Pioneer tree species
It is important to understand which trees will succeed, especially in forestry and productive woodland planting and whilst by no means experts in this topic, this blog attempts to explain which of the tree species we grow are termed pioneer trees and in simple terms, what that means.
The following tree species (all of which we grow) are generally considered to be of most use as pioneer trees when establishing a new woodland - goat willow (Salix caprea), aspen (Populus tremula), silver birch (Betula pendula), bird cherry (Prunus padus) and rowan/mountain ash (Sorbus aucuparia) though the term is sometimes applied more generally to the full range of Salix, Aspen, Betula, and Sorbus species and indeed others in addition.
Pioneer tree species have the following common characteristics
- They grow fast
- They can establish canopies faster than competing vegetation
- They are pretty undemanding in terms of the soil and situation where they will establish but they need to land on bare soil and rely on facing little competition because the seeds are tiny and contain little stored energy (unlike an acorn for example)
- They mature quickly and produce prolific quantities of seed, so many in fact that when we sow seed for these species we have to cover them in grit to improve their contact with the soil and to prevent them blowing away
- Seeds are spread by wind dispersal or trees regrow from suckers (particularly of aspens and poplars)
- They regenerate easily
- The seeds need to be frost hardy
- And last but by no means least, they need plenty of sunlight (as opposed to climax tree species which prefer the dense shade of a closed canopy forest)
They are called “pioneer trees species” because they are the first to colonise sites that have been clear cut or affected by severe storm damage, floods or fires but they were also the first to colonise Britain after the Ice Age. However, rapid growth means that pioneer species tend to be less resistant to decay, increasingly susceptible to branch breaking, and shorter lived than other species of tree. As limbs fall and eventually the whole tree decays, they return organic material to the soil and ready the site for colonisation (or planting) of all manner of longer living trees, like oak and beech.
The pioneer trees create the shade which the shade-loving broadleaf trees need in order to germinate and grow – oak and beech do much better planted into a shady situation than they would planted in full sun and pioneer trees are an ideal way of creating a shady environment from what was once a sunny situation. Equally, if there is a break in the canopy of an established woodland, saplings of the light-loving pioneer species take hold either from seed or suckers, the canopy closes again and then the shade tolerant species then start to develop.
If anyone has any other content they would like to add to our blog on this topic we’d be very pleased to hear from you – particularly foresters with more knowledge than we have of the use of pioneer trees in forestry creation.