(Arboricultural-styled) 'Fact of the Day'

[Kveldssanger]

It was a hard one to read, I admit. Tried to basically take the good bits out and write it an a way that was hopefully easy to digest!

[Kveldssanger]

19/01/2016. Fact #130.

 

Arborists will be all to aware of the benefits of formative pruning young trees, particularly where they are present within an urban environment (near to highways, properties, power lines, or otherwise) or have structural issues (co-dominant forks). However, how can the monetary benefits associated with formative pruning be quantified, and if they can be quantified, what does this mean for those who opt not to formative prune?

 

This study looked at five tree species: Corymbia citriodora (x48), Platanus × acerifolia (x104), Pyrus calleryana cv chanticleer (x79), Quercus palustris (x65), and Ulmus parvifolia (x52). All the trees (348 in total) of these species featured in the study were 3-5 years of age, and no more thn 6.5m in height. Data collected were: health, structure, form, height, and canopy / stem defects.

 

78% of the trees had structural defects (at least one) that required remedial works, and these remedial (formative) works were done with secateurs, a hand saw, or a pole pruner - the latter was most frequently used. The table below shows, in more detail, the average number of cuts (and with what instruments) per tree for each species.

 

 

The time taken to undertake each cut was also noted, and the data is shown in the table below. By calculating the amount of time it took to prune each tree, the cost in man hours could also be calculated, and the average cost per tree (across all five species) was $2.79 AUD.

 

So how does this average cost compare to pruning mature trees? The authors acknowledge that the pruning of eucalypts of 20 years of age costs $78-112 (adjusted for inflation) per tree. When put against the cost of formative pruning young trees, there really is a massive difference (even if young trees receive formative pruning two or three times in the first six years of their life, which may amount to up to $7).

 

Not formative pruning young trees therefore makes little financial sense, and also opens up the tree to far more significant structural issues in maturity. For example, co-dominant stems were frequently observed in this study. The removal of such forks when young is easy and has little impact upon the tree, though in maturity not only may the fork have bark incluson, but dealing with the issue is far more difficult and only ever going to be a firefighting measure that costs a lot of money each time.

 

Perhaps formative pruning could even help local authorities, who have less money available to them than in years gone by. Granted, this won't apply for trees already in maturity, though where new trees are planted ensuring they are formatively pruned can really have marked financial benefits.

 

Source: Ryder, C. & Moore, G. (2013) The arboricultural and economic benefits of formative pruning street trees. Arboriculture & Urban Forestry. 39 (1). p17-24.

[David Humphries]

Chris, see if you can find an English version of Jan Willem De Groot's work, entitled - Concept for pruning young street trees in the Netherlands.

 

It looks at a 25 year prunning regime on young trees.

 

Here's a Dutch version.........

 

http://baumzeitung.de/fileadmin/baumzeitung/JbdB-2010-2014/2011/1-Baumpflegeinternational-Seite-19-68/1.4-Groot-(2011)-Das-Konzept-des-Jungbaumschnitts.pdf

 

I saw Jan Willem present this in English at the seminar in Poland last year.

 

He will be one of the authors of a new book on Young through to Ancient tree management, potentially to be published later this year.

 

 

 

.

[Kveldssanger]

Will have a look and see if I can find anything tomorrow - thanks for that, David.

 

Very much looking forward to that book, whenever it materialises.

[Kveldssanger]

21/01/16. Fact #131.

 

What are the attitudes of residents in urban areas to trees? To what extent do residents consider trees important to quality of life? Do demographic factors influence how residents perceive trees? During 20-minute telephone conversations with 1,038 randomly-contacted residents of the 112 largest metropolitan areas in the USA, these exact questions were asked.

 

The telephone conversations involved the residents being read a series of statements to do with urban trees, and they had to rate each statement from 1-4 (with 1 being strongly disagree and 4 being strongly agree). The age of the survey participant, income, and education levels were some of the demographic qualities obtained during the survey, in order to enable for statistical analyses to be run against these variables.

 

Of the 1,038 participants, 44% were male and 56% female, with an average age of 42 (the range was from 18-90). 75% were white / caucasian, 60% had an income of $50,000 or above, and 41% had a college degree that durated for at least four years. 66% stated that, during childhood, they had not lived in the city environment. The results of the statements read to each participant are shown below.

 

 

 

From these results, it is evident that the highest value held by individuals is that trees cool and shade surroundings (and this ranking is supported by many other studies), though the fact that all results rank higher than 2.5 (which was deemed as 'neutral') is significant. The second highest response, which is that of trees keeping people calmer, is also supported by other studies as a significant factor in why people value urban trees.

