Mass loss and chemical structures of wheat and maize straws in response to ultraviolet-B radiation and soil contact.

Guixiang Zhou,Congzhi Zhang,Lin Chen,Bingzi Zhao,Jiabao Zhang,Xiuli Xin,Jingdong Mao

doi:10.1038/srep14851

Guixiang Zhou, Congzhi Zhang + Show 5 more

Open Access

https://doi.org/10.1038/srep14851

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Abstract

The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14–19% and the ambient radiation by 9–16% for wheat and maize straws without soil contact after 12 months. Elevated UV-B exposure decreased the decomposition rates of both wheat and maize straws when in contact with soil. Light exposure resulted in decreased O-alkyl carbons and increased alkyl carbons for both the wheat and maize straws compared with no-sunlight control. The difference in soil contact may influence the contribution of photodegradation to the overall straw decomposition process. These results indicate that we must take into account the effects of photodegradation when explaining the mechanisms of straw decomposition in mesic ecosystems.

Highlights

Surface, while further facilitating microbial decomposition[9,15]
Compared with wheat straw without either soil contact or sunlight (Block), the mass loss of wheat straw increased by 9% (P < 0 .05) for ambient solar radiation without soil contact (Ambient) and 14% (P < 0 .05) for elevated UV-B exposure without soil contact (UVB) (Fig. 1e)
The results indicated that the role of UV-B radiation in straw mass loss varied among treatments with and without soil contact (Fig. 1) and soil contact influenced straw mass loss to a highly significant degree (P < 0.001, Table 1)

Summary

Introduction

Surface, while further facilitating microbial decomposition[9,15]. Photochemical mineralization is the direct breakdown of litter to CO2 in the absence of microbial activity[11,16], and microbial facilitation is the breakdown of large organic compounds by solar radiation into smaller compounds that can be utilized by microbes[5,14,17]. Barners et al.[22] found that the combination of litter and soil can reduce the direct effect of UV photodegradation and can ameliorate the development of soil-microbial films in the Santa Rita Experimental Range in SE Arizona, USA. This may be due to the fact that soil acts as a vector for microbial colonization, while protecting the microorganisms from high temperatures and desiccation in this ecosystem. The effect of UV-B exposure on litter decomposition depends on the relative contribution of photodegradation and microbial decomposition It is unclear how the difference in soil contact changes the effect of UV-B radiation on straw decomposition, nor is it known how UV-B radiation drives straw degradation. We hypothesized that UV-B exposure would influence straw decomposition, with a dependence on soil contact

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