Silicon Affects Plant Stoichiometry and Accumulation of C, N, and P in Grasslands.

Qian Hao,Changxun Yu,Shilei Yang,Hongyan Liu,Guozheng Hu,Zichuan Li,Fan Ding,Zhaoliang Song

doi:10.3389/fpls.2020.01304

Abstract

Silicon (Si) plays an important role in improving soil nutrient availability and plant carbon (C) accumulation and may therefore impact the biogeochemical cycles of C, nitrogen (N), and phosphorus (P) in terrestrial ecosystems profoundly. However, research on this process in grassland ecosystems is scarce, despite the fact that these ecosystems are one of the most significant accumulators of biogenic Si (BSi). In this study, we collected the aboveground parts of four widespread grasses and soil profile samples in northern China and assessed the correlations between Si concentrations and stoichiometry and accumulation of C, N, and P in grasses at the landscape scale. Our results showed that Si concentrations in plants were significantly negatively correlated (p < 0.01) with associated C concentrations. There was no significant correlation between Si and N concentrations. It is worth noting that since the Si concentration increased, the P concentration increased from less than 0.10% to more than 0.20% and therefore C:P and N:P ratios decreased concomitantly. Besides, the soil noncrystalline Si played more important role in C, N, and P accumulation than other environmental factors (e.g., MAT, MAP, and altitude). These findings indicate that Si may facilitate grasses in adjusting the utilization of nutrients (C, N, and P) and may particularly alleviate P deficiency in grasslands. We conclude that Si positively alters the concentrations and accumulation of C, N, and P likely resulting in the variation of ecological stoichiometry in both vegetation and litter decomposition in soils. This study further suggests that the physiological function of Si is an important but overlooked factor in influencing biogeochemical cycles of C and P in grassland ecosystems.

Highlights

Silicon (Si) is the second most abundant element in the Earth’s crust but the beneficial function of this element for plants was overlooked until studies found that Si is actively taken up by many plants (Epstein, 1994; Carey and Fulweiler, 2012; Ma and Yamaji, 2015)
Our analysis showed that N:P stoichiometry decreased with an increasing Si concentration (Figure 2F), suggesting that Si may partly enable plants to govern the nutrient balance and alleviate P deficiency in the grasslands of northern China
Results showed that C concentrations in aboveground grass tissues were significantly negatively correlated with Si concentrations (0.23% to 2.27%)

Summary

Introduction

Silicon (Si) is the second most abundant element in the Earth’s crust but the beneficial function of this element for plants was overlooked until studies found that Si is actively taken up by many plants (Epstein, 1994; Carey and Fulweiler, 2012; Ma and Yamaji, 2015). After being absorbed by plants dissolved Si is deposited as amorphous SiO2 (or phytoliths) in plant tissues (Ma and Yamaji, 2006; Cooke and Leishman, 2016), while less Si binds to semicellulose of the cell, potentially improving the strength and rigidity of plants (Broadley et al, 2012; He et al, 2015) This physiological function of Si enhances plant resistance against abiotic stresses such as drought and salt environments (Hattori et al, 2005; Liang et al, 2007; Rios et al, 2017) and biotic stresses including plant pathogens and insect pests (Ma, 2004). Most of these studies were carried out in farmlands in either pot or field experiments and comprehensive investigations of natural ecosystems are still lacking

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Discussion

Conclusion