 

With regards to problems trees cause, none of the statements read ranked above 2.5 (neutral). Therefore, many survey respondents would have strongly disagreed (or disagreed) with the statements. Obviously, those who took the survey did not consider these statements as major reasons for why trees cause problems, suggesting either wrong statements were used or residents just don't consider the issues trees cause as being as important as the benefits they provide.

 

So how did demographics impact upon the results obtained? The table below displays all of the variables, though we can see that females strong consider trees to be important for quality of life (85%) slightly more than males (80%), though both genders rate trees highly. The results also show that the better the education of a person the more likely they are to see trees as important, and the same applies to yearly earnings (up to $75,000 - above this, and the positive view of trees drops slightly). Growing up on a farm also seems to be most significant in terms of valuing trees for what they provide, though all forms of upbringing - from urban to rural - are rather similar.

 

 

Therefore, it can be said with at least a reasonable degree of confidence that people generally do value trees. The adverse impacts trees offer the urban environment, whilst still recognised as problems, are far less significant in how an average resident living in a city will form their view of trees. Those who are least likely to value trees however, according to this study, will have a profile of being male, of a young age, have received little education, have been raised in the city, and be African American or Asian American.

 

Of this data, perhaps the most concerning thing is that more individuals are being raised in cities than ever before, so will the data drawn from this study signify what the future may hold? It would certainly be curious to have follow up studies undertaken, particularly of younger generations.

 

Source: Lohr, V., Pearson-Mims, C., Tarnai, J., & Dillman, D. (2004) How urban residents rate and rank the benefits and problems associated with trees in cities. Journal of Arboriculture. 30 (1). p28-35.

Edited January 21, 2016 by Kveldssanger

[Kveldssanger]

I shall be doing a huge amount of research into the benefits of trees for the foreseeable future, so it is very likley that a lot of what I write about for the next few months will be related to such a topic. I shall vary it up a bit, but just a heads up that I'll be ramming home why trees are good (and also why they may not be so good, at times).

[Kveldssanger]

22/01/16. Fact #132.

 

Historically, trees had a marked spiritual value and thus had significant importance for religions (many ancient civilisations worshipped the sun and the trees - the two drivers of life) and for meditation. Over time the value has evolved from the religious and spiritual one, though such value stretched back even to 96AD where Roman senator Tactius defined woodlands and groves as "sacred depositories" and "revered", and not to be "profaned by the steps of men". Similar religious values can be found in Norse mythology, where the Yggdrasil (Tree of Life), an ash tree depicted growing from the depths of the earth to the heavens above and containing all life within, was of significance to Norse culture. Even in modern times the religious values continue however, such as in Lithuania where great Pagan feasts are marked by the wearing of masks to celebrate the natural world. Not only this, but the spiritual importance of trees can be seen in literature, such as with the Ents in the Lord of the Rings book series.

 

An ash grows atop Mysselhøj, a Nordic Bronze Age burial mound in Roskilde, Denmark.

 

Source: Latham, J. (2015) The Development of Forest Conservation in Europe. In Kirby, K. & Watkins, C. (eds.) Europe's Changing Woods and Forests: From Wildwood to Managed Landscapes. UK: CABI.

[Kveldssanger]

22/01/16. Fact #133.

 

An investigation into the spatial distribution of trees within urban communities of Campos dos Goytacazes, Rio de Janeiro State, Brazil – of which some areas were highly affluent (1), some moderate to lowly affluent (2), and some very poor (3) – was undertaken during the early 2000s, and sought to assess whether there were environmental inequalities between the areas and, if so, what the causes and implications were.

 

Campos dos Goytacazes, established in 1835, was principally an area whose growth was fuelled by the sugarcane industry. On the surrounds of the settlement, sugarcane fields were therefore aplenty. However, during the early 1950s the industry went in to decline and much of these sugarcane fields were built on in the resulting period of rapid urban sprawl into the surrounding rurality. In fact, the authors note that this makes the city a good place for such a study, as the sugarcane fields were entirely cleared for construction – no trees existed before the construction took place. This allows for easy comparisons to be made between communities’ tree populations.

 

An overhead view of much of the city.

 

In order to draw comparisons, ten random communities were selected and then devided into the three categories aforementioned. Only one neighbourhood from the very poor category was sampled, because governments are not required to upkeep the area there as the residents do not pay taxes. Therefore, the government does not look after the tree population. From these communities, data in relation to tree populations were taken, and the results are shown in the table below.

 

Trees per square metre (Tree·m-2); trees per building (Tree·Bldg−1); private gardens per building (Garden·Bldg−1); land value (m2 value); and neighborhood age. Note that the poorest community is left out, likely as there were no trees.

