COS 113-4 - POPULATION DYNAMICS OF AN ENDANGERED ORCHID Dactylorhiza hatagirea (D. DON) SOÓ IN NEPALESE HIMALAYA: EFFECTS OF HABITATS AND HARVESTING

Abstract: Explaining the variation in population growth rate and identifying the causes of that variation is important for effective protection of endangered species. In this study, population dynamics of an endangered medicinal orchid, Dactylorhiza hatagirea was studied and its current status was evaluated in two sites, one protected from commercial harvesting by the locals (Manang) and the other unprotected (Darchula) and thus receiving high harvesting pressure from commercial collectors. In the unprotected site, further comparison of population demography was made in wetland and grassland habitats. Matrix projection models, based on three years of data of seven populations (three in each site in grassland plus one wetland habitat in unprotected site), were used to identify the pattern of variation in the demographic vital rates of this species. Demographic data included 3-year observations on growth, fecundity and survival of individuals classified by size. Transition probabilities for stage-based population projection matrices varied between populations and among years. The population growth rate (l) was 0.826 and 0.553 in the unprotected site, and 1.166 and 1.003 in the protected site for the transition year 2015/2016 and 2016/2017, respectively. The wetland and grassland habitats in the unprotected site had l of 0.847 and 0.826 respectively in 2015/2016 and 0.780 and 0.553 respectively in 2016/2017. The elasticity analysis showed that the stasis in the juvenile stage in unprotected site, and reproductive adult stage in protected site contributed most to λ. Numerical simulations were performed by changing the value of particular matrix entries and directly evaluating their effect on l. Population growth rate reached values above unity only when fecundity was increased 10-fold in unprotected grassland populations. Further, the wetland population in unprotected site required 25-fold increase in fecundity to reach the population growth rate of unity.

Management should prioritize the maintenance of the existing populations. The wetland populations should be conserved with great focus on increasing the existing fecundity. Given these limitations for population growth, along with limited distribution range and low population densities of the species, this study recommends to promote its conservation by favoring management practices aimed at increasing germination and seedling establishment success. The result recommends that in the protected site very limited harvesting can be allowed for local use. In unprotected site commercial harvesting should be strictly banned for certain period of time and then rotational harvest with harvest holidays for few years should be practiced regularly.