Kveldssanger

The authors made no distinction as to what they meant by fall velocity, though one can presume the study tested velocity in perfect conditions, as I believe the test was done in an elevator shaft. I doubt there'd be any wind in such a place (unless from one of the operators, if they had a dodgy dinner the night before...!!). Day off today - got back from my lvl 4 and want to churn out some work on fungi as it's a field I like studying.

I shall indeed keep you informed. Very few confirmed sighting on the FC's map. I doubt it's that rare. Probably a lack of reporting.

12/01/2016. Fact #124. Trees species, such as alder, birch, willow, and poplar, will disperse their seeds via wind. However, just because the seeds are dispersed by wind it does not necessarily mean that they will travel huge distances. In fact, a large percentage of a tree's seed crop will fall within a short distance from the seed tree - perhaps only as far as a few times its height. Despite this, the distance a seed can potentially travel will vary by several orders of magnitude, and therefore seeds do have the capacity to travel huge distances. Storms have been found to enable seeds of poplar to travel up to 30km, maple 4km, scots pine 2km, birch 1.6km, and ash 0.5km. Of course, this really does depend upon the direction and the strength of the wind, and for how long the wind gusts durate for. The 'fall velocity' of a seed (as in, the time it takes the seed to fall from the parent tree to the floor in still air) may also be a determining factor in how far a seed may potentially travel. If a seed is heavy (such as an acorn), it will fall to the ground is a few seconds, though for trees that rely on wind dispersing their seed they will usually have much lighter and more aerodynamic seeds. This increases the time it takes for the seed to fall to the floor and thus increases the likelihood of the seed being 'caught' by wind gusts. To give an example, the average 'fall velocity' of Acer platanoides seeds is 107cm per second, whilst Ailanthus altissima seeds fall at 122cm per second. Comparing this to the 'fall velocity' of an acorn, which unfortunately I cannot find (one article seems to be behind a paywall), there would very likely be a marked difference (with the acorn's 'fall velocity' being much greater). In fact, seed dispersal distance increases disproportionately as greater fall distances are reached. In one study, seeds dropped from a height of 61m in wind speeds of 3.1m per second were recorded from 61-975m from the point of fall, whilst seeds dropped from a height of 30.5m in identical wind speeds were recorded no further than 244m away. Now, as even the authors recognise, such distances don't explain how poplar seeds were found 30km away (or even maple at 4km). To answer this, it is suggested that seeds may, in times of very marked wind storms, 'rise' above their release height due to air turbulence and then steadily glide downwards from this higher point (assuming they are not picked up by further turbulence further along, which would increase distance travelled yet further and / or change the direction of travel). Source: Johnson, W., Sharpe, D., DeAngelis, D., Fields, D., & Olson, R. (1981) Modelling Seed Dispersal and Forest Island Dynamics. In Burgess, R. & Sharpe, D. (eds.) Forest Island Dynamics in Man-Dominated Landscapes. Germany: Springer-Verlag.

Neat story, that - very creative! The mycologist was right, though you did blitz the brackets hah!

Free! They didn't expand, though I shall ask. There's little scientific info on the species in this country (phenology), it seems.

FC are coming down next Tuesday to test for P. lateralis.

Indeed. Sent it first class last Wednesday, and heard back from Martyn earlier today. They're interested in DNA sequencing if another bracket forms. Very cool stuff!

Ganoderma lucidum confirmed. Just as well I sent it - thanks, David! Will keep a tabs on the tree next year and see if it fruits again.

