Conserving Threatened Species

Last year we initiated a study on a rare and Federally listed plant, Penstemon penlandii, in partnership with colleagues from the Gardens’ Horticulture Department. We tested the suitability of transplanting individuals to mitigate the damage that will be caused by road and utility work within the population over the next few years. One year after transplanting 200 plants, we have initial results. 

Plants to transplant were randomly selected, and we ended up with a variety of small and larger reproductive individuals. We transplanted 100 plants in the spring and 100 plants in the fall. We found that larger reproductive plants had a nearly 75% chance of survival regardless of which season they were transplanted. However, smaller vegetative plants faired far worse if they were transplanted in the fall compared to the spring. Last summer saw above average precipitation following the spring transplant and below average precipitation following the fall transplant. It is not surprising that larger, robust plants appeared less affected by the dry stretch while small plants were more likely to succumb to a lack of moisture. 

To understand how much the act of transplanting individuals causes stress and reduces fitness, we need to compare the survival and growth rates of surrounding P. penlandii plants that are experiencing the same environmental conditions. We transplanted individuals into small plots of suitable habitat with few to no P. penlandii. We selected comparison plots adjacent to our transplant plots to measure the survival rates of existing plants. When we looked at the survival rates of the few P. penlandii that were within the plots that received the transplants compared to the adjacent control plots, we found that survival was slightly lower in the transplant plots. There are a few reasons why we might see this pattern. It is possible that these locations that appeared suitable held few plants because they are not as good a habitat as adjacent locations. The other reason could be that planting individuals caused a disturbance in those plots. Either way, this is an interesting pattern that we will continue to watch to measure the success of transplanting as a mitigation strategy over the next few years.