Fire frequency, state change and hysteresis in tallgrass prairie
Fire frequency, state change and hysteresis in tallgrass prairie
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DOI：
10.1111/ele.13676
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发表时间：
2021-01-14
期刊：
影响因子：
8.8
通讯作者：
Ratajczak, Zak
中科院分区：
文献类型：
--
作者：
Collins, Scott L.;Nippert, Jesse B.;Ratajczak, Zak
滞后现象是替代稳态理论的基本特征，但滞后现象的证据很少。在中等草原中，火灾频率调节着从草为主的系统状态向灌木为主的系统状态的转变。然而，尚不确定增加火灾频率是否可以逆转灌木扩张，或者草灌木动态是否表现出滞后现象。对两处不常烧毁的草原实行年烧，对两处常年烧毁的草原停止烧毁。在每年的火灾中，由于草覆盖的迅速恢复，草地的组成趋于于每年长期烧毁的植被的组成，尽管灌木仍然存在。当每年的燃烧停止时，灌木覆盖增加，但由于灌木的随机和滞后扩散，群落组成并未与长期不常燃烧的参考地点趋同，反映了滞后现象。我们的结果表明，每年的燃烧可以减缓但不能逆转灌木侵蚀。此外，扭转火灾频率会导致滞后，因为从草地到灌木丛的植被轨迹与从灌木丛到草地的植被轨迹不同。
Hysteresis is a fundamental characteristic of alternative stable state theory, yet evidence of hysteresis is rare. In mesic grasslands, fire frequency regulates transition from grass- to shrub-dominated system states. It is uncertain, however, if increasing fire frequency can reverse shrub expansion, or if grass-shrub dynamics exhibit hysteresis. We implemented annual burning in two infrequently burned grasslands and ceased burning in two grasslands burned annually. With annual fires, grassland composition converged on that of long-term annually burned vegetation due to rapid recovery of grass cover, although shrubs persisted. When annual burning ceased, shrub cover increased, but community composition did not converge with a long-term infrequently burned reference site because of stochastic and lagged dispersal by shrubs, reflecting hysteresis. Our results demonstrated that annual burning can slow, but not reverse, shrub encroachment. In addition, reversing fire frequencies resulted in hysteresis because vegetation trajectories from grassland to shrubland differed from those of shrubland to grassland.