In this study, we examined the spatial genetic structure (SGS) in extensively managed, but naturally regenerated forest stands of Pinus cembroides Zucc., Pinus discolor Bailey et Hawksworth, Pinus durangensis Martínez, and Pinus teocote Schiede ex Schltdl. & Cham. at local (within the stands) and large (among the stands) scales using amplified fragment length polymorphisms (AFLP), with respect to conservation and sustainable management of genetic resources of these species. Because these four pine species grow in different landscape structures, we expected to find differences in their SGS, although all of them are widely spread, wind pollinated, and often occur at high population densities. At the local scale, there was no evidence of significant SGS in the four species under study (except in 1 out of 18 seed stands), suggesting that the genetic variants of these species are almost always randomly distributed in space, probably due to high wind pollination and seed dispersal. At a larger scale, the significant SGS found may be the result of isolation by distance among populations. We recommend (i) establishing a tight network of seed stands, with a maximum distance of 3–11 km between seed stands, to prevent greater loss of local genetic structure, and (ii) using these seeds to establish reforestations within a maximal radius of 3–5 km from seed provenances.

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Societal Impact Statement Syntheses clearly show that global warming is affecting ecosystems and biodiversity around the world. New methods and measures are needed to predict the climate resilience of plant species critical to ecosystem stability, to improve ecological management and to support habitat restoration and human well‐being. Widespread keystone species such as aspen are important targets in the study of resilience to future climate conditions because they play a crucial role in maintaining various ecosystem functions and may contain genetic material with untapped adaptive potential. Here, we present a new framework in support of climate‐resilient revegetation based on comprehensively understood patterns of genetic variation in aspen. Summary Elucidating species' genetic makeup and seed germination plasticity is essential to inform tree conservation efforts in the face of climate change. Populus tremuloides Michx. (aspen) occurs across diverse landscapes and reaches from Alaska to central Mexico, thus representing an early‐successional model for ecological genomics. Within drought‐affected regions, aspen shows ploidy changes and/or shifts from sexual to clonal reproduction, and reduced diversity and dieback have already been observed. We genotyped over 1000 individuals, covering aspen's entire range, for approximately 44,000 single‐nucleotide polymorphisms (SNPs) to assess large‐scale and fine‐scale genetic structure, variability in reproductive type (sexual/clonal), polyploidy and genomic regions under selection. We developed and implemented a rapid and reliable analysis pipeline (FastPloidy) to assess the presence of polyploidy. To gain insights into plastic responses, we contrasted seed germination from western US and eastern Canadian natural populations under elevated temperature and water stress. Four major genetic clusters were identified range wide; a preponderance of triploids and clonemates was found within western and southern North American regions, respectively. Genomic regions involving approximately 1000 SNPs under selection were identified with association to temperature and precipitation variation. Under drought stress, western US genotypes exhibited significantly lower germination rates compared with those from eastern North America, a finding that was unrelated to differences in mutation load (ploidy). This study provided new insights into the adaptive evolution of a key indicator tree that provisions crucial ecosystem services across North America, but whose presence is steadily declining within its western distribution. We uncovered untapped adaptive potential across the species' range which can form the basis for climate‐resilient revegetation.

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Developing methods for successfully grafting forest species will be helpful for establishing asexual seed orchards and increasing the success of forest genetic improvement programs in Mexico. In this study we investigated the effects of two grafting techniques (side veneer and top cleft) and two phenological stages of the scion buds (end of latency and beginning of sprouting), in combination with other seven grafting variables, on the sprouting and survival of 120 intraspecific grafts of Pinus engelmannii Carr. The scions used for grafting were taken from a 5.5-year-old commercial forest plantation. The first grafting was performed on January 18 (buds at the end of dormancy) and the second on February 21 (buds at the beginning of sprouting). The data were examined by analysis of variance and a test of means and were fitted to two survival models (the Weibull’s accelerated failure time and the Cox’s proportional hazards model) and the respective hazard ratios were calculated. Survival was higher in the top cleft grafts made with buds at the end of latency, with 80% sprouting and an estimated average survival time of between 164 and 457 days after the end of the 6-month evaluation period. Four variables (grafting technique, phenological stage of the scion buds, scion diameter and rootstock height) significantly affected the risk of graft death in both survival models. Use of top cleft grafts with buds at the end of the latency stage, combined with scion diameters smaller than 11.4 mm and rootstock heights greater than 58.5 cm, was associated with a lower risk of death.