Branches and cones of oyamel populations along different altitudinal zones in an area close to the Monarch Butterfly Reserve were collected and analyzed considering their form and structure. Results indicate that low altitude populations have shorter needles and longer cones than those at high altitudes. Consequently, the research team suggests reforesting in three provisional altitudinal zones using seedlings originated from each zone. If climate change is considered, sites should be reforested in the zone immediately above the zone where the seeds were collected to assist the migration of seeds.
To test the altitudinal upward shift assisted migration, the team initiated a field experiment in July 2015. They planted 2-year old seedlings at an altitude of 3440 m to anticipate the climatic change expected for the year 2030. Additionally, this field experiment includes two treatments: seedlings planted with and without coverage of local bushes to test the feasibility of using nurse plants to protect young Abies religiosa seedlings from extreme temperatures. The research is ongoing and will provide valuable information to decide when it is viable to allow the forest to naturally regenerate and when to reforest.
During 2016, Dr. Saénz and his team of researchers discovered that oyamel seedlings originated from seed collected at an altitudinal difference of 350m, resulted in genetic variations in growth potential and frost resistance. This highlights the importance of considering the altitudinal origin of the seed source used to produce seedlings in the nurseries for reforestation programs, and the importance of carefully considering the altitudinal difference between the site of seed collection and that of reforestation. They also discovered that after one year of planting on a reforestation site, survival under open fields is 77%, while under the shade of local shrubs it rises to 95%. Based on these results, in 2017, the researchers will conduct additional tests and experiments to assess the differences in survival and growth of trees relative to the seeds source and the planting site based on climate and altitudinal changes. To view a newspaper article about this research published by the Texas Butterfly Ranch click here.
In December 2017, Marisol Ortiz-Bibian, one of Dr. Saénz Romero’s students and lead author published the results of this study in a paper titled Genetic
Variation in Abies religiosa for Quantitative Traits and Delineation of
Elevational and Climatic Zoning for Maintaining Monarch Butterfly
Overwintering Sites in Mexico, considering Climatic Change
The research consisted in collecting seeds from fifteen oyamel (A. religiosa) populations along 50-meter intervals at elevations between 2850-3550 meters. Seedlings were evaluated in a common garden test over a period of 30 months. Significant differences were found among populations in total elongation, height, date of growth cessation, foliage, stem, and total dry weight, as well as frost damage. These differences were strongly associated with the cold temperatures. When collecting seeds close to mountain peaks, the altitudinal shift would exceed the highest elevations within the MBBR. This led the authors to conclude that A. religiosa stands need to be established outside the MBBR, on higher mountains and volcanoes, such as Nevado de Toluca, Popocatépetl, Iztaccíhuatl and Pico de Orizaba, as potential future overwintering sites. Food for thought as the future approaches and climate change is upon us and the monarchs!
After one year in the field, an evaluation performed in 2018 revealed 96% tree survival rate. Seedlings were originally rescued from natural regeneration sites and grown for two years in a nursery. Afterwards they were planted under the shade of nurse plants on a deforested site.
This amazing survival is due to several reasons including the fact that the seeds originated from the core zone in the Monarch Butterfly Biosphere Reserve, were rescued from natural regeneration in mossy sites which were carefully transplanted into nursery containers, were grown at a communal nursery at high altitude (3000 m) and planting on the field was done under the shade of nurse plants.
This made Cuauhtémoc and his team realize that it is necessary to produce local shrubs in communal forest nurseries and plant them on perturbed sites that don’t have any shrubs, two years before planting the oyamel seedlings.
The series of photos below show the assisted migration field tests for pine (Pinus pseudostrobus, reforestation site at 3010 m of altitude), with treatments of: (a, b) 30 % of rain exclusion, (c) shade without rain exclusion, and (d) control (no rain exclusion or shade). The project’s aim is to see the effect of rain reduction, projected by some climatic change scenarios.