Summer 2018 Newsletter

Find out what Norfolk Wildlife Services has been up to over the Spring and Summer 2018. Read highlights of our projects and work in our 2018 summer newsletter, or alternatively you can select individual articles from the newsletter below.

This issue:

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Keep in touch, if you need any advice or protected species surveys undertaken please contact us!

Hazardous tree inspection for TPO

NWS Aborist Jim Allitt recently advised on the management of a substantial oak tree subject to a Tree Preservation Order and within the Broads National Park.

Our client, Mr Coleman, had concerns over the extent of deadwood in the canopy, especially where it was close to his and a neighbouring property, but as also keen to retain it as a beautiful feature of his home.

Mr Coleman asked NWS to determine the condition of the tree and make future management recommendations. The tree was surveyed to look at issues such as weak unions or forks, cavities, and especially any defects hidden higher in the canopy.

Hazard tree feature – Branch failure

Sometimes hazards are obvious but subtler hazards may go unnoticed and mechanical failure may occur without specialist management.

Under the Occupiers’ Liability Act (1957 and 1984) the ‘occupier of the land’ where the tree is rooted has a duty of care to ‘take reasonable steps to prevent or minimise the risk of personal injury or damage to property’, both for visitors to the occupiers land (1057) and other persons (1984). The law is quite complicated.

To avoid or deal with risks while retaining the tree, a reasonable and balanced approach to future management requirements is needed, with a full understanding of calculated risk involved. In this case, NWS suggested a 2m, crown reduction and to clear larger deadwood from the canopy so that ‘sailing’ from the wind stressed the branch unions less.

Aerial tree inspection by Jim

Since the tree was protected, the works had to be agreed with the local planning authority, the Broads Authority. NWS’s successful application demonstrated that the works retained the screening the tree provided but were also necessary to reduce the risk the tree posed to the adjacent house and property.

Trees as assets : 7 rules for designing with trees

Trees on a site increase visual attractiveness, are great for wildlife and add considerably to property values. Maximising use of existing tree assets in designs will maximise the financial benefits for new developments. Here are NWS’s 7 tips:

  1. To maximise value from tree assets start at the concept stage; here a simple tree survey will suffice: a ‘Tree Constraints Plan’ with ‘Root Protection Areas’ (RPA).
  2. RPAs are minimum core areas to protect your trees; seek specialist advice if RPA conflicts with your design as to whether redesign is required.
  3. On sites with many trees, use BS5837 categorisation to prioritise the importance of individual trees, based on amenity, wildlife and landscape value.
  4. Allow room for future growth based on tree’s longevity; shading plans help design building orientation and fenestration.
  5. Allow for “hidden” issues for trees such as visibility splays, drainage (esp SUDS) and utility connection; trees with faults may need intervention to help them.
  6. An Arboricultural Impact Assessment (AIA) will help when instructing the contractor to protect trees plus organise site clearance, construction and final landscaping and planting.
  7. Find an arborist you can work with, seek their advice early and get their regular input.

If you are interested in how much your trees might add in value to your site, there are various techniques from the Capital Asset Value for Amenity Trees (CAVAT) through to ecosystem services calculations.

Jim calculates a tree’s RPA

 

What to do if you find a stag beetle

During work, tree surgeons ( especially while removing decaying tree stump) sometime find large black beetles. They may be concerned that they are Greater Stag Beetle Lucanus cervus and want to know what action to take to protect them.

Greater Stag Beetles are protected against sale in the UK under the Wildlife and Countryside Act, 1981 and are also a Priority Species under the NERC Act and an Annex II European Species.  They do occur in Norfolk, but are much commoner futher south in Ipswich and Suffolk.

Often though they will be stag beetles but the easily confused Lesser Stag Beetle Dorcus parallelipipedus , which is more widely distributed.

Lesser stag beetle Lucanus cervus

Decaying wood is important to all mini-beasts, especially in the “tidier” urban areas like Norwich.  An easy approach if possible is to reduce any stump in large sections and re-sited somewhere safer (something the lesser stag beetle colony will appreciate).

If you do find any text a photograph to us and we are happy to identify for you and let you know what to do.

We are also happy to carry out full invertebrate surveys of sites and make recommendations for managing them for charismatic stag beetles.

What is a root protection area ?

The root protection area

The root protection area is the minimum area around a tree that it is considered is necessary to protect its root system from damage such as construction or compaction.

Arborists calculate it either by a formula or by drawing it manually.

How is a root protection area calculated?

