Kveldssanger

Some of those photos are incredible!

Considering going to this, having read Karban's Plant Sensing and Communication a few months ago. Anyone else here thinking of going? Current seminar ? Treework environmental practice

Nothing beats the book itself

Saw it here first hah!

Nice shot.

02/02/16. Fact #144. I recently looked into how neighbourhood affluence levels influenced tree populations (abundance and diversity) in a city in Brazil, and have since come across a similar research article that looked into such issues (amongst others) in southern California. In this instance however, it appears that the authors take a slightly different angle of approach, and assess whether residents’ preferences across different communities impacts upon constituent tree populations as well. Ultimately however, this study had three main aims, and they are: (1) to determine whether the socio-economic and environmental status of an area will influence tree cover and species diversity; (2) to ascertain whether patterns exist across spatial areas within an urban forest (such as between street trees and trees within residential properties, and across the three counties studied), and; (3) to assess the level of influence residents have in terms of determining tree species composition within the urban environment. The three counties featured within this study were Los Angeles, Orange, and Riverside, and street tree inventories were completed during 2010-11. In each county, 12-13 residential neighbourhoods were identified (that differed in their characteristics) and subsequently surveyed. In these neighbourhoods surveyed, data relating to socio-economic and environmental variables (temperature, precipitation, population density, average income, etc), ecosystem services of the trees (growth rate, likelihood of root damage, flower showiness, and so on), and also tree type (native or exotic), were collected. The macro-scale urban forest of southern California Across all of the neighbourhoods surveyed, it was found that only 7% of all trees were native, whilst 46.5% were exotic species with the ability to regenerate naturally, and the other 46.5% unable to regenerate naturally. In terms of species diversity, all three areas were found to be somewhat similar, though Riverside had the lowest at 45 and Orange had the highest at 75. Los Angeles has 64 tree species identified in the survey. Only Quercus agrifolia, a native to the region, was found in significant numbers – all other abundant species were exotics, such as Cupressus sempervirens and Syagrus romanzoffiana, of which some were unable to reproduce naturally. Los Angeles County (as well as the other Counties) was found to be home to a great number of Mexican fan palms (Washingtonia filifera), which can be seen lining this street within the County. Source: LA City Urban Forestry. In terms of tree cover, Los Angeles and Orange County had a greater number of trees per neighbourhood than Riverside, though residential and parkland areas across all three counties had the highest diversity of tree species, as well as the highest canopy cover. Most trees in all counties were planted, in place of growing naturally. Drivers behind differing urban forest characteristics Socio-economic factors, in light of the data collected, were shown to have a significant influence upon urban forest structure and richness – the average income of the neighbourhood, the year in which the neighbourhood was built, and the level of education residents received (in this case a college degree or higher) were the most important influencing factors. There were greater numbers of trees (as well as a greater species richness) per neighbourhood in the wealthier (and better-educated) areas of all three countries, and Orange County and Riverside County had more trees in older neighbourhoods. Conversely, tree species diversity was low in cramped (high density) neighbourhoods. Spatial differences in urban forest structure In terms of differences between richness of street tree populations and residential tree populations, there was only a significant difference (in favour of residential trees) for Orange County (and between counties, street tree species composition was not significantly different). There was also a difference