Effects of Forest Succession on the Occurrence of Orchid Species

The orchid species, Neottia cordata and Goodyera repens found in large parts of Europe and North America, but rarely found in the Netherlands. Hence, the Forestry Services of Netherlands is working to preserve these endangered orchid species by maintaining the current forest structure and applying different forest management strategies. The aim of the study were, (1) to identify an environmental factors which determine the occurrence of the orchid species, mainly G. repens and N. cordata, (2) to recommend management options to preserve identified suitable environmental factors in a mixed forest and forest structure. The study was conducted in Hoornsebos. In each sample plot, we recorded the vegetation composition, forest structure and composition, humus and litter layer, and canopy openness. In the study forest, we found two plant communities (i,e, Vaccinio-Piceetalia and Quercetalia-roboris). Both N. cordata and G. repens were abundant in Vaccinio-Piceetalia plant community, but were rare in the Quercetalia-roboris plant community. Our results showed that both orchids’ species are dependent on the occurrence of needle litter and need to grow in low productive environment, where they are not outcompeted by other plants. There is also a general trend of development towards more broadleaved tree composition which has a negative effect on the occurrence of both orchid species. The development of a shrub layer leads to increased shading and canopy closure and likely to decrease the abundance of N. cordata in the study forest. Aging of coniferous forests will lead to further build-up of the litter layer which negatively affects G. repens. Without good forest management, the existing suitable environmental conditions for both G. repens and N. cordata, will likely to degrade, hence active management is required for sustainable conservation of these orchid species.