 

From these results, the authors state that the number of trees present within a community is positively correlated with land value, whilst area age is not correlated with tree presence in any significant manner (meaning that just because an area has existed for a longer period of time it does not mean it will be more heavily populated with trees).

 

Additionally, tree diversity (and the number of trees from each tree species) in relation to the abundance of trees was also shown to be more even in more affluent areas, meaning that there is a more equally diverse yet plentiful tree population. These results are shown in the table below.

 

Shannon-Weaver Diversity Index (H) for the nine formal areas in Campos dos Goytacazes.

 

At this point the authors note that, contrary to past research, the age of an area plays little role in its tree population and species diversity. Instead, the level of affluency of an area is perhaps the significant determining factor. For example, in class 2 areas (moderate to low levels of affluency), 54% of the tree population comprised of the fast-growing Caesalpinia peltophoroides, whereas in class 1 areas the same species did not exceed 25% of the total tree population. In fact, in Parque Prazeres, which ranked lowest in the study, the species accounted for 70% of the tree population. However, it was always the most dominant species, regardless of its abundance. Other species within the city, many of which were also fast-growing (including Ficus benjamina and Licania tomentosa), indicates that fast-growng were preferenitally favoured – as, interestingly, were exotic species, which accounted for 40% of tree populations. Such data are supported by other studies from the wider region.

 

We can see how a poorer area exists in the foreground, with a slightly more affluent region behind.

 

In summary, it can be confidently stated that areas of high affluency in the city will benefit from diverse and abundant tree populations – in contrast to poorer areas. The authors remark that “the practical result is that wealthier neighborhoods that already have access to better public and private infrastructure also have an advantage in terms of the environmental amenities provided by trees”, which of course has a positive feedback loop for such affluent areas and much the opposite for poor areas. This is exacerbated by local government targeting its tree planting to rich areas, and ignoring the poorer communities. Until the local authorities recognise that their efforts are a causal factor behind the evident environmental inequality, there is little scope for change. More trees, or a wider variety of species, must be planted across the city, with no discrimination between areas based on level of affluence.

 

Caesalpinia peltophoroides within the urban environment.

 

Perhaps this case study rings true of cities and towns in other countries across the world. Do arborists preferentially target affluent areas for planting, and select a richer array of species to plant in such areas, as they are more comfortable in planting the trees in such areas? Based on anecdotal evidence, I imagine so. Maybe it is because the level of risk with regards to tree survival is lower. Ultimately however, does the cause really matter, as long as environmental inequality exists? At least in Campos dos Goytacazes, there needs to be a drive to allow all areas to benefit from diverse and abundant tree populations, which would help remove environmental inequality and potentially act as a catalyst for further change.

 

Source: Pedlowski, M., da Silva, V., Adell, J., & Heynen, N. (2002) Urban forest and environmental inequality in Campos dos Goytacazes, Rio de Janeiro, Brazil. Urban Ecosystems. 6 (1-2). p9-20.

[Kveldssanger]

24/01/16. Fact #134.

 

Nature doesn’t stop at the doorstep of a town or city. Ecosystems exist the world over, though they vary in their health, diversity, and other properties. Therefore, urban environments do have a capacity to serve the ‘needs’ of species other than humans, and in this case an urban green space’s ability to meet the ecological needs of bird species is assessed.

 

According to past research, in many urban environments – particularly those with a low abundance of trees and a lack of structural diversity – bird species that can be found are usually generalist ones. Therefore, there is scope to use bird species diversity in an urban environment to indicate its overall green space structural diversity.

 

This study looked at sixteen green spaces (including woodlands) within two cities in Italy: Milan (13), and Bari (3). The selected green spaces were clustered into three categories – the three largest green spaces in Milan, the three largest in Bari, and the remaining ones in Milan. Within the selected green spaces, bird species were counted over the course of a breeding season at eighty different point-counts, and the great tit (Parus major) and serin (Serinus serinus) were used as the principal indicator species – this was because both species were observed at over fifty of the point-counts, across Milan and Bari.

 

The European serin (Serinus serinus) was one of the two indicator species used to analyse how the different green spaces investigated varied in their ability to support avifauna. Source: The Internet IBC Bird Collection.

 

From the survey, a total of 56 bird species were recorded, which amounted to a total of 4,393 individual specimens. Many of the species observed were either ‘forest species’ (including the wren (Troglodytes troglodytes), short-toed treecreeper (Certhia brachydactyla), jay (Garrulus glandarius), and great spotted woodpecker (Dendrocopos major)) or ‘farmland species’ (including the stonechat (Saxicola torquata) and red-backed strike (Lanius collirio)). Other species observed were far more generalist in nature, and included the feral pigeon (Columba livia), hooded crow (Corvus corone), and starling (Sturnus vulgaris), though ‘aquatic species’ were also identified because of the presence of ponds (including the little grebe (Tachybaptus ruficollis) and great crested grebe (Podices cristatus)).

