Effects of litter quality and soil enzyme activity on litter decomposition rate in typical grassland subject to nitrogen addition

doi:10.11686/cyxb2019417

Abstract

Abstract: Global atmospheric nitrogen (N) deposition has increased in recent years, affecting key processes of the carbon (C) cycle in terrestrial ecosystems. Litter decomposition is one of the key processes in the carbon cycle. We conducted a litter bag experiment at N addition rates ranging from 0 to 25 g·m^-2·yr^-1 in the typical temperate grasslands of Inner Mongolia. The effects of N addition on decomposition of litter samples were investigated by measuring the decomposition rate, quality index and soil enzyme activity of litter in different stages of decomposition. Our results showed that dry weight loss of litter mainly occurs in the growing season, which accounts for 91.3% of the total mass loss. N addition increased the rate of dry weight loss in the growing season, while decreasing the rate of dry weight loss in the non-growing season. N addition promoted litter decomposition by increasing the activity of β-glucosidase and reducing the content of cellulose and tannin in the first growing season. In the first non-growing season, low-N treatments enhanced urease activity, decreased lignin:N ratio, and accelerated decomposition, while high-N treatments inhibited the activity of polyphenol oxidase, thereby reducing the decomposition rate of lignin. High-N treatment promoted leucine aminopeptidase activity, improved N:P ratio, and facilitated the decomposition of litter in the second growing season. During the whole decomposition process, N addition reduced the content of tannin and cellulose, while showing a trend toward increased lignin content. This result may indicate that during decomposition, litter C showed a release pattern while phosphorus showed an immobilization-release pattern. In addition, the contents of calcium, manganese and N in litter increased with the progression of decomposition, showing an enrichment phenomenon. Our results indicate that the quality of litter samples and soil enzyme activity were the main factors influencing litter decomposition, and the dominant factors differ at different stages of the decomposition process. These results will provide a theoretical basis for understanding of the key processes of the grassland carbon cycle under different levels of N deposition in the future.

Key words: grassland ecosystem, N addition, litter decomposition, litter quality, soil enzyme

YUE Ke-xin, GONG Ji-rui, YU Shang-yuan, BAOYIN Taogetao, YANG Bo, WANG Biao, ZHU Chen-chen, ZHANG Zi-he, SHI Jia-yu. Effects of litter quality and soil enzyme activity on litter decomposition rate in typical grassland subject to nitrogen addition[J]. Acta Prataculturae Sinica, 2020, 29(6): 71-82.

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