics predict macro-moth responses to forest fragmentation. Ecology. 94 (7). p1519-1530.

 

Tinoco, B., Astudillo, P., Latta, S., Strubbe, D., & Graham, C. (2013) Influence of patch factors and connectivity on the avifauna of fragmented Polylepis forest in the Ecuadorian Andes. Biotropica. 45 (5). p602-611.

Edited November 27, 2015 by Kveldssanger

[Kveldssanger]

29/11/15. Fact #88.

 

This one isn't so much a fact as it is an observation, though I consider it a comment that is pretty much on-the-point. I shall quote:

 

"In recent years, there has been a step change in society that appears on one level to demand a more natural holistic provision of green infrastructure and outdoor space. At the same time, it also demands that people are increasingly cosseted from the rough edges of nature when they use or interact with it. This dilemma seems to stem from a societal change that encourages litigation as a means of resolving disputes, creating a driver that makes some tree owners greatly more risk-averse than they would otherwise have been."

 

May be a useful point for discussion, though I am sure that has already been done to great lengths by many.

 

Source: NTSG. (2011) Common sense risk management of trees. UK: Forestry Commission.

[Kveldssanger]

29/11/15. Fact #89.

 

Many may already be aware of these statistics, though for those that aren't, or for those that just fancy reading them again, the table below outlines the level of mortality involved with many activities / health-related issues, and where trees rank within this matrix of death.

 

For context, the research undertaken for this data identified that 64 people died in the ten years since 1st January 1999 as a result of a fallen branch or entire tree. As the population of the UK was assumed to be 60,000,000, it was calculated that there was a 1/10,000,000 chance, per year, of an individual dying from a fallen branch / tree. This is ten times lower than the 1/1,000,000 risk that the HSE declares as insignificant or trivial, as people conduct their daily routines.

 

The study also identified that 55 people per year, on average, suffer non-fatal injuries that require A&E treatment as a result of falling tree branches or the entire structure. This pales in comparison to the 2,900,000 injuries (severe enough to go to A&E) a year related to leisure activities. For context, 262,000 are football-related, 10,900 are as a result of accidents on children's swings, and 2,200 as a result of wheelie bins (?!).

 

 

Source: NTSG. (2011) Common sense risk management of trees. UK: Forestry Commission.

 

 

...in related news, councils across the country are declaring war on wheelie bins after it was revealed that the country's largest wheelie bin manufacturer was found to have rigged performance tests relating to the bins' carbon efficiency. 97% of scientists now agree that wheelie bins are "bad for the environment", and wheelie bin manufacturers must be "held to account".

Edited November 29, 2015 by Kveldssanger

[JaySmith]

I was just looking at this table about an hour ago, are you doing your lvl 4 assignment on tree inspection by any chance too?! Unfortunately when somebody is hurt/killed by a tree it will always grab the headlines but you rarely hear about radon and lung cancer. Driving on the m25 at rush hour scares me more than any tree ever could!

[Kveldssanger]

I am doing the lvl 4 but not got to trees & the law yet! We're on mechanics at present.

 

Yes, you are right. As it says in the NTSG guidance, the media will over-play tree deaths and injuries as it's so rare. The shock factor, so to speak. The M25 is nasty - had to drive back that way last week and I don't envy drivers who use it daily. Some lorry drivers are so unecessarily aggressive with their driving.