Key Laboratory of Vegetation Ecology, Ministry of Education, Institute of Grassland Science/School of Environment, Northeast Normal University, Changchun, Jilin, 130024, China.
Eastern Forest Environmental Threat Assessment Center, Southern Research Station, USDA-FS, Research Triangle Park, NC, 27709, USA.
Sci Rep. 2018 Jun 14;8(1):9089. doi: 10.1038/s41598-018-26835-1.
Large herbivores act as a major driver of plant litter decomposition in grasslands. The modifications of soil biotic and abiotic properties, as well as the changes in quality (C/N ratio) of plant litter, are two key pathways by which large herbivores can affect litter decomposition. Yet we know little about the relative role of these two mechanisms in mediating decomposition. Here, by combining a large-scale and a small-scale field manipulative experiment, we examined how livestock (cattle and sheep) grazing affects standing litter decomposition of a dominant grass, Leymus chinensis in grasslands in northeast China. We found that livestock grazing affected litter decay rate both by its influences on soil property (soil moisture, nutrient content, and microbial communities) and on plant litter quality (C/N ratio). Due to their distinct body size and diet preference, cattle and sheep affected soil property and litter quality, thus litter decay rate, differently by causing varying disturbance regimes and by feeding on different dominant species. Our study provides evidence that herbivore grazing can influence litter decomposition by modifying soil conditions and litter quality independently. Therefore, choosing the proper large herbivore(s) in grazing regimes may be important in maintaining nutrient cycling in grassland ecosystems.
大型食草动物是草原植物凋落物分解的主要驱动因素。土壤生物和非生物特性的改变，以及植物凋落物质量（C/N 比）的变化，是大型食草动物影响凋落物分解的两个关键途径。然而，我们对这两种机制在介导分解过程中的相对作用知之甚少。在这里，我们通过结合大规模和小规模野外操作实验，研究了家畜（牛和羊）放牧如何影响中国东北草原中一种主要草种——羊草的地上凋落物分解。我们发现，家畜放牧通过影响土壤性质（土壤水分、养分含量和微生物群落）和植物凋落物质量（C/N 比）来影响凋落物的分解速率。由于牛和羊的体型和食性不同，它们通过造成不同的干扰模式和取食不同的优势种，对土壤性质和凋落物质量产生不同的影响，从而影响凋落物的分解速率。我们的研究提供了证据，表明食草动物放牧可以通过独立改变土壤条件和凋落物质量来影响凋落物分解。因此，在放牧制度中选择适当的大型食草动物可能对维持草原生态系统的养分循环很重要。
