(Arboricultural-styled) 'Fact of the Day'

[David Humphries]

It seems there is. Pages 97-101. Some really good pictures, and some good accompanying text. By no means extensive, though there are probably a few bits I could have added to my coursework / subsequent blog post. Not sure why I didn't consult it when writing it, to be honest.

 

I've only ever leafed through the book, as I don't have a copy.

That's why I asked.

 

I did ask the author his thoughts about invasiveness of resistographs and other dd equipment and he basically inferred similar to what you state in the last paragraph of your piece.

 

I recall he said something in his finest gutterall German/English along the lines of "Zee problem being, ven multiple vounding on ein single tree occurs each year, it becomes like zee cheese from Switzerland, yah"

 

Apologies Dr Dujesiefken

 

 

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[Kveldssanger]

I've only ever leafed through the book, as I don't have a copy.

That's why I asked.

 

I did ask the author his thoughts about invasiveness of resistographs and other dd equipment and he basically inferred similar to what you state in the last paragraph of your piece.

 

I recall he said something in his finest gutterall German/English along the lines of "Zee problem being, ven multiple vounding on ein single tree occurs each year, it becomes like zee cheese from Switzerland, yah"

 

Apologies Dr Dujesiefken

 

 

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Get the book, as it's so easy to read and really very good! I'm sure it can be justified as a gift to yourself, but if met with protest then demand that it becomes a gift from someone else.

 

I suppose it becomes a 'lesser of two evils' thing, and notably if we're dealing with a tree in a setting where there is a target zone (so not in the middle of a forest). If there is reason to suspect internal decay, and there is therefore reason to suspect something has to be done to the tree else it might be deemed reasonably likely to cause an issue down the line (this is where expediency comes in), then using such an invasive device to help influence a management decision is most probably going to be justifiable.

 

A bit like that beech we worked on, David. Having identified Kretz (U. deusta), it was evident some form of management was likely going to be necessary, and in that case we'd need to be understanding internal wood proeprties. Using a PICUS would have been feasible, though given it can give improper reading if there are shakes / cracks in the tree, then a Resi is probably the best option. Using this to drill four (five) holes to study the extent of decay, and to subsequent influence (and probably justify) a management decision, then you're covered in two ways:

 

1. you know what the current state of decay was like at the cross-sections studied

2. you have satiated the desire to justify works, and in light of any hazard manifesting into actuality then there is supporting evidence to add context to why a decision was made to do works A instead of works B or works C.

 

All about painting a picture, and in spite of the issues with invasive devices maybe meaning you run out of red paint slightly too early and finish with too much green, it's still better than not finishing the painting at all (or painting it and having it look absolutely dire). Poor analogy, but hope it makes sense. All I can think of whilst frying eggs at 6 in the morning before college!

 

Oh, and zat German accent ist vunderbar!

Edited March 2, 2016 by Kveldssanger

[David Humphries]

.........I suppose it becomes a 'lesser of two evils' thing, and notably if we're dealing with a tree in a setting where there is a target zone (so not in the middle of a forest). If there is reason to suspect internal decay, and there is therefore reason to suspect something has to be done to the tree else it might be deemed reasonably likely to cause an issue down the line (this is where expediency comes in), then using such an invasive device to help influence a management decision is most probably going to be justifiable.

 

A bit like that beech we worked on, David. Having identified Kretz (U. deusta), it was evident some form of management was likely going to be necessary, and in that case we'd need to be understanding internal wood proeprties. Using a PICUS would have been feasible, though given it can give improper reading if there are shakes / cracks in the tree, then a Resi is probably the best option. Using this to drill four (five) holes to study the extent of decay, and to subsequent influence (and probably justify) a management decision, then you're covered in two ways:

 

1. you know what the current state of decay was like at the cross-sections studied

2. you have satiated the desire to justify works, and in light of any hazard manifesting into actuality then there is supporting evidence to add context to why a decision was made to do works A instead of works B or works C

 

 

This is the crux I feel, having as much information (understanding of site/target/occupancy, VTA, DD and regularity of inspection) as possible, aids an informed decision, it may not be the correct decision from certain angles but it is a defensible one.

 

This Copper beech will be an interesting case study to follow over the next few growing seasons (and beyond) as it adapts to having a smaller sail (which benefits stability though perhaps diminishes vitality due to reduced photosynthesis)

 

a few shots for visual context for those interested in the tree Chris & I are talking about.

