Recovery of the threatened economic plant goldenseal (Hydrastis canadensis).

摘要

The native woodland herb, goldenseal (Hydrastis canadensis), is threatened in Canada. Recovery to a non-risk category is particularly desirable given its medicinal and potential crop value. Woodland herbs probably evolved in an environment with severe and frequent disturbances, including massive floods and impacts of extinct and extirpated fauna. Lack of specific disturbance may limit growth and spread. Ecological observations and analysis (Part I) refined this hypothesis. Comparison of recent and 10 year old surveys, and stem numbers over two years, indicated lack of growth and spread. Pollination and dispersal appeared nonlimiting based on observation of abundant polylectic bees and syrphid flies and rapid removal of fruit. Chi-square tests, comparing frequencies of goldenseal and random points along transects throughout woodlands, revealed a significant association with paths and edges. This suggested a positive disturbance effect and justified an extensive random block field experiment (Part II). Each block contained four one metre square treatment plots: substrate turned, fertilized, both, and control. Transplants in 100 blocks and seeds in 40 blocks were evaluated over two years. Multi-factor analysis of variance, through an extension of the Kruskal-Wallis test, followed by multiple comparisons using modified Tukey tests, was used to analyse the highly variable and discontinuous data. Significantly greater growth occurred in substrate turnover plots after one year. Each year soil turnover plots had significantly more fruit, and after two years, soil turnover + fertilization plots had significantly more fruit and seeds per fruit. Lack of significant increase in germination was attributed to dry conditions. Results represent the first experimental evidence for a positive effect of substrate disturbance on growth and reproduction of a woodland herb exclusive of canopy gap effects. Management involving transplanting with substrate turnover may be essential for recovery according to projection matrix analysis (Part III) of two sets of transition years for 14 populations. The overall growth rate was 0.986 +/− 0.133 (SD) per year. Survival of established stems and vegetative propagation were critical for spread given lack of seedling development. The hypothesis that some woodland herbs are rare due to lack of certain disturbances that were more prevalent in the past was supported.