11/01/2016. Fact #123. The presence of trees on UK urban streets is indicative not only of the state of the economy (a recession was oft marked by a decline in urban tree management and landscaping), but also of the spending priorities associated with maintaining street scenes. This was particularly the case during the early 1800s, when the Industrial Revolution was gaining serious momentum. Not only had a recession (which hit the growing lower class very significantly – the divide between rich and poor was growing ever-larger) in the 1830s struck harshly the horticultural sector, but there was little desire to plant and maintain urban street trees for multiple reasons (including a lack of space, and a lack of interest in ‘providing’ for the poor). During the 1830s-1840s, the advancing industrial age had enticed many rural populations to migrate into cities and, for the first time ever, urban populations (54%) were greater than their rural counterparts (as marked by the 1851 census). This flooding of people into cities, compiled with Irish migrants following the famine in 1845, brought about problems, particularly as such a surge in population was not anticipated. Towns and cities were not ready and thus the infrastructure was not there. In-filling was rife, and any pockets of land in residential areas were used to build houses – such as was the case in Nottingham, where a population of 10,000 swiftly rose to 53,000 and, as a result, many gardens and cherry orchards were destroyed and used to construct homes (for factory workers). Once in-filling was completed, the towns and cities expanded from their perimeters, and were constructed in a similarly property-dense fashion. A further issue with such an influx of such people was that they were typically poor (particularly those from Ireland), and thus their presence lead to densely crowded ‘slums’ manifesting. Ironically, the poor, who left (in some cases absolute) poverty in rural areas, were now just as poverty-stricken but instead in an urban area. Unfortunately, these citizens, once surrounded by trees and green space, now lacked that entirely (no back gardens, no public parks, and so on). Additionally, whlst in rural areas they were spread apart over the country, in the cities they were densely crammed together in small back-to-back houses. Tensions between the rich and the poor thus began to rise. As all of this was going on, the well-off (middle class and above) decided it was time to get out of the city and move into the suburbs, and instead commute into the city to work via horse and carriage. Not only were the suburbs cleaner, but they were safer (they may have been gated communities), and actually had space to accommodate trees in communal and private gardens and – perhaps at times – along streets. Such estates within the suburbs (and also the cities) thus began to form, and by 1875 around 150 of these estates existed. The curious aspect of the middle class moving out of the city and moving into estates was that the very same middle class began to push for the city areas to have public parks for the working class to be able to utilise. Perhaps the more affluent, who would have had far more say in political matters at the time (particularly with being able to vote), realised that those stuck within the slums deserved a better standard of life (that may have been fuelled, at least partially, by the growing tensions between rich and poor), though even once such public parks were created they were rarely visited by the middle class – they still desired the segregation they achieved by living in the suburbs and gated estates. Following the Industrial Revolution trees progressively, over the course of the remainder of the 1800s, and then over the early to mid 1900s, became more desired (and thus more frequently planted) within urban areas. This has culminated into what we see today – plenty of parks and, for the most part, plenty of urban trees. The author goes into great detail on the years after the Industrial Revolution, though I won’t spoil that as I’d rather you read the book! Source: Johnston, M. (2015) Trees in Towns and Cities – A History of British Urban Arboriculture. UK: Windgather Press.

Always good to come back to a discussion! RE: magnolia. Longest-surviving flowering (woody?) plant genus, is what I took from the book. And Jon knows who I am, now!

Lunacy. Such is the extent of quality of life that people actually get offended over something so small. Get a sense of perspective.

In your example there is a very evident risk, given the tree has actually failed in the crown. In this example on the front page, as someone pointed out there is distinct ribbing - this may suggest the tree has responded to the decay, and it's clearly an old wound. Granted, there is some serious decay of that exposed section at the very least, its growth form isn't ideal, and the decay is at a point in the stem where failure will usually occur if the stem were to fail (at around 1.5-2m up). Because of the tree's setting, likely future management (utility lines), and so on, its retention is possible with some management - I suppose it could be argued entire removal is potentially heavy-handed without doing some further tests on the structure (resistograph) to ascertain whether that decay patch really is extensive in vertical and radial arrangement. In short, the pine's condition was outwardly suggestive of a definite major hazard. In the case of the first post, it's outwardly suggestive of a degree of dysfunction, but not necessarily suggestive of definite major hazard.

Aye, Acer campestre by the looks of it.

You raise some very important points, and my thread on the suffering Lawson is indeed a good example of that. I would say it is easier to propose 'sustainable' solutions, or even push one's own ideology, when money is not involved - as in, the one pushing forward ideas doesn't own, nor is responsible for, maintenance of the tree. The third, unassociated party, can almost work only in hypotheticals, as it is unlikely they'll ever be the one looking after the tree they're proposing management for (and nor will they be impacted by it if it does fail). NTSG had it penned well in Common Sense Risk Management of Trees, I think - the perception of danger is perhaps, more often than not, greater than the actual level of danger. But they do state that this should not be ignored, as perception of fear can of course impact upon peoples' quality of life. Controversial, but would you not agree that some arborists are risk entrepreneurs - both professionally-trained and not? When money is involved, it may, at times, tend to trump ideology.

