Grazing weakens temporal stabilizing effects of diversity in the Eurasian steppe |
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| Authors: | Haiyan Ren Friedhelm Taube Claudia Stein Yingjun Zhang Yongfei Bai Shuijin Hu |
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| Affiliation: | 1. College of Agro‐grassland Science, College of Prataculture Science, Nanjing Agricultural University, Nanjing, China;2. Institute of Crop Science and Plant Breeding‐Grass and Forage Science, Christian‐Albrechts‐University, Kiel, Germany;3. Tyson Research Center and Department of Biology, Washington University St. Louis, St. Louis, MO, USA;4. Department of Grassland Science, China Agricultural University, Beijing, China;5. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China;6. College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China;7. Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA |
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| Abstract: | Many biodiversity experiments have demonstrated that plant diversity can stabilize productivity in experimental grasslands. However, less is known about how diversity–stability relationships are mediated by grazing. Grazing is known for causing species losses, but its effects on plant functional groups (PFGs) composition and species asynchrony, which are closely correlated with ecosystem stability, remain unclear. We conducted a six‐year grazing experiment in a semi‐arid steppe, using seven levels of grazing intensity (0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep per hectare) and two grazing systems (i.e., a traditional, continuous grazing system during the growing period (TGS), and a mixed one rotating grazing and mowing annually (MGS)), to examine the effects of grazing system and grazing intensity on the abundance and composition of PFGs and diversity–stability relationships. Ecosystem stability was similar between mixed and continuous grazing treatments. However, within the two grazing systems, stability was maintained through different pathways, that is, along with grazing intensity, persistence biomass variations in MGS, and compensatory interactions of PFGs in their biomass variations in TGS. Ecosystem temporal stability was not decreased by species loss but rather remain unchanged by the strong compensatory effects between PFGs, or a higher grazing‐induced decrease in species asynchrony at higher diversity, and a higher grazing‐induced increase in the temporal variation of productivity in diverse communities. Ecosystem stability of aboveground net primary production was not related to species richness in both grazing systems. High grazing intensity weakened the temporal stabilizing effects of diversity in this semi‐arid grassland. Our results demonstrate that the productivity of dominant PFGs is more important than species richness for maximizing stability in this system. This study distinguishes grazing intensity and grazing system from diversity effects on the temporal stability, highlighting the need to better understand how grazing regulates ecosystem stability, plant diversity, and their synergic relationships. |
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| Keywords: | diversity– stability relationship grazing intensity plant diversity plant functional groups semi‐arid steppe species asynchrony temporal stability |
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