Identification of ecological factors affecting the occurrence and abundance of Dactylorhiza hatagirea (D.Don) Soo in the Himalaya

Abstract

Multiple ecological factors acting at different spatial scales are responsible for abundance and distribution of plant species. Therefore, in order to conserve and manage various species, it is crucial to examine species relationships with these factors. This study is aimed to model current distribution and assess the various factors influencing distribution of Dactylorhiza hatagirea (D.Don) Soo, a medicinally important terrestrial orchid endemic to Himalaya. Further, the study also elucidates habitat characteristics and the influence of climatic and edaphic factors on its abundance. Current distribution was determined using MaxEnt and the environmental variables (climatic, topographic and landcover) responsible for its distribution were elucidated using ‘Jackknife test’. The climatic and edaphic factors affecting D. hatagirea population density were identified using ‘Distance Based-Redundancy Analysis’. Further, co-occurring species and habitat indicator species were also identified. The MaxEnt model results revealed that precipitation of coldest quarter (Bio19), topographic vector ruggedness measure (VRM), solar radiation, herbaceous vegetation, mean temperature of driest quarter (Bio9), annual mean temperature (Bio1) and mean diurnal range (Bio2) are the most important variables that determine distribution of D. hatagirea. Western Himalaya was found to be the most suitable region for its occurrence. We also found that D. hatagirea populations occurred only in marshy habitats limited by soil phosphorus, and its population density was favoured towards higher soil calcium content. Further, a total of 186 species co-occurred with D. hatagirea out of which 27 acted as habitat indicators. Our results could be important in adopting most appropriate management and conservation strategies by identification of suitable habitats based on niche characteristics. We conclude that assessment of multiple ecological factors involving climatic, topographic, edaphic and community structure is important to gain insights into the distribution and population dynamics of rare and threatened species.