Subalpine forests that historically burned every 100-300 years are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (< 30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and non-serotinous) after a stand-replacing fire that burned young (≤30 yrs) and older (>100 yrs) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n = 18) extending from live forest edges of varying age (18, 30 and >100 yrs) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (~8 seeds m-2 ) and similarly greater in 30- and 100-yr old stands (~32 seeds m-2 ). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4 seeds m-2 ) and concentrated within 10 m of the live edge, whereas seed delivery from >100-yr old edges was >4.9 seeds m-2 out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds ha-1 ) in >70% of areas that burned in short-interval fire (<30 yrs). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.

中文翻译：

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繁殖体不会落在离树很远的地方，尤其是在短间隔、高强度的火灾之后

随着气候变暖，历史上每 100-300 年燃烧一次的亚高山森林预计会更频繁地燃烧，这可能是在树木达到生殖成熟或产生含血清的种子库之前。短间隔（< 30 年）高强度火灾后的树木再生将越来越依赖于未燃烧树木的种子传播，但人们对传播如何随年龄和周围森林结构的变化知之甚少。我们研究了三种针叶树（Picea engelmannii、Abies lasiocarpa 和 Pinus contorta var. latifolia，可以是浆液性和非浆质性）在燃烧年轻（≤ 30 岁）和更老（> 100 年）的替代火后的风传播) 大提顿国家公园（美国怀俄明州）的 P. contorta 森林。我们询问自上次火灾以来繁殖压力如何随时间变化，种子输送到烧毁森林中的方式如何随活林边缘的年龄和结构而变化，哪些变量解释了种子输送到烧毁森林中的原因，以及整个烧毁区域的种子输送空间模式如何随周围活林年龄的交替模式而变化。沿 100 米横断面（n = 18）收集种子，从不同年龄（18、30 和 >100 年）的活森林边缘延伸到最近（2 年）高强度火灾的区域，并沿着活的森林来测量繁殖压力。18 年龄林分（~8 粒种子 m-2 ）的繁殖压力较低，而 30 年和 100 年龄林分（~32 粒种子 m-2 ）的繁殖压力同样较大。平均散布距离在 18 年前的边缘最低，在 > 100 年前的边缘最大。进入被烧毁森林的种子交付量随着距离的增加而下降，并随着活林边缘树木高度的增加而增加，并且 P. contorta 始终高于其他针叶树。经验性分散籽粒显示，来自 18 年龄边缘的种子交付量非常低（≤2.4 粒种子 m-2 ）并且集中在活边缘的 10 m 内，而来自 > 100 年龄边缘的种子交付量 > 4.9 粒米-2 到 80 m。当在整个燃烧的景观中进行外推时，在超过 70% 的在短时间间隔火灾（<30 年）中燃烧的区域中，估计的种子交付量很低（<49,400 颗种子 ha-1）。随着火灾频率的增加，短间隔火灾中的未成熟风险将更加复杂，因为周围幼树的种子传播有限。经验性分散籽粒显示，来自 18 年龄边缘的种子传递非常低（≤2.4 粒种子 m-2 ）并且集中在活缘的 10 m 内，而来自 > 100 年龄的种子传递的种子>4.9 粒米-2 到 80 m。当在整个燃烧的景观中进行外推时，在超过 70% 的在短时间间隔火灾（<30 年）中燃烧的区域中，估计的种子交付量很低（<49,400 颗种子 ha-1）。随着火灾频率的增加，短间隔火灾中的未成熟风险将更加复杂，因为周围幼树的种子传播有限。经验性分散籽粒显示，来自 18 年龄边缘的种子传递非常低（≤2.4 粒种子 m-2 ）并且集中在活缘的 10 m 内，而来自 > 100 年龄的种子传递的种子>4.9 粒米-2 到 80 m。当在整个燃烧的景观中进行外推时，在超过 70% 的在短时间间隔火灾（<30 年）中燃烧的区域中，估计的种子交付量很低（<49,400 颗种子 ha-1）。随着火灾频率的增加，短间隔火灾中的未成熟风险将更加复杂，因为周围幼树的种子传播有限。在超过 70% 的在短时间间隔火灾（<30 年）中燃烧的区域中，估计种子交付量较低（<49,400 颗种子 ha-1）。随着火灾频率的增加，短间隔火灾中的未成熟风险将更加复杂，因为周围幼树的种子传播有限。在超过 70% 的在短时间间隔火灾（<30 年）中燃烧的区域中，估计种子交付量较低（<49,400 颗种子 ha-1）。随着火灾频率的增加，短间隔火灾中的未成熟风险将更加复杂，因为周围幼树的种子传播有限。