between the counties with regards to the amount of shade trees found, with Riverside County possessing more shade trees than Los Angeles County and Orange County – though there was always a greater proportion of shade trees found in streets, when compared to residential properties. Residential properties also had trees that, on average, were more water-demanding, and required more maintenance. Tree species preference of residents More fruit trees were found in older, more affluent neighbourhoods, compared to high-density neighbourhoods where trees were typically far less ‘showy’. Newer developments also had fewer trees that were demanding in terms of maintenance. Hotter areas were found to be home to the most shade trees, which correlated with the increase demand by residents in those areas for shade trees. So what does this mean? Because many of the trees in all of the neighbourhoods were planted, the authors suggest that socio-economic factors feature heavily in what is planted and where. As most of the tree species identified were not as common 20-30 years ago within the same counties, the demands of residents must have changed and the alteration in tree species composition would have shifted as a result. This is, according to the authors, perhaps because nurseries stock what is in demand. However, it is concerning that most trees are not native, though this may be because the counties’ generally arid conditions mean that the areas were largely void of trees prior to development. The fact that species richness is higher in affluent neighbourhoods is also interesting, though perhaps not surprising given other studies showing much the same. The authors consider that because wealthier neighbourhoods have existed for longer periods of time than the newer low-income neighbourhoods, and because wealthier neighbourhoods can afford to heavily irrigate their trees, their tree species diversity is, on average, higher. Interestingly, the concept of ‘prestige trees’ is also raised, perhaps suggesting that wealthier households will seek to plant exotic and perhaps less common tree species as a means of ‘showing-off’. The ‘wood streets’ in Riverside County are lined with trees, in this case what appear to be cypresses. Source: Grow-a-brain. Residents’ levels of education, whilst shown to be an influencing factor in more diverse and plentiful tree populations, may not relate exclusively with affluence. Of course, well-educated individuals may live in poorer regions, for varying reasons. It is perhaps because they are likely more aware of the need for trees that areas of well-educated individuals were found to have ‘better’ urban forests. The greatest species diversity, which was found in parks and residential areas, may be explained by (in the case of the latter) the desire by residents to have functional trees with good amenity value (traits are more important than species, and therefore there is a wide species diversity). The fact that street trees required little maintenance and had low water demands may be because municipal foresters are principally concerned with reducing the costs associated with their trees. Hence, we can observe a difference in the rationale behind the decisions made with regards to species selection, though publicly-owned parks do allow for more innovation on behalf of the municipality’s officers (given more space and a lack of a need to prune park trees, in general). Focussing on resident preference for trees, whilst the data collected here was not robust enough to draw wholly accurate conclusions, the greater abundance of trees in affluent areas correlates with such residents’ desires to have trees within their neighbourhoods. Similarly, the desire by residents in hotter neighbourhoods to have shade trees was shown to also hold true in actuality (more shade trees were found in hotter areas). More research would need to be done to ascertain whether resident preferences do influence street tree populations and species compositions, however. Source: Avolio, M., Pataki, D., Gillespie, T., Jenerette, G., McCarthy, H., Pincetl, S., & Clarke, L. (2015) Tree diversity in southern California’s urban forest: the interacting roles of social and environmental variables. Frontiers in Ecology and Evolution. 3 (73). p1-15.

