Kveldssanger

No changes as far as I know. Scraped some bark off - nothing looked off.

Hahah I don't hate you, man! It's a tree we manage - I'm a tree officer. It's within a churchyard and I am curious as to the cause of the decline. It'll be one that will be taken down, I would very much imagine, in the coming time. Depending on the diagnosis, it may influence what is replanted.

Hah! Such cynicism.

06/01/2016. Fact #119. Anecdotally, I am certain that many of you will attest to tree presence being highly favoured in urabn environments - not only for the environmental and ecological benefits they provide, but for the benefits they offer humans on an economic and social level. The focus of this post is a study by Frances Kuo, published in 2003, entitled The Role of Arboriculture in a Healthy Social Ecology. Kuo sought to analyse exactly how, in the US city of Chicago, urban trees influence human social interactions, and the results are - whilst not unexpected - very interesting. In terms of methodology, Kuo remained brief in description (instead referring readers to the respective journal articles for each study that was only summarised in this article) selected different housing areas of Chicago that met four different criteria: (1) a variation in green cover immediately surrounding the area (from areas laden with trees to aread void of them); (2) a constant with regards to other environmental features, for control purposes; (3) housing areas contained residents that were randomly assigned abodes (publix housing), so to negate the bias encountered where studying social populations where people have chosen to live in the area, and; (4) residents have no influence over how the vegetation in the area is managed. In light of these criteria, two housing developments were identified (shown below - the first Robert Taylor Homes and the second Ida B. Wells), and the residents' social undertakings were assessed and subsequently separated into different categories. Results are listed below. Enticing residents to venture 'outdoors' When shown different pictures of trees within an urban landscape, residents were found to strongly prefer more trees in a landscape than less (54 per hectare, in this study), and stated that if their courtyards had more trees contained within them then they would feel more encouraged to utilise the grounds. This suggests that trees can be strategically planted to entice residents to actually use the outdoor space surrounding their property, which in itself brings social interaction in - largely - a positive manner. Encouraging adults to use outdoor spaces Whilst the above study was hypothetical, Kuo found that, when transferred into reality, results were very similar. Not only are adults more likely to use outdoor space if the space contains plenty of trees, but venturing adults will be disproportionately concentrated in areas where there are many trees compared to where there are few or no trees. Additionally, the closer the trees were to properties, the more likely it was to have adults use the outdoor space nearby - to the point that, where there were no trees at all, the space was not used. Encouraging children to use outdoor spaces Much like with adults, children also are disproportionately drawn to areas with plenty of trees. In these heavily-treed areas, it is also more likely that the children are engaged in play (in place of other activities) - particularly creative play. Kuo suggests here that not only can it be said that trees draw both adults and children out in greater concentrations, but this greater density of people encourages social interaction among communities. Promoting social interactions between residents Building on the comments above, results suggest that the frequency of activities such as talking, playing card games, and reparing cars, is positively linked to tree cover. 73% more individuals were shown to interact socially where tree cover was significant, with the results showing adults were most noticably impacted. Facilitating child-adult interactions Mixed-age groups consisting of children and adults are more likely to be observed in areas of high tree cover. This is important for children in particular, as it enables them to develop the necessary skills for adulthood, and also stops children from engaging in ani-social behaviour (due to adult supervision). Improving neighbourhood social 'ties' Trees encourage neighbours to interact informally with one another, improving social ties amongst communities and making communities stronger as a unit - to the point that residents will share resources with one another out, particularly where there is poverty. Individuals living in areas with higher tree cover also reported significantly greater amounts of social interactions with neighbours, compared to barren areas. This ties in with the greater use of outdoor space by residents in heavily-treed areas. Heightening the sense of safety Kuo concludes that, as a result of studies into how safe residents feel in areas with plenty of trees and areas lacking, those in locations with many trees reported feeling much safer. Additionally, residents with nearby access to tree cover reported feeling more adjusted to their home, compared to those where trees were not available nearby. Reducing graffiti and other minor disorders Vandalism, graffiti, and incidences of littering were found to be at lower rates in areas with higher green cover, as were anti-social activities such as strangers loitering, individuals making a lot of unecessary noise, and such forth. Kuo suggests this may be because green space improves peoples' level of care and awareness, making anti-social behaviour both less attractive harder. However, the increased cohesiveness of areas with many trees may also make anti-social behaviour less enticing. Impacting crime levels Put simply: the greener the surrounds of the building, the lower the observed crime rate - this applies to crimes such as property crime and violent crime. Source: Kuo, F. (2003) The role of arboriculture in a healthy social ecology. Journal of Arboriculture. 29 (3). p148-155.