We'll put a separate thread up later in the year......

 

 

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[David Humphries]

Oh, and zat German accent ist vunderbar!

 

zee country of my birth

 

 

 

 

 

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[Kveldssanger]

It's all about doing what is reasonable in light of what is foreseeable, and a resi / PICUS / etc. will supplement understanding both aspects.

 

Nice shots.

 

Ah, so you're German! I take it you don't have The CODIT Principle because you bought the real copy Das CODIT Prinzip.

[Kveldssanger]

02/03/16. Fact #165.

 

Trees must feature heavily within urban environments, if the adverse impacts of man-made and artificial landscapes are to be lessened in magnitude. However, in many instances, tree cover is not where it could be. Roadside verges may be void of trees (even those that are rather wide) and other public areas may also be somewhat lacking in tree cover. In an attempt to counteract the harshness of the urban environment, many local authorities (public bodies) are stating their desire to improve the tree cover within their realms, or at least make areas more ‘green’. Many suitable areas likely exist to feasibly support such a pursuit, though what is straightforward on paper may not be so in actuality.

 

In this post, we focus on a case study undertaken in the tree-lacking and intermittently concrete-laden East Baltimore, where the municipal authority is seeking to double the city’s tree cover over the coming years (to 40% canopy cover). Specifically, the study looks at two areas of East Baltimore (Madison-Eastend and Berea), where tree planting en masse is potentially possible (due to a current lack of trees – only one tree for every 83m and 62m of street, respectively!) though, since the 1960s, planting schemes there have routinely failed (at the time, many residents were in opposition to tree planting).

 

In fact, residents in East Baltimore during the 1960s preferred clean concreted areas, and considered trees to be directly in opposition to their values. Locally, they were dubbed “tree rebels”. Since then however, the population of East Baltimore has drastically altered. Gone is the largely European immigrant population, and in its place is a growing community of African Americans that moved in from rural areas. The lack of trees has remained, however. In addition, to reach the 40% canopy cover desires it has been recognised that residents must also start to plant trees in their gardens, as planting street and park trees alone will not enable East Baltimore to reach its target goal of canopy cover. Below, we can observe a broad break-down of existing canopy cover and potential future canopy cover levels if tree planting is successfully completed.

 

Current canopy cover and the potential future canopy cover levels of the two areas in East Baltimore.

 

The authors therefore have two (or three) principal questions to answer: (1) is there ample space to support “aggressive” tree planting regimes, and (2) do current residents of the two areas want more trees and, even if they do, are they willing to support planting schemes. A third question builds on the second one a little, and asks whether the changing ethnic composition of the areas has an influence upon desires relating to tree presence and planting. Madison-Eastend and Berea were selected as areas for the study, as they are near to where the principal “tree rebel” groups were, and are also suitable for accomodating a large-scale increase in tree presence. The two areas also vary enough in terms of house ‘plot’ size (property and surrounding garden) and available public green space (Madison-Eastend is lacking significantly within properties and along roadways, and Berea is most certainly not), which enables for views to be obtained across a wider spectrum. Granted, both areas have ample potential space for trees (as shown below, in the two figures).

 

In Berea, there is a massive amount of space in front and back yards for trees to be planted. Some space also exists along highway verges, and in open spaces. Tree pits also exist, which are currently empty. If needed, more tree pits can be made.

 

Berea contrasts with Madison-Eastend, where we can observe little space along streets and in the grounds of properties to plant trees. Instead, a large park area, and some empty tree pits, will support tree planting. Again, more tree pits can be made, if necessary.

 

In order to obtain the data for the study, the authors interviewed 16 residents from Berea and 10 from Madison-Eastend. The interviews lasted for roughly 15 minutes, and had some form of structure, though did allow for interviewees to diverge from the interview and expand upon other tree-related issues if they so desired. All interviewees were African American.

