Abstract
The occlusion of carbon (C) by phytoliths, the recalcitrant silicified structures deposited within plant tissues, is an important persistent C sink mechanism for croplands and other grass-dominated ecosystems. By constructing a silica content-phytolith content transfer function and calculating the magnitude of phytolith C sink in global croplands with relevant crop production data, this study investigated the present and potential of phytolith C sinks in global croplands and its contribution to the cropland C balance to understand the cropland C cycle and enhance long-term C sequestration in croplands. Our results indicate that the phytolith sink annually sequesters 26.35±10.22 Tg of carbon dioxide (CO2) and may contribute 40±18% of the global net cropland soil C sink for 1961–2100. Rice (25%), wheat (19%) and maize (23%) are the dominant contributing crop species to this phytolith C sink. Continentally, the main contributors are Asia (49%), North America (17%) and Europe (16%). The sink has tripled since 1961, mainly due to fertilizer application and irrigation. Cropland phytolith C sinks may be further enhanced by adopting cropland management practices such as optimization of cropping system and fertilization.
Highlights
Present understanding of the global carbon (C) cycle and climate feedbacks is limited by uncertainty over terrestrial C balance [1,2,3,4,5]
Distribution of Phytolith-occluded C (PhytOC) in Dominant Arable Crops The global area of croplands is 1532.6 106 hm2, about half of which is covered by cereals (Table 1)
The phytolith C sinks generated by rice, wheat and maize (6.6061.99, 4.9362.30 and 6.1462.46 Tg CO2 yr21, respectively) are much higher than other crops
Summary
Present understanding of the global carbon (C) cycle and climate feedbacks is limited by uncertainty over terrestrial C balance [1,2,3,4,5]. As one of the largest terrestrial ecosystems deeply influenced by human activities, the croplands cover an area of 15.336108 hm globally and may play a significant role in terrestrial C balance [3,6]. PhytOC is highly resistant against decomposition [18,23,24,25] and may accumulate in soil for several thousands of years after plant decomposition [18], demonstrating the potential of phytoliths in the long-term biogeochemical sequestration of atmospheric carbon dioxide (CO2) [5,26]. The present and potential of global cropland phytolith C sink have not been revealed
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