Moderate grazing increases newly assimilated carbon allocation belowground

Newly assimilated carbon (C) allocated to soil is the main source of C and energy for microorganisms and has a high impact on long-term C sequestration. The removal of aboveground plant biomass by grazing may increase, decrease or have no effects on belowground C allocation. Therefore, it is important to understand how grazing modifies the allocation of assimilates between above- and belowground. An in situ 13C labeling experiment was carried out in a temperate grassland with three grazing intensities: no grazing, moderate grazing (6 sheep·ha−1) and heavy grazing (9 sheep·ha−1). Eighty-one days after 13C labeling, plants under moderate grazing allocated more recently assimilated C (8.2% of assimilated 13C) to shoots than plants under no grazing and heavy grazing (5.5% each). Substantially more 13C was allocated belowground under moderate grazing, and was mainly stored in roots (11%) and soil (15%), than under no grazing (3.2% in roots and 7.5% in soil) and heavy grazing (4.1% in roots and 6.9% in soil). Moderate and heavy grazing release less 13CO2 (15%) through root and rhizomicrobial respiration than no grazing (19%). Without grazing, the decomposition rate of rhizodeposits and their utilization for root and rhizomicrobial respiration (0.22 ± 0.07 day−1) was much faster than that under grazing (moderate grazing: 0.050 ± 0.01 day−1, heavy grazing: 0.065 ± 0.01 day−1). In summary, moderate grazing increases the stock and stability of newly assimilated C of soil by increasing belowground allocation of photosynthates and decreasing CO2 efflux from soil. Therefore, compared to without and heavy grazing (9 sheep·ha−1), moderate grazing (6 sheep·ha−1) may be more suitable for soil C sequestration in temperate grasslands. © 2022 Elsevier B.V.

Авторы
Zhao Y.1, 2 , Tian Y.1, 2 , Gao Q.3 , Li X. 1, 2 , Zhang Y. 4 , Ding Y.4 , Ouyang S.1, 2 , Yurtaev A.5 , Kuzyakov Y. 6, 7
Журнал
Издательство
Elsevier B.V.
Язык
Английский
Статус
Опубликовано
Номер
100547
Том
22
Год
2022
Организации
  • 1 State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, 100875, China
  • 2 School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
  • 3 Department of Environmental Sciences, University of Puerto Rico, Rio Piedras, San Juan, PR 00936, United States
  • 4 Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot, 010010, China
  • 5 X-Bio Institute, University of Tyumen, Tyumen, 625003, Russian Federation
  • 6 Agro-Technological Institute, Peoples Friendship University of Russia (RUDN University), Moscow, 117198, Russian Federation
  • 7 Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, University of Goettingen, Göttingen, Germany
Ключевые слова
13C pulse Labeling; Belowground C allocation; Grazing intensity; Land use; Newly assimilated C; Rhizosphere processes; Temperate grassland
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