Low assimilate partitioning to root biomass is associated with carbon losses at an intensively managed temperate grassland
Aims: This study aimed to investigate how efficiently assimilated carbon (C) is incorporated in plant biomass at an intensively managed old permanent grassland, how C is partitioned between shoots and roots and what are the implications for C sequestration. Methods: Using the eddy covariance technique, the atmosphere-biosphere exchange of CO2 was measured for two years at a sandy grassland site in northern Germany. In addition to aboveground net primary production (ANPP), belowground NPP (BNPP) was observed using the ingrowth core method. Results: The grassland showed a high productivity in terms of biomass yield (14.8 Mg dry matter ha−1 yr−1) and net CO2 uptake (−2.82 Mg CO2-C ha−1 yr−1). Photosynthetically assimilated C was converted to biomass with a high carbon use efficiency (CUE) of 71% during the growing season. However, a comparably low fraction of 17% of NPP was allocated to roots (fBNPP). Consequently, the main fraction of NPP was removed during harvest, turning the site into a net source of 0.29 Mg C ha−1 yr−1. Conclusions: Our study showed the flexibility of grass root growth patterns in response to alterations in resource availability. We conclude that highly fertilized grasslands can lose their ability for C sequestration due to low belowground C allocation.
| Main Authors: | , , , , , |
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| Format: | Article/Letter to editor biblioteca |
| Language: | English |
| Subjects: | Black sands, Carbon equilibrium, Carbon partitioning, Eddy covariance, Permanent grasslands, Plant carbon use efficiency, Root growth, |
| Online Access: | https://research.wur.nl/en/publications/low-assimilate-partitioning-to-root-biomass-is-associated-with-ca |
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| Summary: | Aims: This study aimed to investigate how efficiently assimilated carbon (C) is incorporated in plant biomass at an intensively managed old permanent grassland, how C is partitioned between shoots and roots and what are the implications for C sequestration. Methods: Using the eddy covariance technique, the atmosphere-biosphere exchange of CO2 was measured for two years at a sandy grassland site in northern Germany. In addition to aboveground net primary production (ANPP), belowground NPP (BNPP) was observed using the ingrowth core method. Results: The grassland showed a high productivity in terms of biomass yield (14.8 Mg dry matter ha−1 yr−1) and net CO2 uptake (−2.82 Mg CO2-C ha−1 yr−1). Photosynthetically assimilated C was converted to biomass with a high carbon use efficiency (CUE) of 71% during the growing season. However, a comparably low fraction of 17% of NPP was allocated to roots (fBNPP). Consequently, the main fraction of NPP was removed during harvest, turning the site into a net source of 0.29 Mg C ha−1 yr−1. Conclusions: Our study showed the flexibility of grass root growth patterns in response to alterations in resource availability. We conclude that highly fertilized grasslands can lose their ability for C sequestration due to low belowground C allocation. |
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