Hi all, Anyone able to help with this? A mature Lawson cypress has hugely contrasted dieback in its crown, and the remaining side is now starting to die back from the bottom upwards, with the youngest foliage dying first. I was leaning somewhat towards phytopthora or cypress aphid (C. cupressi). Images are here and are supported by some blurb, though the images exclusively I have posted below. Any help is appreciated massively. Thanks.

I am looking at the listing and I notice a few odd things: In the description it says "slight deterioration to part of bole and one branch", but then later on says "this tree has been classified as in need of major surgery and dangerous". What one is it? If it's only got slight deterioration, how can it be in need of major surgery and be deemed dangerous? "We have taken the difficult decision to remove the 150 Year (Professional Estimate)Old Tree". Difficult enough to put it up for auction! Such tact. "There is some decay to the bole and one of the larger branches which has led to us taking the safety decision to remove." As above.

Email the TO and mark it as urgent? Save the ebay page as well, in case they pull it.

Quick, get it TPOd!

I realise these latest ones have been a bit longer - I'll start breaking them up with the photos I use on my blog, I think! Better than a wall of text. That Magnolia book can be ordered for 1p on Amazon.

06/01/16. Fact #118. Frequently residing in front gardens, the Magnolia is appreciated by-and-large for its amenity value. Whilst there is no question that the genus produces some stunning specimens, its rich history is also something to be admired. The origin of the Magnolia Fossil records suggest that the genus has existed from the Cretaceous period (145-66 million years ago), making the Magnolia the first flowering plant. Before this time, only conifers and cycads graced the earth - which themselves came after both ferns and horsetails. Its historic distribution, prior to the last age, would have been across most of mainland Europe and the rest of the northern hemisphere, though since the last ice age its native range has predominantly been Asia and eastern America - the mountain ranges across Europe, which span east to west, restricted the retreat of plant species (as seed could not feasibly retreat over mountains), thus trapping them and sentencing them to death. Its method of pollination was, and still is largely, through beetle-type insects. These beetles, which would travel between specimens, were attracted by the fragrance of the flowers, and the edible tissues and pollen contained within. In fact, to improve its means of successful pollination, the inner tepals of the flower could remain tightly shut for days on end, which allowed visiting beetles to feed safely and - at the same time - get covered in pollen. The Magnolia is however monoecious, meaning both male and female organs are found on the same specimen. To counteract the risk of self-fertilisation by visiting beetles, individuals will not mature their male and female organs at the same time. This enables pollen from one specimen's male flower to reach the female organ of another. The Magnolia hunters The first Magnolia came to the UK in 1688 from the USA, courtesy of John Bannister. Bannister, a missionary, on his travels to Virginia, returned with Magnolia virginiana. Since then, a cascade of introductions occurred from the USA, and by 1800 most American species had been introduced and started being cultivated. Records are less clear over when the Magnolia was first introduced from Asia, though it is considered that Magnolia denudata and Magnolia coco were both introduced around a century later than Magnolia virginiana - the former was brought over, in 1780, by Sir Joseph Banks. The author of this book remarks that it was not these early Asiatic introductions that were so significant, but introductions from two plant hunters in the 20th century. The first, George Forrest, was sent by the Royal Botanic Gardens in Edinburgh to collect plant specimens in Asia, though during his travels in China he remarked how dangerous it was - to the point that, in 1905, after the British begun invading China's Lama (Tibet) region, any foreigner was seen as a threat. As a result, he and his team of 17 plant collectors had to flee, with hostile natives on their tail. After a period of nine days, and having stumbled into a village inhabited by friendly Lissoos (a sub-tribe of the Tibetans) at death's door, the village leader managed to smuggle him and the only other survivor of his team out of China. On his travels, George Forrest managed to collect 31,000 plant species, of which eight were of the genus Magnolia and three new to cultivation. The second, Ernest Henry Wilson, whilst having far less of a tale, introduced over 1,000 plant species from Asia into cultivation, including eight new species of Magnolia, making him the most significant 'Magnolia hunter' the world has ever seen. His introductions were: M. wilsonii, M. dawsoniana, M. delavayi, M. sprengeri, M. officinalis, M. sinensis, M. sargentiana, and M. s. robusta. Source: Rankin, G. (1999) Magnolia. China: Hamlin.