 

Upon completion, 14 of the 26 interviewees held a generally positive perception of trees. The authors remark that the shading benefits of trees was particularly valued in Madison-Eastend, given the area (and Baltimore as a whole) has a potentially uncomfortably warm and generally humid subtropical climate (exacerbated by the lack of trees, no doubt). For those interviewed in Madison-Eastend who did not have access to shaded locations, the desire for larger trees to bring shade to the area directly outside of properties was particularly evident. If such areas were not available, or even if they were, interviewees would “gravitate” to the side of the street that did not receive direct sunlight. In Berea, interviewees echoed sentiments from those in Madison-Eastend, and even whilst a few streets did already have large trees that cast shade, it was recognised that the urban heat island effect was an issue area-wide as a whole. Remarks were also made as to tree shade reducing costs associated with running air-conditioning systems.

 

A few empty tree pits can be seen here in Madison-Eastend, that have been turned to grass. We can also observe a lack of front yards or gardens. Source: Roadsnacks.

 

Other positive values held by residents interviewed included the amenity value trees provided and their beneficial impacts upon tackling climate change (or just generally improving the environment, because trees are needed for humans to live).

 

Turning towards negatives, interviewees (even those who generally liked trees) stated that the wildlife attracted by trees was annoying – bird poor was a principal nuisance, though insects and also rats were raised as concerns residents had. Tree pollen and its associated allergies was also a concern outlined, with one interviewee stating they didn’t want to have to start taking tablets again to combat their allergic reactions. However, quite selflessly, one interviewee stated that they would champion large-scale tree planting operations, even in spite of their allergic reaction to pollen. A necessary trade-off, they claimed.

 

Overhanging branches and roots entering drain pipes were also issues raised. An interviewee in Berea, for example, exclamated that they did not want trees because of the issues with roots in water pipes. Similarly, an interviewee from Madison-Eastend used an example of vacant properties with tree branches encroaching upon them to outline why trees may be bad. Falling limbs in storms was also a concern, of which limbs from large trees were particularly an issue.

 

Echoing past planting failures, one resident in Madison-Eastend stated that they had watched trees die before, so questioned why the city hadn’t cared for previous trees planted. Perhaps, the same thing will just happen again, they assume. Where dead trees still remained, residents also wished that East Baltimore authorities would remove the dead ones before stating they want to plant more, as the dead trees were not amenable and, in some cases, had been left for over a year without removal.

 

On a more profound level, one resident interviewed was concerned that tree planting en masse would lead to gentrification of the area, meaning a potential destruction or displacement of the community they had grown up within. On a similar note, political agendas were a concern, where trees may simply be planted to further the career of a politician. Drug issues were also a concern, as trees could be a place to hide drugs (that residents were keen to stop occurring at the current high drug-use rates). However, no remarks were made on the concrete landscape being more preferable than one with trees, in contrast to the 1960s era of “tree rebels”.

 

Focussing on aftercare of trees, views were mixed. Some who were interviewed said they would care for the trees, though were concerned other residents nearby would not (or even if they did, children may break them). Others stated that, as so many trees had died before, they were lacking the confidence in any future tree planting schemes being any different. It was also mentioned that whilst homeowners may water trees, those who rent may not (because homeowners have a greater vested interest in the area surrounding their property). Changing culture was also cited as a reason for why aftercare undertaken by residents may be poor. Whilst the initial wave of African Americans was from rural areas who had a closer affinity with nature, the current younger generation grew up in the concreted city landscape. Therefore, would they even care for trees and nature in the same way as the older generation do?

 

In light of the results from the interviews, we can observe how there are mixed views on tree planting and the associated aftercare by residents. Whilst trees bring shade and look good, they may cause mess, not be loved by renters in the same way they may be by homeowners, and be viewed as a vehicle for furthering political agendas. However, because no interviewees stated they preferred concrete landscapes, the views from the 1960s may no longer be held (though we must accept this was a very limited sample size). From this, we can suggest that tree planting to any large degree is far more of a possibility than it once was, and it may be wise to try again. It should also be noted that all points raised both for and against trees were also entirely valid, and would probably be relatively similar for other areas across the western world. Of course, it then comes down to balancing those values aforementioned, and ensuring that current negative views of trees are challenged in a constructive and informative manner. If this can be achieved, the goal of 40% tree cover across Baltimore may become a more achievable dream.

 

Source: Battaglia, M., Buckley, G., Galvin, M., & Grove, M. (2014) It’s not easy going green: obstacles to tree-planting programs in east Baltimore. Cities and the Environment (CATE). 7 (2). Article 6.

