Root exudation of mature beech forests across a nutrient availability gradient: the role of root morphology and fungal activity

Root exudation is a key plant function with a large influence on soil organic matter dynamics and plant–soil feedbacks in forest ecosystems. Yet despite its importance, the main ecological drivers of root exudation in mature forest trees remain to be identified. During two growing seasons, we analyz...

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Bibliographic Details
Published in:The New phytologist 2020-04, Vol.226 (2), p.583-594
Main Authors: Meier, Ina C., Tückmantel, Timo, Heitkötter, Julian, Müller, Karolin, Preusser, Sebastian, Wrobel, Thomas J., Kandeler, Ellen, Marschner, Bernd, Leuschner, Christoph
Format: Article
Language:English
Subjects:
Acidic soils
Availability
Bedrock
Beech
Bioavailability
Biomass
carbon release
Ecosystem
extracellular soil enzymes
Exudates
Exudation
Fagus
Fagus sylvatica
Fagus sylvatica (European beech)
Forest ecosystems
Forests
Fungi
Mineral nutrients
Morphology
Nitrogen
nitrogen availability
Nutrient availability
Nutrients
Organic matter
Organic soils
Plant Roots
rhizodeposition
Soil
Soil chemistry
Soil dynamics
Soil organic matter
Soil pH
Soils
specific root length
Terrestrial ecosystems
Trees
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Summary:Root exudation is a key plant function with a large influence on soil organic matter dynamics and plant–soil feedbacks in forest ecosystems. Yet despite its importance, the main ecological drivers of root exudation in mature forest trees remain to be identified. During two growing seasons, we analyzed the dependence of in situ collected root exudates on root morphology, soil chemistry and nutrient availability in six mature European beech (Fagus sylvatica L.) forests on a broad range of bedrock types. Root morphology was a major driver of root exudation across the nutrient availability gradient. A doubling of specific root length exponentially increased exudation rates of mature trees by c. 5-fold. Root exudation was also closely negatively related to soil pH and nitrogen (N) availability. At acidic and N-poor sites, where fungal biomass was reduced, exudation rates were c. 3-fold higher than at N- and base-richer sites and correlated negatively with the activity of enzymes degrading less bioavailable carbon (C) and N in the bulk soil. We conclude that root exudation increases on highly acidic, N-poor soils, in which fungal activity is reduced and a greater portion of the assimilated plant C is shifted to the external ecosystem C cycle.
ISSN:0028-646X
1469-8137
DOI:10.1111/nph.16389