Pinus Pseudostrobus Assisted Migration Trial with Rain Exclusion: Maintaining Monarch Butterfly Biosphere Reserve Forest Cover in an Environment Affected by Climate Change

In the Trans-Mexican Volcanic Belt in central-western Mexico, drought stress causes the decline of two of the most ecologically and economically important conifers: Abies religiosa and Pinus pseudostrobus. Since P. pseudostrobus is distributed immediately below the lower elevation limit of A. religiosa, it would be a logical choice of species to fill gaps that may be created by the decline of A. religiosa. We assessed the feasibility of upward assisted migration and explored the effect of rain reduction using four P. pseudostrobus provenances in a rain exclusion field test at the border of the Monarch Butterfly Biosphere Reserve (MBBR) in Mexico. Our results show that, although populations were transferred between − 1.4 and − 3.3 °C mean annual temperature, and 30% of the precipitation (− 200 mm) was excluded, no statistically significant differences were found among treatments or populations for height increment (overall average 1.52 m) or survival (overall average 87%). These findings suggest that it is feasible to migrate P. pseudostrobus upward, towards the MBBR border, which also coincides with the sites where A. religiosa is in decline. This may present the additional benefit of discouraging change in land use from forestry to potato production by maintaining a healthy barrier of trees. If assisted migration is not included in management and reforestation programs, climate change could induce significant mortality in the present A. religiosa forest, facilitating expansion of the agricultural frontier toward the MBBR.