Some very good points you raise there, Jules. I find, from going through the ISA conference proceedings publications (The Landscape Below Ground series and Trees & Building Sites) are a little lacking in terms of background information and setting context. I realise they're overviews of what was presented in spoken word, though I find myself still wanting having read many of the articles.

05/01/2016. Fact #117. The effect of acid rain on trees manifests in two ways – upon foliage, and roots (Kimmins, 1997). The symptoms include direct damage to plant tissue (particularly the foliage), reduced density of foliage within the crown, distinct areas of dieback, and whole tree death (Singh & Agrawal, 2007). Studies into the impact of acid rain upon the foliage of forest trees conclude that necrotic (dead) patches are particularly common, with injuries being primarily to the epidermis (outer-most layer of a leaf). Acid rain therefore may have potentially severe impacts upon leaf structure (Fan & Wang, 2006). The foliage of coniferous species is more prone to the foliar effects from acid rain, likely given conifers do not shed foliage annually (Percy, 1986). Persistent (long-term) damage via acid rain may actually bring about a potential shift away from coniferous forests and towards deciduous forests. Exactly how this will impact upon the boreal (northern) forests however is not fully known, though the observed transition between northern broadleaved forests and boreal coniferous forests is seemingly rapid (Johnson, 1983). Forest ecosystems either at high altitude or prone to misty conditions can also be damaged by the acidic nature (both sulphur and nitrogen are present) of the water droplets that constitute the clouds (Kimmins, 1997). A study into how such acidic mist impacted upon forest trees identified that growth was rapidly reduced and calcium was directly leached from the foliage, in turn leading to foliar injury (DeHayes et al., 1999). Turning attention towards the impact upon the root system of a tree, as the forest soil increases in acidity – due to acid rain – seedling germination lowers (Percy, 1986). Therefore, if soils do continue to acidify, the future of forests may be under threat as a result of a possible lack of regeneration. The lowering of soil pH via the accumulation of sulphur and nitrogen ions within the soil (Kimmins, 1997) means important nutrients are leached from the soil, and increases in the abundance of phytotoxic (toxic to plants) heavy metals, such as aluminium, occur. Such changes in the soil chemical characteristics reduce soil fertility, which ultimately has a negative impact on growth and productivity of forest trees both above and below the ground (DeHayes et al., 1999; Singh & Agrawal, 2006; Menon et al., 2007), with the example of a reduction in fine root mass being evident. The accumulation of toxic heavy metal ions, which may be brought about (at least in part) by acid rain, is also known to have negative impacts upon the ability for decomposers (fungi and insects) of a forest ecosystem to function properly. This leads to imbalances in nutrient cycling, litter decomposition, and productivity of the ecosystem (Pennanen et al., 1998), which in turn can impact upon vegetation life, and may lead to stresses that can increase in severity over the years. Such soil acidification ultimately can change the entire vegetation composition of a forest – much like how acid rain damage to leaves can alter composition – with one study highlighting how a pine and spruce forest transitioned towards and