Yeah they told me last year when I asked for the APNs. Good to hear it's now under way!

Always a work in progress, though am getting there. Lately I've been going through entire articles I find interesting. I'll have shorter ones, though doing a lot of writing about trees at the moment and am trawling so much literature that I have so much I want to write about.

01/02/16. Fact #143. When a species of tree suffers mortality as a result of a pest or disease, and such mortality occurs on a large scale, there is significant risk of co-extinction. Other species reliant upon the tree for habitat, be it exclusively (they spend their whole life using that tree species) or partially (a segment of a species’ lifecycle is spent on that tree species), stand a higher chance of also suffering large scale mortality, either immediately or soon after (a lag period). With around 10% of all tree species being threatened with extinction by a pest or pathogen, understanding the co-extinction effects of mass tree mortality is critical. In this study, located on Gotland (an island in the Baltic Sea; off of the coast of Sweden), the authors look at the relationsip between Fraxinus excelsior mortality associated with ash dieback (Hymenoscyphus fraxineus), and the species’ epiphytic lichen community. In total, 20 wooded sites (including meadows, pasture, and of course woodlands of varying canopy closure levels) were selected that contained ash populations (at least 50 individuals of the species), and all 20 sites had been inventoried for lichens in 1989-1991. This allowed for the authors to compare current populations of lichen with populations prior to the onset of ash dieback. The study was undertaken during July of 2009. By completing the study during this time, symptoms of ash dieback could be seen more readily, and the ash populations could be segmented into categories: dead (16%), dying (18%), infected (36%), and visually healthy (28%). In total, 1,066 ash were surveyed, and all 20 sites were found to be home to ash infected with ash dieback (though managed sites showed higher infection rates at 84%, compared to 63% in unmanaged sites and 66% in grazed sites – likey as managed trees, such as pollards, have an abundant amount of sprouts that may be more susceptible to the pathogen). The authors expect that the infected ash will all succumb to the pathogen in the coming 10 years. With the current figures from this study, the authors suggest that at least 34% of the ash (classed as dead and dying) will die, though as trees do not appear to routinely recover from infection, a further 36% may also die. Ash pollards such as this are considered to be at higher risk of infection (and subsequent mortality). How will this impact upon local lichen populations, and the populations of other tree affiliates? Source: Explore South Lakeland. As a result of this anticipated mortality, the authors suggest that the best case scenario will see 12-95% of the lichen species to suffer the same fate as the ash, though it is likley that at least 38% of the lichen community will disappear. Once 60-65% of the host ash are infected on a site, lichen communities will begin to suffer significantly as a result. Of course, lichen species that are not exclusively associated with ash will not suffer so greatly compared to those species reliant perhaps exclusively on ash, though their populations will still suffer losses. Concerningly however, most of the lichen species likely to suffer huge losses are red-listed species found only on ash. Additionally, extinction of lichen species is most likely on traditionally-managed sites, given their higher infection rates. The below tables outline such predicted extinction rates. Graph ‘a’ shows how lichen species, either fully or partially reliant upn ash for habitat, will fare as a result of the infection and subsequent extinction of ash (both optimistic and expected co-extinctions are displayed). Graph ‘b’ shows how lichen species, again both exclusively found on ash and found across all tree species, will fare in different land use types. Because extinctions only begin to significantly rise in occurrence at around 60-65% of ash being infected, the fact that few co-extinctions of lichens has been observed is perhaps not surprising – dead and dying individuals, at least in the area surveyed, were not high enough to cause such large-scale mortality of lichens. However, the authors note that lichen species may in fact go extinct before the ash do, at least on a local level, which highlights the need for further research into the relationship. Furthermore, sexually-reproducing lichen species are more likely to suffer extinction than vegetatively-reproducing species, as the latter is a much more rapid means of colonisation on a host tree. However, all species will ultimately be caught in a ‘bottle-neck’, where many lichen species are seeking to colonise few remaining ash hosts (particularly mature individuals), and this will see host-specific lichen species suffer most markedly. Such associated mortality in fact crosses over into other affiliate species associated with ash, however (such as insects, fungi, and other epiphytes), meaning that lichen will not be the only affiliate to suffer as ash dieback takes a hold. Perhaps, as highlighted in this research, areas with infection rates of above 60% should be targets for conservation management, in an attempt to reduce the loss of affiliate species. Such management may in fact encourage traditional management methods, such as pollarding, to cease upon ash, given managed ash are at a higher risk of infection. Source: Jönsson, M. & Thor, G. (2012) Estimating coextinction risks from epidemic tree death: affiliate lichen communities among diseased host tree populations of Fraxinus excelsior. PLoS One. 7 (9). e45701.

Yep! I saw it from that link as well! So did another member, who scarily PMd me very soon after I ordered it (within the hour).

:goodnight: :goodnight: :banghead: :thumpdown: :cry:

A heads-up to all you bookworms out there, this book is coming out later this year. Pre-ordered my copy now, so I get a nice surprise come October. Only £18! [ame=http://www.amazon.co.uk/dp/1771642483/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=2Q2JK15U2MXWW&coliid=I3MJP8LYIFTW9O]The Hidden Life of Trees: What They Feel, How They Communicate--Discoveries from a Secret World: Amazon.co.uk: Peter Wohlleben: 9781771642484: Books@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51OZeo%2BMHtL.@@AMEPARAM@@51OZeo%2BMHtL[/ame] Buy it somewhere else if you don't like Amazon, of course.

