Phenotypic plasticity facilitates resistance to climate change in a highly variable environment

Abstract

Increased summer drought will exacerbate the regeneration of many tree species at their lower latitudinal and altitudinal distribution limits. In vulnerable habitats, introduction of more drought-tolerant provenances or species is currently considered to accelerate tree species migration and facilitate forest persistence. Trade-offs between drought adaptation and growth plasticity might, however, limit the effectiveness of assisted migration, especially if introductions focus on provenances or species from different climatic regions. We tested in a common garden experiment the performance of Pinus sylvestris seedlings from the continental Central Alps under increased temperatures and extended spring and/or summer drought, and compared seedling emergence, survival and biomass allocation to that of P. sylvestris and closely related Pinus nigra from a Mediterranean seed source. Soil heating had only minor effects on seedling performance but high spring precipitation doubled the number of continental P. sylvestris seedlings present after the summer drought. At the same time, twice as many seedlings of the Mediterranean than the continental P. sylvestris provenance were present, which was due to both higher emergence and lower mortality under dry conditions. Both P. sylvestris provenances allocated similar amounts of biomass to roots when grown under low summer precipitation. Mediterranean seedlings, however, revealed lower phenotypic plasticity than continental seedlings under high precipitation, which might limit their competitive ability in continental Alpine forests in non-drought years. By contrast, high variability in the response of individual seedlings to summer drought indicates the potential of continental P. sylvestris provenances to adapt to changing environmental conditions.

Constraints to and conservation implications for climate change adaptation in plants

“…Conversely, reciprocal transplant experiments of grassland species along an elevational gradient showed no indication of local adaptation, with consistent advanced reproductive phenology due to plasticity observed in all three species studied (Frei et al 2014). Plasticity has also been demonstrated to assist Pinus species growth and survival under a warmer, drier climate (Richter et al 2012). However, their findings were based on early seedling growth and the effectiveness of adaptive plastic responses in trees over the long term is unknown.…”

Root architecture might account for contrasting establishment success of Pseudotsuga menziesii var. menziesii and Pinus sylvestris in Central Europe under dry conditions

“…The mesocosms were filled with 30 cm of sand and gravel from the local Rhone riverbed (subsoil), covered by 15 cm of humus (Oekohum GmbH, Herrenhof, Switzerland; topsoil), similar to the two-layered forest soils of the Rhone valley with a parent material horizon and an organic surface horizon (Richter et al 2012). All mesocosms were shaded with white knitted polypropylene shade cloth that blocked out 22 % of the sunlight, generating light to medium shade conditions optimal for Pseudotsuga menziesii seedling establishment (Brodie and DeBell 2013;Mailly and Kimmins 1997).…”

“…In particular, Central Alpine populations are known for their high phenotypic plasticity, which enables them to grow in changing environments (Richter et al 2012). Nevertheless, Pinus sylvestris has suffered high mortality in dry Alpine valleys after the exceptional summer drought in 2003, for instance in the Valais, Switzerland (Bigler et al 2006;Rigling et al 2013) and the Aosta valley, Italy (Vacchiano et al 2012).…”

Fine-scale spatial patterns of the Tertiary relict Zelkova abelicea (Ulmaceae) indicate possible processes contributing to its persistence to climate changes

“…Herbivory should therefore be considered in conservation planning as well, mainly by promoting controlled grazing as a management tool in some selected cases rather than favoring their complete removal by fencing. Generally, morphological and reproductive plasticity could possibly represent an advantageous strategy to track changing conditions due to disturbance, in particular mosaic disturbance (Valladares and Gianoli 2007;Keppel et al 2012) which characterizes Mediterranean refugia, and further facilitate resistance to climate change in highly variable environments (Richter et al 2012). Noteworthy in this context, fencing of the Psiloritis population (Rouvas forest) has proven unsuccessful as heavy snow has partially destroyed the fences, and as local shepherds do not prevent their animals from entering fenced areas.…”