then into a mixed and birch forest (Koptsik et al., 2001). Further studies have concluded similarly, by identifying that certain tree species will begin to die from ill-health following the change in soil properties (Johnson, 1983; Swaine, 1996; van Breemen et al., 1997). As a result, acid rain can initiate a transition away from forests dominated by particular species, and towards forests dominated by different species. This has impacts for the species that rely on the trees for habitat and food, as well – birds, insects, fungi, lichens, mammals, and bacteria are but just a few examples of the types of organisms that will be impacted. Soil acidification within forests may therefore be very destructive, in time. However, as germination is only significantly stunted at a pH of 2.0-3.5 (Percy, 1986), such an issue may only be a distant concern for now. Despite this, one study that looked at modelling future soil profiles on a heavily acidified site concluded that pH is unlikely to revert back towards what it once was, even if drivers of acidification (such as acid rain) slow. This is because soil profiles suffer from past inputs into their system (Małek et al., 2005), thereby meaning that the future extents of acid rainfall upon forest soils could be very damaging. Sources: DeHayes, D., Schaberg, P., Hawley, G., & Strimbeck, G. (1999) Acid rain impacts on calcium nutrition and forest health alteration of membrane-associated calcium leads to membrane destabilization and foliar injury in red spruce. BioScience. 49 (10). p789-800. Fan, H. & Wang, Y. (2000) Effects of simulated acid rain on germination, foliar damage, chlorophyll contents and seedling growth of five hardwood species growing in China. Forest Ecology and Management. 126 (3). p321-329. Johnson, A. (1983) Red spruce decline in the northeastern US: hypotheses regarding the role of acid rain. Journal of the Air Pollution Control Association. 33 (11). p1049-1054. Kimmins, H. (1997) Balancing Act: Environmental Issues in Forestry. Canada: UBC Press. Koptsik, G., Koptsik, S., & Aamlid, D. (2001) Pine needle chemistry near a large point SO2 source in northern Fennoscandia. Water, Air, and Soil Pollution. 130 (1-4). p929-934. Małek, S., Martinson, L., & Sverdrup, H. (2005) Modelling future soil chemistry at a highly polluted forest site at Istebna in Southern Poland using the “SAFE” model. Environmental Pollution. 137 (3). p568-573. Menon, M., Hermle, S., Günthardt-Goerg, M., & Schulin, R. (2007) Effects of heavy metal soil pollution and acid rain on growth and water use efficiency of a young model forest ecosystem. Plant and Soil. 297 (1-2). p171-183. Pennanen, T., Perkiömäki, J., Kiikkilä, O., Vanhala, P., Neuvonen, S., & Fritze, H. (1998) Prolonged, simulated acid rain and heavy metal deposition: separated and combined effects on forest soil microbial community structure. FEMS Microbiology Ecology. 27 (3). p291-300. Percy, K. (1986) The effects of simulated acid rain on germinative capacity, growth and morphology of forest tree seedlings. New Phytologist. 104 (3). p473-484. Singh, A. & Agrawal, M. (2007) Acid rain and its ecological consequences. Journal of Environmental Biology. 29 (1). p15-24. Swaine, M. (1996) Rainfall and soil fertility as factors limiting forest species distributions in Ghana. Journal of Ecology. 84 (3). p419-428. van Breemen, N., Finzi, A., & Canham, C. (1997) Canopy tree-soil interactions within temperate forests: effects of soil elemental composition and texture on species distributions. Canadian Journal of Forest Research. 27 (7). p1110-1116.

