Abstract
Increasing cross-border trade of medicinal and aromatic plants (MAPs) has put heavy pressure on a considerable number of species in the Himalayas. One of the threatened species in Nepal is Aconitum spicatum. Unfortunately for this species and for many others, our knowledge on population ecology and performance across the distribution range is insufficient, hindering the formulation of species-specific management plans. We therefore studied density and population structure of A. spicatum and assessed variation in its life history traits among three populations (subalpine, lower alpine and alpine) along an elevation gradient (3,000–4,200 m a.s.l.) in Annapurna Conservation Area, north-central Nepal. The results show that human disturbances and topographic factors contributed to the variation in density and life history traits. The overall density ranged between 0.56 ± 0.09 (Mean ± SE) and 2.48 ± 0.24 plants/m2 with highest mean density in the lower alpine and lowest in the subalpine population. The subalpine population was also characterized by lower investment in reproductive structures with lowest seed mass and low seed viability and fecundity. Among the environmental variables tested, harvesting, animal droppings and fire appeared to be the most important factors affecting density of different life stages of A. spicatum. The prevailing harvesting pattern is destructive as it involves uprooting of the whole plant and this appears to be a main reason for low recruitment and reduced density of the subalpine population. The level of disturbance decreased with increasing elevation. In terms of reproductive effort, the alpine population performed best. Our results indicate that the viability of A. spicatum populations depends on controlling over-harvesting and pre-mature harvesting of tubers and protecting younger life stages from grazing, trampling and fire. We therefore recommend that when formulating management guidelines, measures aiming to mitigate such anthropogenic disturbances should be considered.
Highlights
The study of variation in life history traits of a species is crucial to understanding the role of particular types of ecological pressure in shaping population demographicsHow to cite this article Chapagain DJ, Meilby H, Ghimire SK. 2019
Examining populations located within three consecutive elevation ranges, the goal of this study was to answer the following questions: (i) do the impacts of anthropogenic disturbance on population structure and density of A. spicatum vary along an elevation gradient? (ii) How do plant size and reproductive performance of A. spicatum vary along an elevation gradient?
Among the environmental variables tested, harvesting, animal droppings and fire appeared to be the most important factors affecting the density of A. spicatum
Summary
The study of variation in life history traits of a species is crucial to understanding the role of particular types of ecological pressure in shaping population demographicsHow to cite this article Chapagain DJ, Meilby H, Ghimire SK. 2019. Topographic variation affects microclimatic conditions, which may contribute to variation in life history traits These variations are coupled with disturbance regimes, like harvesting, fire and grazing which themselves are structured along elevation gradients. The concentration of these anthropogenic disturbances, especially in alpine and subalpine ecosystems may put high-altitude plants under stress. To cope with such stressful conditions, high-altitude plants develop self-sustaining adaptation strategies (Körner, 2003), including a long floral axis, more globular flowers (Molau, 1993), persistent sepals, larger root systems (Körner, 1999), vegetative apices or perennating buds at safe depth below ground (Körner, 2003), higher proportion of belowground biomass (Webber & May, 1977) and increased number and size of seeds (Körner, 1999), which contribute to enhance the persistence of their populations
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