Drought and small-bodied herbivores modify nutrient cycling in the semi-arid shortgrass steppe
Drought and small-bodied herbivores modify nutrient cycling in the semi-arid shortgrass steppe
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干旱和小型食草动物改变了半干旱短草草原的养分循环
DOI：
10.1007/s11258-019-00908-1
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发表时间：
2019
期刊：
影响因子：
1.7
通讯作者：
Smith, Melinda D.
中科院分区：
文献类型：
--
作者：
Lemoine, Nathan P.;Smith, Melinda D.
气候变化将在下个世纪增加干旱的频率，对半干旱草原的生态系统功能造成严重后果。短草草原(SGS)经历了陆地生物群中降水量的最大年际变化，并对干旱表现出极高的敏感性。然而，尽管几十年来的研究描述了干旱对SGS生态系统功能的影响，但我们目前对干旱对除氮以外的重要营养物质的生物可获得性的影响、草食动物对这些养分的生物可利用浓度的贡献以及干旱是否改变了草食动物衍生的养分循环的信息很少。为了量化长期干旱和小型食草动物对养分循环和地上净初级生产力(ANPP)的影响，我们在科罗拉多州北部的SGS对降雨量和食草动物的存在进行了因子操纵。具体来说，我们测量了干旱和食草动物对十种重要营养素：铝、钙、铁、钾、镁、锰、硝酸盐、磷、硫和锌的生物有效性的影响。然后，我们将这些营养物质与牧草产量相关联，以确定干旱条件下植物生长减少是否会导致地下营养物质的积累。干旱像预期的那样降低了ANPP，也改变了除N以外的许多营养物质的浓度，N在干旱反应中聚集在一起。相比之下，小型草食动物不影响ANPP或土壤N，但它们确实有助于土壤中两种重要养分PO4-P和S的生物可用浓度。重要的是，干旱一般不会改变草食动物对养分循环的贡献，这表明在半干旱草原上，无论降雨量如何，草食动物可能是生物地球化学循环的关键组成部分。
Climate change will increase the frequency of droughts over the next century, with severe consequences for ecosystem function in semi-arid grasslands. The shortgrass steppe (SGS) experiences some of the largest interannual variation in precipitation among terrestrial biomes and exhibits extremely high sensitivity to drought. Yet despite decades of research describing the consequences of drought for ecosystem function in the SGS, we currently have little information regarding the impact of drought on bioavailability of important nutrients other than nitrogen, the contribution of herbivores to bioavailable concentrations of these nutrients, and whether drought alters herbivore-derived nutrient cycling. To quantify the impacts of long-term drought and small-bodied herbivores on nutrient cycling and aboveground net primary production (ANPP), we factorially manipulated rainfall and herbivore presence in the SGS of northern Colorado. Specifically, we measured the impacts of drought and herbivores on bioavailability of ten important nutrients: aluminum, calcium, iron, potassium, magnesium, manganese, nitrate, phosphorus, sulfur, and zinc. We then correlated these nutrients with grass production to determine whether reduced plant growth under drought conditions causes a belowground buildup of nutrients. Drought reduced ANPP as expected, and also altered concentrations of many nutrients apart from N, which clustered in their drought response. In contrast, small-bodied herbivores did not affect ANPP or soil N. However, they did contribute to the bioavailable soil concentrations of two important nutrients: PO4-P and S. Importantly, drought generally did not modify the contribution of herbivores to nutrient cycling, suggesting that herbivores might be a critical component of biogeochemical cycling regardless of precipitation in semi-arid grasslands.
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