favor further stabilization and soil development, and possibly increased rates of
succession (Jones et al. 2007, 2008), but this may be offset or even reversed by a
higher incidence of summer droughts and intense storm events.
8.5 Internal Factors Influencing Stabilization
8.5.1 Soil Development
Studies by Jones et al. (2007, 2008) trace the progress of soil development at two
major dune systems in Wales (Newborough Warren and Merthyr Mawr). Soil
development rates at the two sites were similar. Organic matter content (measured as
% loss on ignition) was around 0.2 % in the bare sand of the mobile dunes, increasing
to about 1 % when vegetation cover reached 100 %. This initial phase of soil
development may take up to 40 years. There was then a steeper increase in the rate of
soil development and by 60 years after the onset of stabilization, soils in dry dune
habitats reached an organic matter content of around 4 %, becoming comparable to
the much older soils. In dune slacks, soil development was much faster, and reached
higher levels of organic matter. On average, wet dune habitats took only about
12 years to become fully vegetated and some soils attained organic matter contents
of up to 5 % in under 60 years. The fact that soil development progresses faster under
full vegetation cover has important implications for management and suggests that
soil development can be retarded if open areas are maintained. Jones et al. (2008)
suggest that these rates appear to be faster than rates for comparable habitats reported
in the Netherlands and those from the UK at the beginning of the twentieth century.
The influences of physico-chemical factors affecting rates of soil development were
also assessed using the chronosequences developed for dry and wet dune habitats at
Newborough. Large-scale factors such as temperature and atmospheric nitrogen
deposition showed positive correlations with changing rates of soil development
over time, while site-specific factors such as soil pH, microclimate, slope angle, and
slope aspect did not have any significant effect.
8.5.2 Human Activity and Grazing
Sand dunes have been subject to centuries of human exploitation, with much of
this activity being instrumental in causing extensive destabilization. One example
was the practice of A. arenaria (marram) harvesting for thatching or for making
mats, ropes, and baskets. The practice started in the sixteenth century and eventually became a thriving domestic industry. However, it led to extensive sand drift
and so legislation promoting dune stabilization came into force in 1779 and 1792,
8 The Impact of Dune Stabilization
135
succession (Jones et al. 2007, 2008), but this may be offset or even reversed by a
higher incidence of summer droughts and intense storm events.
8.5 Internal Factors Influencing Stabilization
8.5.1 Soil Development
Studies by Jones et al. (2007, 2008) trace the progress of soil development at two
major dune systems in Wales (Newborough Warren and Merthyr Mawr). Soil
development rates at the two sites were similar. Organic matter content (measured as
% loss on ignition) was around 0.2 % in the bare sand of the mobile dunes, increasing
to about 1 % when vegetation cover reached 100 %. This initial phase of soil
development may take up to 40 years. There was then a steeper increase in the rate of
soil development and by 60 years after the onset of stabilization, soils in dry dune
habitats reached an organic matter content of around 4 %, becoming comparable to
the much older soils. In dune slacks, soil development was much faster, and reached
higher levels of organic matter. On average, wet dune habitats took only about
12 years to become fully vegetated and some soils attained organic matter contents
of up to 5 % in under 60 years. The fact that soil development progresses faster under
full vegetation cover has important implications for management and suggests that
soil development can be retarded if open areas are maintained. Jones et al. (2008)
suggest that these rates appear to be faster than rates for comparable habitats reported
in the Netherlands and those from the UK at the beginning of the twentieth century.
The influences of physico-chemical factors affecting rates of soil development were
also assessed using the chronosequences developed for dry and wet dune habitats at
Newborough. Large-scale factors such as temperature and atmospheric nitrogen
deposition showed positive correlations with changing rates of soil development
over time, while site-specific factors such as soil pH, microclimate, slope angle, and
slope aspect did not have any significant effect.
8.5.2 Human Activity and Grazing
Sand dunes have been subject to centuries of human exploitation, with much of
this activity being instrumental in causing extensive destabilization. One example
was the practice of A. arenaria (marram) harvesting for thatching or for making
mats, ropes, and baskets. The practice started in the sixteenth century and eventually became a thriving domestic industry. However, it led to extensive sand drift
and so legislation promoting dune stabilization came into force in 1779 and 1792,
8 The Impact of Dune Stabilization
135