种子特性决定了物种在不同土壤加热情况下对火灾的反应,Functional Ecology

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种子特性决定了物种在不同土壤加热情况下对火灾的反应
Functional Ecology ( IF 4.6 ) Pub Date : 2020-07-23 , DOI: 10.1111/1365-2435.13623
Ryan Tangney _{1,

2} , David J. Merritt _{2,

3} , J. Nikolaus Callow ₄ , Joseph B. Fontaine ₅ , Ben P. Miller _{2,

3}

Affiliation

1. 火灾易发环境中的许多植物物种通过土壤种子库在火灾中保持持久性。然而，储存在土壤中的种子有因火灾期间土壤温度升高而死亡的风险。埋藏可以保护种子免受火温影响，但埋藏太深的种子可能会发芽但无法出苗。因此，成功的火灾后种子再生取决于埋藏深度和通过火灾生存之间的权衡。2. 我们研究了澳大利亚西南部 13 种本地林地和 4 种非本地林地物种在火灾期间的幼苗出苗行为、种子存活率和土壤温度之间的关系。我们评估了在 8 个深度（0、1、2、3、4、5、7、10 厘米）种植的种子的每个深度的总出苗深度、最大出苗深度和出苗速度。土壤温度使用光纤 (DTS) 中的分布式温度传感进行量化，在 8 到 20 之间操纵精细燃料的床中进行五次实验火灾期间，在 1 到 10 厘米深度之间连续测量（温度随后被分类为 1 厘米增量以进行分析）吨/公顷。使用相对于土壤温度的种子存活和出苗成功率，我们确定了幼苗出苗相对于通常在林地中观察到的燃料量燃烧产生的土壤温度的脆弱性。3. 物种之间的最大出苗深度从 2 厘米到 >10 厘米不等，与种子质量呈线性正相关。来自两种最高燃料质量的最大土壤温度超过了至少五个物种的种子致死阈值（T 50 - 代表对 50% 的种子致死的温度）。所有三种草种和所有四种非本地物种的所有潜在出现深度都超过了致死温度。在其余 10 个物种中，在任何测试的燃料质量水平下，温度都没有超过致死阈值。我们发现致死温度阈值与最大出现深度之间没有关系。4. 我们的数据表明，种子对土壤加热的反应和从深处出现的能力不同，在我们的研究物种中具有三种不同的功能反应，可以在火灾中持续存在，并在火灾后补充。物种属性和燃料质量的这种变化可能会导致在变化的火灾情况下社区响应的异质性（火灾内）或不同的轨迹（火灾之间）。

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Seed traits determine species responses to fire under varying soil heating scenarios

1. Many plant species in fire‐prone environments maintain persistence through fire via soil seedbanks. However, seeds stored within the soil are at risk of mortality from elevated soil temperatures during fire. Seeds may be protected from fire‐temperature impacts by burial, however, those buried too deeply may germinate but fail to emerge. Thus, successful post‐fire seed regeneration is contingent upon a trade‐off between burial depth and survival through fire. 2. We examined the relationships between seedling emergence behaviour, seed survival and soil temperatures during fire in 13 native and four non‐native woodland species in southwestern Australia. We assessed total seedling emergence per depth, maximum seedling emergence depth and seedling emergence speed from seeds planted at eight depths (0, 1, 2, 3, 4, 5, 7, 10 cm). Soil temperatures were quantified using distributed temperature sensing in optic fibre (DTS), measured continuously between 1 and 10 cm in depth (temperatures were subsequently categorized into 1 cm increments for analysis) during five experimental fires in beds with fine fuels manipulated between 8 and 20 t/ha. Using seed survival and emergence success relative to soil temperatures, we determined vulnerability of seedling emergence relative to soil temperatures generated by combustion of fuel quantities typically observed in woodlands. 3. Maximum depth of emergence varied between species from 2 to >10 cm, with a positive linear correlation to seed mass. Maximum soil temperatures from the two highest fuel masses exceeded seed lethal thresholds (T 50—representing temperatures lethal to 50% of seeds) of at least five species. Lethal temperatures were exceeded at all potential emergence depths for all three grass species, and all four non‐native species studied. Of the remaining 10 species, temperatures did not exceed the lethal thresholds under any of the fuel mass levels tested. We found no relationship between lethal temperature thresholds and maximum emergence depth. 4. Our data demonstrate that seeds exhibit variation in their response to soil heating and capacity to emerge from depth, with three distinct functional responses amongst our study species, which enable persistence through, and recruitment following, fire. Such variation in species attributes and fuel mass may lead to heterogeneity (within fires) or divergent trajectories (among fires) in community response under changed fire regime.

更新日期：2020-07-23

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