I was thinking that. Only when I started writing my blog did I figure how horrendously dire some of my long posts must have been, in terms of a wall-of-text appearance! Curious to know whether most people access this thread from within arbtalk, or via internet searches. Stacking up a nice load of hits lately, which is great.

Quick question - are you all content with the new 'direction' of the posts, complete with pictures and longer write-ups?

31/01/16. Fact #142. We could discuss this topic to the ends of the earth, outlining both positives and negatives of tree presence within urban environments, though there is a mounting pile of evidence to suggest that trees really do have a (largely) beneficial impact upon humans in terms of health and well-being. However, most studies have looked at trees on a macro-environmental scale (such as exposure to general green spaces), and not looked at the linkages between individual trees and the impacts such trees have upon residents in the close locale. Therefore, the authors of this study sought to change this, by investigating the health benefits of trees to a “low granularity”, and instead of assessing such ‘greenery’ from the ground, they related their study to tree canopy sizes only – it was considered (by the authors) that tree canopy is the most important of all the ‘green’ available within urban areas. Thus, the study was planned, and the city of Toronto, Canada, was chosen as the location for the project. The authors particularly sought to assess the relationship between street tree canopy density and its impacts upon: (1) overall health ‘perception’ (this was chosen as subjective perceptions of personal health has been found to influence mortality rates, and is considered a strong indicator of actual health of an individual); (2) cardio-metabolic conditions (including high blood pressure, obesity, high blood glucose, high cholesterol, and diabetes), and; (3) mental health problems (depression, anxiety, and addiction). Similarly, the benefits of trees in parks was also assessed, enabling for comparisons to be drawn between trees in differing locations. In terms of the results found, I have segmented the three aforementioned categories into different sections. The manner in which the results section was written was rather disjointed by tables and seemingly tangential (but still contextually beneficial) points, though I pulled out the most important parts and included them below. One of Toronto’s residential streets, which in this case appears to have a good number of small, medium, and large trees. Health perception It was found that people who live on streets where there are more trees, and / or trees with larger canopies, report better health perceptions (after accounting for demographic factors: age, income, etc) – for every 400 square centimetre increase in ‘treed area’ per one metre squared of neighbourhood area, it was shown that health perceptions would rise by around 1% (around an extra 10 trees per block, of which there are 25 blocks per district area). In fact, this incremental increase in health perception as a result of there being more trees, or larger trees, was on par with an income increase of $10,200 per year per household, or an individual being 7 years younger. However, the authors note that trees alone do not majorly influence health perception (they only do so by a few percent) – there are many others factors that will impact upon an individual’s view of themselves. Cardio-metabolic conditions Where trees are present within streets, the authors found that fewer cardio-metabolic issues were present in individuals. For every 11 trees within a city block, the occurrence of such health issues fell by around 0.5%, and is as impactful as an average increase of $20,200 in household income per year, or being 1.4 years younger. Again, tree presence isn’t the sole driver behind better cardio-metabolic health, though certainly plays a role (albeit, perhaps a rather small one – a few percent). Mental health The authors found no statistical significance of tree presence upon the mental health of individuals, so will be undertaking further investigations to further analyse the relationship. Concluding remarks In light of the survey data, the authors conclude that an increase in tree presence along urban streets will have a beneficial impact upon an individual’s health perception, and to their cardio-metabolic health. With regards to their comparisons to annual income increases, the authors make an interesting point in that a household earning $10,200 more than another household, whilst on paper would be ‘better off’ in terms of health perception, may not actually be so – if the other family has over 10 additional trees in their block compared to the block where the higher income household is, the lower-income household may perceive themselves as healthier than the higher income household. Toronto has around 28% tree canopy cover, and in this image we can see a heavily-treed parkland area with a building-clad backdrop. Therefore, as Toronto’s street tree density is on average between 0.2%-20.5% (including parks, it is around 28%), if tree planting rates increase (by as little as 10 more per block) – and canopy cover subsequently increases – then the health of residents will improve. However, the authors do note that Canada has a nationalised healthcare system, and therefore other countries where no such healthcare programme exists then the average income of a household may hold more weighting. This means that an increase in 10 trees per block in another country may equate to less of an increase in comparison to household income increase – 10 more trees may only equate to a $4,000 increase in household income, for example. Curiously, the improved health of residents did not rank so significantly for trees within green spaces. This means, so the authors hypothesise, that it is the trees that are situated directly within the locality of a household (and within view) that will have the most beneficial impact on health, though the authors recognise that the other benefits of the street trees (such as reducing air pollution) will play a role. However, parks are still beneficial – that is not being disputed. The results simply underline the necessity for street trees – we cannot rely on parks exclusively to bolster the health of a populace. It is also suggested that once tree density becomes significant (perhaps once over 20%) that the health benefits of trees becomes less significant (though are still evident). Additionally, an area with many evergreen trees does not mean residents who may view them have a better perception of their health – a great variety of trees, both deciduous and coniferous, are required to improve health perceptions of individuals impacted by their presence. However, residents living within areas occupied by many evergreen trees do report a better cardio-metabolic status. Source: Kardan, O., Gozdyra, P., Misic, B., Moola, F., Palmer, L., Paus, T., & Berman, M. (2015) Neighborhood greenspace and health in a large urban center. Scientific Reports. 5 (11610). p1-14.