Giving this a push for the weekend crowd. Put a lot of new stuff up over this last week, which I hope people will find useful. Many of the factual bits I will cross-post to my thread in the Training and Education forum here.

Wow. I love this comment! Going to make a note of this one.

10/01/2016. Fact #122. Bulk density is an indicator of soil compaction. It is calculated as the dry weight of soil divided by its volume. This volume includes the volume of soil particles and the volume of pores among soil particles. Bulk density is typically expressed in g/cm³. Soil bulk density is, to some degree and in combination with other soil characteristics, reflective of the mechanical resistance roots meet in the soil. At higher bulk densities, root growth can be restricted as the forces exerted by the roots as they push through the soil cannot 'overcome' the resistant forces of the compacted soil. Further to this, increased bulk density reduces soil porosity and therefore offers less viable space for roots to grow within (given roots grow most often within aerated pockets of the soil structure). By-and-large, root growth is optimal at 1.2g/cm³ and limited seriously when bulk densities exceed 1.6 g/cm³ (Bassett et al., 2005). Road foundations in Denmark are typically compacted to bulk densities exceeding 2 g/cm³ however (Buhler et al., 2007), which indicates the extent of the problem for urban trees in particular. Studies with tree seedlings in containers have shown that soil compaction reduces vertical root penetration, thereby meaning areas of high bulk density might increase the likelihood of shallow rooting. In larger, mature trees, higher bulk density can decrease the fine root density profile quite significantly – by up to 60% (Watson & Kelsey, 2006). This can impact upon water and nutrient uptake. Therefore, if a tree develops and matures in a soil with high bulk density, not only may it have shallow roots but also have a reduction of fine root mass. Research has however shown that trees have a remarkable ability to reach down to points of lower soil bulk density, where surface compaction is an issue (Nambiar & Sands, 1992) – assuming deeper root penetration is actually possible. Interestingly, a certain amount of compaction, in turn increasing bulk density, can aid with root growth – given the increase in root-soil contact (Alameda & Villar, 2009). This is particularly the case for roots within very loose, sandy soils (such as sand dunes). Additionally, with the loss of macro-pore space as soil density increases, water infiltration and gas diffusion is reduced, soil oxygen concentration is decreased, and carbon dioxide concentration can increase – possibly to toxic levels (Watson & Kelsey, 2006). This deterioration in quality of the soil environment thereby renders the soil less favourable for root growth and nutrient uptake (respiration for active transport is less feasible, for instance) (Batey, 2009; Day et al., 2010; Kozlowski, 1999), as well as mycorrhizal fungi establishment (Shigo, 1986). The overall impact of soil bulk density upon root morphology and function does ultimately vary between species however (Bassett et al., 2005). Species will preferentially reside at different places upon a larger continuum of bulk densities, with tolerance ranges also differing – certain species may tolerate a wider range of soil densities than other species. Sources: Alameda, D. & Villar, R. (2009) Moderate soil compaction: implications on growth and architecture in seedlings of 17 woody plant species. Soil and Tillage Research. 103 (2). p325-331. Bassett, I., Simcock, R., & Mitchell, N. (2005) Consequences of soil compaction for seedling establishment: Implications for natural regeneration and restoration. Austral Ecology. 30 (8). p827-833. Batey, T. (2009) Soil compaction and soil management–a review. Soil Use and Management. 25 (4). p335-345. Buhler, O., Kristoffersen, P., & Larsen, S. (2007) Growth of street trees in Copenhagen with emphasis on the effect of different establishment concepts. Arboriculture & Urban Forestry. 33 (5). p330-337. Day, S., Wiseman, P., Dickinson, S., & Harris, J. (2010) Tree root ecology in the urban environment and implications for a sustainable rhizosphere. Journal of Arboriculture. 36 (5). p193-205. Kozlowski, T. (1999) Soil compaction and growth of woody plants. Scandinavian Journal of Forest Research. 14 (6). p596-619. Nambiar, E. & Sands, R. (1992) Effects of compaction and simulated root channels in the subsoil on root development, water uptake and growth of radiata pine. Tree Physiology. 10 (3). p297-306. Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates. Watson, G. & Kelsey, P. (2006) The impact of soil compaction on soil aeration and fine root density of Quercus palustris. Urban Forestry & Urban Greening. 4 (2). p69-74.

