Productivity, moisture and competition—Habitat conditions affecting population viability of the wet grassland orchid <i>Dactylorhiza majalis</i> under conservation‐oriented management

Abstract Central European semi‐natural wet grasslands are targeted for conservation due to their high biodiversity. However, many typical wet grassland species continue to decline, questioning whether regular conservation schemes need re‐adjustment. Identifying environmental factors that threaten the population viability of endangered species despite conservation‐oriented management is needed. However, key components of population viability, such as recruitment, fecundity and growth, can respond differently to environmental factors, necessitating investigation of several viability proxies simultaneously. We combined five different viability proxies of Dactylorhiza majalis , a characteristic orchid of Central European semi‐natural wet grasslands, across 95 protected wet‐grassland sites in NE Germany. We tested the effect of six environmental factors on all viability proxies (long‐term population trends, abundance of mature and juvenile individuals, plant size, fecundity) and whether these effects differed among viability proxies. Further, we identified co‐occurring species associated with the high viability of D. majalis . Despite conservation efforts (extensive biomass removal, drainage prevention and no fertilization), increased productivity and vegetation height were the primary threats. Both characterized sites with negative long‐term population trends and reduced abundance of mature and juvenile D. majalis individuals. High base saturation and moist, but not wet hydrological conditions appeared particularly beneficial for conserving D. majalis and species‐rich types of wet grasslands. Interestingly, larger plant size in D. majalis was associated with low population viability, deteriorating site conditions and rather tall, generalist co‐occurring species. Synthesis and applications . Our results suggest that adjusting regular conservation‐oriented management may be beneficial for many wet grassland sites. Observing few but large D. majalis individuals may serve as a warning sign for deteriorating site conditions that can help prioritise conservation efforts to stabilise populations early on. In rather productive sites, more frequent or earlier biomass removal can benefit D. majalis and other wet grassland specialists.