[Kveldssanger]

04/03/16. Fact #166.

 

Ivy (Hedera helix), which is classed as a woody liana, can be both good or bad for a tree, depending upon the setting. For example, in urban locations where trees exist as solitary specimens for largely amenity purposes then ivy may be an issue, because its presence increases the wind sail of a tree and also detracts from its amenity value (one cannot appreciate the tree’s structure so readily). Conversely, in a setting where a tree is retained for ecological value, or it simply sits amongst a group (copse, woodland, or forest) of trees, then ivy may be hugely beneficial. The love that ivy receives is therefore relative.

 

This pine (Pinus sp.) was so laden with ivy in its crown that it got blown over in the wind.

 

Looking beyond the mere pros and cons of ivy however, what drives its colonisation? Does ivy discriminate between trees as to which it will ascend and thus colonise extensively (in time), or does it simply colonise whatever host it has in its immediate grasp? In a recent study from 2013 undertaken in the Siro Negri forest in Italy, such questions are answered.

 

Before looking at the results from the study however, it is important to understand a bit more about the Siro Negri forest. Located in northern Italy, it is a small remnant (9ha) of alluvial forest once more abundant across the landscape. A habitat considered ideal for ivy (climatically), tree species include field maple (Acer campestre), hornbeam (Carpinus betulus), hawthorn (Crataegus monogyna), white poplar (Populus alba), black poplar (Populus nigra), oak (Quercus robur), false acacia (Robinia pseudoacacia), and elm (Ulmus minor). Many trees are over 100 years of age, and there has been no significant disturbance since 1970.

 

Back to the study, the authors first identified four plots of 250-320 square metres in 2005 and 2009, and within these plots measured the DBH all trees. Those with a DBH of over 7.5cm were tagged. In 2011 (I don’t know why there was such a wait), the authors returned and undertook an assessment of all ivy stems growing upon the tagged trees that had a DBH of greater than 0.5cm. For all tagged trees, they were assigned one of five categories relating to the colonisation extent of ivy upon their structure: (0) ivy not present / below 1.3m on the trunk; (1) ivy present upon lower half of trunk; (2) ivy extending up into second half of trunk but not yet into the crown; (3) ivy within lower crown’s principal branching structure, and (4) ivy across entire crown.

 

In terms of further data gathered, on top of the DBH measurements undertaken in 2005-2009, radial cores at a 50cm height were taken from each tree to estimate age in 2011. If age was not evident as ring growth was asymmetrical or decay was present, the core was discarded. Similarly, radial cores from 50 randomly-selected ivy stems (43 once some were discarded) were taken at a 50cm height, again in 2011. The number of ivy stems present on each tree was also measured.

 

Moving on to the all-important results, the authors found that there were a greater number of ivy stems of 0.5cm-1cm in diameter than there were of diameter between 1cm-2.5cm, and 2.5cm+ (657, 345, and 225 stems, respectively). 52% of tree surveyed were host to more than one ivy stem, though only 17% of trees had ivy growing throughout their crown (category 4).The ivy stem of most significant size was 14cm in diameter, and had 53 growth rings. However, an older ivy stem of 69 years was found, albeit with a stem diameter of just 9.5cm.

 

In addition to this, not only was it was found that areas where tree density was lower and trunk diameter was greater that ivy stems greater than 0.5cm were more abundant, but that tree age was also associated with increased ivy colonisation (which is expected, considering older age usually means a greater trunk diameter and, at least in woodlands, lower tree density per hectare). Therefore, isolated oaks (Querus robur) of more significant age and size were observed to be host to a greater abundance of ivy stems and overall extent of ivy than the smaller and denser field maples (Acer campestre) and hawthorns (Crataegus monogyna). Other tree species sat in between these two ‘extremes’. However, tree age and size did not appear to majorly influence growth rate of ivy stems; asides from if the tree trunk had no extra space for the ivy stems to grow into. In this sense, the growth rate of ivy across trees of all age and sizes (and also species) was not found to be markedly different.

 

In this image, ivy can be seen to have colonised upon the trunks quite significantly, though not yet into the crowns of the trees. Source: Weed Wise.

