Monitoring the status and conservation management of the rare orchid Orchis robusta

= Anacamptis palustris subsp. robusta (T.Stephenson) R.M.Bateman, Pridgeon & M.W.Chase.

Florent Prunier

Nick J. Riddiford

Resumen: the taxon is only known from S’Albufera and single sites in Algeria and Morocco. Therefore it is one of the priority species in P.N. S’Albufera de Mallorca. Because of its special conservation value and habitat requirements, it was selected as a key species for a monitoring programme as long ago as 1991. One observation has been that grazing livestock can have either a helpful or damaging impact on the Orchis population. Cattle, horses and buffalo permanently in place had a negative effect at s’Albufera on the numbers of Orchis in flower, but the partial presence of stock could be beneficial. The results of these 15 year s of monitoring are reported here, and include an analysis of annual fluctuations, their causes, the ecological requirements of the species and recommendations for the conservation and enhancement of the only European population of this internationally rare taxon.
An annual survey of flowering Orchis robusta spikes is carried out each year between the last two weeks of April and fir st two weeks of May, depending on the timing of flowering which may vary slightly between years. The survey is timed to coincide with the peak flowering.

Figure 3 presents the results of the survey of Orchis robusta counts across the park. The total for 2006, 383 spikes, is only 61% of the 624 flowering spikes recorded in 1991. However, a range of 166 to 3057 over the monitoring period reflect the fact that the situation is far from being either a trend of steady decrease nor within the range of oscillations of a stable population.
Closer analysis of the data reveals that the large variations were both in time and between compartments. A dramatic increase of the Orchis robusta population in s’Albufera in 1994 resulted from the conversion of large Phragmites australis beds through fire and subsequent grazing management to open water and marsh. The general decrease after 1997 is best explained as the results of overgrazing, or poor grazing management. The poor success of orchids in 1995 is not explained.
The marsh orchid population has followed complex patterns of distribution over time in the park. As an opportunist species, the local population reacts strongly to its changing environment. It colonizes new sites quickly when conditions are appropriate and disappears equally fast. It is though that park management, especially grazing throughout the park, is the key factor in explaining the success or failure of orchids in the marshland areas. Positive and negative effects of management have been identified for Orchis robusta.

Agradecimientos: We gratefully acknowledge all the many participants in The Albufera International Biodiversity team activities for their help with fieldwork and other aspects of the study; and the staff of the Parc Nat ural S’Albufera de Mallorca for their friendly support and in particular Matias Rebassa, Biel Perello, Pere Vicens (naturalist) and Miquel Cantallops (grazings manager) all of who provided important additional information. This part of the report was prepared by F. Prunier, N. Riddiford, I. Férriz and C. Portero.


Grup Balear d’Ornitologia

Ficha de la especie