My second month here at the CO state office is coming to a close. Field season has officially started. Last week we went out near Rifle CO to monitor several plots of Astragalus debequaeus, Bebeque milkvetch. This plant is a rare endemic of Colorado, and is found on fine textured, seleniferous, saline soils of barren outcrops of dark clay intermixed with sandstone. A. debequaeus inhabits areas dominated by pinyon-Juniper woodlands, but is found in areas generally devoid of vegetation. I’m going to go into a lengthy description of our monitoring.
Last Monday we monitored one macroplot known as North Webster Mesa, one seedling plot, and five circular plots for presence and life stage. There are two more macroplots closer to Grand Junction that we hope to monitor later this week, weather allowing. The N. Webster Mesa plot was established in 2010 with a total of 613 plants recorded in 12 transects. This year we recorded 55 plants in those transects, none of which were reproductive. In 2014, 19 tags were placed within this plot by groups of seedlings or individual juveniles. This year only 2 tags had living plants and only one with the remnant of a plant. We set out to detect a 10% difference in mean population density between years with 90% certainty, while accepting a 10% chance of making a false-change error. So, this is a significant decrease. We have a few ideas as to why we are seeing this decrease. We think the last few years of drought have played a large roll in this decline. A. debequaeus at this site does inhabit a fairly unstable, highly erodible, steep slope devoid of much vegetation where several cm deep cracks in the soil are common. So, we have also hypothesized that seeds might be unable to establish in these cracks where they fall deeper than the first few cm from the soil surface. We’ve also considered the impact we might be having on the plot while monitoring. Given the erodible nature of the soil, it’s possible our walking through the plot may effect plant growth. This site is only visited once a year, is in a low to no traffic area, and researchers are always mindful of where they step while monitoring. But it is a possibility that human traffic is contributing to the observed decline. It has been suggested that next year we GPS a few individuals outside but near this plot where we do not walk to observe, in order to compare life history data. Overall, individuals at this site are fewer and less robust than those at the other two macroplots that we’ll measure later this week. My boss believes that the microclimate at the other sites is more favorable due to slightly higher vegetation cover, which may hold moisture better.
Photograph: Peter Gordon. A. debequaeus in flower and fruit. Picture taken near Atwell Gulch, CO.
I did not take any pictures of the species, so this one is from a former intern at one of the other macroplot locations closer to Grand Junction.
The seedling plot was originally established in 2003 to shed light on seedling and juvenile mortality and life history. This site is also a dry-land canyon with steep slopes. This year had the fewest individuals recorded, although there has been variation in the past.
Total Numbers of Astragalus debequaeus in the Seedling Plot from 2003-2015
I don’t know how to make this bigger, sorry.
The circular plots are a few meters from the seedling plot and a few meters from one another. Given the terrain of this site, circular plots were more plausible than one large macroplot. Established in 2004, plant number and age class are recorded within these plots. Plant numbers have varied fairly significantly in each plot over the course of this study. We have also compared total plant number to average annual precipitation using a linear regression. There does not seem to be a strong correlation, but precipitation data is from the Rifle CO weather data location. Location-specific precipitation data would allow for a more accurate analysis, and we are considering purchasing soil moisture readers for instillation at these, or other, sites.
Another exciting part of this past month was the National Native Seed Conference I was able to attend in Santa Fe, NM. This was my alternative training opportunity since I attended the CLM training in Chicago last year. There were so many great talks at this conference, and too many to attend. I want to highlight one of my favorite presentations; one that I’m sure was a favorite of many people. Spatial climate trends in western vegetation: Implications for restoration by Healy Hamilton discussed the current work by Dr. Hamilton and several others at NatureServe. They have been analyzing climate trends of the past decades in order to predict geographic and seasonal shifts of ecosystems across the west, identify seed sources of plants already adapted to climatic changes, identify populations already greatly affected by climate change, identify populations that are stable and may act as refugia, and identify where certain ecosystems are likely to be lost, remain stable, or expand. On top of all of this, they are also putting together a user-friendly webpage where this information can be accessed. Not only is this very interesting, critical, and highly useful research, the actual presentation was conducted really well. I’m looking forward to the completion of their work and the launch of the webpage.
There were several people from various other countries in attendance too. Dr. Stuart W. Smith gave an interesting presentation on his work restoring peatlands in the Falkland Islands, Laura Victoria Perez-Martinez talked about the work of she and her colleagues at the Bogota Botanical Gardens in Bogota, Colombia where they have created the county’s first native seed bank for the conservation of the tropical high mountain ecosystem, and Kay Evelina Lewis-Jones, an ethnobotanist from the University of Kent, UK, held an open forum to discuss the future of native seeds as we, the attendees, saw it. These are the only four talks which I attended, but there were many more I was unable to attend (since I can’t be in two places at once) that looked just as interesting and I’m sure were just as educational. Overall, the conference was a great experience where I learned a lot more about the various kinds of work and research going on in the native seed world, and I was able to meet several prominent people in the native seed world.
Month 2 has been fun and educational. I’m looking forward to the month ahead.
Colleen Sullivan