Revealing the decline and expansion of orchids of NW European Russia
A new approach to reveal the dynamics of taxa on incompletely investigated territories was developed. The decline/expansion rate of orchids in the North Western part of European Russia (Leningrad, Novgorod and Pskov Regions, an area approx. 195 000 km2.) was estimated using this method. The method is based on comparison of numbers of grid cells where a certain species was recorded in various time intervals using specially designed software. More than 9000 records were used, however the territory remained insufficiently and unevenly studied both spatially and over time. The study revealed a statistically significant (p<0.01) decrease for Coeloglossum viride, Corallorhiza trifida, Cypripedium calceolus, Gymnadenia conopsea, Herminium monorchis, Malaxis monophyllos, Neotinea ustulata and Orchis militaris and a significant increase for Dactylorhiza baltica, D. fuchsii and Platanthera chlorantha. In several taxa, the trend was changed over the time. Of them, Gymnadenia conopsea displayed significant decline only since the middle of XX century, and Orchis militaris and Epipactis atrorubens decreased significantly only in the end of XIX and the beginning of XX century. The reasons for these patterns of dynamics were discussed. Parallels between the dynamics of orchids and land use in different periods of time in Russia are provided.
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