Under the British Standard BS5837 for each tree, the arborist calculates the RPA by multiplying the diameter breast height ( DBH ) of the tree in meters by 12.  A simple circle is then drawn around the centre point of the trunk to this distance.  A maximum RPA of a radius of 15m is assumed.  There are more complex rules for calculating trees with multiple stems.

The arborist can hence provide a simple diagram of the root protection areas for trees, which is easy to calculate and understand.

How is a root protection area estimated manually ?

Although root protection areas are drawn simplistically as a circle, often in practice they are asymetrical or even irregular shapes.

Drawing a root protection area manually is more complicated than the formula approach  and requires input from an experienced arborist. The estimation may also often involve further ground investigations. This might include digging of small test pits to look for roots or other specialist equipment. The arborist will allow for the factors like :

  • hard surfaces,
  • previous trenching works,
  • water sources,
  • soil conditions
  • and the ecology of the tree.

Accurate manual drawing of root protection areas is particularly important on resticted sites or for large trees and important specimens.

How is a root protection area used ?

Architects and planners can use root protection area in site design for buildings and roads, but service trenches as well.  The arborist will use it later for a detailed Arboricultural Method Statement to show how to protect tree roots in constuction.

 

 

TLC for trees : watering in hot weather

Why do trees need TLC in hot weather ?

A newly planted tree arrives from the carefully controlled conditions of a tree nursery into a potentially hostile setting with all the attendant stresses.  Hot dry weather can quickly kill a newly planted tree during the first five years before it becomes established, especially if planted into a hot urban environment.

Birch trees dead from water stress ( not ours !)

The right tree for the right location

Picking the right tree species is key : where a tree is planted into an unsuitable location then it becomes more easily stressed by extremes of weather, especially prior to it becoming fully established in the first five years.

We always suggest to our clients that they make their choice of species based on what we know will thrive in an area rather than what looks nicest in the catalogue.  Whilst you can grow most trees in most locations, an unsuitable location will most likely lead to higher maintenance needs and either potentially slower growth or complete failure.  Obvious examples include many conifer or Japanese maple species planted in chalky soils.

Good preparation

Getting the root environment right for your tree is key to it flourishing in its’ new environment.  The planting pit and surrounds should provide well prepared soil to easily expand into and after planting the surface should be mulched heavily with compost or manure.

How much, how often to water

For your trees survival regular frequent irrigation is more important than the volume, so maintenance plans should include the logistics of staff getting water out to site.  When you consider the “how often” and “how much” of your irrigation regime, you need to consider the water holding capacity of the soils.  These points should be covered in the design stage so that irrigation can be done.  Trees though aren’t fussy, so any water (including grey water sources like washing-up water) will serve in a pinch.

As a rough indication, then 40-60 litres ( 3-4 buckets of water ) twice per month are likely to be required in areas of low rainfall and high temperatures.  When you water a tree, take into account the prevailing weather conditions, soil moisture release characteristics (sandy/ chalky/ clay ) and how that tree species responds to potential water deficits (drought ) or prolonged soil saturation ( flooding ).

Watering creates significant issues where drainage is poor, as adding water will create waterlogging and airless conditions for roots. Poor pit preperation for planting is a frequent cause of this, creating a bucket effect that gathers water.

Techniques for avoiding drought stress in trees

Tree planting will normally be designed with a watering pipe or tube, embedded underground, which allows water to quickly reach the roots rather than flow down the pavement. This also avoids disturbing roots during watering and reduces risk of fungal infection.

Where the soil becomes hard baked ( as in many clay soils in East Anglia ) then mulches can help not only be reducing evaporation, but by increasing organic content of the soil.  They may need a top up regularly post planting.  Gaiter bags and mulch mats can reduce water stress by reducing evaporation.

Good tree stakes and ties with appropriate irrigation system.

Monitoring tree stress is especially important if there are prolonged high temperatures. As a guideline for East Anglia, check trees when there are ten consecutive days during the growing season with temperatures of 25 oC or greater.  When monitoring be aware of the visual signs, something we come back to below.

Overwatering for some species can be as deleterious as underwatering as roots will waterlog and rot.  The symptoms of waterlogging are easily confused with those of water stress, includiong wilting. A waterlogged plant actually is water stressed due to roots drowning and not functioning to absorb any water or nutrients for the tree.

What does this mean in practice ?

Looking after trees in the first few years whilst they become established is critical to their survival and water stress can either quickly kill them or lead to die-back causing later poor growth or fungal infection.