Plenty of recipe websites you could check for cooking lamb, some with videos to watch I would imagine. If you're that concerned over not cooking it well, go out for a meal and save yourself the discomfort of feeling very uneasy throughout the entire process. Or, practice it one time cooking it for yourself, and if that works then do the same a second time over for your partner.

Thanks, guys. I was thinking it would be a root issue, principally because of the fact it's isolated to one stem of the two. I only threw aphids out there as there was dieback in the lower section of the live crown. I shall email the FC on Monday at work. There are some other conifers very close by - cedars, pines, other lawsons, and an allegedly 1,500 year old yew tree (it's at least half that age, by the mere fact it existed before the church alongside). One of the pines, as well as the other lawson, are showing signs of ill-health.

I am getting through stuff at a rate of knots at the moment, though am finding learning is an exponential curve! Putting the jigsaw together gets more enjoyable and a little easier, in time. I am glad you'll nonetheless go through everything, and hope there's plenty of stuff you can use for your own research or learning needs.

08/01/2016. Fact #121. The importance of a diverse, plentiful, and healthy urban tree population of a town or city is well understood. For local authorities, who typically will own the largest amount of a town or city's tree population, there is normally a 'strategy' employed that involves retaining and replacing trees for the (direct and indirect) benefits of the residents. However, many trees also exist within private property (such as front and rear gardens) and, unless a tree has statutory protection (a Tree Preservation Order, for UK trees), there is no means of safeguarding its presence. This study, which looks at homeowner attitudes to private tree maintenance, therefore offers a good insight into how residents seek to manage their own trees. Perhaps, the results of this study can be used as an indicator for homeowner attitudes in other urban areas, in the USA and beyond. Before we go on, I think it is worth noting that the two questions the authors of the study sought to answer were: (1) What are urban homeowners’ past and future tree planting and care behaviour patterns?, and (2) Are there variations in perceptions, attitudes, and behaviour patterns by geographic district? In order to answer these two questions, the authors set up a web-based survey and encouraged a randomly-selected sample of homeowners (not those who rent) from across all of Seattle's 53 districts to respond - personalised and hand-signed letters were sent out to inform the randomly-selected homeowners of the survey, and a week later personalised postcards were sent to those who had yet to respond. In addition to the personalised means of contacting the homeowners, each respondent was informed that if they completed the survey they would be able to claim a free meal at a local restaurant that was, at the time, being featured heavily in local newspapers due to their advertising regime. In total, 2,485 homeowners were contacted, and 751 (31%) of the homeowners responded to the survey. Response rates varied between districts, with Central Seattle (including areas such as Madison Park and Capitol Hill) having the highest response rate at 41%, and South East Seattle having the lowest (15%).Demographically, the average respondent age was 51, and the average time the respondent had lived at their property was 14.6 years. Furthermore, 38% of respondents had a college degree, and 44% having a graduate or professional degree - this reflected in total earnings per year, with over 50% earning between $75,000-$150,000. In terms of ethnicity, 88% were white, 5% were Asian, 3% mixed race, and the remaining 4% of other ethnicity - this reflected the overall ethnic distribution of Seattle rather accurately. It is important to stress that the authors did not analyse how* demographics in the same - and across different neighbourhoods - impacted upon private tree management. Moving onto the results of the study, the authors segmented the results for city-wide analysis into two sections - planting behaviour and pruning behaviour. Planting behaviour The respondents of the survey showed a distinct preference towards planting small ornamental trees, in addition to alack of desire to plant large coniferous and deciduous trees. However, there was a very marked intent by respondents to have their next planting be a fruit tree. Respondents were also asked as to what fuelled their most recent tree planting, of which nearly half stated it was either as part of a larger landscaping project within their property's grounds, or to replace a tree that had previously existed within their property. Of these recent plantings, 48% of respondents said they planted the saplings in spring, whilst 36% planted in autumn, 13% in summer, and 3% in winter. Additionally, the survey asked whether the respondents would consider the