Assessing production of phytolith and phytolith occluded carbon in above-ground biomass of intensively cultivated rice ecosystems in India

摘要

Carbon (C) occluded in phytoliths is stable and an important source of long-term C storage into the agroecosystems. As a silicon (Si) accumulator crop, rice produces a large amount of phytolith occluded carbon (PhytOC) and which plays a crucial role in the coupled biogeochemical cycle of C and Si. In this study, we sampled above ground biomass from 22 intensively cultivated rice ecosystems to evaluate the rate of C sequestration through phytoliths. Depending on the rice varieties there exist a great variability in PhytOC content (0.12-0.26%) across the rice ecosystems. The collected samples were further classified into three groups: viz., long (140 days), medium (125-140 days) and short duration (125 days). The above-ground net primary productivity (ANPP) varied from 5174 to 13,394 kg ha(-1) and recorded significantly (p 0.05) higher in the relatively long duration variety compared to medium and short duration variety. The collected rice varieties showed a strong positive correlation (p 0.05, R-2 = 0.45) between ANPP and crop duration. With the increase in varietal duration, phytolith content was non-significant (p 0.05) whereas, the PhytOC content found to be significant (p 0.05). The long-duration (140 days) varieties showed 69.7% and 164.0% higher PhytOC sequestration flux over medium and short-duration varieties, respectively. Our results suggest that the Indian rice ecosystems sequester 0.95 Tg CO2 yr(-1) through Phytoliths, which is equivalent to the 15.5% of PhytOC sink in the global rice field. Considering the PhytOC flux of relatively higher PhytOC accumulating long duration varieties, the annual PhytOC sink rate in the Indian rice ecosystems can be increased to similar to 4 folds over the current rate. It was revealed that the selection of higher PhytOC accumulating long duration varieties can enhance the phytolith C sequestration.