background pattern

Assisted Migration 2022

Common garden experiments to improve survival of oyamel using shrubs as nurse plants.

July 03, 2023

Dr. Cuauhtémoc Sáenz-Romero, his colleagues, and graduate students continue working on their assisted migration experiments. Preliminary results of four field sites at Nevado de Toluca, State of México indicate that after a year of having been planted, oyamels (Abies religiosa) have an overall survival rate of 80.6 % (August 2022). Mortality increases significantly if the shift upwards exceeds 600 m of altitudinal difference between the seed source and the planting sites.

This research and the challenges faced by the conservation and survival of oyamels in the overwintering sites of the monarch and its assisted migration has received international recognition! Some of the recent articles on popular media published on this topic can be found on USA Today, Reader’s Digest, and National Geographic.

Nurse plant experiment at El Rosario
Nurse plant experiment at El Rosario

To improve the survival of the oyamel (Abies religiosa) in future reforestations, Dr. Saénz's team also conducted experiments on the propagation of Coyote brush (Baccharis conferta) and Snakeroot (Ageratina glabrata) nurse plants in nurseries. Using shrubs as nurse plants, provides protection to young oyamel seedlings from excessive heat and extreme temperatures.

An experimental reforestation was carried out planting these two species of shrubs at 3400 m altitude at Cerro Prieto Ejido in Sierra Chincua to try to cover a site that was highly disturbed by the winter storm of March 2016 with shrubs. Once established, the shrub cover will serve as a nurse plants for subsequent reforestation with oyamel in the future. Survival after eight months of planting was 78% in Baccharis conferta and 65% for Ageratina glabrata. These results are considered encouraging, especially considering that these shrubs had never been planted in nurseries before or used for reforestation since traditionally they have been considered marginal. A video of the process is shown below.

Production of coyote brush (Baccharis conferta)
Coyote brush (Baccharis conferta)

Another experimental site was set up at El Rosario where oyamels are being planted at three altitudes (3335, 3240, 3230) with nurse plants(Bacharis conferta – coyote brush and Eupatorium labratum– snakeroot) to see how well oyamel trees survive under the shade provided by the nurse plants at the different altitudes. The experiment was set up at the beginning of July, 2022 and we will have to wait and see how long it takes the nurse plants to grow enough to provide enough shade for the oyamels at the different altitudes.

Back to all projects