30/01/16. Fact #141. Having recently shared a study that looked at the urban forest and bird species diversity, I thought we could use the momentum from that article and build upon it by looking at bats and the urban forest. The bird species diversity article highlighted the criticality of good landscape connectivity within urban environments (the opposite of habitat fragmentation), and the authors of this study suggest much the same from the very beginning – alongside fragmentation (usually coupled with urban sprawl / urbanisation) comes a decline in species diversity within urban areas, and it can be anticipated that bats are no exception to this. The authors undertook this study in Vitoria, a city in the southeastern part of Brazil, with an intent of assessing whether wooded streets were used by bats (this would allow the authors to conclude whether urban street trees are beneficial in terms of connectivity for bats). Vitoria, home to 1.8 million people, expanded significantly during the 1940s and onwards, following industrial advancements. Such expansion lead to the destruction of the surrounding environment (including the Atlantic Forest) and its ecosystems, and the increased pollution levels have further taxed remaining vestiges. However, the city is still marked as a site important for biodiversity conservation, likely because of its eight municipal parks acting as habitat for a great variety of wildlife to the now (locally) fragmented Atlantic Forest. This study chose to look at three of those eight parks for the presence of bats: (1) Pedra da Cebola Municipal Park, with 100,005 square metres of land that once acted as a transition between coastal shrubland at the Atlantic Forest; (2) Horto de Maruipe Municipal Park, with 60,000 square metres of land and covered by native Atlantic Forest vegetation (though with many introduced species of wildlife), and; (3) Fazendinha Municipal Park, with 22,653 square metres that – like Pedra da Cebola Municipal Park – was a transition zone between the coast and the Atlantic Forest. Three wooded streets, and three non-wooded streets, were also surveyed for bat presence. By surveying the parks and the streets, comparisons could be drawn between the two, and there would be scope to determine whether bats remain isolated to the parks. Sampling for the bats (with the use of mist nets) took place over the course of a year, with visits taking place for three days each month. In total, 172 individuals were captured a total of 174 times. Most were found within the municipal parks, followed by the wooded streets, and then the non-wooded streets. However, the vast majority were only found within the urban parks (both in terms of species diversity and species abundance), with wooded and non-wooded streets not displaying a marked difference between one another. The authors do note that limited samplings perhaps lead to this, and suggest that more sampling visits to all areas would potentially show more individuals of more species using all three environments (only 10 species were recorded, whilst the region has 36 bat species – the authors do suggest that Vitoria may not harbour all species, however). The table below breaks down species presence by environment. The number of individuals of each bat species recorded during the study period of one year. In light of their research, the authors in fact suggest that wooded streets are not particularly important for bat species, though they do recognise that increasing sampling visits and having sampling methods utilise ultrasonic devices may have improved the results obtained. For example, Noctilo sp. bats were observed, though not recorded with the netting method. The fact that Artibeus lituratus was the most frequently observed one across all three environments, the authors allege, is due to its opportunistic behaviour. It has previously been recorded using urban environments, and may have a tolerance to urbanisation as a result (unlike other species). However, other research papers have suggested more species of bat (some found in this study) do use urban areas for feeding, particularly where lights attract insects (insectivorous bat species will benefit most for this). Artibeus lituratus (giant fruit-eating bat). So what does this study mean? As sampling was admittedly quite limited, perhaps it’s not a foregone conclusion that bats don’t use street trees as vehicles to move between larger park areas (or for other reasons), though it does suggest that maybe the urban forest is not structurally supportive of many bat species. Could more be done in the planning stages of development, or even following development, to attract more bats to the urban streets of Vitoria? The authors suggest that using native trees in place of exotic ones may be a good starting point. Source: 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.

