Making seedlings suffer

Meagan Owens, Alex Gibson, Jess Guzzo, Emily Luberto, Katrina Urrea, and Megan Wilkinson in the greenhouse measuring 2500 ponderosa pine seedlings.

Can we induce drought resistance in ponderosa pine seedlings in the greenhouse before outplanting them to the field? An amazing group of undergraduates (Meagan Owens, Alex Gibson, Jess Guzzo, Emily Luberto, Katrina Urrea, and Megan Wilkinson) worked hard in the greenhouse all year growing 2500 ponderosa pine seedlings and subjecting them to different propagation strategies. The motivation for this study was two-fold: there is a dire need to replant and restore ponderosa pine sites all over the southwest, but typical greenhouse propagation techniques produce seedlings that are unprepared to face the harsh/dry conditions in the field. The students tested alternative watering and fertilization strategies, which appeared to make the seedlings suffer: they grew smaller. However, they were actually more drought-resistant because they grew more roots! Stay tuned to see how they performed once we outplanted them in the field.

Grazed and confused

Dr. Souther traverses a rocky outcrop to collect seeds from a relict mesa in the Grand Canyon.

Is the legacy of grazing in the Southwest written in the DNA of plants? The introduction of large numbers of domesticated livestock by 1800s by European settlers is believed to have dramatically altered vegetative communities in the Southwest. Since few records proceeding the introduction of livestock exist, we know very little about how grazed shaped current southwestern landscapes. Relict mesas, inaccessible areas that have received little or no grazing, offer clues to what these arid and semiarid grasslands were like prior to European settlement. We visited several relict mesas in the Southwest to collect seed for trials looking at how grazing affects traits and trait expression in grassland plant species. Understanding differences between historically grazed and un-grazed plant populations may allow us to better understand how grazing changed plant communities and altered ecosystem function, in order to develop improve methodology to restore degraded rangelands.

Tag! You’re it!

Dr. Aslan poses with a tag used to mark individual beardless chinchweed plants. After collecting years of detailed demographic data, researchers will build models to determine beardless chinchweed’s extinction risk and identify threats to this species’ long-term persistence.

Are populations of beardless chinchweed going extinct? In 2021, beardless chinchweed (Pectis imberbis), a small plant in the daisy family, was listed as an Endangered Species. Now government agencies and researchers are trying to figure out how to rescue this species from extinction. Demographic models are a key tool to look at variation in population growth across the landscape to identify threats to species persistence. Importantly, demographic models can be built from data collected in a way that does not disturb the species. Researchers tag and follow plants through time, measuring them, assessing reproduction, and looking for signs of disease or stress on an annual basis. Results are pending, but initial findings indicate that Pectis imberbis has an interesting form of rarity, occurring infrequently across the landscape, but at high densities in suitable habitat. Moreover, grazing and drought may depress population growth. Researchers will continue visiting these beardless chinchweeds in order to support species recovery efforts.  

Hang in there!

Sara Souther, with Clare Aslan and Martha Sample, establishing a germination trial to examine factors influencing germination of Kearney’s bluestar seeds. Photo courtesy of Clare Aslan.

Why don’t we see many Kearney’s Bluestar seedlings? With funding from the Arizona Department of Agriculture, Sara Souther, Clare Aslan, and Martha Sample scaled the steep hillsides of the Baboquivari Mountains to look at seedling recruitment in the Endangered Species Act (ESA) listed species, Kearney’s Bluestar (Amsonia kearneyana). Factors such as seed predation or inhospitable microsite characteristics may prevent the establishment of the next generation of plants within a population. In this experiment, researchers tested whether soil moisture, predation by small and mid-sized mammals, and genetically-based differences in site preferences influenced the ability of Kearney’s Bluestar seeds to germinate, survive and grow. This research will provide parameters for future conservation efforts to aid recovery of this endangered species!