Divergent carbon cycle response of forest and grass‐dominated northern temperate ecosystems to record winter warming
Divergent carbon cycle response of forest and grass‐dominated northern temperate ecosystems to record winter warming
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DOI：
10.1111/gcb.14850
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发表时间：
2019-10
影响因子：
11.6
通讯作者：
Rebecca Sanders‐DeMott;A. Ouimette;L. Lepine;S. Fogarty;E. Burakowski;A. Contosta;S. Ollinger
中科院分区：
文献类型：
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作者：
Rebecca Sanders‐DeMott;A. Ouimette;L. Lepine;S. Fogarty;E. Burakowski;A. Contosta;S. Ollinger
北方温带生态系统正在经历更温暖和更多变的冬季，预计这种趋势将持续到可预见的未来。尽管如此，大多数研究都集中在生长季节的气候变化影响，特别是在比较不同植被覆盖类型的响应时。在这里，我们研究了美国新罕布什尔州的多年生草地和邻近的混交林生态系统如何应对2014年至2017年期间高度多变的冬季，其中包括迄今为止有记录以来最温暖的冬季。在草原，2015/2016年冬季破纪录的气温导致植物在2月开始生长，生态系统在冬季结束前成为一个持续的碳汇，在冬季到春季的过渡期间比其他记录年份多吸收约90 g/m2的碳。在同一时期，森林是一个非常大的碳源。虽然森林光合作用受到落叶物候学的限制，但暖冬温度导致生态系统呼吸的大脉冲，从2月到4月释放近230 g C/m2，是较冷年份期间碳损失的两倍多。这些研究结果表明，随着冬季持续变暖，生长季节外生态系统呼吸的增加可能超过较长生长季节内碳吸收的增加，特别是在依赖落叶时间启动碳吸收的森林中。在具有常年生叶习性的生态系统中，冬季气温变暖更有可能通过延长活跃的生长季节来增加生态系统的碳吸收。我们的研究结果强调了了解前期冬季条件与土地覆盖类型之间的碳交换关系的重要性，以了解在预计的气候变暖下景观碳交换将如何变化。
Northern temperate ecosystems are experiencing warmer and more variable winters, trends that are expected to continue into the foreseeable future. Despite this, most studies have focused on climate change impacts during the growing season, particularly when comparing responses across different vegetation cover types. Here we examined how a perennial grassland and adjacent mixed forest ecosystem in New Hampshire, United States, responded to a period of highly variable winters from 2014 through 2017 that included the warmest winter on record to date. In the grassland, record‐breaking temperatures in the winter of 2015/2016 led to a February onset of plant growth and the ecosystem became a sustained carbon sink well before winter ended, taking up roughly 90 g/m2 more carbon during the winter to spring transition than in other recorded years. The forest was an unusually large carbon source during the same period. While forest photosynthesis was restricted by leaf‐out phenology, warm winter temperatures caused large pulses of ecosystem respiration that released nearly 230 g C/m2 from February through April, more than double the carbon losses during that period in cooler years. These findings suggest that, as winters continue to warm, increases in ecosystem respiration outside the growing season could outpace increases in carbon uptake during a longer growing season, particularly in forests that depend on leaf‐out timing to initiate carbon uptake. In ecosystems with a perennial leaf habit, warming winter temperatures are more likely to increase ecosystem carbon uptake through extension of the active growing season. Our results highlight the importance of understanding relationships among antecedent winter conditions and carbon exchange across land‐cover types to understand how landscape carbon exchange will change under projected climate warming.