Bramble scrub - the Mother of Oak

Seen by many as wasted space, scrubland can actually harbour many species and have high conservation value. A variety of thorny and prickly plants can make up scrub, including gorse, hawthorn and blackthorn. One species common in scrub across the country is bramble (Rubus fructicosus). This species is often thought of as a nuisance due to its voracious growth habit, but is also valued for its plentiful berries which ripen in summer. 


Brambles are in the Rosaceae family and its flowers have the typical family
traits of 5 petals and many stamens. They can be white or pink.

The success of brambles in colonizing new areas is party due to its asexual vegetative reproduction - new shoots grow from the rootstock, advancing the bramble cover. Each shoot (or cane) is biennial - they grow in their first year, flower and fruit the following year, then die back. This growth habit allows bramble scrub to grow in height, as new canes can grow over the framework of dead ones from previous years. The dense cover created by this growth can be an important resource for many species, for example robins, wrens and long-tailed tits nest in bramble thickets.

In spring, bramble is an abundant source of nectar and pollen, visited by many invertebrate species including some of conservation concern, such as the brown-banded carder bee. Some bee species also use the hollow stems of bramble to nest in - the blue carpenter bee nests in the ends of cut stems. After pollination, bramble flowers develop into blackberries, which are technically aggregate fruits. These are a valuable food resource for many species including birds and dormice. Bramble leaves provide food for herbivores such as deer and some caterpillars. In the UK, around 450 rare or threatened species of plants, insects and birds are associated with scrub habitats.


Left: a bumble bee visiting a bramble flower. Right: a meadow brown butterfly using the nectar resource of bramble

Foresters may regard bramble as an inconvenient species as it is often thought to slow or prevent woodland regeneration. In some cases, this is true - a thick bramble understory has been shown to inhibit the establishment of oak saplings in woodland, likely through competition for nutrients and light. However, the old phrase 'the thorn is the mother of the oak' suggests otherwise. Though bramble is technically has prickles rather than spines (see below) the same principle applies - spikey scrub plants can protect tree saplings from grazing by herbivores. The effectiveness of this varies depending on the tree species - willow and birch grow well under the protection of bramble- and type of grazing pressure - sheep browse bramble heavily so reduce protection. In systems other than woodland, such as wood pasture, thorny scrub may also facilitate the establishment of oak. 


Types of stem armature 

Because scrub helps the growth of large trees it is generally a transient habitat, as trees grow and succession continues. This means that in places where scrub is wanted (eg nature reserves) management is required to maintain land as scrub. Vegetation can be cut back in rotation and allowed to grow back, to ensure a mosaic of young and mature scrub. Recent conversion of land for agriculture and development has led to a decline in the amount of scrubland in the UK, so conservation is important to maintain wildlife corridors, nest sites and food resources. 

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