Globally consistent influences of seasonal precipitation limit grassland biomass response to elevated CO2
Globally consistent influences of seasonal precipitation limit grassland biomass response to elevated CO2
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DOI：
10.1038/s41477-018-0356-x
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发表时间：
2019-02-01
期刊：
影响因子：
18
通讯作者：
Langley, J. Adam
中科院分区：
文献类型：
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作者：
Hovenden, Mark J.;Leuzinger, Sebastian;Langley, J. Adam
大气二氧化碳浓度的上升将通过碳同化的生化刺激直接刺激生物质生产，并通过提高植物水分利用效率引起的节水间接刺激生物质生产。由于这些节水作用，CO2施肥效应（CFE）应该在干旱地区更强，但不同实验间草地生物量对CO2升高响应的差异似乎与年降水量无关，因此无法进行有用的推广。结果表明，在19个全球分布的温带草地试验中，CO2浓度升高对生物量产量的影响随着春季以外季节平均降水量的增加而降低，但随着春季平均降水量的增加而意外增加。此外，由于春季降水较多的地点在其他时间也倾向于降水较多，因此春季和非春季降水对CO2响应的影响相互抵消，限制了生态系统生产力对CO2上升的响应。这就解释了为什么以前的分析无法辨别出站点干燥度和CFE之间的可靠趋势。因此，全球温带草原的CFE将受到其自然降雨季节性的限制，因此二氧化碳上升对生物量的刺激可能大大低于预期。
Rising atmospheric carbon dioxide concentration should stimulate biomass production directly via biochemical stimulation of carbon assimilation, and indirectly via water savings caused by increased plant water-use efficiency. Because of these water savings, the CO2 fertilization effect (CFE) should be stronger at drier sites, yet large differences among experiments in grassland biomass response to elevated CO2 appear to be unrelated to annual precipitation, preventing useful generalizations. Here, we show that, as predicted, the impact of elevated CO2 on biomass production in 19 globally distributed temperate grassland experiments reduces as mean precipitation in seasons other than spring increases, but that it rises unexpectedly as mean spring precipitation increases. Moreover, because sites with high spring precipitation also tend to have high precipitation at other times, these effects of spring and non-spring precipitation on the CO2 response offset each other, constraining the response of ecosystem productivity to rising CO2. This explains why previous analyses were unable to discern a reliable trend between site dryness and the CFE. Thus, the CFE in temperate grasslands worldwide will be constrained by their natural rainfall seasonality such that the stimulation of biomass by rising CO2 could be substantially less than anticipated.