Transformative changes in tree breeding for resilient forest restoration

Abstract

Deciding how to establish woodland in forest restoration is not straightforward as different outcomes may be obtained from different establishment approaches, each with cost implications and degree of success limitations attached. Planning restoration requires knowledge of site conditions, including how sites are likely to respond under climate change. For objectives of production and high timber quality it is likely that ground preparation will be used, and planting with forest reproductive material (FRM) of known traits, such as: high survival and growth in establishment, drought tolerance adequate for climate projections, good resistance to pests and pathogens. For objectives associated with biodiversity, carbon sequestration, water supply protection, soil protection, natural regeneration could be a less costly solution with a limited amount of assisted translocation of selected FRM to improve resilience. If objectives are for rewilding forest areas, a degree of natural colonisation perhaps with translocation of some FRM could be a solution. Ignoring site conditions and suitability of available sources of FRM for forest restoration is likely to provide unexpected results with a mix of open ground, scrub and scattered trees resulting from climate, herbivore, and browsing impacts. The recent B4EST EU Horizon 2020 project examined progress in novel rapid approaches for testing the quality of FRM from existing genetic trials. Here we review the work of B4EST to show the opportunities from transformative tree breeding in forest restoration schemes, including: new climate projection ensembles at high temporal and spatial resolution to develop norms of reaction and transfer models with genetic components; multi-environment genotype-phenotype associations and multi-locus genotype-environment associations in identifying drivers of local adaptation; techniques for genomic selection using single nucleotide polymorphism (SNP) arrays to derive functional traits from polygenic associations; work on seed orchard site and climate specific FRM and zones for deployment; and work on some of the forest ecosystem service benefits derived at a landscape scale. We conclude that tree-breeding will provide robust forest restoration for planting, and rewilding (assisted natural regeneration), and if not “ignoring” but instead assisting natural colonisation processes – tree breeding may improve long-term forest resilience under environmental change.

Genomic evaluation for breeding and genetic management in Cordia africana, a multipurpose tropical tree species

“…To ensure increased resilience of managed production plantations under climate change, it is crucial to plant tested forest reproductive material [ 42 ]. The availability of improved material serves a dual purpose; meeting the demand for timber and wood products but also relieving the pressure on the natural forests and helping restore locally endangered species.…”

Heat-Priming during Somatic Embryogenesis Increased Resilience to Drought Stress in the Generated Maritime Pine (Pinus pinaster) Plants

“…It is important to note that besides the tree-level effects, global warming causes a major disruption of Mediterranean stands, increasing soil erosion, the frequency and intensity of forest fires, and pest outbreaks, all threatening the continued supply of forest ecosystem services in Southern Europe [5].…”

“…Furthermore, chronic lower growth and higher dieback rates in P. pinaster stands have been linked to drought events [22], and cumulative impacts of stress events on tree growth and vigor have been related to higher vulnerability to drought [23]. To promote the long-term continuity of South European forests in the climate change-driven scenario, it is recommended to select reproductive material with improved resilience [5]. For this purpose, P. pinaster infra-specific variability can be exploited by identifying and cloning superior genotypes; although, conventional breeding programs face several constraints such as the long gen-eration time, the polygenic regulation of many adaptive and growth traits, and the large and complex genome of this plant species [13,24].…”

Integrating environmental gradients into breeding: application of genomic reactions norms in a perennial species

“…However, these benefits of forest plantation will require the adaptation of forest to a new, more challenging climate (Allen et al ., 2010; Pawson et al ., 2013; Payn et al ., 2015) One of the major levers for ensuring sustainable wood productivity for forest plantations will be the deployment of trees capable of maintaining high growth rates even in extreme environments. To meet this goal, the integration of phenotypic plasticity, which is defined as the ability of a genotype to produce different phenotypes in different environmental conditions (Bradshaw, 1965), is becoming a major issue in forest tree breeding programs (Ray et al ., 2022). A genotype is considered here as a unique genetic combination found in a single individual, or in several vegetative copies genetically identical.…”