**Author details**

*Plant Communities and Their Environment*

succession stage.

**5. Conclusion**

community levels.

the early 1980s.

**Acknowledgements**

explained the differences of decomposition rates between them. As the dominant species in late succession stage of grassland, C:N ratio of *S. przewalskyi* litters did not show a lower value as predicted from other studies [51], possibly due to the divergences of climate and species between two regions. C:N ratio has been proven to be negatively correlated with decomposition rate. Besides, the lower k-value after 2 years' decomposition process could be explained by the increased C:N ratio of leaf litters. Compared with nutrient concentrations, nutrient accumulation indices indicated that C, N and P were all mineralised into soils during the decomposition process. There was no significant difference between species for carbon-releasing pattern. Still, NAI value for C of *S. przewalskyi* was higher than two other *Stipa* species after 2 years' decomposition (**Figure 9**). The lower NAI values for N and P of *S. bungeana* indicated that *S. bungeana* released more N and P to soil than the two other *Stipa* species. From this perspective, replacement of *Stipa* species after long-term grazing exclusion might inhibit nutrient cycling of grassland ecosystem, due to the lower nutrient mineralisation in leaf litters of two *Stipa* species at middle and late

The present study indicated that grazing exclusion induced positive effects on grassland vegetative characteristics, with peak values in the 20th year (2002), and long-term grazing exclusion led to decreased species diversity and biomass and can inhibit grassland renewing due to the litter accumulation. Besides, nutrient cycling in grassland might be slowed down through replacement of dominant species during long-term grazing exclusion. Grassland productivity was more influenced by temperature than precipitation. Results indicated that analysis of productivity responses should account not only for the magnitude of climate variation but also for its timing. Climate warming might prolong/shorten growing season by advancing/delaying onset of greenness of plant community. Warmer winter further decreases ANPP, and impacts of warming in early spring should also be considered in evaluating ANPP variability. Therefore, more scientific attention should be paid to trends in spring phenology and their impacts on productivity at species and

This work was supported by the National Key Research and Development Program of China (2016YFC0500700), National Natural Science Foundation of China (41601586, 41230852, 41701606, 31602004, 31601987, 41601053), Deployment Program of the Chinese Academy of Sciences (KJZD-EW-TZ-G10), Technical System of Modern Forage Industry of the Ministry of Agriculture (CARS-35-40) and Key Cultivation Project of the Chinese Academy of Sciences—the promotion and management of ecosystem functions of restored vegetation on the Loess Plateau, China. We thank the staff at the management bureau of Yunwu Mountain National Nature Reserve for fieldworks and weather data collection since

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Jimin Cheng1,2, Wei Li1,2\*, Jishuai Su3 , Liang Guo1,2, Jingwei Jin1,2 and Chengcheng Gang1,2

1 Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China

2 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, China

3 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China

\*Address all correspondence to: liwei2013@nwsuaf.edu.cn

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
