Broadleaved regeneration dynamics in the Pine plantation

In an Island of the Netherlands, Pine (Pinus nigra) was planted to stabilize the dunes and to protect the arable lands from the blowing sand. This research was conducted to understand the most important environmental factors responsible for a vegetation change in the Pine plantation and effect of this change on the rare orchid population: Goodyera repens and Listera cordata. Vegetation sampling was carried out according to the Braun-Blanquet phytosociologic method within the three sites of this Island. Twinspan analysis confirmed the definition of three site types and redundancy analysis showed a significant difference between the pure Pine stands and the plots with regeneration. The results revealed that the most significant explanatory variables were litter cover, broadleaved tree cover, and shrub cover indicating the vegetation change under the Pine plantation. The abundance of Goodyera repens is strongly associated with the Pine forest and negatively related to broadleaved cover. Listera cordata could apparently cope with vegetation change. Controlling the herbaceous layer in the Pine plantation can promote the orchid population but on the contrary, promoting the natural regeneration of broadleaved species might endanger them.