Carbon storage in the Dutch dune ecosystems (literature study)

Introduction

PWN is responsible for the conservation of 7300ha of dune area in the province of North-Holland. The area is part of the Natura 2000 network and comprises more than 50% of the biodiversity of the Netherlands. Conservation of the valuable habitats and characteristic species of this area faces several challenges. Nitrogen deposition, fixation of originally dynamic dunes and the decline of rabbit populations are responsible for an accelerated overgrowth of the open dune vegetation. In order to sustain and improve the quality of the N2000 habitats, management measures are needed that are described in a Natura 2000 management plan. Recently the concept N2000 management plans for the next 5 years were published and are now open for comments from the public.

One of the measures included in the N2000 management plans is the transformation of coniferous plantations to deciduous forest or dune grasslands. Non-native pine (Pinus nigra) trees were planted in large numbers in the first half of the previous century. This has had a considerable impact on the original dynamic character and current succession stage of the landscape. The natural forest line (originally determined by the influence of wind and salt) has been moved seaward and the presence of pine plantations also influences the water balance of the system. In order to restore the original open character of the landscape several patches of coniferous plantation are planned to be transformed to open dune grassland (for which we have a large responsiblity within the N2000 network), or (more native) deciduous forest in the coming years.

However, a constantly recurring question about the N2000 management plans is referring to the effect of deforestation on the carbon cycle and storage in the ecosystem. A nowadays popular and (politically) strongly promoted measure for climate change mitigation is afforestation or reforestation. Deforestation is therefore seen as a contradictory action in an effort to diminish global CO2 emission.

Assignment

For that reason PWN would like to get more insight in the CO2 balance of the nature conservation measures we perform. More knowledge in this field will primarily help in answering the above question, but will also allow us to minimize the carbon footprint of our nature management actions (thereby always putting the ecological benefits first). The following questions will be interesting to answer:

  • What is the carbon storage capacity of the different habitat types involved (coniferous plantations and deciduous forest, dune grasslands and wet dune slacks)? Thereby we should not only taking into account the carbon stored in biomass, but also the soil organic carbon. It is clear that forests have the largest aboveground storage capacity, but soils can also store a significantly amount of carbon. This capacity probably differs substantially between the various habitats.
  • What is the influence of habitat transformation on the carbon balance in the dune ecosystem? What are the carbon storage losses and gains? It is important to include the whole carbon cycle in order to answer this question. So also the carbon emission of the machines that are used to perform the management measures and the ‘afterlife’ of the wood (is it used to make furniture or burned as biofuel for example?).
  • What is the influence of ecosystem processes on the carbon storage capacities of the different habitat types? Grazers play an important role in nutrient cycling and convert plant biomass to animal biomass, which will eventually flow back into the system provided that the animal dies here (which is not the case when it comes to our big grazers). Also dynamic processes may play an important role in carbon storage in the soil. What is the effect of regular sand sprays covering the dune grasslands? Will this result in layers of biomass stored in the soil or just a rapid turnover?
  • In what way is climate change influencing the above considerations? Think for example about the elevated risk of natural fires (perhaps aggrevated by beetle attack leading to mortality and altered wood quality of pine trees), expected higher decomposition rates and increase of groundwater levels.

Answering these questions will contribute to a better understanding of the carbon balance of the different habitat types of the dune ecosystem and will give insight in the influence of habitat transformation and climate change on these balance.

PWN will provide the student with information about the dune areas and the different measures that are planned (number of hectares, machines used, timespan, final destination of the wood etc.).

For more information contact:

Hans Cornelissen (VU Amsterdam): j.h.c.cornelissen@vu.nl

Myrthe Fonck (PWN): myrthe.fonck@pwn.nl

Marieke Kuipers (PWN): marieke.kuipers@pwn.nl