Note it's the tree behind the front one that gets blasted. Literally just gets blown to shreds. Would be interested to see if it sprouts up from the base. Also note the little puff of smoke to the right hand side of the video - a root got smouldered, perhaps?

Very cool! Here's a Lightning Bolt Striking and Destroying a Tree

28/01/16. Fact #140. The manner in which a tree is planted will have an impact upon the likelihood of that tree surviving beyond not only the first few years, but also into maturity. For amenity trees, this may be a particular problem, as trees planted incorrectly will not provide the amount of value intended, and they may even detract from the environment in an aesthetic sense. A particular importance with regards to transplanting of a tree into the landscape is that of planting depth. In essence, the root collar should not be planted too far above or below grade. In the article that is featured within this post, the authors undertook five different experiments on five different tree species, and assessed how they fared in response to different planting depths (and other variables, which varied between studies). Study #1: Planting depth and soil amendment effects on Quercus virginiana The oaks in this study were planted at 7.6cm above grade, at grade, and 7.6cm below grade, and various soil amendments were made to individual specimens (native soil, and soil incorporated with sand, peat, clay, or sandy topsoil). From these variables, tree growth and physiology were assessed. Results from the study concluded that oaks grew best when planted at grade, and where the soil was amended with an application of sand. Study #2: Planting depth and soil amendment effects on Taxodium distichum The variables for this study were identical to those from the study on Quercus virginiana, and much akin to that study, Taxodium distichum specimens grew best when planted at grade and with soil containing sand. When planted above grade, the specimens has reduced coarse root growth, and also produced numerous roots that may potentially act as girdling roots later in life. Similarly, trees planted below grade had reduced stem water potentials, and greater levels of mortality. Across all soil types however, adverse impacts of planting below grade were observed, though the severity varied with soil composition (clay soils lead to the greatest impact, however). Study #3: Planting depth during container growth and subsequent landscape establishment on Ulmus parvifolia This study investigated how planting depth of individuals during container production (at 5cm above grade, at grade, and 5cm below grade), when planted into 10.8L containers and then later into 36.6L, impacted upon landscape establishment. During the first transplanting phase, where individuals were placed into 10.8L containers, those planted at grade were observed to grow most, whilst where planted below grade growth was stunted. Following the second transplanting phase into 36.6L containers, individuals planted above grade both times were observed to suffer the most in terms of growth, though responses by all trees was generally varied. When transplanted out into the field however, as long as extreme variations from grade level were avoided, there was no observed significant difference in growth rates. This suggests that the species fares differently during container production than it does out in the landscape. Study #4: Planting depth and irrigation extent effects on Platanus occidentalis The depth individuals were planted at (7.6cm below grade, at grade, and 7.6cm above grade), in addition to the amount of water received via irrigation (0, 1, 2, or 4 spray stakes, each applying 0.42L per minute), were the variables assessed in this study. Results outlined that planting depth was a significant determining factor for tree survival, though irrigation was not (which suggests the adverse impacts of planting depth were not influenced by soil moisture levels). Individuals at 7.6cm below grade, even after just one year, had significantly increased mortality rates. When planted at grade, and in a sandy loam, the best growth was observed. Study #5: Planting depth and season of transplanting effects on Taxodium distichum Individual specimens in this study were planted either during spring or autumn (fall), and at grades 7.6cm below, level, or 7.6cm above. Depth was shown to be a significant factor in determining growth (with trees planted at or 7.6cm below being taller and thicker in the stem), whilst transplanting season was not. Conclusions From the studies mentioned in brief during this report by the authors, it can be seen how planting depths impacts different species in different ways. Curiously however, the authors note that ecotypes may have an effect upon establishment success rates, with seeds sourced from trees growing in the environment in which they are intended to grow offering a potentially higher rate of success than those sourced from environments of other kinds. It is doubtful that this relates to planting depth, though certainly is food for thought with regards to selecting individuals to plant in harsh urban environments. These two alders, due to improper planting (they were planted in their non-degradable bags) and aftercare (no watering regime), have died during their first season. Source: Bryan, D., Arnold, M., Volder, A., Watson, W., Lombardini, L., Sloan, J., & Cartmill, A. (2009) Overview of selected studies on the influence of planting depth on landscape establishment of container-grown trees. In Watson, G., Costello, L., Scharenbroch, B., & Gilman, E. (eds.) The Landscape Below Ground III. USA: International Society of Arboriculture.

