Department of Geological Sciences, Stanford University, Stanford, California, USA.
Department of Earth and Planetary Science, University of California, Berkeley, California, USA.
Geobiology. 2023 Jan;21(1):86-101. doi: 10.1111/gbi.12519. Epub 2022 Aug 10.
Evolution of high-productivity angiosperms has been regarded as a driver of Mesozoic ecosystem restructuring. However, terrestrial productivity is limited by availability of rock-derived nutrients such as phosphorus for which permanent increases in weathering would violate mass balance requirements of the long-term carbon cycle. The potential reality of productivity increases sustained since the Mesozoic is supported here with documentation of a dramatic increase in the evolution of nitrogen-fixing or nitrogen-scavenging symbioses, including more than 100 lineages of ectomycorrhizal and lichen-forming fungi and plants with specialized microbial associations. Given this evidence of broadly increased nitrogen availability, we explore via carbon cycle modeling how enhanced phosphorus availability might be sustained without violating mass balance requirements. Volcanism is the dominant carbon input, dictating peaks in weathering outputs up to twice modern values. However, times of weathering rate suppression may be more important for setting system behavior, and the late Paleozoic was the only extended period over which rates are expected to have remained lower than modern. Modeling results are consistent with terrestrial organic matter deposition that accompanied Paleozoic vascular plant evolution having suppressed weathering fluxes by providing an alternative sink of atmospheric CO . Suppression would have then been progressively lifted as the crustal reservoir's holding capacity for terrestrial organic matter saturated back toward steady state with deposition of new organic matter balanced by erosion of older organic deposits. Although not an absolute increase, weathering fluxes returning to early Paleozoic conditions would represent a novel regime for the complex land biota that evolved in the interim. Volcanism-based peaks in Mesozoic weathering far surpass the modern rates that sustain a complex diversity of nitrogen-based symbioses; only in the late Paleozoic might these ecologies have been suppressed by significantly lower rates. Thus, angiosperms are posited to be another effect rather than proximal cause of Mesozoic upheaval.
高生产力被子植物的进化被认为是中生代生态系统重构的驱动力。然而，陆地生产力受到岩石衍生养分（如磷）的限制，而风化的永久性增加将违反长期碳循环的质量平衡要求。中生代以来生产力持续增加的潜在现实在这里得到了支持，有证据表明固氮或氮掠夺共生关系的进化急剧增加，包括 100 多个外生菌根和地衣形成真菌以及具有特殊微生物共生体的植物谱系。鉴于氮供应广泛增加的证据，我们通过碳循环建模来探索如何在不违反质量平衡要求的情况下维持增强的磷供应。火山作用是主要的碳输入，决定了风化输出的峰值高达现代值的两倍。然而，风化速率抑制的时间可能对设定系统行为更为重要，而晚古生代是唯一一段风化速率预计低于现代水平的延长时期。模型结果与伴随古生代维管植物进化的陆地有机物质沉积一致，通过提供大气 CO 的替代汇，抑制了风化通量。随着地壳储层对陆地有机物质的容纳能力随着新有机物质的沉积和旧有机物质的侵蚀而达到稳定状态，抑制作用将逐渐解除。尽管不是绝对增加，但风化通量恢复到早古生代条件将代表一个新的复杂陆地生物群的复杂生态系统。中生代风化的基于火山作用的峰值远远超过了维持复杂氮基共生体多样性的现代速率；只有在晚古生代，这些生态系统才可能因明显较低的速率而受到抑制。因此，被子植物被认为是中生代剧变的另一个结果，而不是直接原因。
