In the past decades, biodiversity of dune areas in the Netherlands decreased
further because of large-scale pine plantation during the first half of the last century.
The planting of pine forest was mainly done to stop sand blowing, but it prevented
the formation of new dune habitats. A surge in mass recreation and high atmospheric
nitrogen deposition from agricultural areas, and even industrial areas in neighboring
countries contributed to the further decline in biodiversity in the coastal areas (Van
Dijk and Grootjans 1993). These changes have led to a severe reduction in the
natural regeneration potential owing to the lack of aeolian dynamics. As a result,
open dune habitats have become very rare; the pH of the topsoil has decreased owing
to increased decalcification, which has generally led to loss of characteristic plant
and animal species (Van der Maarel et al. 1985). Similar changes have been recorded
in other countries in Europe (Provoost et al. 2009).
15.1.2 Ecosystem Development in Dry Dunes
In dry dune systems, succession rate and soil development are largely controlled
by decomposition rates of organic matter and cycling of nutrients within the
ecosystem. Young dune soils are covered with low productive pioneer vegetation,
consisting of small grasses or mosses such as Corynephorus canescens or Syntrichia ruralis respectively. The vegetation is usually N-limited, because organic
matter content is low and the pH is high, especially in areas with calcareous sand
(Kooijman and Besse 2002). At high pH levels, microbial communities in the soil
are dominated by bacteria, which have higher N demand than the fungi predominating in acid soils. A high microbial N demand may lead to relatively low N
availability to the vegetation, even when decomposition and gross N mineralization are high. During succession, soil organic matter content increases and pH
decreases owing to the dissolution of lime and leaching of base cations from the
soil exchange complex. The availability of N increases, partly because of greater
nitrogen pools in the soil’s organic matter (Gerlach et al. 1994), but more so
because of the higher litter input from the vegetation (Kooijman and Besse 2002).
In later successional stages the vegetation becomes more productive, but there are
differences in soil formation between the calcareous and iron-rich Holland coast
and the rather acidic soils of the Dutch Wadden Sea islands, where the initial
beach sand is very low in lime and iron.
Along the Holland coast, the availability of P is very low in pioneer stages,
since available P is stored in calcium phosphate, which is insoluble at high pH
(Kooijman et al. 1998). During succession, soils are leached owing to a net surplus
of precipitation over evapotranspiration. Dissolution of calcium and phosphate
occurs and the soil gradually becomes more acidic. However, along the Holland
coast, this acidification process takes a long time, because the initial lime content
is high (5–10 %). Calcareous dunes typically contain 60 mg m
-2 P in calcium
phosphate per millimeter of soil (Kooijman et al. 1998), which becomes available
during the decalcification process. Partly decalcified soils thus have high
238
A. P. Grootjans et al.
further because of large-scale pine plantation during the first half of the last century.
The planting of pine forest was mainly done to stop sand blowing, but it prevented
the formation of new dune habitats. A surge in mass recreation and high atmospheric
nitrogen deposition from agricultural areas, and even industrial areas in neighboring
countries contributed to the further decline in biodiversity in the coastal areas (Van
Dijk and Grootjans 1993). These changes have led to a severe reduction in the
natural regeneration potential owing to the lack of aeolian dynamics. As a result,
open dune habitats have become very rare; the pH of the topsoil has decreased owing
to increased decalcification, which has generally led to loss of characteristic plant
and animal species (Van der Maarel et al. 1985). Similar changes have been recorded
in other countries in Europe (Provoost et al. 2009).
15.1.2 Ecosystem Development in Dry Dunes
In dry dune systems, succession rate and soil development are largely controlled
by decomposition rates of organic matter and cycling of nutrients within the
ecosystem. Young dune soils are covered with low productive pioneer vegetation,
consisting of small grasses or mosses such as Corynephorus canescens or Syntrichia ruralis respectively. The vegetation is usually N-limited, because organic
matter content is low and the pH is high, especially in areas with calcareous sand
(Kooijman and Besse 2002). At high pH levels, microbial communities in the soil
are dominated by bacteria, which have higher N demand than the fungi predominating in acid soils. A high microbial N demand may lead to relatively low N
availability to the vegetation, even when decomposition and gross N mineralization are high. During succession, soil organic matter content increases and pH
decreases owing to the dissolution of lime and leaching of base cations from the
soil exchange complex. The availability of N increases, partly because of greater
nitrogen pools in the soil’s organic matter (Gerlach et al. 1994), but more so
because of the higher litter input from the vegetation (Kooijman and Besse 2002).
In later successional stages the vegetation becomes more productive, but there are
differences in soil formation between the calcareous and iron-rich Holland coast
and the rather acidic soils of the Dutch Wadden Sea islands, where the initial
beach sand is very low in lime and iron.
Along the Holland coast, the availability of P is very low in pioneer stages,
since available P is stored in calcium phosphate, which is insoluble at high pH
(Kooijman et al. 1998). During succession, soils are leached owing to a net surplus
of precipitation over evapotranspiration. Dissolution of calcium and phosphate
occurs and the soil gradually becomes more acidic. However, along the Holland
coast, this acidification process takes a long time, because the initial lime content
is high (5–10 %). Calcareous dunes typically contain 60 mg m
-2 P in calcium
phosphate per millimeter of soil (Kooijman et al. 1998), which becomes available
during the decalcification process. Partly decalcified soils thus have high
238
A. P. Grootjans et al.