Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901-83 Umeå, Sweden.
Biol Lett. 2012 Oct 23;8(5):805-8. doi: 10.1098/rsbl.2012.0429. Epub 2012 Jun 13.
Plant productivity is predicted to increase in boreal forests owing to climate change, but this may depend on whether N inputs from biological N-fixation also increases. We evaluated how alteration of climatic factors affects N input from a widespread boreal N-fixer, i.e. cyanobacteria associated with the feather moss Pleurozium schreberi. In each of 10 forest stands in northern Sweden, we established climate-change plots, including a control (ambient climate) plot and three plots experiencing a +2°C temperature increase, an approximately threefold reduction in precipitation frequency, and either 0.07, 0.29 or 1.16 times normal summer precipitation. We monitored N-fixation in these plots five times between 2007 and 2009, and three times in 2010 after climate treatments ended to assess their recovery. Warmer temperatures combined with less frequent precipitation reduced feather moss moisture content and N-fixation rates regardless of total precipitation. After climate treatments ended, recovery of N-fixation rates occurred on the scale of weeks to months, suggesting resilience of N-fixation to changes in climatic conditions. These results suggest that modelling of biological N-inputs in boreal forests should emphasize precipitation frequency and evaporative water loss in conjunction with elevated temperature rather than absolute changes in mean precipitation.
由于气候变化，预计北方森林的植物生产力将会提高，但这可能取决于生物固氮所带来的氮输入是否也会增加。我们评估了气候因素的变化如何影响广泛分布于北方森林的固氮生物，即与羽藓（ Pleurozium schreberi ）相关的蓝细菌的氮输入。在瑞典北部的 10 个森林中，我们建立了气候变化实验区，包括对照（环境气候）区和三个试验区，试验区的温度升高 2°C，降水频率降低约三倍，夏季降水分别为正常水平的 0.07、0.29 或 1.16 倍。我们在 2007 年至 2009 年期间五次监测这些实验区的固氮作用，在气候处理结束后的 2010 年进行了三次监测，以评估它们的恢复情况。无论总降水量如何，温度升高和降水频率降低都会降低羽藓的水分含量和固氮速率。气候处理结束后，固氮速率在数周到数月的时间内恢复，这表明固氮作用对气候条件变化具有弹性。这些结果表明，北方森林生物氮输入的建模应该强调降水频率和蒸发水分损失，同时结合升高的温度，而不是平均降水量的绝对变化。
