Current Status of <i>Pulsatilla patens</i> in Latvia—Population Size, Demographic and Seed Viability Indicators, Soil Parameters and Their Relationships

<i>Pulsatilla patens</i> (L.) Mill. (Eastern pasque flower) is classified as a highly endangered and declining species in Europe. The present research assessed the current status of <i>P. patens</i> in Latvia by collecting data on its distribution in historical places, Natura 2000 territories, and other areas, largely covering the entire country. We aimed to analyze the relationships between <i>P. patens</i> populations size, demographic indicators, and soil parameters, in order to gain knowledge on the impact of local ecological factors and optimal growth conditions, which are important for conservation and potential reintroduction. Although <i>P. patens</i> was not detected in more than a third of the surveyed 624 locations, more than 18 thousand individuals were recorded. Our results indicate that optimal growth conditions for <i>P. patens</i> occurred near highways, forest roads, and paths, that is, in places with reduced competition from other species and improved lighting conditions. The seed viability ranging from 22% to 62% can be considered potentially sufficient for the continuation of the species if enough flowering plants and moss-free spaces for germination are maintained. Although <i>P. patens</i> tolerates a broad soil pH range, in Latvia this species mainly grows in acidic sandy soils with an average pH_KCl of 4.07. The soil parameters that most strongly positively correlated with <i>P. patens</i> regional population size and performance included higher soil pH level and plant available nutrient content, particularly P, K, Ca, Mg, Mn and B. Increased soil P and Mn levels significantly enhanced flowering, while high organic matter content could be associated with reduced population sizes. Despite its still large current population, long-term risks remain without active management. Conservation measures, such as creating open soil areas, where vegetation is removed and shading is reduced, are necessary to mitigate population decline.