C4 grasses prosper as carbon dioxide eliminates desiccation in warmed semi-arid grassland
C4 grasses prosper as carbon dioxide eliminates desiccation in warmed semi-arid grassland
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DOI：
10.1038/nature10274
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发表时间：
2011-08-11
期刊：
影响因子：
64.8
通讯作者：
West, Mark
中科院分区：
文献类型：
--
作者：
Morgan, Jack A.;LeCain, Daniel R.;West, Mark
据预测，全球变暖将通过增加蒸发需求在世界许多地区导致干燥化(1-3)。二氧化碳的增加可能会通过提高植物的水分利用效率来扭转这一趋势(4，5)。然而，目前尚不清楚这种二氧化碳增强的水分利用效率在抵消变暖引起的干旱方面的重要性，因为更高的二氧化碳也会导致更高的植物生物量，从而导致更大的蒸腾表面(2，6，7)。此外，尽管气候变暖预计将有利于暖季的C-4草本植物，但不断上升的二氧化碳应该有利于C-3或冷季的植物(8)。在这里，我们展示了在半干旱的草原上，二氧化碳浓度升高可以完全逆转温和变暖造成的干燥效应。尽管空气浓度升高到600p.pm/v.v.CO2会增加土壤水分含量(SWC)，但1.5/3.0℃的昼夜升温会导致土壤干化，因此与对照小区相比，CO2浓度升高和增温共同作用对土壤水分含量没有影响。正如预测的那样，二氧化碳升高有利于C-3牧草并提高林分生产力，而变暖有利于C-4牧草。在土壤水分最限制植物生产力的2~3年，气候变暖和CO2的共同作用促进了C-4牧草的地上生长。结果表明，在一个更温暖、富含二氧化碳的世界中，半干旱草原的SWC和生产力都可能比之前预期的要高。
Global warming is predicted to induce desiccation in many world regions through increases in evaporative demand(1-3). Rising CO2 may counter that trend by improving plant water-use efficiency(4,5). However, it is not clear how important this CO2-enhanced water use efficiency might be in offsetting warming-induced desiccation because higher CO2 also leads to higher plant biomass, and therefore greater transpirational surface(2,6,7). Furthermore, although warming is predicted to favour warm-season, C-4 grasses, rising CO2 should favour C-3, or cool-season plants(8). Here we show in a semi-arid grassland that elevated CO2 can completely reverse the desiccating effects of moderate warming. Although enrichment of air to 600 p. p. m. v. CO2 increased soil water content (SWC), 1.5/3.0 degrees C day/night warming resulted in desiccation, such that combined CO2 enrichment and warming had no effect on SWC relative to control plots. As predicted, elevated CO2 favoured C-3 grasses and enhanced stand productivity, whereas warming favoured C-4 grasses. Combined warming and CO2 enrichment stimulated above-ground growth of C-4 grasses in 2 of 3 years when soil moisture most limited plant productivity. The results indicate that in a warmer, CO2-enriched world, both SWC and productivity in semi-arid grasslands may be higher than previously expected.