The overall decomposition of the spring‐lodged litter is faster than the autumn‐lodged litter in a steppe ecosystem

Résumé fourni par la source

In grasslands, a large proportion of senescent plant shoots in autumn pass the winter period as standing dead materials instead of becoming detached litter immediately. However, the information is hardly available on the decomposition of plant standing dead materials during the winter period and its impacts on the subsequent decomposition of these materials after littering in the coming spring. We conducted a two‐year experiment to compare the decomposition process of the litters lodged in autumn versus that lodged in spring of two dominant plant species, Leymus chinensis and Stipa grandis , in a native steppe ecosystem in Inner Mongolia. Throughout the whole decomposition period, the autumn‐lodged litter was directly positioned upon the soil surface, while the spring‐lodged litter suspended as standing dead for the first 7 months in the autumn and winter period before being detached. We found that the overall decomposition rate of spring‐lodged litter was faster than that of autumn‐lodged litter over the experimental period. The decomposition rate was correlated positively with the N content, but negatively with the C/N ratio, lignin concentration and lignin/N ratio in litters. The spring‐lodged litter showed a sharp decrease in lignin remaining during the standing‐dead stage, while the autumn‐lodged litter did not, which suggested an important role played by photodegradation in the breakdown of lignin over the winter period that facilitated the litter decomposition in subsequent stages. These findings highlight the difference in the decomposition rates of the litters lodged in autumn versus in spring, and suggest it important to incorporate the effects of the standing‐dead stage on litter decomposition in calculating or modeling the nutrient turnover rates in semi‐arid steppe ecosystems.

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