Abiotic and biotic factors controlling fine root biomass, carbon and nutrients in closed-canopy hybrid poplar stands on post-agricultural land

Julien Fortier,Daniel Gagnon,France Lambert,Benoit Truax

doi:10.1038/s41598-019-42709-6

Julien Fortier, Daniel Gagnon + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-42709-6

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Abstract

Fine roots (diameter <2 mm) have a pivotal role in resource acquisition, symbiosis development, and for elemental cycling in forests. Various abiotic and biotic factors affect their biomass and nutrient content. Understanding the effect of these factors on root traits could improve biogeochemical modelling, nutrient management and ecosystem services provision in planted forests. Data from 14-year old poplars planted along a fertility/climatic gradient in Southeastern Canada, show that live fine root biomass varied with genotype and environment, was negatively correlated to soil fertility, and uncorrelated to tree size. Dead fine root biomass varied with genotype and peaked during fall and in colder environments with slower element cycling. Root chemistry also varied with environment, genotype and season. The genotype producing recalcitrant leaf litter had the highest root biomass, suggesting a compensation strategy. Along the studied gradient, plasticity level observed for some root traits (biomass, element contents) was genotype-specific and high for some genotypes. Regionally, such plasticity patterns should be considered in elemental budgets, for nutrient management and ecosystem services provision in plantations (carbon storage, nutrient retention). The small inter-site aboveground productivity differences observed suggest that plasticity in fine root growth may contribute to overcome nutrient limitations on less fertile marginal lands.

Highlights

Worldwide, approximately 8.6 million ha are planted with fast-growing poplars for timber production and environmental protection[1]
Limited and inconsistent information exists about the effect of soil fertility, and of other environmental and genetic factors, on fine root biomass of planted poplars[8]
Previous field studies with planted poplars have reported different conclusions related to the effect of abiotic and biotic factors on fine root biomass[35,36,37,38,40,41]

Summary

Introduction

Approximately 8.6 million ha are planted with fast-growing poplars for timber production and environmental protection[1]. Limited and inconsistent information exists about the effect of soil fertility, and of other environmental and genetic factors, on fine root biomass of planted poplars[8]. Several abiotic and biotic factors can affect fine root biomass and its nutrient concentrations and contents. In forests, these root traits vary widely between tree species and functional groups[9,13,17,18]. Across different forest biomes, mean basal area and nutrients in leaf litter best predicted fine root biomass[17,20]. In fast-growing poplars, few regional studies have evaluated the effect of abiotic and biotic factors on fine root biomass, nutrient concentrations and contents. Allometric relationships between fine root biomass and aboveground traits were mostly observed in younger plantations[10,25], probably because fine root biomass of many species only increases until canopy closure, and afterward remains constant and uncoupled with aboveground growth[18]

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