# 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.

# 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 ?

• 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.

# Update: Great Crested Newt licencing and mitigation review

Natural England is reviewing its approach to great crested newt licencing and mitigation approach, which will be introduced across the country. In each county, the approach will begin with a study to identify where newts are, and then create a map of the potential impacts of development to form appropriate conservation strategies in partnership with local government bodies. In the meantime, the existing methods of great crested newt mitigation for development projects withstand and there are no plans to abolish the laws protecting this species.

Great Crested Newt on hand

# 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

# Licencing Spotlight: Water voles

Water voles, their breeding sites and resting places are fully protected by law under Schedule 5 of the Wildlife and Countryside Act 1981, making it a criminal offence to injure, damage or disturb them. They like soft-shored banks for burrowing, wide swathes of soft vegetation growing from the banks and water and slow-flowing and relatively deep water courses.

Water vole: Photo courtesy of Ann Roberts

Surveys of a development site for water voles are required if either:

• Known local distribution and historical records suggest their presence
• There is suitable habitat for water voles in or adjacent to it.

After these surveys we assess the impacts a development would have on water voles without mitigation measures . This can be used to support any relevant planning application or discussions with the drainage board or Environment Agency.

In most cases, you could avoid harming water voles by adjusting your planned work. If you can’t  and will damage their habitats, you may need a licence from Natural England. Some displacement activity can be done under a class licence by a registered person; other activities will require a site-specific licence.

A licence will be required if development would need to displace water voles or if trapping and translocation is necessary. Any licence application needs to show an overall net conservation benefit for the water voles. For example, increasing the amount of habitat available to water vole population and/or improving the quality of habitat.

We can advise you on delivering water vole mitigation and licencing and anything else water vole related, please contact the NWS team: office@norfolkwildlifeservices.co.uk

# Can eDNA detect great crested newts later in year?

Natural England [1] only accept “negative” eDNA results for newt licencing where efficacy has been proven ( e.g. between the above dates and by trained personnel ) . “Positive” results clearly have no such limitation.

The pilot work [2] on using eDNA for detecting newts relied on comparing conventional field survey techniques to eDNA and comparative results were therefore only available during their sampling period i.e. mid-April and late June. Detection rates for sites where newts were known to be present were 99.3% using professionals and 91.2% using volunteers.

The report [ 2 ] states that “Overall, collecting eDNA appears to be a highly effective method for determining whether Great Crested Newts are present or absent during the breeding season. We do not know how effective the method is outside this period.”

Natural England indicates the peak season for surveying for larvae is August, so in theory these should be detected by later eDNA tests.

eDNA declined rapidly once great crested newts were removed from experimental ponds [3] – to undetectable levels over 1-2 weeks. Ponds could therefore have been utilised by adults earlier in the season e.g. for foraging, but the absence of larvae would point towards absence of successful breeding.

References

[1] https://www.gov.uk/guidance/great-crested-newts-surveys-and-mitigation-for-development-projects

[2] Biggs, J., Ewald, N., Valentini, A., Gaboriaud, C., Griffiths, R.A., Foster, J., Wilkinson, J., Arnett, A., Williams, P. and Dunn, F., 2014. Analytical and methodological development for improved surveillance of the Great Crested Newt. Defra Project WC1067. Freshwater Habitats Trust: Oxford. http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&ProjectID=18650&FromSearch=Y&Publisher=1&SearchText=wc1067&SortString=ProjectCode&SortOrder=Asc&Paging=10#Description

[3] Thomsen, P., Kielgast, J.O.S., Iversen, L.L., Wiuf, C., Rasmussen, M., Gilbert, M.T.P., Orlando, L. and Willerslev, E., 2012. Monitoring endangered freshwater biodiversity using environmental DNA. Molecular ecology, 21(11), pp.2565-2573.

# Happy dog, happy wildlife

## Dog walking can be one of the best ways to get people out and about experiencing nature but our faithful hounds and our beloved wildlife often have conflicting needs, making it difficult to create green spaces suitable for both. Follow these top five tips to plan a greenspace that will result in happy dogs, and happy wildlife:

Emily and Stig (the world’s first water vole detection dog) enjoying a dog walk and experiencing nature.

1.  Provide areas of enclosed greenspace. Offering safe areas for dogs to run off-lead makes dog-owners more likely to respect on-lead areas.
2. Create a circular dog walking route, with clear, defined paths. Obvious paths will encourage dog walkers to stick to a set route meaning they are less likely to disturb more valuable wildlife areas.
3. Ensure these areas and routes are within 500m of new homes. Placing suitable areas within walking distance will deter owners from driving to areas further-a-field that they perceive to be suitable greenspace.
4. A range of all-weather surfaces with a naturalistic feel will guarantee dog walkers consistent access without having to invest in walking boots.
5. Construct an area of clean water with safe access for dogs. Providing an assigned ‘splash-about’ area will keep dogs out of water which contains sensitive wildlife.