Not a good sight whatsoever. A shame people feel the need to do this! Disposable products galore. A disposable society. Just buy a new one. Buy a new woodland. Plant one now and it's OK, don't worry about looking after what we have as future old-growth woodland.

You must offer back any arisings to the grower. If they refuse, fine, but you must offer them back. Else, they may suddenly decide they liked those arisings and seek compensation as a result.

04/01/2016. Fact #116. For some, the idea of "urban agriculture" may be somewhat of an oxymoron, though when we understand what agriculture is - basically either cultivating land to produce crops or to raise livestock - perhaps the term isn't so audacious. However, for this post, I am not talking about small-scale urban agriculture, but large-scale, city-wide agriculture. For this post, we must head off to Spain - specifically, the city of Seville. Here, some 14,000 citrus trees grace the city's streets, and unleash a beautiful aroma during the spring blossom, and then transform the streets in summer by providing shade. Unlike many street trees in the UK, where plenty of fruit trees in urban areas have their crop left to rot on the ground (I'm looking at you, Prunus cerasifera - for those of you that haven't tried its fruit, please do!), these citrus fruits are used once they ripen. In fact, they are sold! And one of the importers of this citrus fruit crop is the UK, where cooks will make Seville orange marmalade during January and February. The author notes, at this point, that whilst urban agriculture is "gaining ground", it may always be limited by legal issues associated with cultivating fruit and nut trees on city streets. For example, whilst there is a growing trend of public apple orchards in Seattle, USA, there is a street-wide ban on cherries and pears. The reason? Public safety. Cherries and pears are a threat to national security, it seems! I jest, but even the author is a little bedazzled as to why such a heavy-handed approach has been adopted. Quite hilariously, and again in the USA (but this time in the city of San Francisco), there has been a recent rise in 'Guerilla Grafters'. People are, in essence, going around the streets of San Francisco and grafting, onto ornamental fruit trees, fruit-bearing wood. Such is the desire for street trees to produce fruit, it appears - and that's not a bad thing, as the benefits are many. Source: Dover, J. (2015) Green Infrastructure - Incorporating plants and enhancing biodiversity in buildings and urban environments. UK: Earthscan.

Glad you enjoyed reading it, Gary. To be honest, my interests are so varied I even considered doing a post on trees found on the covers of music LPs, though then people would realise what a different taste in music I have hah! I enjoyed doing the artist one (Albert Bierstadt). Incredible artist, he was. I try to link to book sites that aren't Amazon or other mainstream ones, if I can. Plus, it's easier for people as they can jump right to the site if they are interested in purchasing it. All journal articles are linked to, for ease of access to everyone! Got a few more posts I want to do tonight, though I try to limit myself so I have content that can keep coming. What I'm doing is, once I have had my assignments marked, sharing some of them (such as the healthy urban trees one). Considering I put a lot of work into them, I want more than two people (me and my tutor) to be able to read the information within. Sharing knowledge is crucial, and not enough people do it!

Good stuff. Thanks! Hopefully our journals are still moist with the sweat and tears of T&F. The audacity to withhold the most important journal in the world from us...!

I'm sold. Selling everything as we speak.

Good stuff. It's a great accumulator of data for intelligence agencies and companies that look to market you specific products. At the very least, getting rid of facebook should be a pursuit of better privacy. No longer will you get to see an abundance of pictures of new borns, pets, cupcakes, star wars characters, and any other associated drivel!

Thanks for the help here, Paul. I look forward to hearing back from you. Hope everything is OK, Gary! Will be doing my AA membership this week via direct debit. Waiting to hear back from Jess or someone else first.