Pick the right tree for the right location and consider their watering needs.

Once established with a well-established root system, trees are drought-proof and will not generally need watering. Getting them to this stage is critical for successful establishment.

How can we help ?

We can help you with a full planting plan for your site, including :

  • Soil testing and ground preparation
  • Choice of species and sizes
  • Design of planting pits
  • Costings for plantings
  • Alternatives to pit planting
  • Planting and aftercare
  • Monitoring

If you have issues with your existing plantings, then please do call us as we may still be able to offer advice.

 

 

Suction solution for no-cut root route

In June 2017, Anglian Water began work on a pipeline renewal scheme at Belstead Water Tower, Ipswich. Trenching 1.2m deep by 0.5m wide was required to allow pipe-laying, but the only route out of the compound was in the Root Protection Area (RPA) of large oak, an important group of TPO trees.

Norfolk Wildlife Services worked with Anglian Water and Conroys to create an Arboricultural Method Statement [AMS].   An innovative solution  practical  technology –  a suction excavator [Conroy Vac Ex] – to prevent need to cut roots with ground protection techniques to protect tree roots of the protected trees from vehicle damage.

The suction excavator removes the soil around the roots, eliminating the need to cut through them in order to create the trench.  Major roots were left intact which means the trees ability to take up water and nutrients was not compromised.  Exposed roots were wrapped with wet hessian to prevent desiccation.  The pipe was then laid underneath the routes and the trench was then backfilled with the original soil, minimising disruption to the trees’ water supply in a period of dry weather.

Ground protection techniques help prevent compaction of the soil around the tree roots

 

Work begins on suction excavation of trench around tree roots using Conroy Vac Ex

Work with Conroy Vac Ex suction excavator continues on open trench and tree roots

 

Wet hessian bags were wrapped around the roots to avoid desiccation.

 

Pipe laying commences

 

 

 

Blackthorn flowers and hedgerow assessments

March marks the meteorological start of spring and it’s also the time to start looking out for the first blackthorn [Prunus spinosa] flowers.

blackthorn flower

Photo © Ian Calderwood

Blackthorn flowers are easy to spot because they appear before any of the hedgerow leaves.
As soon as you spot the first flowers you’ll suddenly begin to notice whole swathes of them.  At this time of year of you might be forgiven for thinking all hedgerows are predominantly blackthorn, but our hedgerow assessments can offer an insight into the diversity of hedgerows.

 

Why are hedgerow assessments important?

Hedgerows are protected under the Hedgerows Regulations Act 1997 and these are part of planning regulations. The Regulation was brought into effect due to the changes in agricultural practices which saw a rapid removal of hedgerows from the countryside.

“Hedgerows have their part to play in helping us to respond and adapt to climate change, providing conduits through which wildlife may move, and protecting soil, livestock and property against extreme weather events. They even help to lock up carbon and provide a sustainable source of fuel. ” Hedgerow survey Handbook (2007)

This protection covers hedgerows over 30 years old and over 20 metres long (or if shorter, connected to other hedgerows at both ends or part of a longer hedgerow).

Hedgerow removal is a tricky subject and a landowner who wishes to remove a hedgerow must serve a Hedgerow Removal Notice in writing on their local planning authority. The authority then has to determine whether or not the hedgerow is ‘important’ and whether or not to issue a Hedgerow Retention Notice.

What makes a hedgerow important?

This is where hedgerow assessments come into their own.

hedgerow

Photo – Emily Nobbs

We need to assess how many woody species are within the hedgerow, how old it is and whether the hedgerow is associated with any archaeological sites of interest.

There are lots of different combinations of features that make a hedgerow important, such as being at least 30 years old and have a minimum of 6 woody species and a supporting bank and/or ditch running along its length.

Woody species include alder, wild cherry, dogwood, black-poplar, hawthorn and of course blackthorn.

The NWS Arboriculturist can help

Jim Allitt is our resident Arborculturist and can help with any questions you have regarding hedgerows and what you can and can’t do.  Having a hedgerow assessment early on in any proposed development will allow you to understand more about the hedgerows you are working with and help you to plan any mitigation.

So the next time you see a hedgerow full of blackthorn flower don’t dismiss it, you may be looking at a very important hedge!

Get a tree-mendous survey

On development sites trees are both important assets, but also potential constraints. Did you know that NWS offers the same development-advice service for trees as it already offers to clients for ecology ?

