Hou Longyu, Liu Yan, Du Jiancai, Wang Mingya, Wang Hui, Mao Peisheng
Forage Seed Lab, China Agricultural University, Beijing Key Laboratory of Grassland Science, Beijing 100193, China.
State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China.
Sci Rep. 2016 Jul 1;6:29028. doi: 10.1038/srep29028.
Grassland ecosystems play a critical role in regulating CO2 fluxes into and out of the Earth's surface. Whereas previous studies have often addressed single fluxes of CO2 separately, few have addressed the relation among and controls of multiple CO2 sub-fluxes simultaneously. In this study, we examined the relation among and controls of individual CO2 fluxes (i.e., GEP, NEP, SR, ER, CR) in three contrasting temperate steppes of north China, as affected by livestock grazing. Our findings show that climatic controls of the seasonal patterns in CO2 fluxes were both individual flux- and steppe type-specific, with significant grazing impacts observed for canopy respiration only. In contrast, climatic controls of the annual patterns were only individual flux-specific, with minor grazing impacts on the individual fluxes. Grazing significantly reduced the mean annual soil respiration rate in the typical and desert steppes, but significantly enhanced both soil and canopy respiration in the meadow steppe. Our study suggests that a reassessment of the role of livestock grazing in regulating GHG exchanges is imperative in future studies.
草原生态系统在调节地球表面二氧化碳通量的进出方面发挥着关键作用。以往的研究往往分别探讨二氧化碳的单一通量，很少同时研究多种二氧化碳子通量之间的关系及其控制因素。在本研究中，我们考察了中国北方三种不同温带草原中各二氧化碳通量（即总生态系统生产力、净生态系统生产力、土壤呼吸、生态系统呼吸、冠层呼吸）之间的关系及其控制因素，这些草原受放牧影响。我们的研究结果表明，二氧化碳通量季节模式的气候控制对于每种通量和草原类型都是特定的，仅在冠层呼吸方面观察到显著的放牧影响。相比之下，年模式的气候控制仅针对每种通量是特定的，放牧对各通量的影响较小。放牧显著降低了典型草原和荒漠草原的年均土壤呼吸速率，但显著提高了草甸草原的土壤呼吸和冠层呼吸。我们的研究表明，在未来的研究中，必须重新评估放牧在调节温室气体交换中的作用。
