Moderate anthropogenic disturbance does not affect the demography of Magnolia schiedeana, an endangered species from Mexico

Abstract

Among the many Magnolia species that are endangered by anthropogenic disturbance, some are known to have the capacity to produce new shoots. Demographic studies are an important tool to evaluate the impact of disturbances as well as the resilience and resistance of endangered species. Our study looked at the demographic dynamics of two Magnolia schiedeana populations, with an aim to determine the role played by disturbances. The questions were: 1) what demographic trends characterize this species? 2) What differences are there between disturbed and undisturbed populations? 3) Is M. schiedeana a disturbance-resilient species in general? 4) How important is the contribution of the resprouting trait to λ in a population under anthropogenic disturbance? The demographic attributes evaluated were: elasticity, population growth rate (λ), and sensitivity to concrete disturbances (LTRE, Life Table Response Experiment). The results indicated that the λ of the two populations did not differ significantly. The transitions that contributed the most to λ and presented the largest variation were similar in both populations under study. More than 90% of the contribution came from those individuals measuring≤5cm in diameter. Surprisingly, M. schiedeana is not sensitive to moderate anthropogenic disturbance. Resprouting contributed to λ with less than 0.2%.