I swear I could smell it, hah! I bloody hate aniseed so know the smell. Perhaps just mental! Going mad in the old age.

(Pseudo)Trametes gibbosa, it was. Martyn said that whilst the pore structure was different to how it would usually appear, it was gibbosa nonetheless. Staying in Kew's collections as they don't have a sample from Prunus spp.

What a shame. That hedge was lovely.

Figured half of my forum posts are probably from this thread! Hah.

I'd have that as a tiling scheme on my floor. Very avant-garde.

27/01/16. Fact #139. Urban street trees must cope adequately with numerous adverse factors, in order for maturity to be reached. But a few of the stressors our urban trees face include: (1) high ambient temperatures in the summer bringing about water deficits that impact upon efficient photosynthate production; (2) reduced moisture availability as a result of restricted rooting space and an impermeable surface layer; (3) mechanical damage associated with mowing operations and road vehicle collisions; (4) pollution of various forms within both the air and the soil; (5) deficiencies of necessary nutrients within the soil, and; (6) a lack of sufficient solar irradiation (principally because of the shade cast by buildings). In light (no pun intended) of the aforementioned factors, and the ones not eludicated to, research must be undertaken in order to ascertain exactly how each factor may impact upon the ability for an urban tree to survive. This study seeks to achieve exactly that, by looking at the urban trees of Montreal, Canada. The city of Montreal has 4,460km of road, streets, and boulevards, with a total of over 240,000 public trees. These highway networks are situated amongst downtown, residential, institutional, and commercial areas, and therefore the authors decided to analyse trees from all four areas in order to have a suitable range for the study – though they split them into street types of (1) intensive commercial, (2) commercial, (3) institutional, (4) intensive residential, and (5) residential. In the five catergories, locations were selected based on the height of the buildings surrounding the trees, the orientation of the buildings compared to the trees, the rate at which highways are used, size of tree pits, and street width. In total, 1,532 trees were surveyed. The species assessed were representative of 75% of Montreal’s trees, and were: Acer platanoides, Acer saccharinum, Celtis occidentalis, Fraxinus pennsylvanica, Gleditsia triacanthos, Tilia cordata, and Ulmus pumila. Each tree had data captured including DBH, crown diameter, height, crown volume, annual DBH increment, and annual height increment. Similarly, many abiotic factors were measured, including street type (the five categories were outlined above), distance from tree to the closest building, volume of the tree pit, soil penetration resistance, and the type of ground cover. Soil samples were also taken and analysed for theit nutrient content. From the above perameters (and those not mentioned), the table below outlines the significance of each perameter for each species. Emboldened statistics, which are for a probability of 0.02 or less, indicate the most significant influencing factors for each species. The significance between growth of each tree species compared to the variables assessed. For a better view of this table, please access the article (linked at the end of this post). From the above data, we can see how different species have different variables that have significant influences upon their growth. For example, iron availability in the soil is significantly related to the growth of Celtis occidentalis, whilst it is not for Acer saccharinum. Similarly, Acer saccharinum growth is not significantly impacted by the volume of the tree pit, whilst it is for Gleditsia triacanthos. It is likely that species-specific traits govern this, as Acer saccharinum is known to tolerate encorachment into its root zone very well. The authors note that it is interesting how the presence of a metal grate atop the surface of the