03/01/2016. Fact 115. In urban areas, street trees will normally exist within a length of grass verge (of varying width) running parallel to the highway (path and / or road), or within planting pits inside the highway. As these trees mature, both the roots and the root collar can cause damage to the highway - particularly if rooting space is limited. When such damage occurs, there is generally the need for remedial works to take place. However, such remedial works can have an impact upon tree health, survival, and economic value (CAVAT, CTLA, and so on) - particularly as roots may be damaged or severed during the construction works. In light of the above, research was undertaken during the late 1980s to early 1990s in Milwaukee, USA to establish exactly the above impacts to trees that have had highway repair works undertaken within their rooting environments. The reason for Milwaukee being the choice location was because the city had a third of its trees valued with the CTLA system in 1979, so there was relatively recent data to compare results to with regards to economic impacts. The authors looked at construction schedules for the 1981-1985 period within the areas where trees were assessed with the CTLA valuation system, and pinpointed locations where highway repair or widening had been undertaken (in order of descending 'disturbance severity', the four criteria established by the authors were: street widening and curb setback, curb and pathway replacement, curb replacement, and pathway replacement). One hundred projects were then randomly selected over the 1981-1985 period, with 20 per year (allowing for tree condition to be assessed 4-8 years after highway repair works were undertaken). From each study, a single block where the repair works took place was identified. Then, using the criteria mentioned above, 50 blocks (10 per year) were selected based on the highest 'disturbance severity'. These 50 blocks were then examined, and the top 25 in terms of species diversity were selected to feature within the study. The authors then chose the nearest block to those 25 blocks that did not have repair works undertaken and contained tree populations, and used them as the controls. The first 25 trees in both the construction and control blocks were then identified (from the 1979 survey) for surveying. This lead to 989 trees being sampled in total - 510 from construction blocks, and 490 from control blocks. From each tree, the following data was collected: DBH at 1.4m, species, verge width (from pathway edge to curb), and the CTLA tree condition rating (100, 80, 60, 40, 20, and 0). The type of construction activity was also identified. Then, comparisons were drawn to the 1979 CTLA valuation survey, to determine whether the trees, assessed in 1989, had suffered as a result of repair works between 1981-1985. Of the 989 trees sampled, only 670 had actually survived from 1979-1989. 175 trees had been replaced since 1979, and another 144 were newly planted in different locations. The trees were of 15 different species, though Acer platanoides, Fraxinus pennsylvanica, and Gleditsia triacanthos were the only three to feature enough to have statistical analyses run on them. With regards to tree condition, no significant difference was found between the construction (77.2%) and control (77.7%) blocks in the 1979 survey, though by 1989 there was a significant difference between construction (71.2%) and control (76.7%) blocks. In terms of tree survival between these years, 81.4% of the trees on control blocks survived, whilst only 77.3% survived on the construction blocks - again, a significant difference. In relation to verge width, significant differences were again found. In both control and construction blocks, a lower width resulted in trees being poorer in condition, though where construction had occurred the decrease in condition was more distinct. Significant difference in tree condition between construction and control blocks was also observed between tree species (in this case, only Acer platanoides, Fraxinus pennsylvanica, and Gleditsia triacanthos could be analysed, as other species were not in enough abundance), using two-way ANOVA. However, using one-way ANOVA, there was no significant difference. No significant difference between construction and control blocks was found with regards to tree diameter. The authors then begin their conclusions by asserting that highway repair works has a significant impact upon both tree condition and survival. For instance, a 22.7% mortality rtate was observed in trees on the construction blocks, compared to 18.6% on control blocks. Similarly, whilst the condition of control trees did not significantly change during the survey period, it declined by 6.1% for trees affected by construction. Results also suggest that the width of the verge has a direct impact upon tree condition on both construction and control blocks, though trees on narrow verges that also were imapcted by construction suffered more significantly. Conclusions drawn from the data also suggest that tree species is not a significant determinant in tree condition and survival rate following construction. The authors state that this was to be expected, because all three species aforementioned are hardy species that are tolerant of urban conditions and disturbance. In terms of tree size (DBH), the authors note that they were surprised no significant difference was found between control and construction blocks, though because many of the trees were young (319 were under 10 years of age, and many more were planted in the 1960s and 1970s), this may have impacted upon the data. If all trees were mature, it may have been a different story entirely. Turning attention towards economic implications of highway repair works to trees, assuming each tree was worth $1,100 (as was, I suspect, concluded in the 1979 survey), the 200,000 trees of Milwaukee would value in at $220,000,000. As around 3% of the tree population had a decline in condition resulting from highway repair works each year during the study period of 1981-1985, a total of 6,000 trees per annum (with a value of $6,600,000) would suffer, meaning an annual loss of $521,500 can be calculated. Additionally, as tree mortality associated with construction works was 4.1% higher than for control blocks, an additional hit of $270,600 would be taken. Therefore, the effect of highway repair works on the value of Milwaukee's tree population was $792,100 per annum, between 1981-1985. Source: Miller, R. & Hauer, R. (1995) Street Reconstruction and Tree Decline. In Watson, G. & Neely, E. (eds.) Trees & Building Sites. USA: International Society of Arboriculture.

It seems issue 2 is out. But I didn't get one through the post yet?

Quite a fruitful day for posting stuff and generally learning. Once I finish reading Mycelium Running I'll be posting a book review, as it really is a darn good book.

Probably nearly as much as that book's price! But no, I completely agree with you. Plus, it's the right thing to do - else we're just avoiding the cause of the problem in favour of tackling the symptoms with money.