 

Perhaps these results are not all too surprising, given the longer a tree has been in existence the longer that ivy has the potential to grow up alongside and into the tree’s crown. Granted, a younger tree with a greater trunk diameter than an older tree would, as suggested by the authors, still very likely support better ivy growth. The ‘ascension’ strategy of ivy may be also an important factor in why larger trees are more extensively colonised, however. Because ivy will attach itself to its host via adhesive adventitious roots, larger trees with rough bark (such as Quercus robur) can support ivy far more successfully than a younger tree with smooth bark. In fact, given bark typically roughens quite extensively with age (excluding species such as Fagus sylvatica), it can perhaps also be suggested that older trees are more abale to support significant ivy growth by mere virtue of older age bringing with it the rougher bark.

 

Looking at the crown of a tree, the fact ivy was observed to colonise large oaks of a healthy age is actually quite interesting. Oaks usually have dense foliage crowns, which would mean any constituent ivy is less able to obtain the light it needs to photosynthesise (which is identified, by the authors, as a reason for why ivy will prefer to grow into the crowns of tall trees with smaller leaves and generally lighter foliage crowns). Therefore, we can potentially conclude three things: (1) ivy will ‘rank’ large trunks with rough bark as more important than lighter crowns, (2) the oaks in the study had thin crowns, or (3 – as suggested by the authors) that isolated large trees, even if they have dense crowns, can still provide prferable light conditions (the adverse impact in negligible) for ivy.

 

A more isolated tree also means that its trunk is exposed to more light, which is also beneficial for ivy. This may explain why isolated trunks had more ivy stems than similar trunks in denser stands. Crossing over into urban areas therefore (this study was done in woodland), we can begin to understand why exposed, older, and larger trees (particularly oaks, though interestingly also hawthorns) can become so laden with ivy.

 

Having understood the above, such a sight should perhaps now be wholly understandable. Source: Cronodon.

 

In light (pun intended) of the above therefore, hopefully we can begin to understand what drives ivy colonisation. From looking around on Google Scholar, further articles exist on lianas (and herbaceous vines) of other species and their growth rate / extent upon trees, though it largely appears to be an unexplored topic. Perhaps scope exists for additional research, and particularly for ivy.

 

Source: Castagneri, D., Garbarino, M., & Nola, P., (2013) Host preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest. Plant Ecology. 214 (1). p1-9.

[David Humphries]

We often get members of the public demanding to know why we let ivy kill the trees on the Heath.

 

They know friends who are you 'experts' who tell them that ivy is pure evil and prays on poor trees and will ultimately be the successional species in woodlands

 

I don't know the answer to that but it i can appreciate the biodiversity that it helps to support.

 

We sever Ivy on road side trees to aid inspection and on dead path/roadside elm regeneration as the weight and sail often results in wind throw, but let it do its thing elsewhere.

 

Andy Cowan started an interesting thread on the subject some years back........

 

http://arbtalk.co.uk/forum/tree-health-care/3875-climate-change-increasing-growth-ivy.html

 

 

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[Kveldssanger]

We often get members of the public demanding to know why we let ivy kill the trees on the Heath.

 

They know friends who are you 'experts' who tell them that ivy is pure evil and prays on poor trees and will ultimately be the successional species in woodlands

 

I don't know the answer to that but it i can appreciate the biodiversity that it helps to support.

 

We sever Ivy on road side trees to aid inspection and on dead path/roadside elm regeneration as the weight and sail often results in wind throw, but let it do its thing elsewhere.

 

Andy Cowan started an interesting thread on the subject some years back........

 

http://arbtalk.co.uk/forum/tree-health-care/3875-climate-change-increasing-growth-ivy.html

 

 

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I get it all the time as well, even when the ivy is only just starting to climb up the lower stem! I don't understand how the myth has become so widespread, as rarely do I see a tree that is wholly struggling as a result of ivy colonisation (apart from a few hawthorns and the odd oak). In theory, ivy is part of the senescence process of a tree, as over its lifetime its vigour will reduce and ivy will have a greater likelihood of establishing significantly. In time, the ivy may finish the tree off, though not before it has (almost certainly) been declining prior to that (and perhaps for a long period of time).

 

I would agree that the only times to remove ivy would be to reduce wind sail on exposed urban trees, and to safeguard specimen trees from the adverse structural impacts of ivy (altering crown structure, etc).

[Kveldssanger]

A good bit by Jeremy Barrell here on ivy (see p7).