The aim of this guide is to describe methods of assessing Willow Scrub habitat relevant to deer managers.*
Willow scrub is a rare plant community in Scotland and consists of small fragmentary stands of sub-arctic or alpine willow species (downy, woolly, mountain and whortle-leaved willows — see species listed) on steep slopes and cliff ledges, usually between altitudes of 600 - 900 m. This represents the top edge of ‘natural tree line’ habitat and the willows tend to be short and scrubby small plants or bushes as opposed to trees.
Gnarled, many-branched shrub. Height: up to 1m. Leaves 3.5-7cm x 3-6.5cm
Shrub. Height: up to 0.5m. Leaves 1.5-7cm x 0.5-2.5cm
Shrub. Height up to 0.7m. Leaves: 1.5-3cm x 1-1.5cm
Much-branched shrub. Height: 0.2-1m. Leaves: 1.5-7cm x 1-2.5cm
Willow scrub species:
Downy willow/ Salix Lapponum
Woolly willow/ Salix Lanata
Mountain willow/ Salix Arbuscula
Whortle-leaved willow/ Salix Myrsinites
The main impact that deer have on willows is browsing. Direct deer browsing impacts are assessed by measuring the shoots browsed by deer and the frequency of flowering.
Other herbivores particularly goats and hares may also gain access to and browse willows. For information on what time of year to measure, see BPG Habitat Impact Assessment: Principles and Practice.
|What to measure||How to analyse|
|Record the number of shoots browsed on each willow plant by deer (based on the angle of cut**)||Average the number of shoots browsed per willow|
|Record whether willow plant is flowering or not||For each site, summarise the frequency*** of flowering willow plants (for example: 2/16 willow plants, flowering; 14/16 willow plants not flowering.|
|Record height of each willow plant: straight vertical distance from the ground to the highest point on the plant WITHOUT lifting or stretching the plant||Average the height of all willows|
|Record the annual growth by measuring the shoot extension to last years node on five random shoots on each willow (see illustration below)||Average the annual shoot growth of all willows|
|Take digital photo of each willow from fixed point (see illustration above)||Will enable detection of gross changes in willow size and shape over time|