Does fire always accelerate shrub expansion in Arctic tundra? Examining a novel grass-dominated successional trajectory on the Seward Peninsula
Does fire always accelerate shrub expansion in Arctic tundra? Examining a novel grass-dominated successional trajectory on the Seward Peninsula
复制标题
DOI：
10.1080/15230430.2021.1899562
复制
发表时间：
2021-01-02
影响因子：
2
通讯作者：
Mack, Michelle C.
中科院分区：
文献类型：
--
作者：
Hollingsworth, Teresa N.;Breen, Amy L.;Mack, Michelle C.
在过去的世纪，在环北极地区，显著的陆地生态系统变化包括灌木的扩张和野火的加剧。灌木入侵苔原可能会进一步加快野火干扰，这创造了机会，建立招聘，否则是罕见的。苏厄德半岛目前经历的火灾比阿拉斯加其他苔原地区更频繁，规模更大。有一些重叠的烧伤疤痕可以追溯到20世纪50年代。利用时间序列的方法，我们研究了植被和生态系统的动态在草丛冻原。增加烧伤的严重程度和火灾频率对应的增加，草覆盖和减少灌木断面积。我们使用多变量排序分析来创建一个单一的火灾效应的积分变量，占火灾后的时间，烧伤的严重程度，和烧伤的次数。这种火灾的影响显着相关的土壤有机层厚度和整体植物生物量的减少。与以往在北极阿拉斯加苔原的研究不同，我们发现火灾频率和严重程度的增加并没有增加灌木覆盖率和生物量。相反，加剧火灾干扰，特别是重复火灾，导致草的优势。我们的研究结果支持这一假设，即加强苔原火灾制度启动替代火灾后的轨迹，不是灌木为主，在结构和功能上完全不同的莎草或灌木为主的苔原。
Over the last century in the circumpolar north, notable terrestrial ecosystem changes include shrub expansion and an intensifying wildfire regime. Shrub invasion into tundra may be further accelerated by wildfire disturbance, which creates opportunities for establishment where recruitment is otherwise rare. The Seward Peninsula currently experiences more frequent and larger fires than other tundra regions in Alaska. There are areas of overlapping burn scars dating back to the 1950s. Using a chronosequence approach, we examined vegetation and ecosystem dynamics in tussock tundra. Increasing burn severity and fire frequency corresponded with an increase in grass cover and a decrease in shrub basal area. We used multivariate ordination analysis to create a single integrator variable of fire effect that accounted for time after fire, burn severity, and number of times burned. This fire effect was significantly associated with decreases in soil organic layer thickness and overall plant biomass. Unlike previous studies in Arctic Alaska tundra, we found that increases in fire frequency and severity did not increase shrub cover and biomass. Instead, intensifying fire disturbance, and particularly repeat fires, led to grass dominance. Our findings support the hypothesis that intensifying tundra fire regimes initiate alternative post-fire trajectories that are not shrub dominated and that are structurally and functionally quite different from sedge or shrub-dominated tundra.