Underlying mechanism on source-sink carbon balance of grazed perennial grass during regrowth: Insights into optimal grazing regimes of restoration of degraded grasslands in a temperate steppe

Zihe Zhang; Jirui Gong; Xiaobing Li; Yong Ding; Biao Wang; Jiayu Shi; Min Liu; Bo Yang

doi:10.1016/j.jenvman.2020.111439

Underlying mechanism on source-sink carbon balance of grazed perennial grass during regrowth: Insights into optimal grazing regimes of restoration of degraded grasslands in a temperate steppe

J Environ Manage. 2021 Jan 1:277:111439. doi: 10.1016/j.jenvman.2020.111439. Epub 2020 Oct 6.

Authors

Zihe Zhang¹, Jirui Gong², Xiaobing Li³, Yong Ding⁴, Biao Wang⁵, Jiayu Shi⁶, Min Liu⁷, Bo Yang⁸

Affiliations

¹ Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: 201931051070@mail.bnu.edu.cn.
² Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: jrgong@bnu.edu.cn.
³ Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: xbli@bnu.edu.cn.
⁴ Grassland Research Institute, Chinese Academy of Agricultural Sciences, 120 Ulanqab East Street, Saihan District, Hohhot, Inner Mongolia, 010021, China. Electronic address: dingyong228@126.com.
⁵ Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: wangbiao@mail.bnu.edu.cn.
⁶ Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: 201831051069@mail.bnu.edu.cn.
⁷ Key Laboratory of Tourism and Resources Environment, Taishan University, Tai'an, Shandong province, 271021, China. Electronic address: liumin@tsu.edu.cn.
⁸ Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China. Electronic address: 201631190013@mail.bnu.edu.cn.

PMID: 33035939
DOI: 10.1016/j.jenvman.2020.111439

Abstract

Overgrazing is the main driver of grassland degradation and productivity reduction in northern China. The restoration of degraded grasslands depends on optimal grazing regimes that modify the source-sink balance to promote best carbon (C) assimilation and allocation, thereby promoting rapid compensatory growth of the grazed plants. We used in situ¹³CO₂ labeling and field regrowth studies of Stipa grandis P.A. Smirn.to examine the effects of different grazing intensities (light, medium, heavy, and grazing exclusion) on photosynthetic C assimilation and partitioning, on reallocation of non-structural carbohydrates during regrowth, and on the underlying regulatory mechanisms. Light grazing increased the sink demand of newly expanded leaves and significantly promoted ¹³C fixation by increasing the photosynthetic capacity of the leaves and accelerating fructose transfer from the stem. Although C assimilation decreased under medium and heavy grazing, S. grandis exhibited a tolerance strategy that preferentially allocated more starch and ¹³C to the roots for storage to balance sink competition between newly expanded leaves and the roots. Sucrose phosphate synthase (SPS), sucrose synthase (SS), and other plant hormones regulated source-sink imbalances during regrowth. Abscisic acid promoted accumulation of aboveground biomass by stimulating stem SPS activity, whereas jasmonate increased root starch synthesis, thereby increasing belowground biomass. Overall, S. grandis could optimize source-sink relationships and above- and belowground C allocation to support regrowth after grazing by the regulating activities of SPS, SS and other hormones. These results provide new insights into C budgets under grazing and guidance for sustainable grazing management in semi-arid grasslands.

Keywords: (13)C labeling; C assimilation; C partitioning; Grazing response; Regrowth; Stipa grandis.

MeSH terms

Biomass
Carbon* / analysis
China
Grassland
Poaceae*

Substances

Carbon