Neolithic and Bronze Age Landscapes of North Mayo: Report 2011

(E109). This is the only site on which alder is an important taxa and probably underlines the
wetland nature of the area. Birch, oak and hazel were also important from this site. The
roundhouse at Belderg Beg was made from oak posts, preserved by waterlogging (Caulfield
et al 2009b). Possible hazel, willow and pomaceous burnt wattle was also identified from
Belderg Beg.
Hazel was burnt in varying degrees on all sites with the exception of Glenulra. It will
frequently be found growing in association with oak. It is a medium sized, deciduous tree,
and can reach a height of 15m. It will grow on a wide range of soils, including limestone,
mildly acid soils and clays (Lipscombe and Stokes 2008, 102). Hazelnut shells dominated the
plant remains assemblage from Rathlackan, in comparison to the high levels of hazel wood
burnt on the site. No plant remains were evident in the samples from Glenulra scatter, which
had similar high percentages of hazel charcoal to Rathlackan (Mc Clatchie 2010). The tree
can re-generate rapidly and thus can be an indicator for secondary woodland expansion
(O’Connell and Molloy 2001, 104).
It is likely that local oak woodlands did grow in the vicinity, possibly on the upland slopes,
although continued presence of light dependent wood taxa does not indicate closed canopy
oak woodlands. It has the most importance on Glenulra, Rathlackan and Belderg Beg, indeed
it was used for building at the latter site. There are two native Irish oaks, and they cannot be
separated by wood anatomy. The two species will grow in quite different habitats. The
pedunculate oak (Quercus robur) will usually grow on heavy, lowland soils, where it will also
tolerate flooding. In contrast, the sessile oak (Quercus petraea) will grow on less fertile,
acidic soils. Oaks can reach a height of 40 metres and live for 1,000 years or more (Hickie
2002, 60). Pedunculate oak grows up to 25m high and can attain a girth of 9m. Sessile oak
can grow up to 40m high, and can reach a girth of 13m. Both trees can live up to 500 years
(Stuijts 2005, 142).
The importance of birch in the overall charcoal assemblage (25.8%) and its role in all sites
(except the Glenulra scatter) is interesting and unusual from a charcoal perspective. A
considerable impact on birch is evident at approximately 3890+-60BP, the switch from birch
to grasses may be indicative of increased pastoral farming (Molloy and O’Connell 1995, 220-
221). It is not possible to separate silver birch (Betula pendula) and downy birch (Betula
pubescens) through wood anatomy. Silver birch prefers dry conditions and will grow well on
light, dry soils (Lipscombe and Stokes 2008, 140), in contrast, however, the downy birch
prefers wetter conditions and will grow on poorly drained soils (Lipscombe and Stokes 2008,
178). It is likely that birch grew on shallow peat and in areas that were peat free (O’Connell
and Molloy 2001, 101) the species identified represents downy birch.
Two of the main wetland indicators from archaeological charcoal are willow and alder.
Willow was frequently identified at Rathlackan, Belderg Beg and Ceide. It was also identified
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