On the positive side, when managed well trees form key opportunities for wildlife, offer visual amenity to complement the architectural elements and can add a strong sense of place to new developments. They also create micro-climate buffers to sites by contributing screening and shade, reducing wind speed and turbulence, intercepting dust and rainfall, and stabilising temperatures. Mature trees add significant value to properties.

Conversely though, development that doesn’t consider tree roots, hazards, future growth and how the built environment relates to these natural assets will swiftly run into problems. Planning authorities – normally via a BS5837 survey – will carefully check how any new development relates to trees in and around the development site, and how they will be managed in the future.

Tree surveysAs part of the BS5837 survey report, we will assess the value of trees based on their health, remaining lifespan and amenity impact. We provide a Tree Constraints Plan (TCP) showing root protection areas and existing and future crown spreads in a format to suit the client. This is used to initially inform architects when designing site layouts. The TCP helps to inform future tree management and immediately identifies necessary tree works – including hazards.

An Arboricultural Implications Assessment (AIA) follows final design, where the impact of the design proposal on the surrounding trees is assessed as well as the interaction the trees will have on the finished development. This information informs the Tree Protection Plan (TPP) which gives advice on protective measures for the trees on site. The TPP also gives clear indications of potential conflict between trees and the proposed site layout.

Often following planning permission is the Arboricultural Method Statement (AMS), which specifies tree protection measures and any specialised construction techniques. An AMS provides the information package for contractors to fully protect trees during construction and is helpful for tendering works. In our tree surveys and reports, we will also offer guidance on replacements for trees removed and any new planting specifications.

If you have questions about the services offered by our new arboriculturist or if you would like to discuss how a tree survey would help your planning proposals please contact Jim Allitt on: Email: jamesa@norfolkwildlifetrust.org.uk Telephone: 01603 625540

 

Which tree survey do I need ?

Sycamore canopy in spring bud

Clients are often asked by planners or others for a tree survey, but are not always sure what type is needed.   We have outlined the different types of tree surveys and the reasons they are needed.

A. Development survey = BS5837:2012 ‘Trees in relation to design, demolition and construction- Recommendations’

A Development Survey also called BS5837 survey is the one normally required by Local Planning Authorities (LPA) for development and planning permission.

A competent “arboriculturalist” [ = tree person ] must inspect the trees on and adjacent to the site. The trees on site are assessed in terms of their retention value which includes their health, longevity and amenity impact.

Trees that are marked for retention, as well as any adjacent trees not on site but affected by development need to be protected from any potential harm that may occur during the demolition and construction phases of the project. This involves both above and below ground precautions. Above ground, the crown spread and dimensions of the tree will need protecting, below ground the roots of the tree are a constraint governed by the Root Protection Area (RPA).

( The RPA is the area the tree’s roots occupy – this requires fencing and ground cover to protect it from above ground operations.) Information on protective measures for the trees on site will be provided as part of the BS5837 report.

B. Tree Hazard Surveys

Where you are concerned about your “duty of care” over a tree, then a Tree Hazard Survey is the one you require.

All tree owners have a legal responsibility as their “duty of care” to ensure others are not at risk from falling trees and branches. You need to assess the level of risk involved on your land. The risk is generally assessed based on :

  1. The level, extent and type of access that people have to the land on which the tree stands or where the branches could fall.
  2. The condition and health of the tree.

The factors underlying the condition and health of the tree will dictate how often the tree should be re-inspected for potential hazards. Advice on mitigating hazards by undertaking tree work can be suggested as part of the inspection, which you need to act upon.

C: Advice on Tree Works

Tree works on trees in Conservation Areas or on those with Tree Protection Orders on them need a “Tree Works” application.

When carrying out any tree work it is always advised that a competent arborist be consulted, whether it is a consultant or a tree surgeon. Work should be carried out in line with the British Standard, BS3998:2010 ‘Tree Work- Recommendations’. Trees should be inspected before the work is carried out too ensure the best management practices are employed.

Trees in Conservation Areas and with TPOs often have high amenity value and are well loved by their owners, so are felt to be worth the extra investment.

D: Surveys for underground utility installations

As stated in NJUG Guidelines for the Planning, Installation and Maintenance of Utility Apparatus in Proximity to Trees, there are generally low incidence of damage to underground apparatus by trees where these installed within hard surfaces ( e.g. pavements ). However trees can have variable growing patterns in term of root structure, especially if there are below ground obstructions to root growth. This can make any changes on site in the trees RPA potentially hazardous. Work on operational land for utilities often requires no LPA application, however it is considered good practice to follow BS3857 to implement tree protection methods where possible.