The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sprouting tree Proteacaffra in temperate grasslands
The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sprouting tree Proteacaffra in temperate grasslands
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炎热天气：蕨菜（Pteridium aquilinum）频繁发生的高强度火灾导致温带草原发芽树 Proteacaffra 死亡
作者：
H. Adie;S. Richert;K. Kirkman;M. Lawes
我们研究了火灾频率和强度对南非夸祖鲁-纳塔尔省西北部温带山地草原上一种卡夫拉树种群的影响。通过比较离散蕨类斑块与周围草地基质中黑桫椤的种群结构，评价了火灾的影响。草地和蕨类植物的燃料生物量差异不大，但蕨类植物的燃料明显比草干。蕨类植物生境的地上火温和火线强度（以柏树焦炭高度测量）显著高于其他生境。在草原和蕨类植物中，42%的卡芙拉种群因火灾而失去了原有的茎，靠灌木林的再生枝生存。与草地乔木相比，暴露于较高强度的蕨类植物火会抑制黑桫椤的再生，造成更高的成虫死亡率。结果表明，蕨类植物种群年龄偏大，大部分树木遭受严重火灾破坏。小乔木在草地上的高发率表明，2 ~ 3年的定期取火间隔期对羊草的再生没有负面影响。然而，在蕨类植物斑块中，经常性的高强度火灾会导致所有蕨类植物的高死亡率，并最终导致局部灭绝。因此，蕨菜有可能显著改变这些山地草原的树-草相互作用。
We examined the effect of fire frequency and intensity on a Protea caffra tree population in the temperate montane grasslands of north-western KwaZulu-Natal, South Africa. We assessed the effect of fire by comparing the population structure of the resprouter P. caffra in discrete bracken (Pteridium aquilinum) patches with that in the surrounding grassland matrix. Fuel biomass did not differ between grassland and bracken, but bracken fuel was significantly drier than grass. Above-ground fire temperatures and fireline intensity, measured by P. caffra char height, were significantly higher in the bracken habitat. Forty-two percent of the P. caffra population in grassland and in bracken persisted by coppice resprouts, having lost their original stem to fire damage. Exposure to higher intensity bracken fire suppressed P. caffra regeneration and caused greater adult mortality compared with trees in grassland. Consequently, the P. caffra population in bracken was skewed towards old age with most trees severely fire damaged. The high incidence of small trees in grassland indicates that a regular fire interval of 2–3 years does not negatively affect regeneration of P. caffra. However, in bracken patches regular high intensity fires cause high mortality among all P. caffra size classes and will ultimately result in local extinction. Bracken thus has the potential to significantly alter tree–grass interactions in these montane grasslands.