ground is a significant factor in effective growth of nearly all tree species. It is almost certain that this is because the grate stops soil compaction from manifesting as a result of traffic (be it on foot, or vehicular). However, it is solar irradiation that is the most significant determining factor for tree growth, suggesting that the most important thing an urban tree needs is light (which may not always be provided in urban areas). Location of urban trees also appears to be a significant factor for all species studied, and the below table breaks down growth rates for each species for every urban zone – though the authors outline that annual DBH increments for zones 1 and 2 were 0.53cm and 0.78cm respectively, whilst for zones, 3, 4 and 5, increments were 1.18cm, 1.03cm, and 1.02cm respectively (suggesting institutional locations provided for best radial growth of trunks). The authors also make note of stressed trees being most present within commercial zones (1 and 2), meaning 82% of the poorly-growing trees were located within these two sectors alone. Conversely, non-commercial zones were home to the greatest number of fast-growing trees, indicating better vitality. It is suggested that the reasons for this difference may be that residential and institutional areas are more open, and therefore there are greater levels of sun exposure for the trees (which was seen as the most significant factor impacting upon tree growth). Respectively, commercial and non-commercial zones receive, on average, 205-480 hours and 1,495 hours of solar irradiation during the growing season – a stark contrast. A statistical analysis of the frequency of each tree species and its growth rate in each area. For a larger version, please access the article (at the bottom of this post). In fact, when looking at total solar irradiation hours across the growing season for each species in commercial zones, it is highly evident exactly how significant a factor it is for tree growth. The below table does a very simple job of explaining the significance, though also shows how different species’ growth rates fare differently at different total irradiaton hours. For example, Celtis occidentalis grows well only at very high levels of irradiation exposure, whereas Fraxinus peensylvanica can tolerate around 200 hours less across a growing season. Irradiation levels per species and growth rate in commercial zones. The closeness of a tree to a street also appears to ensure the tree has a greater level of sun exposure, though if the width of the verge is narrow then growth may markedly suffer as a result. This may be because a narrow verge restricts the ability for the tree to grow radially, though also means the tree is more likely to be pruned because of its proximity to the highway. Additionally, wide streets was also a marked factor for influencing tree growth, and this may likely be because wide streets are usually busier (hence they have more lanes), and thus the amount of pollution emanating from the vehicles is greater – as is there a greater chance of de-icing salts being used. Such pollutants have adverse effects on trees, stifling tree growth at higher rates and at greater frequencies. For a better understanding of exactly how each factor impacts upon tree growth, I highly suggest you visit the article page and have a read for yourself. It’s certainly a very information-dense piece (though the first table in this post explains it all very well). However, I hope that this post goes some way to outlining the important factors that shape a tree’s future, and hope that such information is of use to tree officers and urban foresters in towns and cities across the world. These urban trees (Populus x canadensis, Populus nigra ‘Italica’, and x cuprocpyaris leylandii) have plenty of light, and also a fair amount of space. They are located within a busy industrial area near to where I work. Source: Jutras, P., Prasher, S., & Mehuys, G. (2010) Appraisal of key biotic parameters affecting street tree growth. Journal of Arboriculture. 36 (1). p1-10.