possible future installation of solar panels as a determining factor in deciding what tree to plant, if at all, of which 7.5% said yes. Also, the survey results showed that the respondents have less of a desire to plant trees in the future, with an average of 3.4 trees planted oer household in the past dropping to 2.1 per household in the future. Pruning behaviour 88% of respondents stated that the tree(s) within their property had been pruned. Of this 88%, 60% did their own pruning work, 28% hired in certified arborists, and 10% hired uncertified persons. The motivation behind the pruning was, from the results, down to an attempt to improve the tree's shape (64.2%), to remove dead or damaged wood (59%), to provide clearance for utility lines (23.4%), to increase sunlight levels (22.1%), to increase fruit production (19%), and to improve the view (13%). Multiple reasons could be ticked, per respondent. Neighbourhood differences On a neighbourhood level, past research has suggested that planting of 6.4 trees per acre is needed to reach Seattle's goal of achieving 33% canopy cover (not including trees planted to replace old ones). However, no districts in Seattle, according to the results of this survey, will have enough trees planted to meet this target. Of course, the amount of future tree plantings varied between districts (from 2.4-5.4 trees per acre). Respondents were also asked whether they felt they had the knowledge needed to be able to select the right tree to plant, of which it was found between 8-32% of respondents were confident in their ability to select the correct tree. Analysing the results In light of the aforementioned results, the authors were concerned over the falling desire by respondents to plant more trees. They were unable to assert whether this is a city-wide phenomenon, or is a trend across the USA. However, it was noted that the desire for tree planting by respondents may rise (or even fall) in the future. Regardless, the Seattle urban forest managers are concerned over the lack of intent to plant trees as the needed rate. Turning attention towards the time of planting, concerns were raised following results showing 84% of trees were planted during periods of the year that were unfavourable. A reason for this, the authors allege, is that nurseries advertise during the spring, and as many homeowners reported they didn't have the knowledge needed to be able to select the right tree, it is very likely their knowledge also was lacking on awareness of when to plant. Furthermore, there is a discernible trend in "downsizing" mature tree height, with a very small desire for big trees to be planted. This may have marked implications for stormwater management, pollution reduction, and so on. As there are fewer spaces for large trees to be planted, mainly due to in-filling within cities, the future for large urban trees looks bleak in Seattle. The authors therefore suggest that there may be a need for the Seattle urban forest managers to work with homeowners to encourage, and even subsidise, large tree plantings. Looking at the clear desire for homeowners to begin planting fruit trees (42% want to plant tem in the future), the authors remark that this desire could be harnessed to get homeowners more interested in urban forestry on the whole. As there is a clear desire for homeowners to grow their own fruit (at least, in part), there may be scope to encourage homeowners to consider the needs of the urban forest on the whole, which may help the city achieve its 33% tree cover target. However, as fruit trees are generally small, there is a risk that an over-use of fruit trees may be detrimental to the goal. Respondents' desire to not use certified arborists for tree work was also a concern for the authors. As tree health can be greatly impacted by improper pruning works, the fact that only 28% of the 88% of respondents who had pruned their trees had used certified arborists, means many trees may not be receiving the appropriate level of care. Again, there may be scope here to enocurage the use of trained arborists. Survey limitations The authors recognise that non-response bias (due to a lack of interest, or alanguage barrier) will have likely skewed the results obtained, particularly in districts where there is greated cultural diversity and / or the average income per household is lower. In fact, higher rates of response were received from the more affluent districts, which means data from poorer regions of Seattle may be both lacking and not as reflective of homeowner attitudes. Source: Dilley, J. & Wolf, K. (2013) Homeowner Interactions with Residential Trees in Urban Areas. Arboriculture & Urban Forestry. 39 (6). p267-277.

I seem to have scared everyone off bar Jules, lately! I hope people aren't commenting because they are too busy reading or researching, in place of feeling like their potential comments would be out of place. Comments on the style of stuff I'm putting out are also welcome, and what I write is to help everyone learn - not just myself.

Good to hear you got paid.