If you’d like more advice on planning for wildlife and dogs, Hampshire County Council have produced a wonderful document: Planning for dog ownership in new developments: reducing conflict – adding value.

Stig, pictured is the world’s first water vole detection dog. He is trained in the art of water vole poo detection. To find out more about Stig, his partner in training Lola, and their handler Ali, visit Ecology Dogs. Alternatively, keep regularly up-to-date with their water vole finds by following @EcologyDogs on Twitter.

# What chemicals can I use in bat roosts ?

Natural England guidance on chemicals not affecting bats is hard to find on gov.uk. We have uploaded a copy of “Natural England Technical Information Note TIN092 Bat roosts and timber treatment products” [TIN092_Bat_Friendly_Timber_Treatment], which is the First edition dated 15 March 2011. This gives a list of those commonly available products currently approved as remedial timber treatment chemicals and products in bat roosts. This was an update to the information in the 3rd edition of the Bat Workers Manual.

We know the list is not comprehensive. If you can’t find what you are looking for, you may be best to get us to ring Natural England on your behalf.  They are very friendly and generally able to make a quick response on the subject.

# Schedule 9 invasive plants and development

Schedule 9 plants are invasive and generally need controlling on a development site. After talking to a client about yellow archangel, we thought a list of schedule 9 would be helpful. It is an offence to “plant or otherwise cause to grow in the wild invasive non-native plants listed on Schedule 9 of the Wildlife and Countryside Act.”

A lot of the most invasive are aquatic or live in marshy environments e.g. Crassula helmsii, but brownfield sites also harbour species such as knotweed.  We can advise on control methods to incorporate into construction management for you.

### Plants listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales

 Common Name Latin Name Elodea (waterweeds) eg Canadian waterweed Elodea Canadensis All species of the Elodea genus Aquatic – widespread in Norfolk Curly waterweed Lagarosiphon major Aquatic Duck potato Sagittaria latifolia Aquatic Entire-leaved cotoneaster Cotoneaster integrifolius Garden escape Knotweed Fallopia japonica x Fallopia sachalinensis (a hybrid knotweed) Brownfield sites False Virginia creeper Parthenocissus inserta Garden escape Fanwort (Carolina water-shield) Cabomba caroliniana Aquatic Few-flowered leek Allium paradoxum Floating pennywort Hydrocotyle ranunculoides Aquatic – highly invasive Floating water primrose Ludwigia peploides Aquatic Giant hogweed Heracleum mantegazzianum Fairly commonly encountered Giant knotweed Fallopia sachalinensis Brownfield sites Giant rhubarb Gunnera tinctoria Too cold in Norfolk Giant salvinia Salvinia molesta Aquatic Green seafingers Codium fragile Himalayan cotoneaster Cotoneaster simonsii Hollyberry cotoneaster Cotoneaster bullatus Hottentot-fig Carpobrotus edulis Too cold in Norfolk Indian balsam Himalayan balsam Impatiens glandulifera Water courses and rivers Japanese knotweed Fallopia japonica Brownfield sites Japanese rose Rosa rugosa Montbretia Crocosmia x crocosmiiflora New Zealand pigmyweed (Australian swamp-stonecrop) Crassula helmsii Aquatic – highly invasive in Norfolk Parrot’s-feather Myriophyllum aquaticum Aquatic Perfoliate Alexanders Smyrnium perfoliatum Purple dewplant Disphyma crassifolium Red algae Grateloupia luxurians Rhododendron Rhododendron ponticum Acid soils only Rhododendron Rhododendron ponticum x Rhododendron maximum Acid soils only Small-leaved cotoneaster Cotoneaster microphyllus Garden escape Shallon Gaultheria shallon Three-cornered garlic Allium triquetrum Too cold in Norfolk ? Variegated yellow archangel Lamiastrum galeobdolon subsp. argentatum Garden escape Virginia creeper Parthenocissus quinquefolia Garden escape Water fern Azolla filiculoides Aquatic Water hyacinth Eichhornia crassipes Aquatic Water lettuce Pistia stratiotes Aquatic Water primrose Ludwigia grandiflora / Ludwigia uruguayensis Aquatic Yellow azalea Rhododendron luteum Acid soils only