Extended leaf phenology has limited benefits for invasive species growing at northern latitudes
Extended leaf phenology has limited benefits for invasive species growing at northern latitudes
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DOI：
10.1007/s10530-020-02301-w
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发表时间：
2020-07
影响因子：
2.9
通讯作者：
E. O’Connell;J. Savage
中科院分区：
文献类型：
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作者：
E. O’Connell;J. Savage
北美的许多林下木本入侵植物比它们的本地伙伴落叶早或留叶晚。这种延长的叶物候被认为是授予入侵物种比本地物种的优势，因为春天和秋天是关键的时候，光的访问和碳收购林下栖息地。然而，目前还不清楚这种优势是否持续在北方纬度地区，那里的冰冻温度限制了生长季节的长度，低光照水平减少了碳的增加。为了研究在北方纬度延长叶物候的成本和效益，我们观察了叶物候，估计总碳增益，测量生长，并测试了四个本地和四个入侵的木本灌木在美国明尼苏达州北方的干扰森林中对冻结温度的敏感性。我们发现，入侵者在春季与本地物种同时长出叶子，但在秋季保留叶子的时间比本地物种晚。这种延长的秋季物候并没有使入侵者获得更大的总碳收益，因为他们在一年中吸收的碳比当地人少。本地种和外来种对冰冻温度的敏感性也没有显著差异。相反，耐冻性与本地范围，然后叶物候。我们的研究结果表明，冰冻温度并不限制入侵物种的北方扩张，而是表明，在其范围的北方边缘，这些物种可能会失去任何竞争优势，延长叶物候超过他们的本地联营公司。这项研究表明，在调查物候和生长时，考虑纬度和森林结构的重要性。
Many understory woody invasive plants in North America leaf out earlier or retain leaves later than their native associates. This extended leaf phenology is thought to grant invasive species an advantage over native species because spring and fall are crucial times for light access and carbon acquisition in understory habitats. However, it is unclear whether this advantage persists at northern latitudes where freezing temperatures constrain growing season length and low light levels reduce carbon gain. To investigate the costs and benefits of extended leaf phenology at northern latitudes, we observed leaf phenology, estimated total carbon gain, measured growth, and tested susceptibility to freezing temperatures for four native and four invasive woody shrubs in a disturbed forest in northern Minnesota, USA. We found that the invaders leafed out simultaneously with the natives in the spring but retained their leaves later in the autumn than native species. This extended fall phenology did not enable greater total carbon gain for the invaders because they assimilated less carbon earlier in the year than the natives. There was also no significant difference between native and invasive species in their susceptibility to freezing temperatures. Instead freezing tolerance related more to native range then leaf phenology. Our results suggest that freezing temperatures do not limit invasive species’ northern expansion and instead indicate that at the northern edge of their ranges, these species may lose any competitive advantage granted by extended leaf phenology over their native associates. This study demonstrates the importance of considering latitude and forest structure when investigating phenology and growth.