07/01/2016. Fact #120. The manner in which woody plants grow vegetatively is impacted by many different environmental qualities – light availability, water supply, frequency of flooding, ambient temperature, soil fertility, soil salinity, soil bulk density, atmospheric and soil pollution, wind speeds, frequency of fire, and pests and diseases. The focus of this post will be exclusively on how wind affects vegetative growth. First and foremost, we must recognise that wind can be both good and bad for vegetative growth. For example, whilst the wind can aid with seed dispersal to ensure the species can continue to exist, the wind may also be the cause of major limb failure, entire windthrow, or soil erosion – additionally, the wind can be the harbinger of arboreal pestilence (as we have seen, to some degree, with Hymenoscyphus fraxineus). Furthermore, not all tree species are equal in their response to wind – conifers are more likely to suffer from the wind than are broadleaved trees. To complicate matters here however, it is also important to understand that fast-growing pioneer species (such as birch, pine, poplar, and willow) will be more adversely impacted than later-successional species (such as beech and oak), given they are far more exposed as a result of both their quick growth rate and unestablished environmental surrounds (these species create woodland; they don’t enter into stabilised woodlands). In addition, strong winds following periods of heavy rainfall, or a marked lack of rainfall (drought), are likely to have significant adverse impacts – windthrow at the root plate and stem failure are the most notable impacts, respectively. Not only this, but disease and dysfunction manifesting within the roots and stems of trees will leave them more susceptible to windthrow when compared to the susceptibility of a healthy tree. This may be particularly apparent after a dense stand has been thinned, exposing once-sheltered trees to wind gusts they have not adapted to (in both their rooting and aerial structures). Building on the concept of exposure, forests that reside along the coastline have their ‘edge trees’ damaged by the wind. For example, exposed sycamores suffered damage to 46% of their leaves as a result of strong coastal winds. Damage manifested as a result of foliar tearing, the collapse of epidermal and mesophyll cells, and dehydration via the disruption of protective foliar waxes. Even mild winds of 6m per second will oft dehydrate leaves (such as of aspen). Mild winds will also bring about a decrease in primary elongation whilst initiating increased secondary thickening, thus altering the form of the main stem. Trees in exposed settings and therefore shorter, thicker, and more tapered than sheltered counterparts, in order to resist swaying violently and to retain uniform stress throughout. In conifers, the adaptive secondary thickening (xylem increment) actually is more discernible on the leeward (compression) side – this may be exacerbated when the very same conifer leans with the wind, given conifers lay down reaction wood on the compression side in an attempt to self-right themselves (becoming a ‘sabre tree’, as penned by Mattheck). In essence, all the above changes can be attributed to three different types of change brought about by wind – a change in water relations, food relations, and hormone relations. Looking firstly at water relations, wind has been shown to actually have varying effects depending upon species. To demonstrate, Norway spruce and Swiss stone pine are observed to transpire less during wind, whilst larch and alder transpire more. It is considered that this is due to varying stomatal responses, with stomatal size being a particular determinant – smaller stomata dehydrate quicker and thus closer faster. However, as a general rule of thumb, woody plants exposed to wind will initially have their transpiration rates increase rapidly, with rates then tailing-off gradually (dependent upon the species) as the stomata close because of dehydration. Turning towards food relations, exposure to strong winds will usually lead to reduced photosynthetic rates. This is because the strong winds cause foliar injury and / or foliar shedding. However, the effect wind has upon leaf temperature also drives the change in photosynthesis. As winds will cool leaves, the conductance of leaves will alter – this will impact upon photosynthesis. Strong winds may also increase respiration rates of leaves, with the consequence of reduced carbohydrate supplies. Lastly, hormone production and translocation is markedly impacted by wind, with auxin and ethylene being the main hormones affected. This drives the physiological changes mentioned earlier – namely a decrease in primary elongation and an increase in secondary thickening. For example, the reaction growth laid down on the compression side of conifers is attributed to a high auxin gradient, which prompts carbohydrates to be mobilised and used in the leeward region for growth. Conversely, tension wood laid down by broadleaved trees in identical conditions is linked to a deficiency in auxin. Source: Kozlowski, T. & Pallardy, S. (1997) Growth Control in Woody Plants. UK: Academic Press.