Glossary

rhizodermisprimary surface layer of the root. similar to epidermis but of different origin and function.

rhizospheresoil area immediately adjacent to. and affected by. plant roots. Typically has a high level of microbial activity.

RHSRoyal Horticultural Society

RIDDORReporting of Injuries. Diseases. and Dangerous Occurrences Regulations

rigging1) in tree pruning or removal. method of using ropes and hardware to control or direct the descent of cut material or to handle heavy loads. 2) with cranes. loaders. or other equipment. method of using ropes and hardware to lift heavy loads.

rigging linerope. usually the load line. used in rigging operations.

rigging pointthe place in the tree (natural or false crotch) that the load line passes through to control limb removal in rigging operations.

right-of-way (ROW) (pl. rights-of-way)defined area of land. usually a linear strip. reserved for the passage of traffic (e.g.. paths and roadways) or the construction. maintenance. and operation of various aboveground or underground utilities. Rights-of-way may be granted by easement rights and may be across a single property or(...)

ring porousa pattern of wood development in which the large-diameter vessels are concentrated in the earlywood (contrast with diffuse porous).

ring shake(s)see shake(s).

riskthe combination of the likelihood of an event and the severity of the potential consequences. In the context of trees. risk is the likelihood of a conflict or tree failure occurring and affecting a target. and the severity of the associated consequences-personal injury. property damage. or(...)

risk abatementapplying treatments that mitigate hazards and reduce risk.

risk assessmentthe process of risk identification. analysis. and evaluation.

risk avoidancerisk control strategy in which an activity is avoided to eliminate the possibility of loss (injury or damage).

risk controlcomponent of a risk management program in which proactive measures or strategies are used to reduce risk.

risk managementthe application of policies. procedures. and practices used to identify evaluate mitigate. monitor. and communicate tree risk.

risk management plandocument that defines a tree risk management policy. describes tree inspection and documentation procedures. and provides an action plan to minimize risk.

risk rating systemmethodology by which factors affecting the degree of risk are evaluated and assigned a rating.

risk reductionprocess of taking action to lower risk of injury or damage.

risk transferrisk control strategy that moves part. if not all. of the responsibility for risk assessment and/or abatement to another party.

RLARegistered Landscape Architect

rootplant organ. usually underground. that serves as anchorage. and also absorbs and conducts water and minerals.

root ballsoil that contains all (i.e.. container grown) or a portion (i.e.. B&B) of the roots that are moved with a plant when it is planted or transplanted.

root barriermembranes or sheets installed vertically in the soil to limit or direct the growth of tree roots.

root boundcondition in which plant roots are overcrowded in a container or site and root growth is restricted.

root capgroup of cells protecting the apical meristem at the root tip.

root collarflared area at the tree trunk base where the roots and trunk come together (see root crown. root flare. and trunk flare) .

root crownarea where the main roots join the plant stem. usually at or near ground level. Root collar.

root crown excavation(root collar excavation) process of removing soil to expose and assess the root collar (root crown) of a tree.

root flaresee trunk flare.

root graftnatural union of two roots. either from the same plant or two different plants. Can result in disease transmission.

root hairsmodified epidermal cells of a root that absorb the majority of water and minerals.

root initiation zoneregion at the base of a palm stem where lateral roots emerge.

root matdense network of roots. In palms. near the base of the stem.

root platethe combination of large structural and smaller roots and soil near the base tree's trunk largely responsible for holding the tree erect.

root protection area(RPA) in British Standards. area of tree root zone to be protected from construction damage. the size of which is based on the size of the tree or trees to be protected.

root protection area (RPA)in British Standards. area of tree root zone to be protected from construction damage. the size of which is based on the size of the tree or trees to be protected.

root protection zonearea of soil around a tree trunk where roots are located to be protected from construction damage. usually soil compaction damage. Rigid fencing is most effective for restricting access to this area.

root pruning

I) process of cutting roots on a field grown tree or pre-digging a root ball to increase the density of root development within the final ball. 2) in tree conservation and preservation. the process of precutting roots behind the line of a planned excavation to prevent tearing and splintering(...)

root rotdecay located in the roots; root decay is usually developed from the bottom up. and crown symptoms may or may not be visible.

root/shoot ratiorelative proportion of root mass to crown mass.

root stockroot or lower part of tree used for plant propagation on which is grafted scion wood to I combine the desirable characteristics of each.

root zone1) horizon or layer within the soil profile where roots exist. 2) volume of soil containing tree roots. 3) horizontal spread of tree roots from the trunk. Typically the root zone of a tree extends well beyond I the drip line.

rosetteShort. bunchy habit of plant growth

rotary cutting headsingle-blade or multiple-blade I attachment that rotates to cut or shred vegetation.

rotation lengthin municipal arboriculture. the length of time between each maintenance pruning for a given geographic area. See cycle.

round turntwo turns of a line around an object.

ROWright-of-way

RPAroot protection area

RPFRegistered Professional Forester