Ecological memory and regional context influence performance of adaptation plantings in northeastern US temperate forests

Abstract

1. Species distribution models predict shifts in forest habitat in response to warming temperatures associated with climate change, yet tree migration rates lag climate change, leading to misalignment of current species assemblages with future climate conditions. Forest adaptation strategies have been proposed to deliberately adjust species composition by planting climate-suitable species. Practical evaluations of adaptation plantings are limited, especially in the context of ecological memory or extreme climate events.2. In this study, we examined the 3-year survival and growth response of future climateadapted seedling transplants within operational-scale silvicultural trials across temperate forests in the northeastern US. Nine species were selected for evaluation based on projected future importance under climate change and potential functional redundancy with species currently found in these ecosystems. We investigated how adaptation planting type ('population enrichment' vs. 'assisted range expansion') and local site conditions reinforce interference interactions with existing vegetation at filtering adaptation strategies focused on transitioning forest composition.3. Our results show the performance of seedling transplants is based on species (e.g. functional attributes and size), the strength of local competition (e.g. ecological memory) and adaptation planting type, a proxy for source distance. These findings were consistent across regional forests but modified by site-specific conditions such as browse pressure and extreme climate events, namely drought and spring frost events. Synthesis and applications.Our results highlight that managing forests for shifts in future composition represents a promising adaptation strategy for incorporating new species and functional traits into contemporary forests. Yet, important barriers remain for the establishment of future climate-adapted forests that will most likely require management intervention. Nonetheless, the broader applicability of our findings demonstrates the potential for adaptation plantings to serve as strategic source nodes for the establishment of future climate-adapted species across functionally connected landscapes.

Seedbed not rescue effect buffer the role of extreme precipitation on temperate forest regeneration

“…Subsequently, this relationship is again modified by seed functional traits whereby differences in seedling survival are unaffected under mesic moisture regimes, but profoundly reduced for species with smaller seed masses relative to nursery transplants. These results are important when considered in the context of natural recruitment dynamics of forests under climate change relative to recent efforts to plant seedlings to enhance forest carbon stocks (e.g., reforestation, afforestation; Domke et al, 2020) or adapt species to shifting ranges (e.g., assisted migration; Clark et al, 2021;Palik et al, 2022). By testing sown seeds (analogous to natural regeneration), our results showed that future precipitation regimes may filter the germination and survival response for certain species (and traits), although these differences are less apparent for planted nursery stock.…”

Operationalizing forest‐assisted migration in the context of climate change adaptation: Examples from the eastern USA

“…Four‐year survival of species planted in gaps (0.1 and 0.4 ha, combined results) to transition the composition of three forest types in New England, USA, to future conditions. The northern hardwood site is located on the Second College Grant (SCG), NH as part of the Adaptive Silviculture for Climate Change (ASCC) (Clark et al, 2021). Additional forest‐assisted migration (FAM) replicates include a spruce–fir–northern hardwood forest in Wolcott, VT (WOL) and a rich northern hardwoods forest in Washington, VT (WASH), USA.…”

“…Essentially, this process revolves around (1) planning for uncertainty by considering how the use of FAM within the climate adaptive strategies of resistance, resilience, and transition may support management goals, (2) assessing the specific application of FAM within a F I G U R E 5 Four-year survival of species planted in gaps (0.1 and 0.4 ha, combined results) to transition the composition of three forest types in New England, USA, to future conditions. The northern hardwood site is located on the Second College Grant (SCG), NH as part of the Adaptive Silviculture for Climate Change (ASCC) (Clark et al, 2021). Additional forest-assisted migration (FAM) replicates include a spruce-fir-northern hardwood forest in Wolcott, VT (WOL) and a rich northern hardwoods forest in Washington, VT (WASH), USA.…”

“…Although differences in survivorship are apparent (Figure 5), one of the primary controls on seedling performance was vegetative competition (Clark et al, 2021). While climate models suggest that many species in this region will require FAM, clear biological barriers still inhibit efforts to transition forest composition.…”

“…Concepts, policies, and decision‐making frameworks for use of FAM have been reviewed extensively over the last decade (e.g., Park & Talbot, 2018; Pedlar et al, 2012; Williams & Dumroese, 2013), with potential outcomes of FAM primarily explored with modeling (e.g., Duveneck & Scheller, 2015; Gray & Hamann, 2013), or inferred from examinations of provenance trials spanning a range of climate conditions (e.g., Aitken et al, 2008). Until recently, however, there have been few published examples that illustrate how to incorporate FAM into climate change adaptation strategies at sufficiently large, operational scales that are translatable to forest conservation and management strategies (Clark et al, 2021; Etterson et al, 2020; Muller et al, 2019; Young et al, 2020). A lack of operational‐scale implementation of FAM, where we define operational as the practice being applied in actual forest management projects, rather than strictly in a research setting, likely reflects the inexperience of forest managers and conservation biologists with the concept, a belief that FAM carries too high a risk (Findlater et al, 2021), a perceived lack of social license to pursue FAM broadly (Neff & Larson, 2014), and strong adherence to the precautionary principle (Ricciardi & Simberloff, 2009).…”