 

Having analysed the data captured, the authors concluded that abundant and more mature tree stands supported a great variety of bird species. However, the connectivity between the sites observed, as well as their connectivity to areas of nearby grassland, open space, hedgerow amongst agricultural land, ponds, and smaller woodland sites not surveyed, also played a discernible role in how many bird species were observed at a site – in essence, if a site contributes to a larger ‘network’ of sites, it is more likely to support a greater array of bird species, whilst a very isolated site will provide the opposite.

 

Parco Nord in Milan has the highest number of bird species found (38), as well as the greatest number of individual specimens observed (1,378). Source: Parks.it.

 

Therefore, for urban environments to support a wide variety of bird species beyond simply the generalist species, then there needs to be: (1) areas of extensive tree cover with mature specimens within, (2) areas of other land type (such as grassland and hedgerows within agricultural fields, though I would posit that street trees would also be critical), and (3) a high degree of connectivity between these different land types (supplemented by larger street trees, perhaps).

 

Thus, if an area of green space can be seen only to support generalist bird species such as the feral pigeon and hooded crow, there is a marked probability that the site lacks connectivity to other green spaces, and is also not situated within a network of a greater variety of land types.

 

Source: Sanesi, G., Padoa-Schioppa, E., Lorusso, L., Bottoni, L., & Lafortezza, R. (2009) Avian ecological diversity as an indicator of urban forest functionality. Results from two case studies in Northern and southern Italy. Journal of Arboriculture. 35 (2). p80-86.

[Kveldssanger]

24/01/16. Fact #135.

 

You may have either not heard of the oak polypore (syn: Buglossoporus pulvinus), or never come across it in the field. That would be because it is very rare in the UK. So rare, in fact, that it is a protected species under Schedule 8 of the Wildlife and Contryside Act 1981 in the UK.

 

This fungus is principally found in the southern half of England, where it can be seen upon mature and veteran oaks in old growth woodlands and pastures where exposed heartwood is present. However, research suggests that the fungus may be so infrequent that it has suffered from genetic drift (as a result of inbreeding) – only four mating alleles were found across six study sites where the fungus exists. This may be as a result of either the loss of old growth woodland stands and veteran oaks within wood pasture, or because the fungus is a very poor competitor when paired with other fungi – it grows slowly and in narrow range of environmental conditions, and simply is not aggressive enough in its competitive ability when other fungi are present.

 

Therefore, if we are to assist with the conservation of this rare fungus, we need to be conserving mature, veteran, and ancient oaks, perhaps with exposed heartwood, and also retaining older woodland stands. Perhaps, where there is a lack of a mature or maturing oak population, veteranisation techniques may assist with the creation of viable habitat for the fungus. However, given it’s suspected inbreeding and lack of competitive ability, conservation management may be challenging.

 

Interestingly, the fungus was supposedly found on a living beech tree (Fagus sylvatica) at Woodstock, England, in 1949. This contrasts with other sources, that states it can only be found on Quercus species.

 

These two sporophores were found growing on an ancient oak in Richmond Park, during 2008. Source: Overall (2010).

 

Sources:

 

Cartwright, K. (1951) Polyporus quercinus on Fagus sylvatica. Transactions of the British Mycological Society. 34 (4). pp.604-606.

 

Crockatt, M. (2008) Ecology of the Rare Oak Polypore Piptoporus Quercinus and the Tooth Fungi Hericium Cirrhatum, H. Coralloides, and H. Erinaceus in the UK. Doctor of Philosophy thesis. Cardiff University.

 

Crockatt, M., Campbell, A., Allum, L., Ainsworth, A., & Boddy, L. (2010) The rare oak polypore Piptoporus quercinus: Population structure, spore germination and growth. Fungal Ecology. 3 (2). p94-106.

 

Overall, A., 2010. Fungi Royale: Some interesting larger fungi of the Royal Parks-Part 1. Field Mycology. 11 (3). p101-104.

 

Rogers Mushrooms. (2016) Buglossoporus pulvinus. [Online] Available at: Rogers Mushrooms - Buglossoporus pulvinus Mushroom [Accessed: 24th January 2016].

 

Wald, P., Crockatt, M., Gray, V. and Boddy, L., 2004. Growth and interspecific interactions of the rare oak polypore Piptoporus quercinus. Mycological Research. 108 (2). p189-197.