02/02/16. Fact #114. Because different artificial surfaces will have varying effects upon the amount of oxygen within the soil beneath, it is important to select the surface that will be of lowest impact where trees are situated nearby. After all, this will ensure constituent trees live longer and healthier lives. This post looks into a study undertaken in the world-famous Vondelpark, Amsterdam. With ten million visitors a year, there is a marked degree of foot traffic on the site, and thus surfaces to direct traffic (pathways, mainly) are absolutely necessary. However, because not only due to the high water table in the park, but also the fact that root inspection of the trees has revealed blue-coloured roots (suggesting poor soil oxygen), the average life expectancy of any tree does not place above 50 years - by this age, the tree will usually become unstable and be left prone to windthrow. Of course, in a public park, the element of risk is likely unsustainable, and therefore the tree is removed. Whilst the water table is not something that can actively be lowered, the poor soil oxygen status of the rooting environment can be. The author suggests that, based on past anecdotal evidence from park managers, the cause of the poor oxygen levels is due to the choice of surface-hardening material used to construct the pathways - following installation of the pathways, tree health was seem to visibly decline. The surfaces used in the park are - in the pursuit of a more natural-looking park - not the archetypal paved or asphalt pathways, but instead comprised of a mix of sand, loam, gravel, and sometimes a cement-like material. Manufacturers of such mixes claim that the surfaces are permeable to both water and oxygen - this conflicts with the views of the park managers who witnessed tree health decline following the installation of pathways made with such mixes. Based on these concerns of the park managers, a study was undertaken and identified that soil oxygen levels were at (on average) 5% - at below 12% (though it varies between species), conditions become highly unfavourable for root growth. Therefore, an in situ study was commissioned to test different mixes, in the hope that the results would provide the park managers with a better direction on what to construct new pathways out of (as the pathways all were in need of renewal, it was the perfect time for a study). The study was therefore set up, and sought to test soil oxygen status (oxygen containers were placed underground and connected to 2mm tubes so that measurements could be taken) 18 times under five different mixes between June 2006 and March 2007. These were: Mix A (crushed natural stones and transparent bitumen fixed with latex material); Mix B (a loamy to gravely mix with a grain size distribution from 0-8mm, with a more loamy composition than Mix D); Mix C (crushed slag from the steel industry); Mix D (another loamy to gravely mix with a grain size distribution from 0-8mm, with a more gravely composition than Mix B), and; Mix E (crushed dolomite with a grain sized distribution from 0-10mm). Exact mix ratios were not available, as all mixes were sourced from manufacturers who could not provide such information. Budget constraints were also noted, which lead to the survey lacking the means of measuring oxygen diffusion rates. Results from the study suggested that oxygen levels in the soil were highest beneath Mix A and C, and lowest under Mix B and E - though, under all mixes, soil oxygen levels dropped after periods of heavy or prolonged rainfall. However, soil beneath Mix B and E not only suffered the most from such rainfall, but took the longest to re-oxygenate to 'normal' levels. Interestingly, the author notes that Mix A, which was said to be wholly impermeable by the manufacturer, had the lowest impact upon oxygen levels in the soil. Because of these findings, the research continued from between the dates of August to December 2008 (where another 10 readings were taken), to assess whether long-term impacts were any different. Curiously, results had changed - Mix B was still very much the worst, though Mix C also had lead to lower oxygen levels in the soil than it had shown during the first study period. Now, Mix A and D were considered to be best. From this research, it was concluded that there was a marked difference in soil oxygen levels beneath the different mixes, though because the study was only done over a short period the long-term impacts of such mixes could not be ascertained - the author notes that such mixes will all deteriorate progressively after the first year, reducing permeability of water and oxygen into the soil (this may have been what occurred with Mix C). The author also notes both that research into more permeable mixes should continue, as they are likely to provide better soil conditions beneath, and that rainfall significantly impacts upon oxygen levels. Unfortunately, beyond this, there is not much of a conclusion in relation to the data captured (and no indication of what mix the paths were repaired with), perhaps because the author states that the reasons for the differences identified in the study were not understood. Instead, the author remarks: "park managers need to consider oxygen permeability of surface-hardening materials of footpaths as well as aesthetic and mechanical properties", and "in future work, the measurements should be repeated with more replicates, a good control, and over extended periods". Source: Couenberg, E. (2009) A preliminary study evaluating oxygen status beneath different surface-hardening materials for park use. In Watson, G., Costello, L., Scharenbroch, B., & GIlman, E. (eds.) The Landscape Below Ground III. USA: International Society of Arboriculture.