Pyrosphere Cycle: Persistent Wildfire Stress as the Long-Term Background Mechanism of Gradual Dinosaur Decline in the Mesozoic — Asteroid Impacts and Volcanism as Short-Term Triggering Disturbances

本文构建一套理想稳态野火思想推演模型,设定标准化简化边界条件,推演千万年尺度周期性大范围野火对陆生脊椎动物形成的持续性生态胁迫;结合多类自然火源差异对比、现代野火沉积观测[1]、古火代用指标[5]、全球碳循环收支、古土壤有机质堆积规律、古生物种群埋藏证据[7],辨析德干火山喷发、希克苏鲁伯小行星撞击两类脉冲式地质事件的演化定位。推演结果表明:以雷电、地层有机质自燃为核心点火源的炎球循环,以数十年至百年为周期反复作用于大陆地表,持续压缩生物栖息空间、形成1–3年植被恢复空白期,在数千万年地质尺度持续压低非鸟恐龙种群规模,构成恐龙在K-Pg界线前长期处于生态脆弱状态的背景胁迫;小行星撞击、晚白垩世大规模火山喷发是在此基础上触发灭绝的短期终结扰动[13]。二者并非互斥对立,形成“长期削弱——短期终结”协同演化关系,共同构成恐龙消亡完整演化链条。 本推演框架不局限于白垩纪恐龙演化,也可作为统一的陆地长期环境胁迫补充视角,辅助解读地质史上其余四次大型灭绝与多期小规模生物衰减[21—24],与各灭绝事件公认核心触发机制形成互补解释。同时该模型能够补充解释一项地质观测矛盾:泥盆纪后陆地林木广泛发育,但多数内陆古土壤剖面原地植物残体、腐殖层十分稀少,大量陆生植被有机质经野火焚烧转化为细粒炭屑,随径流搬运入海埋藏[4],仅极少数快速掩埋、未遭遇火烧的植株可留存为陆地植物化石。 本文模型属于理想化简化推演,无法完全复刻中生代真实野火规模与频次,仅适用于预印本理论思辨、中小学地理生物拓展阅读,不作为实证类科学定论。 This paper constructs an ideal steady-state wildfire theoretical deduction model with standardized simplified boundary conditions to deduce the persistent ecological stress exerted by periodic large-scale wildfires on terrestrial vertebrates over tens of millions of years. Combined with comparative analysis of various natural ignition sources, modern wildfire sedimentary observations[1], paleowildfire proxies[5], global carbon cycle budgets, soil organic matter accumulation rules, and paleontological population burial evidence[7], this paper distinguishes the evolutionary positioning of two pulsed geological events: the Deccan Traps eruptions and the Chicxulub asteroid impact. The deduction results show that the Pyrosphere Cycle, with lightning and subsurface organic matter spontaneous combustion as core ignition sources, repeatedly acts on continental surfaces over decades to centuries, continuously compressing biological habitats and creating a 1–3 year vegetation recovery gap. On a tens-of-millions-year geological timescale, it persistently reduces the population size of non-avian dinosaurs, forming the background stress that left dinosaurs ecologically vulnerable long before the K-Pg boundary. Asteroid impacts and large-scale Late Cretaceous volcanic eruptions serve as short-term terminal disturbances triggering extinction on this basis[13]. The two mechanisms are not mutually exclusive, forming a synergistic evolutionary chain of "long-term weakening — short-term termination" that constitutes the complete evolutionary path of dinosaur extinction. This deductive framework is not limited to Cretaceous dinosaur evolution. It can also serve as a unified supplementary perspective on long-term terrestrial environmental stress to assist in interpreting the other four major mass extinctions and multiple minor biotic declines in geological history[21—24], forming complementary explanations with the recognized core triggering mechanisms of each extinction event. Meanwhile, this model can resolve a contradictory geological observation: after the Devonian, terrestrial forests flourished widely, yet most inland paleosol profiles contain scarce in-situ plant residues and humus layers. A large amount of terrestrial vegetation organic matter was converted into fine charcoal by wildfire combustion and transported to oceans for burial via runoff[4], with only a tiny fraction of rapidly buried, unburned plant specimens preserved as terrestrial plant fossils. The model presented herein is a highly idealized simplified deduction that cannot fully replicate the true scale and frequency of Mesozoic wildfires. It is only applicable to theoretical speculation in preprints and extended reading for middle and high school geography and biology courses, and shall not be regarded as empirically validated scientific conclusions. 中文关键词:炎球循环,野火胁迫,恐龙衰退,K-Pg灭绝,古野火,碳循环,古土壤,黑碳,惰质组,生物大灭绝,古生态 English Keywords: Pyrosphere Cycle, wildfire stress, dinosaur decline, K-Pg mass extinction, paleowildfire, carbon cycle, paleosol, black carbon, inertinite