Warming increases the sensitivity of seedling growth capacity to rainfall in six temperate deciduous tree species.

Vikki L Rodgers,Nicholas G Smith,Jeffrey S Dukes,Susanne S Hoeppner

doi:10.1093/aobpla/ply003

Abstract

Predicting the effects of climate change on tree species and communities is critical for understanding the future state of our forested ecosystems. We used a fully factorial precipitation (three levels; ambient, -50 % ambient, +50 % ambient) by warming (four levels; up to +4 °C) experiment in an old-field ecosystem in the northeastern USA to study the climatic sensitivity of seedlings of six native tree species. We measured whole plant-level responses: survival, total leaf area (TLA), seedling insect herbivory damage, as well as leaf-level responses: specific leaf area (SLA), leaf-level water content (LWC), foliar nitrogen (N) concentration, foliar carbon (C) concentration and C:N ratio of each of these deciduous species in each treatment across a single growing season. We found that canopy warming dramatically increased the sensitivity of plant growth (measured as TLA) to rainfall across all species. Warm, dry conditions consistently reduced TLA and also reduced leaf C:N in four species (Acer rubrum, Betula lenta, Prunus serotina, Ulmus americana), primarily as a result of reduced foliar C, not increased foliar N. Interestingly, these conditions also harmed the other two species in different ways, increasing either mortality (Populus grandidentata) or herbivory (Quercus rubra). Specific leaf area and LWC varied across species, but did not show strong treatment responses. Our results indicate that, in the northeastern USA, dry years in a future warmer environment could have damaging effects on the growth capacity of these early secondary successional forests, through species-specific effects on leaf production (total leaves and leaf C), herbivory and mortality.

Highlights

Climate change is warming air temperatures and shifting precipitation patterns (IPCC 2013; Dai 2013), which will increasingly affect the growth of tree seedlings, leading to long-term changes in the composition and productivity of forests
Predicting the effects of climate change on species composition and quantifying how individual tree species respond to climate variability is critical for understanding the future state of our forested ecosystems (Walther et al 2002; Parmesan and Yohe 2003; Chen et al 2011; Sittaro et al 2017)
Total leaf area Total leaf area was reduced by 83 % under the combination of reduced precipitation and warming as compared to controls

Summary

Introduction

Climate change is warming air temperatures and shifting precipitation patterns (IPCC 2013; Dai 2013), which will increasingly affect the growth of tree seedlings, leading to long-term changes in the composition and productivity of forests. Many of these changes will be consequences of species- and age-specific sensitivities (Martínez-Vilalta and Lloret 2016). Studies have shown that plant tolerances and responses to climatic conditions change over the course of development (Cavender-Bares and Bazzaz 2000; Fisichelli et al 2014). Some adult trees may be predicted to persist through dramatic shifts in the climate, tree species ranges will eventually contract where tree regeneration fails (Bell et al 2014)

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